R Venkataramanan

R Venkataramanan

R Venkat's Blog

R Venkat's Blog
"To be an Inspiring Teacher,one should be a Disciplined Student throughout Life" - Venkataramanan Ramasethu



Wednesday, January 30, 2013

Madras Book Club & Sankara Nethralaya - "In-Sight" Book Reading

Time to recall, honour and add value to the contribution of two dedicated doctors to the cause of pediatric ophthalmology

It was time to recall, honour and add value to the contribution of two dedicated doctors to the cause of pediatric ophthalmology and make their effort more meaningful and far reaching. The Xth Nagamani Dharmapuri Endowment Lecture was held at the Sri VD Swami Auditorium on the 24th of January 2013 to fulfill precisely these objectives. Speakers recalled the concern and dedication of world renowned neo- natology expert Dr Vidyasagar Dharmapuri and his wife Dr. Nagamani Dharmapuri, a world renowned pediatric cardiologist in whose name the Endowment was instituted by him to the field of pediatric ophthalmology.

The function started with a melodious invocation by Dr S.Meenakshi, Director, Academics following which Dr Sumitha Agarkar, Deputy Director, Squint and pediatric ophthalmology Department gave an interesting account of the expanding and exciting scope of pediatric ophthalmology and how it came into prominence rather belatedly, she recalled the long association between Dr Vidyasagar Dharmapuri and Dr SS.Badrinath and the role of the Endowment lectures held annually in furthering the cause of pediatric ophthalmology. Speaking on the occasion Dr Sandeep Mark Thirumalai, Consultant, General Ophthalmology traced the genesis of the pediatric ophthalmology department, citing it as the brainchild of Dr SS.Badrinath on whose request Dr T.S Surendran, Vice-Chairman, Sankara Nethralaya single handedly started and nurtured this specialty department until he was joined by a team of specialists in the field. The guest of honour of the day Dr. T. Janardhana Rao, former Honorary. Consul General of India in Melbourne, an old friend of Sankara Nethralaya was introduced by Dr Kavitha Kalaivani, Consultant, Squint and pediatric department; she gave a detailed account of his achievements, high positions held and for having been the voice of India in Australia for more than 3 decades and his valuable contribution to Indo-Australian unity.

Delivering the Guest of Honour address Dr Janardhana Rao emphasized that the huge number of patients being screened and treated everyday at Sankara Nethralaya gives it an unmatched clinical expertise, which it could share with the West for the great benefit of medical science. This was followed by a most interesting Chief guest’s address by Professor Frank Martin, Visiting Ophthalmologist at the Children’s Hospital at West Mead, Sydney, he emphasized that concern, love and care were paramount to the success of pediatric ophthalmology as the doctors were dealing with children, a quality he demonstrated in abundance by sharing the case histories of more than a score patients whom he had been treating since their childhood and continues to be in touch well after they have become parents.

The function ended with a warm Vote of Thanks by Dr Mohan Rajan, Head of the Rajan Eye care Hospitals.

Sankara Nethralaya family celebrated the 64th Republic Day

The Sankara Nethralaya family celebrated the 64th Republic Day with great enthusiasm at it main campus, the event witnessed participation by the senior management members, Consultants, staff members, students of Sankara Nethralaya’s various educational institutions and SWAN Volunteers in good numbers. The proceedings started with the hoisting of the National tricolor by the Chief Guest Shri M. Murali, Proprietor, Sri Krishna Sweets followed by the rendering of the National Anthem by the entire Sankara Nethralaya family. The patriotic group song by the students of the Elite School of Optometry which followed the flag hoisting captured the spirit of the day.

The day was marked by the delivery of insightful talks by the speakers of the day the Chief Guest, the Chairman Emeritus, Chairman and Senior General Manager, Sankara Nethralaya, providing rich food for thought to the participants. The founder and Head of the institution Dr SS.Badrinath used the August occasion to drive home the need for persistent hard work and faith to reach one’s goals, he started his address with rich compliments to Dr Sundaram Natarajan, Head of the Aditya Jyot Eye hospital Mumbai an alumni and great well wisher and supporter of Sankara Nethralaya for being conferred the Padma Shri and Shri Ramamurthy Thyagarajan, Head of the Shriram Group and a generous supporter of Sankara Nethralaya’s cause for being conferred the Padma Bhushan award by the Government of India. He also paid rich compliments to Dr Shikha Talwar Bassi, Director, Department of Neuro-ophthalmology and Dr Alay Banker former Vision Research Foundation Fellow for being awarded the S.D Athawale award and Colonel Rangachary award at the recently APAO-AIOS 2013 at Hyderabad. Dr SS. Badrinath emphasized that these were fruits of hard labour and cited Dr Alay Banker’s 6 year follow up as a marathon effort to substantiate that hard work never goes in vain and appealed to the members of Sankara Nethralaya to reach Himalayan heights through hard work and honest introspection, he expressed his desire to see the Vision Research Foundation supporting the Medical Research Foundation in the not too distant future and closed his speech with the hope that the Vision Research Foundation should win 82 such awards, implying that every researcher belonging to it is recognized.

This was followed by a warm introduction of the Chief Guest Shri M.Murali, Proprietor, Sri Krishna Sweets by Ms Akila Ganesan, Senior General manager, Sankara Nethralaya, with an inspiring account of how the family run business grew from humble beginnings into one of the most successful confectionary chains in the State and a household name for quality sweets, she highlighted his simplicity and single minded purpose as the primary factors behind the amazing success story. This was followed by a very absorbing Chief Guest’s address by Shri M.Murali, paying his rich tribute and respect to Dr SS.Badrinath he described him as the life and breath of Sankara Nethralaya the institution which served thousands of patients every day, the honourable Chief guest touched upon a broad spectrum of subjects ranging from modern management principles to the spirit of giving and the need to have a value system in place, he described true growth of a man as the forward movement towards the Almighty and one’s fellow human being which is possible only by giving back to society. Speaking on the occasion Dr S.Bhaskaran, Chairman, Sankara Nethralaya underlined the significance of the day as the day when the nation declared itself a sovereign democratic republic, he observed that the Government of India confers its highest civilian awards on this day and announced that Sankara Nethralaya would also be honouring an employee every year for outstanding performance, dedication and most importantly for allegiance to the basic Sankara Nethralaya philosophy in word and spirit from the next Republic Day.

The thoughtful munificence of Shri Ram Dhingra which has helped children of Sankara Nethralaya employees pursue their studies was recalled and the cash certificates to the Dhingra Trust awardees and other deserving students were distributed along with service completion certificates to staff members by the Chief Guest and the senior management members to the loud applause of the gathering.

The function came to an end with a Vote of Thanks by Dr PS.Rajesh, In-Charge of the C.U Shah Sankara Nethralaya.

Key to Sankara Nethralaya’s success is ‘Teamwork’

Pfizer India the Indian subsidiary of global research and pharmaceutical monolith, Pfizer Inc conducted the India Research and Innovation Science (IRIS- Connect) meeting to discuss various research opportunities with medical specialists, at Mumbai, on January 27th 2013. The company honoured 4 eminent personalities with high awards of distinction, for their significant contribution to the medical and healthcare fields, on the occasion. While two awards were in recognition of innovation and research two were in honour of outstanding healthcare leadership, in recognition of individuals who led their institution remarkably and contributed significantly to the upliftment of patient care in India.

Dr SS.Badrinath, Chairman Emeritus, Sankara Nethralaya was chosen for the prestigious ‘Healthcare Leadership’ award for his dynamic leadership and significant role and critical contribution to the delivery of better patient care in India. Receiving the award on his behalf Dr L. Vijaya, Director, Smt Jadhavbhai Nathamal Singhvi Glaucoma Department, Sankara Nethralaya observed that she was indeed fortunate to receive the rare distinction on behalf of the founder and chairman emeritus of the institution, whose dynamic leadership has helped in the establishment and remarkable growth of Sankara Nethralaya, as a great ophthalmic and humanitarian institution. She emphasized that the key to Sankara Nethralaya’s success is ‘Teamwork’ and made a fervent appeal to work together to take the institution to greater heights.

Eye Camp jointly with the Uttaradi Mutt at the Ramanuja Koodam, Singarachari Street, Triplicane

The Sankara Nethralaya Tele-Ophthalmology team conducted a vibrant Eye Camp jointly with the Uttaradi Mutt at the Ramanuja Koodam, Singarachari Street, Triplicane on the 27th of January 2013

The event started with the ceremonial inauguration of the camp by the Pontiff of the Uttaradi Mutt, His Holiness Sri Satyaatma Tirtha Swamiji in the presence of Dr.S.S.Badrinath, Chairman Emeritus, Dr.Vasanthi Badrinath, Director, Clinical Lab and Dr K.S.Vasan, MD, Sankara Nethralaya. The Free Eye camp witnessed an overwhelming response despite the chilly morning, from members of the public keen to participate and benefit from it.

Over 170 patients underwent comprehensive Eye check up at the camp of whom 32 were diagnosed as needing cataract surgery, 5 of whom were brought to the Sankara Nethralaya base hospital and treated absolutely free of cost and discharged the very next day.

The camp concluded with a sumptuous lunch for the participating public and team members.

Tuesday, January 29, 2013

Retinopathy of prematurity

Retinopathy of prematurity (ROP), previously known as retrolental fibroplasia (RLF), is an eye disease that affects prematurely-born babies who have received intensive neonatal care. It is thought to be caused by disorganized growth of retinal blood vessels which may result in scarring and retinal detachment. ROP can be mild and may resolve spontaneously, but it may lead to blindness in serious cases. As such, all preterm babies are at risk for ROP, and very low birth weight is an additional risk factor. Both oxygen toxicity and relative hypoxia can contribute to the development of ROP.

Populations of preterm infants at risk: There is increasing evidence that ROP and blindness due to ROP are now public health problems in the middle income countries of Latin America, Eastern Europe and the more advanced economies in South East Asia and the Middle east region. In these countries ROP is often the most common cause of blindness in children[1][2]. ROP is highly likely to become an increasing problem in India, China and other countries in Asia as these countries expand the provision of services for premature infants.

