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



Friday, December 28, 2012

Low Vision Care Clinic, Sankara Nethralaya, the one of its kind comprehensive vision care facility in Asia gets high end Visual aids

Freedom Scientific the Florida based leader in carrying out research in low vision and manufacturer of vision aids to those with