There is also evidence that the population of premature infants at risk of severe ROP varies depending on the level of neonatal intensive care being provided[3]. In countries with high development indices and very low neonatal mortality rates (e.g. north America, western Europe), severe ROP is generally limited to extremely preterm infants i.e. those weighing less than 1000g at birth. At the other end of the development spectrum, countries with very low development indices and very high neonatal mortality rates (e.g. much of subSaharan Africa) ROP is rare as most premature babies do not have access to neonatal intensive care and so do not survive. Countries with moderate development indices are improving access to neonatal intensive care, and in these settings bigger, more mature babies are also at risk of severe ROP as neonatal care may be suboptimal(i.e. those weighing 1500-2000g at birth). These findings have two main implications: firstly, much can be done in countries with moderate development indices to improve neonatal care, to reduce the risk of severe ROP in bigger babies and increase survival of extremely preterm infants, and secondly, in these settings bigger more mature babies need to be included in ROP programs and examined regularly so as to detect those babies developing ROP requiring treatment (see below).

The World Health Organization has recently published data on rates of preterm birth and the number of premature babies born in different regions of the world[4]. The main findings of this report are threefold: 1. premature birth has many different causes, and prevention is challenging 2. prematurity is the commonest cause of neonatal death in many countries: 1 million infants die every year due to complications of preterm birth, and 3. the number of preterm births is currently estimated to be 15 million, and increasing.

Pathophysiology of ROP

Normally, maturation of the retina proceeds in-utero, and at term, the medial portion of the retina is fully vascularized, while the lateral portion is only incompletely vascularized.[5] If a pre-term infant is treated with oxygen, the oxygen may cause constriction of the retinal blood vessels.[5] This vasoconstriction can lead to a lack of oxygen (ischemia) in the retina. This leads to the production of molecules that cause the growth of new blood vessels (VEGF).[5] These blood vessels are abnormal, and negatively affect the normal development of retinal vasculature. Thus, retinopathy of prematurity occurs when the normal development of retinal blood vessels is prevented.
The key disease element in ROP is fibrovascular proliferation. This is growth of abnormal new vessels that may regress, but frequently progress. Associated with the growth of these new vessels is fibrous tissue (scar tissue) that may contract to cause retinal detachment. Multiple factors can determine whether the disease progresses, including overall health, birth weight, the stage of ROP at initial diagnosis, and the presence or absence of "plus disease". Supplemental oxygen exposure, while a risk factor, is not the main risk factor for development of this disease. Restricting supplemental oxygen use does not necessarily reduce the rate of ROP, and may raise the risk of other hypoxia-related systemic complications.[citation needed]
Other physicians have suggested that supplemental oxygen, specifically oxygen tents given to pre-term infants specifically causes ROP. The hypothesized mechanism involves the degradation and developmental cessation of blood vessels in the presence of excess oxygen. When the excess oxygen environment is removed, the blood vessels begin forming rapidly again and grow into the vitreous humor of the eye from the retina, sometimes leading to blindness.[6] This does not preclude the dangers of hypoxic environments for premature infants.
Patients with ROP, particularly those who have developed severe disease needing treatment are at greater risk for strabismus, glaucoma, cataracts and shortsightedness (myopia) later in life and should be examined yearly to help prevent or detect and treat these conditions.

Following pupillary dilation using eye drops, the retina is examined using a special lighted instrument (an indirect ophthalmoscope). The peripheral portions of the retina are sometimes pushed into view using scleral depression. Examination of the retina of a premature infant is performed to determine how far the retinal blood vessels have grown (the zone), and whether or not the vessels are growing flat along the wall of the eye (the stage). Once the vessels have grown into Zone 3 (see below) it is usually safe to discharge the child from further screening for ROP. The stage of ROP refers to the character of the leading edge of growing retinal blood vessels (at the vascular-avascular border). The stages of ROP disease have been defined by the International Classification of Retinopathy of Prematurity (ICROP).
Retinal examination with scleral depression is generally recommended for patients born before 30–32 weeks gestation, with birthweight 1500 grams or less, or at the discretion of the treating neonatologist. The initial examination is usually performed at 4–6 weeks of life, and then repeated every 1–3 weeks until vascularization is complete (or until disease progression mandates treatment).
In older patients the appearance of the disease is less well described but includes the residua of the ICROP stages as well as secondary retinal responses.
[edit]Differential diagnosis

The most difficult aspect of the differential diagnosis may arise from the similarity of two other diseases:
familial exudative vitreoretinopathy which is a genetic disorder that also disrupts the retinal vascularization in full-term infants.
Persistent Fetal Vascular Syndrome also known as Persistent Hyperplastic Primary Vitreous that can cause a traction retinal detachment difficult to differentiate but typically unilateral.
[edit]International classification of retinopathy of prematurity (ICROP)

The system used for describing the findings of active ROP is entitled The International Classification of Retinopathy of Prematurity (ICROP).[7] ICROP uses a number of parameters to describe the disease. They are location of the disease into zones (1, 2, and 3), the circumferential extent of the disease based on the clock hours (1-12), the severity of the disease (stage 1-5) and the presence or absence of "Plus Disease". Each aspect of the classification has a technical definition. This classification was used for the major clinical trials. It was revised in 2005.[8]

Zones of the retina in ROP
The zones are centered on the optic nerve. Zone 1 is the posterior zone of the retina, defined as the circle with a radius extending from the optic nerve to double the distance to the macula. Zone 2 is an annulus with the inner border defined by zone 1 and the outer border defined by the radius defined as the distance from the optic nerve to the nasal ora serrata. Zone 3 is the residual temporal crescent of the retina.
The circumferential extent of the disease is described in segments as if the top of the eye were 12 on the face of a clock. For example one might report that there is stage 1 disease for 3 clock hours from 4 to 7 o'clock. (The extent is a bit less important since the treatment indications from the Early Treatment for ROP[9])
The Stages describe the ophthalmoscopic findings at the junction between the vascularized and avascular retina.
Stage 1 is a faint demarcation line.
Stage 2 is an elevated ridge.
Stage 3 is extraretinal fibrovascular tissue.
Stage 4 is sub-total retinal detachment.
Stage 5 is total retinal detachment.
In addition, Plus disease may be present at any stage. It describes a significant level of vascular dilation and tortuosity observed at the posterior retinal vessels. This reflects the increase of blood flow through the retina. [1]

Stages 1 and 2 do not lead to blindness. However, they can progress to the more severe stages. Threshold disease is defined as disease that has a 50% likelihood of progressing to retinal detachment. Threshold disease is considered to be present when stage 3 ROP is present in either zone I or zone II, with at least 5 continuous or 8 total clock hours of disease, and the presence of plus disease.[10] Progression to stage 4 (partial retinal detachment), or to stage 5 (total retinal detachment), will result in substantial or total loss of vision for the infant.

In order to allow timely intervention, a system of monitoring is undertaken for infants at risk of developing ROP. These monitoring protocols differ geographically because the definition of high-risk is not uniform or perfectly defined. In the USA the consensus statement of experts is informed by data derived by clinical trials and published in Pediatrics 2006. They included infants with birthweights under 1500 grams or under 30 weeks gestation in most cases. The first examination should take place within the first 4 weeks of life, and regular, weekly examination is required until it is clear that the eyes are not going to develop disease needing treatment, or one or both eyes develop disease requiring treatment. Treatment should be administered within a 48 hours, as the condition can progress rapidly.

The retina (red) is detached at the top of the eye.

The silicone band (scleral buckle, blue) is placed around the eye. This brings the wall of the eye into contact with the detached retina, allowing the retina to re-attach.
Peripheral retinal ablation is the mainstay of ROP treatment. The destruction of the avascular retina is performed with a solid state laser photocoagulation device, as these are easily portable to the operating room or neonatal ICU. Cryotherapy, an earlier technique in which regional retinal destruction was done using a probe to freeze the desired areas, has also been evaluated in multi-center clinical trials as an effective modality for prevention and treatment of ROP. However, when laser treatment is available, cryotherapy is no longer preferred for routine avascular retinal ablation in premature babies, due to the side effects of inflammation and lid swelling. Further more recent trials have shown that treatment at an earlier stage of the disease gives better results[11]
Scleral buckling and/or vitrectomy surgery may be considered for severe ROP (stage 4 and 5) for eyes that progress to retinal detachment. Few centers in the world specialize in this surgery, because of its attendant surgical risks and generally poor outcomes.
Intravitreal injection of bevacizumab (Avastin) has been reported as a supportive measure in aggressive posterior retinopathy of prematurity.[12]
In a recent clinical trial comparing bevacizumab with conventional laser therapy, intravitreal bevacizumab monotherapy showed a significant benefit for zone I but not zone II disease when used to treat infants with stage 3+ retinopathy of prematurity. (New England Journal of Medicine 2011 364(7):603-615. However, the safety of this new treatment has not yet been established in terms of ocular complications as well as systemic complications. The latter are theoretically possible, as the active ingredient of bevacizumab not only blocks the development of abnormal blood vessels in the eye but may also prevent the normal development of other tissues such as the lung and kidney.

A significant time in the history of the disease was between 1941–1953, when a worldwide epidemic of ROP was seen. Over 12,000 babies worldwide were affected by it. Soul musician Stevie Wonder, actor Tom Sullivan as well as jazz singer Diane Schuur are a few famous people who have the disease.
The first case of the epidemic was seen on St. Valentine's Day in 1941, when a premature baby in Boston was diagnosed. Cases were then seen all over the world and the cause was, at that point, unknown. By 1951 a clear link between incidence and affluence became clear: many cases were seen in developed countries with organized and well-funded health care. Two British scientists suggested that it was oxygen toxicity that caused the disease. Babies born prematurely in such affluent areas were treated in incubators which had artificially high levels of oxygen. Studies on rats made this cause seem more likely, but the link was eventually confirmed by a controversial study undertaken by American pediatricians. The study involved two groups of babies. Some were given the usual oxygen concentrations in their incubators, while the other group had "curtailed" oxygen levels. The latter group was shown to have a lower incidence of the disease. As a result, oxygen levels in incubators were lowered and consequently the epidemic was halted.[13]

^ Gilbert C et al. Characteristics of babies with severe retinopathy of prematurity in countries with low, moderate and high levels of development: implications for screening programmes. Pediatrics Electronic Pages. 2005 115 518-525.
^ Limburg H, Gilbert C et al. Prevalence and causes of blindness in children in Vietnam. Ophthalmology. 2012 Feb;119(2):355-61
^ Gilbert C et al. Characteristics of babies with severe retinopathy of prematurity in countries with low, moderate and high levels of development: implications for screening programmes. Pediatrics Electronic Pages. 2005 115 518-525.
^ World Health Oganization, 2012. Born Too Soon The Global Action Report on Preterm Birth
^ a b c Kumar, Vinay (2007). "Chapter 29: Eye, Retina and Vitreous, Retinal Vascular Disease". Robbins basic pathology (8th ed.). Philadelphia: Saunders/Elsevier. ISBN 978-1416029731.
^ Guyton, Arthur; Hall, John (2006). "Chapter 17: Local and Humoral Control of Blood Flow by the Tissues". In Gruliow, Rebecca (in English) (Book). Textbook of Medical Physiology (11th ed.). Philadelphia, Pennsylvania: Elsevier Inc.. p. 200. ISBN 0-7216-0240-1.
^ Committee for the Classification of Retinopathy of Prematurity (1984 Aug). "An international classification of retinopathy of prematurity". Arch Ophthalmol. 102 (8): 1130–1134. PMID 6547831.
^ Committee for the Classification of Retinopathy of Prematurity (2005 Jul). "The International Classification of Retinopathy of Prematurity revisited". Arch Ophthalmol. 123 (7): 991–999. doi:10.1001/archopht.123.7.991. PMID 16009843.
^ Early Treatment for Retinopathy of Prematurity Cooperative Group (2003). "Revised indications for the treatment of retinopathy of prematurity: results of the early treatment for retinopathy of prematurity randomized trial". Arch Ophthalmol. 121 (12): 1684–1696. doi:10.1001/archopht.121.12.1684. PMID 14662586.
^ Phelps, D.L. (2001). "Retinopathy of Prematurity: History, Classification, and Pathophysiology". NeoReviews 2 (7): e153–e166. doi:10.1542/neo.2-7-e153.
^ Early Treatment for Retinopathy of Prematurity Cooperative Group, Dobson V, Quinn GE, Summers CG, Hardy RJ, Tung B, Good WV. Grating visual acuity results in the early treatment for retinopathy of prematurity study. Arch Ophthalmol. 2011 Jul;129(7):840-6.
^ Shah PK, Narendran V, Tawansy KA, Raghuram A, Narendran K. (2007). "Intravitreal bevacizumab (Avastin) for post laser anterior segment ischemia in aggressive posterior retinopathy of prematurity". Indian journal of ophthalmology 55 (1): 75–76. doi:10.4103/0301-4738.29505. PMID 17189897.
^ Silverman, William (1980). Retrolental Fibroplasia: A Modern Parable. Grune & Stratton, Inc..

Sunday, January 27, 2013

Work is my Worship & Humanity my God – Thoughts by Venkataramanan Ramasethu

A thought that kept burning within me about the significance of my profession ,got cleared the day I was allowed to travel safely without any hitch on the road, on a day when my city Kolkata was braving a complete bandh.The reasons and the time period when this incident happened is not significant, but the fact that I was allowed to travel safely in the taxi, I had hired to reach my workplace, an eye hospital, made me realize that I had made the right choice of having chosen health industry as my chosen profession of work. I had to just inform the group, protesting that I was rushing to reach my workplace, as I was about to travel to a remote village in Midnapore to attend an eye camp that day. One of the protesters had undergone free treatment at our hospital, I was employed and he was immediately able to recognize my work place when I had shown my hospital ID.

There was always a debate since my student days, whether it’s wise to work in an institution or practice independently, although both the options have their own pros and cons, an institutional practice would certainly have its edge as it provides ample scope to make one aware and updated on the latest developments and get to enhance clinical skills on new technology and instruments as and when they are launched in the industry.

What could be more satisfying than impacting someone’s life in a positive manner and contribute something in one’s own right for the social upliftment.If we think rationally and logically Healthcare & Academics are the two professions which render ample scope to achieve these goals.

One thing I realized all these years and am still trying to perfect is to achieve the right positive attitude towards every situation in life. Since though Knowledge & Skills could be achieved through rigorous training, the right attitude has to come within. Irrespective of how adverse the situation or the challenge is, by learning to look at the situation positively and by searching opportunities to improve self in every challenge could undoubtedly bail out anyone from any adverse situation.
The biggest curse to our nation is the prevailing Caste, Creed and Gender inequality amongst us. Tolerance levels are fast depleting and intolerance is on rise, to rise above the above differences not just needs courage but also conviction.

The best starting point could be to start telling ourselves from toady, “Work is my Worship & Humanity my God”.

It’s never too late….

Veda Bhavan;50 Lake Avenue;Kolkata - 700 026 - Thoughts by Venkataramanan Ramasethu

Vedas form the rock-bed of Dharma-Vedokhilo Dharma Moolam.The Vedic mantras when chanted produce divine vibrations which benefit one and all.Adi Shankaracharya through his yatras throughout the length and breadth of our country spread the message of the Vedas.Adi Shankaracharya's significant role in National Integration is well-known.

With the Divine Grace of Mahaperiyava and the bountiful anugraha of Sri Tripurasundari Sameta Chandramouleeshwar Swamy,our present Periyava's of Shri Kanchi Kamakoti Peetam have been striving to protect these traditions and practices.

Veda Rakshanam should be one of the prime duties of every one of us irrespective of our race or background.This would ensure ever lasting happiness and divine solace to everyone and ultimately take us close to our purpose of birth,which is to identify the self (Jeevatma) with the omnipresent Brahman (Paramatma).

To be a part of Veda Rakshanam and to ensure Vedokhilo Dharma Moolam & Vedo Nityam Adeeyatam,get in touch with,

Veda Bhavan
50 Lake Avenue
Kolkata - 700 026
Phone : 09830969488
E-mail : vedbhavankolkata@gmail.com


Bionics (also known as biomimicry, biomimetics, bio-inspiration, biognosis, and close to bionical creativity engineering) is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology.

The word bionic was coined by Jack E. Steele in 1958, possibly originating from the technical term bion (pronounced bee-on) (from Ancient Greek: βίος), meaning 'unit of life' and the suffix -ic, meaning 'like' or 'in the manner of', hence 'like life'. Some dictionaries, however, explain the word as being formed as a portmanteau from biology + electronics. It was popularized by the 1970s television series The Six Million Dollar Man and The Bionic Woman, which were based upon the novel Cyborg by Martin Caidin, which was influenced by Steele's work, and feature humans given superhuman powers by electromechanical implants.

The transfer of technology between lifeforms and manufactures is, according to proponents of bionic technology, desirable because evolutionary pressure typically forces living organisms, including fauna and flora, to become highly optimized and efficient. A classical example is the development of dirt- and water-repellent paint (coating) from the observation that the surface of the lotus flower plant is practically unsticky for anything (the lotus effect).

The term "biomimetic" is preferred when reference is made to chemical reactions.

In that domain, biomimetic chemistry refers to reactions that, in nature, involve biological macromolecules (for example, enzymes or nucleic acids) whose chemistry can be replicated using much smaller molecules in vitro.
Examples of bionics in engineering include the hulls of boats imitating the thick skin of dolphins; sonar, radar, and medical ultrasound imaging imitating the echolocation of bats.

In the field of computer science, the study of bionics has produced artificial neurons, artificial neural networks,[1] and swarm intelligence. Evolutionary computation was also motivated by bionics ideas but it took the idea further by simulating evolution in silico and producing well-optimized solutions that had never appeared in nature.

It is estimated by Julian Vincent, professor of biomimetics at the University of Bath's department of mechanical engineering Biomimetics group, that "at present there is only a 12% overlap between biology and technology in terms of the mechanisms used".


The name biomimetics was coined by Otto Schmitt in the 1950s. The term bionics was coined by Jack E. Steele in 1958 while working at the Aeronautics Division House at Wright-Patterson Air Force Base in Dayton, Ohio. However, terms like biomimicry or biomimetics are more preferred in the technology world in efforts to avoid confusion between the medical term bionics. Coincidentally, Martin Caidin used the word for his 1972 novel Cyborg, which inspired the series The Six Million Dollar Man. Caidin was a long-time aviation industry writer before turning to fiction full-time.


Velcro was inspired by the tiny hooks found on the surface of burs.
Often, the study of bionics emphasizes implementing a function found in nature rather than just imitating biological structures. For example, in computer science, cybernetics tries to model the feedback and control mechanisms that are inherent in intelligent behavior, while artificial intelligence tries to model the intelligent function regardless of the particular way it can be achieved.

The conscious copying of examples and mechanisms from natural organisms and ecologies is a form of applied case-based reasoning, treating nature itself as a database of solutions that already work. Proponents argue that the selective pressure placed on all natural life forms minimizes and removes failures.

Although almost all engineering could be said to be a form of biomimicry, the modern origins of this field are usually attributed to Buckminster Fuller and its later codification as a house or field of study to Janine Benyus.

Roughly, we can distinguish three biological levels in the fauna or flora, after which technology can be modeled:

Mimicking natural methods of manufacture

Imitating mechanisms found in nature (velcro)

Studying organizational principles from the social behaviour of organisms, such as the flocking behaviour of birds, optimization of ant foraging and bee foraging, and the swarm intelligence (SI)-based behaviour of a school of fish.


Velcro is the most famous example of biomimetics. In 1948, the Swiss engineer George de Mestral was cleaning his dog of burrs picked up on a walk when he realized how the hooks of the burrs clung to the fur.

The horn-shaped, saw-tooth design for lumberjack blades used at the turn of the 19th century to cut down trees when it was still done by hand was modeled after observations of a wood-burrowing beetle. It revolutionized the industry because the blades worked so much faster at felling trees.

Cat's eye reflectors were invented by Percy Shaw in 1935 after studying the mechanism of cat eyes. He had found that cats had a system of reflecting cells, known as tapetum lucidum, which was capable of reflecting the tiniest bit of light.
Leonardo da Vinci's flying machines and ships are early examples of drawing from nature in engineering.

Resilin is a replacement for rubber that has been created by studying the material also found in arthropods.

Julian Vincent drew from the study of pinecones when he developed in 2004 "smart" clothing that adapts to changing temperatures. "I wanted a nonliving system which would respond to changes in moisture by changing shape", he said. "There are several such systems in plants, but most are very small — the pinecone is the largest and therefore the easiest to work on". Pinecones respond to higher humidity by opening their scales (to disperse their seeds). The "smart" fabric does the same thing, opening up when the wearer is warm and sweating, and shutting tight when cold.
"Morphing aircraft wings" that change shape according to the speed and duration of flight were designed in 2004 by biomimetic scientists from Penn State University. The morphing wings were inspired by different bird species that have differently shaped wings according to the speed at which they fly. In order to change the shape and underlying structure of the aircraft wings, the researchers needed to make the overlying skin also be able to change, which their design does by covering the wings with fish-inspired scales that could slide over each other. In some respects this is a refinement of the swing-wing design.

Some paints and roof tiles have been engineered to be self-cleaning by copying the mechanism from the Nelumbo lotus.

Cholesteric liquid crystals (CLCs) are the thin-film material often used to fabricate fish tank thermometers or mood rings, that change color with temperature changes. They change color because their molecules are arranged in a helical or chiral arrangement and with temperature the pitch of that helical structure changes, reflecting different wavelengths of light. Chiral Photonics, Inc. has abstracted the self-assembled structure of the organic CLCs to produce analogous optical devices using tiny lengths of inorganic, twisted glass fiber.

Nanostructures and physical mechanisms that produce the shining color of butterfly wings were reproduced in silico by Greg Parker, professor of Electronics and Computer Science at the University of Southampton and research student Luca Plattner in the field of photonics, which is electronics using photons as the information carrier instead of electrons.

The wing structure of the blue morpho butterfly was studied and the way it reflects light was mimicked to create an RFID tag that can be read through water and on metal.

The wing structure of butterflies has also inspired the creation of new nanosensors to detect explosives.

Neuromorphic chips, silicon retinae or cochleae, has wiring that is modelled after real neural networks. S.a.: connectivity.
Technoecosystems or 'EcoCyborg' systems involve the coupling of natural ecological processes to technological ones which mimic ecological functions. This results in the creation of a self-regulating hybrid system.[6] Research into this field was initiated by Howard T. Odum,[7] who perceived the structure and emergy dynamics of ecosystems as being analogous to energy flow between components of an electrical circuit.
Medical adhesives involving glue and tiny nano-hairs are being developed based on the physical structures found in the feet of geckos.
Computer viruses also show troubling similarities with biological viruses in their way to curb program-oriented information towards self-reproduction and dissemination.
The cooling system of the Eastgate Centre building, in Harare was modeled after a termite mound to achieve very efficient passive cooling.
Through the field of bionics, new aircraft designs with far greater agility and other advantages may be created. This has been described by Geoff Spedding and Anders Hedenström in an article in Journal of Experimental Biology. Similar statements were also made by John Videler and Eize Stamhuis in their book Avian Flight [8] and in the article they present in Science about LEVs.[9] John Videler and Eize Stamhuis have since worked out real-life improvements to airplane wings, using bionics research. This research in bionics may also be used to create more efficient helicopters or miniature UAVs. This latter was stated by Bret Tobalske in an article in Science about Hummingbirds.[10] Bret Tobalske has thus now started work on creating these miniature UAVs which may be used for espionage. UC Berkeley as well as ESA have finally also been working in a similar direction and created the Robofly [11] (a miniature UAV)and the Entomopter (a UAV which can walk, crawl and fly).[12]
[edit]Specific uses of the term

[edit]In medicine
Bionics is a term which refers to the flow of concepts from biology to engineering and vice versa. Hence, there are two slightly different points of view regarding the meaning of the word.
In medicine, bionics means the replacement or enhancement of organs or other body parts by mechanical versions. Bionic implants differ from mere prostheses by mimicking the original function very closely, or even surpassing it.
Bionics' German equivalent, Bionik, always adheres to the broader meaning, in that it tries to develop engineering solutions from biological models. This approach is motivated by the fact that biological solutions will usually be optimized by evolutionary forces.
While the technologies that make bionic implants possible are still in a very early stage, a few bionic items already exist, the best known being the cochlear implant, a device for deaf people. By 2004 fully functional artificial hearts were developed. Significant further progress is expected to take place with the advent of nanotechnologies. A well-known example of a proposed nanodevice is a respirocyte, an artificial red cell, designed (though not built yet) by Robert Freitas.
Kwabena Boahen from Ghana was a professor in the Department of Bioengineering at the University of Pennsylvania. During his eight years at Penn, he developed a silicon retina that was able to process images in the same manner as a living retina. He confirmed the results by comparing the electrical signals from his silicon retina to the electrical signals produced by a salamander eye while the two retinas were looking at the same image.
In 2007 the Scottish company Touch Bionics launched the first commercially available bionic hand, named "i-Limb Hand". According to the firm, by May 2010 it has been fitted to more than 1,200 patients worldwide.[13]
The Nichi-In group is working on bimomimicking scaffolds in tissue engineering, stem cells and regenerative medicine have given a detailed classification on biomimetics in medicine.[14]
A political form of biomimicry is bioregional democracy, wherein political borders conform to natural ecoregions rather than human cultures or the outcomes of prior conflicts.
Critics of these approaches often argue that ecological selection itself is a poor model of minimizing manufacturing complexity or conflict, and that the free market relies on conscious cooperation, agreement, and standards as much as on efficiency – more analogous to sexual selection. Charles Darwin himself contended that both were balanced in natural selection – although his contemporaries often avoided frank talk about sex, or any suggestion that free market success was based on persuasion, not value.
Advocates, especially in the anti-globalization movement, argue that the mating-like processes of standardization, financing and marketing, are already examples of runaway evolution – rendering a system that appeals to the consumer but which is inefficient at use of energy and raw materials. Biomimicry, they argue, is an effective strategy to restore basic efficiency.
Biomimicry is also the second principle of Natural Capitalism.
[edit]Other uses
Business biomimetics is the latest development in the application of biomimetics. Specifically it applies principles and practice from biological systems to business strategy, process, organisation design and strategic thinking. It has been successfully used by a range of industries in FMCG, defence, central government, packaging and business services. Based on the work by Phil Richardson at the University of Bath[15] the approach was launched at the House of Lords in May 2009.
In a more specific meaning, it is a creativity technique that tries to use biological prototypes to get ideas for engineering solutions. This approach is motivated by the fact that biological organisms and their organs have been well optimized by evolution. In chemistry, a biomimetic synthesis is a chemical synthesis inspired by biochemical processes.
Another, more recent meaning of the term bionics refers to merging organism and machine. This approach results in a hybrid system combining biological and engineering parts, which can also be referred as a cybernetic organism (cyborg). Practical realization of this was demonstrated in Kevin Warwick's implant experiments bringing about ultrasound input via his own nervous system.

Cochlear implant

A cochlear implant (CI) is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing. Cochlear implants are often called bionic ears.

Cochlear implants may help provide hearing in patients that are not deaf because of damage to sensory hair cells in their cochleas. In those patients, the implants often can enable sufficient hearing for better understanding of speech. The quality of sound is different from natural hearing, with less sound information being received and processed by the brain. However, many patients are able to hear and understand speech and environmental sounds. Newer devices and processing-strategies allow recipients to hear better in noise, enjoy music, and even use their implant processors while swimming.

As of December 2010, approximately 219,000 people worldwide have received cochlear implants; in the U.S., roughly 42,600 adults and 28,400 children are recipients.[1] The vast majority are in developed countries due to the high cost of the device, surgery and post-implantation therapy. A small but growing segment of recipients have bilateral implants for hearing stereo sound (one implant in each cochlea).


Neuroprosthetics (also called neural prosthetics) is a discipline related to neuroscience and biomedical engineering concerned with developing neural prostheses. Neural prostheses are a series of devices that can substitute a motor, sensory or cognitive modality that might have been damaged as a result of an injury or a disease. Cochlear implants provide an example of such devices. These devices substitute the functions performed by the ear drum and Stapes, while simulating the frequency analysis performed in the cochlea. A microphone on an external unit gathers the sound and processes it; the processed signal is then transferred to an implanted unit that stimulates the auditory nerves through a microelectrode array. Through the replacement or augmentation of damaged senses, these devices intend to improve the quality of life for those with disabilities.

These implantable devices are also commonly used in animal experimentation as a tool to aid neuroscientists in developing a greater understanding of the brain and its functioning. In wirelessly monitoring the brain's electrical signals sent out by electrodes implanted in the subject's brain, the subject can be studied without the device affecting the results.
Accurately probing and recording the electrical signals in the brain would help better understand the relationship among a local population of neurons that are responsible for a specific function.

Neural implants are designed to be as small as possible in order to be to minimally invasive, particularly in areas surrounding the brain, eyes or cochlea. These implants typically communicate with their prosthetic counterparts wirelessly. Additionally, power is currently received through wireless power transmission through the skin. The tissue surrounding the implant is usually highly sensitive to temperature rise, meaning that power consumption must be minimal in order to prevent tissue damage.[1]
The neuroprosthetic currently undergoing the most widespread use is the cochlear implant, with approximately 100,000 in use worldwide as of 2006.

Saturday, January 26, 2013

Kamal Haasan’s Vishwaroopam banned in Tamilnadu - Creativity is the biggest Casualty – Thoughts by Venkataramanan Ramasethu

It was disheartening to note that Kamal’s Vishwaroopam was banned in Tamilnadu on its scheduled date of release, following protest from a select few sections, on the grounds that the film would portray a particular community in bad light. If an artiste like Kamal who all through had carried on with an impeccable secular image, is today subjected to such a situation,I think we have reached the heights of being not true to ourselves.Amidst all the artistes in our film industry if there was one individual,who never sided any particular political party and who always maintained that he believes in one force and that’s self belief,it was Kamal.As pointed out by Rajnikanth,his close collegue in the industry for 40 years,the mere fact that the actor agreed for a special screening to the members of a particular community reveals the extent to which Kamal had gone to ensure that the sensitivities are respected.To accuse him to have made the movie Vishwaroopam to portray them in bad light is not just unfair but unjustified.Some section were arguing that he had gone that extra mile only on this occasion, but not on earlier occasions where there were revolt from other communities, but is that the way to move forward. In all this clashes, good cinema had been buried down deep down the grave. First there was resistance to implement the Auro 3D sound, then the DTH dilemma and now this.

I was reminded of a scene from Aamir Khans movie “Taare Zameen Par”,when Aamir is confronted in his school by the father of the main protagonist boy,saying that he knows what is Dyslexia all about and he and his wife are capable of taking care of their child,Aamir would say the father a small story about a group of people who would surround a tree and keep hurling abuses and bad language,non stop to that extent,that one day the tree would eventually die a decaying death unable to take the negative language anymore.

I feel sometimes Kamal is like that tree,we have millions of such individuals in and around both within and outside our film industry,who relish icon bashing.As kamal himself said,for sometime now,he is being treated as a punching bag by many self proclaimed professors in cinema,icon bashing could be a favourite profession to some if they are not an icon themselves.

But I am supremely confident & optimistic that the true legendary artiste in Kamal would eventually survive all these attacks and would rise up successfully.

Kamalji you are God’s gift to us & God bless you….continue making many more movies and raise the standards with every attempt as you have been doing all these years,the good will of millions and millions of your admirers are with you.

“S.D Athawale Award” APAO-AIOS 2013 – “The 28th Asia-Pacific Academy of Ophthalmology Congress”

Dr Shikha Talwar Bassi, Deputy Director, Department of Neuro-Ophthalmology, Sankara Nethralaya received the “S.D Athawale Award” at the recently held APAO-AIOS 2013 – “The 28th Asia-Pacific Academy of Ophthalmology Congress” conducted at Hyderabad by the American Academy of Ophthalmology and the International Council of ophthalmology, jointly with the All India Ophthalmological Society, for her well researched white paper on the topic “Optical coherence tomography in papilledema & pseudo papilledema with and without disc drusen” which was presented by her at the AIOS 2012 held at Kochi.

Friday, January 25, 2013


MS Amma and her husband Shri Sadasivam had a special place in their heart for Sankara Nethralaya and its Mission

While there have been voices that have enthralled audience, kept them in spell bound attention or made them break out into a chorus, if there was one voice moved hearts and echoed compassion and love for mankind it was undoubtedly the mellifluous and divine voice of Shrimathi M.S Subbulakshmi, the nightingale of India. Known fondly as MS Amma to millions of her fans and admirers, she mesmerized her audience and transformed them to another world, with her mastery over the ragas and the finer nuances of rendering them.

While she was the unquestioned supremo of classical music who straddled the world of music like a colossus, she was also a simple, down to earth, warm human being with no trace of vanity or pride that such glory brought along with it. MS Amma had a deep empathy for social causes and compassion for alleviating suffering and effectively used the power and reach of her voice to spread awareness on social causes and raise funds to support them and various charitable initiatives. Her jam packed concerts held worldwide helped in raising humanitarian relief for a myriad of causes ranging from rehabilitation of flood/famine victims, support of orphanages/old age shelters to raising funds for the nation’s war effort.

MS Amma and her husband Shri Sadasivam had a special place in their heart for Sankara Nethralaya and its Mission; they shared a warm personal relationship with its Founder Dr SS.Badrinath and Dr Vasanthi Badrinath. The noble couple have graced and blessed many functions and initiatives at Sankara Nethralaya and have performed several concerts in Chennai, Mumbai and the US in aid of Sankara Nethralaya, which have helped in raising a significant volume of funds to support the noble cause of the institution they cherished. They have also bequeathed the royalty accruing from the sale of some of their popular and fast selling records towards the same. Sankara Nethralaya has been receiving a substantial amount from HMV and subsequently Sa Re Ga Ma the companies which own the audio rights of these evergreen classics.

‘Katrin Kural’a musical extravaganza produced as a rich tribute to the legend by Vijay TV came as a good opportunity to Sankara Nethralaya to express its gratitude and fond remembrance of one of its strongest supporters and well wishers , which it did wholeheartedly by sponsoring the same. We take great pleasure in sharing some of most memorable, melodious moments that we cherish, especially with our young readers.

We take this opportunity to share, especially with our young viewers a rare gem from MS Amma’s virtuoso performances, the amazing rendition of the invocation song in 5 languages at the 6th Afro Asian Congress of Ophthalmology held at Madras in 1976, which she did at the request of Dr SS.Badrinath the founder of Sankara Nethralaya.

Visit the link below to view the Youtube video


Sunday, January 20, 2013

Eye Strain - Asthenopia

Asthenopia (aesthenopia) or eye strain is an ophthalmological condition that manifests itself through nonspecific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache and occasional double vision. Symptoms often occur after reading, computer work, or other close activities that involve tedious visual tasks.
When concentrating on a visually intense task, such as continuously focusing on a book or computer monitor, the ciliary muscle tightens. This can cause the eyes to get irritated and uncomfortable. Giving the eyes a chance to focus on a distant object at least once an hour usually alleviates the problem.
A CRT computer monitor with a low refresh rate (<70Hz) or a CRT television can cause similar problems because the image has a visible flicker. Aging CRTs also often go slightly out of focus, and this can cause eye strain. LCDs do not go out of focus and are less susceptible to visible flicker.
A page or photograph with the same image twice slightly displaced (from a printing mishap, or a camera moving during the shot as in this image) can cause eye strain by the brain misinterpreting the image fault as diplopia and trying in vain to adjust the sideways movements of the two eyeballs to fuse the two images into one.

Sometimes, asthenopia can be due to specific visual problems, for example, uncorrected refraction errors or binocular vision problems such as accommodative insufficiency or heterophoria. It is often caused by the viewing of monitors such as those of computers or phones.

Effects of aging

There are many diseases, disorders, and age-related changes that may affect the eyes and surrounding structures.
As the eye ages certain changes occur that can be attributed solely to the aging process. Most of these anatomic and physiologic processes follow a gradual decline. With aging, the quality of vision worsens due to reasons independent of diseases of the aging eye. While there are many changes of significance in the nondiseased eye, the most functionally important changes seem to be a reduction in pupil size and the loss of accommodation or focusing capability (presbyopia). The area of the pupil governs the amount of light that can reach the retina. The extent to which the pupil dilates decreases with age, leading to a substantial decrease in light received at the retina. In comparison to younger people, it is as though older persons are constantly wearing medium-density sunglasses. Therefore, for any detailed visually guided tasks on which performance varies with illumination, older persons require extra lighting. Certain ocular diseases can come from sexually transmitted diseases such as herpes and genital warts. If contact between eye and area of infection occurs, the STD can be transmitted to the eye.[53]
With aging a prominent white ring develops in the periphery of the cornea- called arcus senilis. Aging causes laxity and downward shift of eyelid tissues and atrophy of the orbital fat. These changes contribute to the etiology of several eyelid disorders such as ectropion, entropion, dermatochalasis, and ptosis. The vitreous gel undergoes liquefaction (posterior vitreous detachment or PVD) and its opacities — visible as floaters — gradually increase in number.
Various eye care professionals, including ophthalmologists, optometrists, and opticians, are involved in the treatment and management of ocular and vision disorders. A Snellen chart is one type of eye chart used to measure visual acuity. At the conclusion of a complete eye examination, the eye doctor might provide the patient with an eyeglass prescription for corrective lenses. Some disorders of the eyes for which corrective lenses are prescribed include myopia (near-sightedness) which affects about one-third[citation needed] of the human population, hyperopia (far-sightedness) which affects about one quarter of the population, astigmatism, and presbyopia, the loss of focusing range during aging.

Near response

The adjustment to close-range vision involves three processes to focus an image on the retina.

Vergence movement

The two eyes converge to point to the same object.

When a creature with binocular vision looks at an object, the eyes must rotate around a vertical axis so that the projection of the image is in the centre of the retina in both eyes. To look at an object closer by, the eyes rotate 'towards each other' (convergence), while for an object farther away they rotate 'away from each other' (divergence). Exaggerated convergence is called cross eyed viewing (focusing on the nose for example). When looking into the distance, or when 'staring into nothingness', the eyes neither converge nor diverge. Vergence movements are closely connected to accommodation of the eye. Under normal conditions, changing the focus of the eyes to look at an object at a different distance will automatically cause vergence and accommodation.

Pupil constriction

Lenses cannot refract light rays at their edges as well as they can closer to the center. The image produced by any lens is therefore somewhat blurry around the edges (spherical aberration). It can be minimized by screening out peripheral light rays and looking only at the better-focused center. In the eye, the pupil serves this purpose by constricting while the eye is focused on nearby objects. In this way the pupil has a dual purpose: to adjust the eye to variations in brightness and to reduce spherical aberration.[51]

Accommodation of the lens
A change in the curvature of the lens, accommodation is carried out by the ciliary muscles surrounding the lens contracting. This narrows the diameter of the ciliary body, relaxes the fibers of the suspernsory ligament, and allows the lens to relax into a more convex shape. A more convex lens refracts light more strongly and focuses divergent light rays onto the retina allowing for closer objects to be brought into focus.[51][52]

Optokinetic reflex

The optokinetic reflex is a combination of a saccade and smooth pursuit movement. When, for example, looking out of the window at a moving train, the eyes can focus on a 'moving' train for a short moment (through smooth pursuit), until the train moves out of the field of vision. At this point, the optokinetic reflex kicks in, and moves the eye back to the point where it first saw the train (through a saccade).

Smooth pursuit movement

The eyes can also follow a moving object around. This tracking is less accurate than the vestibulo-ocular reflex, as it requires the brain to process incoming visual information and supply feedback. Following an object moving at constant speed is relatively easy, though the eyes will often make saccadic jerks to keep up. The smooth pursuit movement can move the eye at up to 100°/s in adult humans.
It is more difficult to visually estimate speed in low light conditions or while moving, unless there is another point of reference for determining speed.

Vestibulo-ocular reflex

The vestibulo-ocular reflex is a reflex eye movement that stabilizes images on the retina during head movement by producing an eye movement in the direction opposite to head movement, thus preserving the image on the center of the visual field. For example, when the head moves to the right, the eyes move to the left, and vice versa.


Even when looking intently at a single spot, the eyes drift around. This ensures that individual photosensitive cells are continually stimulated in different degrees. Without changing input, these cells would otherwise stop generating output. Microsaccades move the eye no more than a total of 0.2° in adult humans.


Saccades are quick, simultaneous movements of both eyes in the same direction controlled by the frontal lobe of the brain. Some irregular drifts, movements, smaller than a saccade and larger than a microsaccade, subtend up to six minutes of arc.

Rapid eye movement

Rapid eye movement, or REM for short, typically refers to the sleep stage during which the most vivid dreams occur. During this stage, the eyes move rapidly. It is not in itself a unique form of eye movement.

Extraocular muscles

Each eye has six muscles that control its movements: the lateral rectus, the medial rectus, the inferior rectus, the superior rectus, the inferior oblique, and the superior oblique. When the muscles exert different tensions, a torque is exerted on the globe that causes it to turn, in almost pure rotation, with only about one millimeter of translation.[50] Thus, the eye can be considered as undergoing rotations about a single point in the center of the eye.

Eye movement

The visual system in the brain is too slow to process information if the images are slipping across the retina at more than a few degrees per second.[49] Thus, for humans to be able to see while moving, the brain must compensate for the motion of the head by turning the eyes. Another complication for vision in frontal-eyed animals is the development of a small area of the retina with a very high visual acuity. This area is called the fovea centralis, and covers about 2 degrees of visual angle in people. To get a clear view of the world, the brain must turn the eyes so that the image of the object of regard falls on the fovea. Eye movements are thus very important for visual perception, and any failure to make them correctly can lead to serious visual disabilities.
Having two eyes is an added complication, because the brain must point both of them accurately enough that the object of regard falls on corresponding points of the two retinas; otherwise, double vision would occur. The movements of different body parts are controlled by striated muscles acting around joints. The movements of the eye are no exception, but they have special advantages not shared by skeletal muscles and joints, and so are considerably different.

Eye irritation

Eye irritation has been defined as “the magnitude of any stinging, scratching, burning, or other irritating sensation from the eye”.[7] It is a common problem experienced by people of all ages. Related eye symptoms and signs of irritation are e.g. discomfort, dryness, excess tearing, itching, grating, sandy sensation, smarting, ocular fatigue, pain, scratchiness, soreness, redness, swollen eyelids, and tiredness, etc. These eye symptoms are reported with intensities from severe to less severe. It has been suggested that these eye symptoms are related to different causal mechanisms.[8]
Several suspected causal factors in our environment have been studied so far.[7] One hypothesis is that indoor air pollution may cause eye and airway irritation.[9][10] Eye irritation depends somewhat on destabilization of the outer-eye tear film, in which the formation of dry spots results in such ocular discomfort as dryness.[9][11][12] Occupational factors are also likely to influence the perception of eye irritation. Some of these are lighting (glare and poor contrast), gaze position, a limited number of breaks, and a constant function of accommodation, musculoskeletal burden, and impairment of the visual nervous system.[13][14] Another factor that may be related is work stress.[15][16] In addition, psychological factors have been found in multivariate analyses to be associated with an increase in eye irritation among VDU users.[17][18] Other risk factors, such as chemical toxins/irritants, e.g. amines, formaldehyde, acetaldehyde, acrolein, N-decane, VOCs; ozone, pesticides and preservatives, allergens, etc. might cause eye irritation as well.
Certain volatile organic compounds that are both chemically reactive and airway irritants may cause eye irritation as well. Personal factors (e.g., use of contact lenses, eye make-up, and certain medications) may also affect destabilization of the tear film and possibly result in more eye symptoms.[8] Nevertheless, if airborne particles alone should destabilize the tear film and cause eye irritation, their content of surface-active compounds must be high.[8] An integrated physiological risk model with blink frequency, destabilization, and break-up of the eye tear film as inseparable phenomena may explain eye irritation among office workers in terms of occupational, climate, and eye-related physiological risk factors.[8]
There are two major measures of eye irritation. One is blink frequency which can be observed by human behavior. The other measures are break up time, tear flow, hyperemia (redness, swelling), tear fluid cytology, and epithelial damage (vital stains) etc., which are human beings’ physiological reactions. Blink frequency is defined as the number of blinks per minute and it is associated with eye irritation. Blink frequencies are individual with mean frequencies of < 2-3 to 20-30 blinks/minute, and they depend on environmental factors including the use of contact lenses. Dehydration, mental activities, work conditions, room temperature, relative humidity, and illumination all influence blink frequency. Break-up time (BUT) is another major measure of eye irritation and tear film stability.[19] It is defined as the time interval (in seconds) between blinking and rupture. BUT is considered to reflect the stability of the tear film as well. In normal persons, the break-up time exceeds the interval between blinks, and, therefore, the tear film is maintained.[8] Studies have shown that blink frequency is correlated negatively with break-up time. This phenomenon indicates that perceived eye irritation is associated with an increase in blink frequency since the cornea and conjunctiva both have sensitive nerve endings that belong to the first trigeminal branch.[20][21] Other evaluating methods, such as hyperemia, cytology etc. have increasingly been used to assess eye irritation.
There are other factors that related to eye irritation as well. Three major factors that influence the most are indoor air pollution, contact lenses and gender differences. Field studies have found that the prevalence of objective eye signs is often significantly altered among office workers in comparisons with random samples of the general population.[22][23][24][25] These research results might indicate that indoor air pollution has played an important role in causing eye irritation. There are more and more people wearing contact lens now and dry eyes appear to be the most common complaint among contact lens wearers.[26][27][28] Although both contact lens wearers and spectacle wearers experience similar eye irritation symptoms, dryness, redness, and grittiness have been reported far more frequently among contact lens wearers and with greater severity than among spectacle wearers.[28] Studies have shown that incidence of dry eyes increases with age.[29][30] especially among women.[31] Tear film stability (e.g. break-up time) is significantly lower among women than among men. In addition, women have a higher blink frequency while reading.[32] Several factors may contribute to gender differences. One is the use of eye make-up. Another reason could be that the women in the reported studies have done more VDU work than the men, including lower grade work. A third often-quoted explanation is related to the age-dependent decrease of tear secretion, particularly among women after 40 years of age.,[31][33][34]
In a study conducted by UCLA, the frequency of reported symptoms in industrial buildings was investigated.[35] The study's results were that eye irritation was the most frequent symptom in industrial building spaces, at 81%. Modern office work with use of office equipment has raised concerns about possible adverse health effects.[36] Since the 1970s, reports have linked mucosal, skin, and general symptoms to work with self-copying paper. Emission of various particulate and volatile substances has been suggested as specific causes. These symptoms have been related to Sick Building Syndrome (SBS), which involves symptoms such as irritation to the eyes, skin, and upper airways, headache and fatigue.[37]
Many of the symptoms described in SBS and multiple chemical sensitivity (MCS) resemble the symptoms known to be elicited by airborne irritant chemicals.[38] A repeated measurement design was employed in the study of acute symptoms of eye and respiratory tract irritation resulting from occupational exposure to sodium borate dusts.[39] The symptom assessment of the 79 exposed and 27 unexposed subjects comprised interviews before the shift began and then at regular hourly intervals for the next six hours of the shift, four days in a row.[39] Exposures were monitored concurrently with a personal real time aerosol monitor. Two different exposure profiles, a daily average and short term (15 minute) average, were used in the analysis. Exposure-response relations were evaluated by linking incidence rates for each symptom with categories of exposure.[39]
Acute incidence rates for nasal, eye, and throat irritation, and coughing and breathlessness were found to be associated with increased exposure levels of both exposure indices. Steeper exposure-response slopes were seen when short term exposure concentrations were used. Results from multivariate logistic regression analysis suggest that current smokers tended to be less sensitive to the exposure to airborne sodium borate dust.[39]
Several actions can be taken to prevent eye irritation—
trying to maintain normal blinking by avoiding room temperatures that are too high; avoiding relative humidities that are too high or too low, because they reduce blink frequency or may increase water evaporation[8]
trying to maintain an intact tear film by the following actions. 1) blinking and short breaks may be beneficial for VDU users.[40][41] Increase these two actions might help maintain the tear film. 2) downward gazing is recommended to reduce the ocular surface area and water evaporation.[42][43][44] 3) the distance between the VDU and keyboard should be kept as short as possible to minimize evaporation from the ocular surface area by a low direction of the gaze.[45] And 4) blink training can be beneficial.[46]
In addition, other measures are proper lid hygiene, avoidance of eye rubbing,[47] and proper use of personal products and medication. Eye make-up should be used with care.[48]

Field of view

Field of view

The approximate field of view of an individual human eye is 95° away from the nose, 75° downward, 60° toward the nose, and 60° upward, allowing humans to have an almost 180-degree forward-facing horizontal field of view.[citation needed] With eyeball rotation of about 90° (head rotation excluded, peripheral vision included), horizontal field of view is as high as 170°. About 12–15° temporal and 1.5° below the horizontal is the optic nerve or blind spot which is roughly 7.5° high and 5.5° wide

Dynamic range

The retina has a static contrast ratio of around 100:1 (about 6.5 f-stops). As soon as the eye moves (saccades) it re-adjusts its exposure both chemically and geometrically by adjusting the iris which regulates the size of the pupil. Initial dark adaptation takes place in approximately four seconds of profound, uninterrupted darkness; full adaptation through adjustments in retinal chemistry (the Purkinje effect) is mostly complete in thirty minutes. Hence, a dynamic contrast ratio of about 1,000,000:1 (about 20 f-stops) is possible.[5] The process is nonlinear and multifaceted, so an interruption by light merely starts the adaptation process over again. Full adaptation is dependent on good blood flow; thus dark adaptation may be hampered by poor circulation, and vasoconstrictors like tobacco.

The eye includes a lens not dissimilar to lenses found in optical instruments such as cameras and the same principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm (f/8.3) in a brightly lit place to 8 mm (f/2.1) in the dark. The latter value decreases slowly with age; older people's eyes sometimes dilate to not more than 5-6mm.

Human Eye components

The eye is made up of three coats, enclosing three transparent structures. The outermost layer is composed of the cornea and sclera. The middle layer consists of the choroid, ciliary body, and iris. The innermost is the retina, which gets its circulation from the vessels of the choroid as well as the retinal vessels, which can be seen in an ophthalmoscope.

Within these coats are the aqueous humor, the vitreous body, and the flexible lens. The aqueous humor is a clear fluid that is contained in two areas: the anterior chamber between the cornea and the iris, and the posterior chamber between the iris and the lens. The lens is suspended to the ciliary body by the suspensory ligament (Zonule of Zinn), made up of fine transparent fibers. The vitreous body is a clear jelly that is much larger than the aqueous humor, present behind lens and the rest, and is bordered by the sclera, zonule, and lens. They are connected via the pupil

Human Eye Dimensions

The dimensions differ among adults by only one or two millimeters. The vertical measure, generally less than the horizontal distance, is about 24 mm among adults, at birth about 16–17 millimeters (about 0.65 inch). The eyeball grows rapidly, increasing to 22.5–23 mm (approx. 0.89 in) by three years of age. By age 13, the eye attains its full size. The typical adult eye has an anterior to posterior diameter of 24 millimeters, a volume of six cubic centimeters (0.4 cu. in.),[3] and a mass of 7.5 grams (weight of 0.25 oz.)

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the mammalian eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors.[1]
In common with the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive the light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock.[2]

'Bionic' eye implants

A bionic eye implant that could help restore the sight of millions of blind people could be available to patients within two years.

US researchers have been given the go-ahead to implant the prototype device in 50 to 75 patients.

The Argus II system uses a spectacle-mounted camera to feed visual information to electrodes in the eye.

Patients who tested less-advanced versions of the retinal implant were able to see light, shapes and movement.

"What we are trying to do is take real-time images from a camera and convert them into tiny electrical pulses that would jump-start the otherwise blind eye and allow patients to see," said Professor Mark Humayun, from the University of Southern California.

Retinal implants are able to partially restore the vision of people with particular forms of blindness caused by diseases such as macular degeneration or retinitis pigmentosa.

About 1.5 million people worldwide have retinitis pigmentosa, and one in 10 people over the age of 55 have age-related macular degeneration.

Both diseases cause the retinal cells which process light at the back of the eye to gradually die.

The new devices work by implanting an array of tiny electrodes into the back of the retina.

A camera is used to capture pictures, and a processing unit, about the size of a small handheld computer and worn on a belt, converts the visual information into electrical signals.

These are then sent back to the glasses and wirelessly on to a receiver just under the surface of the front of the eye, which in turn feeds them to the electrodes at the rear.

The whole process happens in real time.

Growing dots

First-generation, low-resolution devices have already been fitted to six patients.

"The longest device has been in for five years," said Professor Humayun.

"It's amazing, even with 16 pixels, or electrodes, how much our first six subjects have been able to do."

Terry Byland, 58, from California was fitted with an implant in 2004 after going blind with retinitis pigmentosa in 1993.

"At the beginning, it was like seeing assembled dots - now it's much more than that," he said.

"When I am walking along the street I can avoid low-hanging branches - I can see the edges of the branches."

Mr Byland is also able to make out other shapes.

"I can't recognise faces, but I can see them like a dark shadow," he said.

Brain change

The new implant has a higher resolution than the earlier devices, with 60 electrodes.

It is also a lot smaller, about one square millimetre, which reduces the amount of surgery that needs to be done to implant the device.

The technology has now been given the go-ahead by the US Food and Drug Administration to be used in an exploratory patient trial.

This will take place at five centres across America over two years, with 50-75 patients aged over 50.

If successful, the device could be commercialised soon after, costing around $30,000 (£15,000). Other devices could then be developed with higher resolution or a wider field of view, said Professor Humayun.

Future work includes studying the effects the implants have on the brain.

"We are actually studying what happens to the visual cortex over time," said Professor Humayun.

The research was presented at the American Association for the Advancement of Science (AAAS) annual meeting in San Francisco, US.

How the Artificial Retina Works

Normal vision begins when light enters and moves through the eye to strike specialized photoreceptor (light-receiving) cells in the retina called rods and cones. These cells convert light signals to electric impulses that are sent to the optic nerve and the brain. Retinal diseases like age-related macular degeneration and retinitis pigmentosa destroy vision by annihilating these cells.

With the artificial retina device, a miniature camera mounted in eyeglasses captures images and wirelessly sends the information to a microprocessor (worn on a belt) that converts the data to an electronic signal and transmits it to a receiver on the eye. The receiver sends the signals through a tiny, thin cable to the microelectrode array, stimulating it to emit pulses. The artificial retina device thus bypasses defunct photoreceptor cells and transmits electrical signals directly to the retina’s remaining viable cells. The pulses travel to the optic nerve and, ultimately, to the brain, which perceives patterns of light and dark spots corresponding to the electrodes stimulated. Patients learn to interpret these visual patterns.


The vertebrate retina (pron.: /ˈrɛtɪnə/ RET-nuh, pl. retinae, pron.: /ˈrɛtiniː/; from Latin rēte, meaning "net") is a light-sensitive layer of tissue, lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These are sent to various visual centres of the brain through the fibres of the optic nerve.

In vertebrate embryonic development, the retina and the optic nerve originate as outgrowths of the developing brain, so the retina is considered part of the central nervous system (CNS) and is actually brain tissue.[1] It is the only part of the CNS that can be visualized non-invasively.

The retina is a layered structure with several layers of neurons interconnected by synapses. The only neurons that are directly sensitive to light are the photoreceptor cells. These are mainly of two types: the rods and cones. Rods function mainly in dim light and provide black-and-white vision, while cones support daytime vision and the perception of colour. A third, much rarer type of photoreceptor, the photosensitive ganglion cell, is important for reflexive responses to bright daylight.

Neural signals from the rods and cones undergo processing by other neurons of the retina. The output takes the form of action potentials in retinal ganglion cells whose axons form the optic nerve. Several important features of visual perception can be traced to the retinal encoding and processing of light.

Bionic contact lens

Bionic contact lenses are being developed to provide a virtual display that could have a variety of uses from assisting the visually impaired to the video game industry.[1] The device will have the form of a conventional contact lens with added bionics technology.[2] The lens will eventually have functional electronic circuits and infrared lights to create a virtual display[3] Babak Parviz, a University of Washington assistant professor of electrical engineering is quoted as saying "Looking through a completed lens, you would see what the display is generating superimposed on the world outside.”[4]


The lenses require organic materials that are biologically safe and also use inorganic material for the electronic circuits. The electronic circuits are built from a layer of metal a few nanometres thick. The light-emitting diodes are one third of a millimetre across. A grey powder is sprinkled onto the lens. Then a technique called microfabrication or 'self-assembly' is used to shape each tiny component. Capillary forces pull the pieces into their final position.

[edit] Development

Harvey Ho, a former graduate student of Parviz who worked at Sandia National Laboratories in Livermore, California presented the results in January 2008 at the Institute of Electrical and Electronics Engineers' International Conference on Micro Electro Mechanical Systems (or microbotics) in Tucson, Arizona.[5] The lens is expected to have more electronics and capabilities on the areas where the eye does not see. Wireless communication, radio frequency power transmission and solar cells are expected in future developments.[6]

[edit] Prototype and testing

In 2011, scientists created and successfully tested a functioning prototype with a wireless antenna and a single-pixel display.[7]

Previous prototypes proved that it is possible to create a biologically safe electronic lens that does not obstruct a person’s view. Engineers have tested the finished lenses on rabbits for up to 20 minutes and the animals showed no problems.[8]

Visual prosthesis - Bionic Eye

A visual prosthesis, often referred to as a bionic eye, is an experimental visual device intended to restore functional vision in those suffering from partial or total blindness. Many devices have been developed, usually modeled on the cochlear implant or bionic ear devices, a type of neural prosthesis in use since the mid 1980s.

Biological considerations

The ability to give sight to a blind person via a bionic eye depends on the circumstances surrounding the loss of sight. For retinal prostheses, which are the most prevalent visual prosthetic under development (due to ease of access to the retina among other considerations), vision loss due to degeneration of photoreceptors (retinitis pigmentosa, choroideremia, geographic atrophy macular degeneration) is the best candidate for treatment. Candidates for visual prosthetic implants find the procedure most successful if the optic nerve was developed prior to the onset of blindness. Persons born with blindness may lack a fully developed optical nerve, which typically develops prior to birth.[citation needed]

[edit] Technological considerations

Visual prosthetics are being developed as a potentially valuable aid for individuals with visual degradation. Argus II, manufactured by Second Sight Medical Products Inc. is the only such device to have received marketing approval (CE Mark in Europe in 2011), all other efforts remain investigational, and most have not yet made it to any clinical use in patients.[citation needed]

[edit] Ongoing projects

[edit] Argus Retinal Prosthesis

Drs. Mark Humayun,and Eugene DeJuan at the Doheny Eye Institute (USC), Dr. Robert Greenberg of Second Sight, and Bio-electronics Engineer Dr Wentai Liu at University of California, Santa Cruz were the original inventors of the active epi-retinal prosthesis[1] and demonstrated proof of principle in acute patient investigations at Johns Hopkins University in the early 1990s. In the late 1990s the company Second Sight was formed by Dr. Greenberg along with medical device entrepreneur, Alfred E. Mann, to develop a chronically implantable retinal prosthesis. Their first generation implant had 16 electrodes and was implanted in 6 subjects between 2002 and 2004. These subjects, who were all completely blind prior to implantation, could perform a surprising array of tasks using the device. In 2007, the company began a trial of its second generation, 60 electrode implant, dubbed the Argus II, in the US and in Europe.[2][3] In total 30 subjects participated in the studies spanning 10 sites in 4 countries. In the spring of 2011, based on the seminal results of the clinical study which were recently published in Ophthalmology,[4] Argus II was approved for commercial use in Europe, and Second Sight launched the product later that same year. An application for FDA approval in the US is pending and a panel review date has been set for 28 September 2012. Three major US government funding agencies (National Eye Institute, Department of Energy, and National Science Foundation) have supported the work at Second Sight, USC, UCSC, CalTech, and other research labs .

[edit] Microsystem-based Visual Prosthesis (MIVIP)

Designed by Claude Veraart at the University of Louvain, this is a spiral cuff electrode around the optic nerve at the back of the eye. It is connected to a stimulator implanted in a small depression in the skull. The stimulator receives signals from an externally-worn camera, which are translated into electrical signals that stimulate the optic nerve directly.[5]

[edit] Implantable Miniature Telescope

Although not truly an active prosthesis, an Implantable Miniature Telescope is one type of visual implant that has met with some success in the treatment of end-stage age-related macular degeneration.[6][7][8] This type of device is implanted in the eye's posterior chamber and works by increasing (by about three times) the size of the image projected onto the retina in order to overcome a centrally-located scotoma or blind spot.[7][8]

Created by VisionCare Ophthalmic Technologies in conjunction with the CentraSight Treatment Program, the telescope is about the size of a pea and is implanted behind the iris of one eye. Images are projected onto healthy areas of the central retina, outside the degenerated macula, and is enlarged to reduce the effect the blind spot has on central vision. 2.2x or 2.7x magnification strengths make it possible to see or discern the central vision object of interest while the other eye is used for peripheral vision because the eye that has the implant will have limited peripheral vision as a side effect. Unlike a telescope which would be hand-held, the implant moves with the eye which is the main advantage. Patients using the device may however still need glasses for optimal vision and for close work. Before surgery, patients should first try out a hand-held telescope to see if they would benefit from image enlargement. One of the main drawbacks is that it cannot be used for patients who have had cataract surgery as the intraocular lens would obstruct insertion of the telescope. It also requires a large incision in the cornea to insert.[9]

[edit] Tübingen MPDA Project Alpha IMS

A Southern German team led by the University Eye Hospital in Tübingen, was formed in 1995 by Eberhart Zrenner to develop a subretinal prosthesis. The chip is located behind the retina and utilizes microphotodiode arrays (MPDA) which collect incident light and transform it into electrical current stimulating the retinal ganglion cells. As natural photoreceptors are far more efficient than photodiodes, visible light is not powerful enough to stimulate the MPDA. Therefore, an external power supply is used to enhance the stimulation current. The German team commenced in vivo experiments in 2000, when evoked cortical potentials were measured from Yucatán micropigs and rabbits. At 14 months post implantation, the implant and retina surrounding it were examined and there were no noticeable changes to anatomical integrity. The implants were successful in producing evoked cortical potentials in half of the animals tested. The thresholds identified in this study were similar to those required in epiretinal stimulation. The latest reports from this group concern the results of a clinical pilot study on 11 participants suffering from RP. Some blind patients were able to read letters, recognize unknown objects, localize a plate, a cup and cutlery. The results were to be presented in detail in 2011 in the Proceeedings of the Royal Society B doi:10.1098/rspb.2010.1747. In 2010 a new multicenter Study has been started using a fully implantable device with 1500 Electrodes Alpha IMS (produced by Retina Implant AG, Reutlingen, Germany), 10 patients included so far; first results have been presented at ARVO 2011. The first UK implantations took place in March 2012 and were led by Professor Robert MacLaren at the University of Oxford and Mr Tim Jackson[disambiguation needed] at King's College Hospital in London.[10][11] Professor David Wong[disambiguation needed] also implanted the Tübingen device in a patient in Hong-Kong.[12] In all cases previously blind patients had some degree of sight restored, confirming that despite the complexity of surgery, the device can be implanted successfully at other specialist centers around the World.

[edit] Harvard/MIT Retinal Implant

Joseph Rizzo and John Wyatt at the Massachusetts Eye and Ear Infirmary and MIT began researching the feasibility of a retinal prosthesis in 1989, and performed a number of proof-of-concept epiretinal stimulation trials on blind volunteers between 1998 and 2000. They have since developed a subretinal stimulator, an array of electrodes, that is placed beneath the retina in the subretinal space and receives image signals beamed from a camera mounted on a pair of glasses. The stimulator chip decodes the picture information beamed from the camera and stimulates retinal ganglion cells accordingly. Their second generation prosthesis collects data and sends it to the implant through RF fields from transmitter coils that are mounted on the glasses. A secondary receiver coil is sutured around the iris.[13]

[edit] Artificial Silicon Retina (ASR)

The brothers Alan Chow and Vincent Chow have developed a microchip containing 3500 photo diodes, which detect light and convert it into electrical impulses, which stimulate healthy retinal ganglion cells. The ASR requires no externally-worn devices.[5]

The original Optobionics Corp. stopped operations, but Dr. Chow acquired the Optobionics name, the ASR implants and will be reorganizing a new company under the same name. The ASR microchip is a 2mm in diameter silicon chip (same concept as computer chips) containing ~5,000 microscopic solar cells called "microphotodiodes" that each have their own stimulating electrode.[14]

[edit] Optoelectronic Retinal Prosthesis

Daniel Palanker and his group at Stanford University have developed an optoelectronic system for visual prosthesis[15] that includes a subretinal photodiode array and an infrared image projection system mounted on video goggles. Information from the video camera is processed in a pocket PC and displayed on pulsed near-infrared (IR, 850–900 nm) video goggles. IR image is projected onto the retina via natural eye optics, and activates photodiodes in the subretinal implant that convert light into pulsed bi-phasic electric current in each pixel. Charge injection can be further increased using a common bias voltage provided by a radiofrequency-driven implantable power supply[16] Proximity between electrodes and neural cells necessary for high resolution stimulation can be achieved utilizing the effect of retinal migration.

[edit] Bionic Vision Australia

An Australian team led by Professor Anthony Burkitt is developing two retinal prostheses. The Wide-View device, combines novel technologies with materials that have been successfully used in other clinical implants. This approach incorporates a microchip with 98 stimulating electrodes and aims to provide increased mobility for patients to help them move safely in their environment. This implant will be placed in the suprachoroidal space. Researchers expect the first patient tests to begin with this device in 2013.

The Bionic Vision Australia consortium is concurrently developing the High-Acuity Device, which incorporates a number of new technologies to bring together a microchip and an implant with 1024 electrodes. The device aims to provide functional central vision to assist with tasks such as face recognition and reading large print. This high-acuity implant will be inserted epiretinally. Patient tests are planned for this device in 2014 once preclinical testing has been completed.

Patients with retinitis pigmentosa will be the first to participate in the studies, followed by age-related macular degeneration. Each prototype consists of a camera, attached to a pair of glasses which sends the signal to the implanted microchip, where it is converted into electrical impulses to stimulate the remaining healthy neurons in the retina. This information is then passed on to the optic nerve and the vision processing centres of the brain.

The Australian Research Council awarded Bionic Vision Australia a $42 million grant in December 2009 and the consortium was officially launched in March 2010. Bionic Vision Australia brings together a multidisciplinary team, many of whom have extensive experience developing medical devices such as the cochlear implant (or ‘bionic ear’).[17]

[edit] Dobelle Eye

Main article: William H. Dobelle

Similar in function to the Harvard/MIT device, except the stimulator chip sits in the primary visual cortex, rather than on the retina. Many subjects have been implanted with a high success rate and limited negative effects. Still in the developmental phase, upon the death of Dr. Dobelle, selling the eye for profit was ruled against in favor of donating it to a publicly funded research team.[5][18]

[edit] Intracortical Visual Prosthesis

Main article: Intracortical Visual Prosthesis

The Laboratory of Neural Prosthesis at Illinois Institute Of Technology (IIT), Chicago, is developing a visual prosthetic using Intracortical Iridium Oxide (AIROF) electrodes arrays. These arrays will be implanted on the occipital lobe. External hardware will capture images, process them and generate instructions which will then be transmitted to implanted circuitry via a telemetry link. The circuitry will decode the instructions and stimulate the electrodes, in turn stimulating the visual cortex. The group is developing a wearable external image capture and processing system. Studies on animals and psyphophysical studies on humans are being conducted to test the feasibility of a human volunteer implant.[citation needed]

[edit] Virtual Retinal Display (VRD)

Main article: Virtual retinal display

Laser-based system for projecting an image directly onto the retina. This could be useful for enhancing normal vision or bypassing an occlusion such as a cataract, or a damaged cornea.[5]

[edit] Visual Cortical Implant

The Visual Cortical Implant
Dr. Mohamad Sawan, Professor and Researcher at Polystim neurotechnologies Laboratory at the Ecole Polytechnique de Montreal, has been working on a visual prosthesis to be implanted into the visual cortex. The basic principle of Dr. Sawan’s technology consists of stimulating the visual cortex by implanting a silicon microchip on a network of electrodes, made of biocompatible materials, wherein each electrode injects a stimulating electrical current in order to provoke a series of luminous points to appear (an array of pixels) in the field of vision of the blind person. This system is composed of two distinct parts: the implant and an external controller. The implant is lodged in the visual cortex and wirelessly receives data and energy from the external controller. It contains all the circuits necessary to generate the electrical stimuli and to monitor the changing microelectrode/biological tissue interface. The battery-operated outer controller consists of a micro-camera, which captures images, as well as a processor and a command generator, which process the imaging data to translate the captured images and generate and manage the electrical stimulation process. The external controller and the implant exchange data in both directions by a transcutaneous radio frequency (RF) link, which also powers the implant.[19]

[edit] Nirenberg Lab Information Processing Prosthesis

Sheila Nirenberg as director of her laboratory team at Weill Cornell Medical College has found a method of treating retinal degeneration by using a deciphering of the retinal code combined with optogenetics. Work on the genetic engineering therapy for human trials is underway (now in the stage of working with mice and monkeys), but meanwhile Nirenberg is working with retinal-prosthesis maker Second Sight in Sylmar, California to upgrade their software currently on the market.[20]

[edit] Other projects

Other note-worthy researchers include Richard Normann (University of Utah) and David Bradley at University of Chicago, Eduardo Fernandez and the European Consortium CORTIVIS (http://cortivis.umh.es), Ed Tehovnik at MIT and Tohru Yagi in Japan Visual Prosthesis Project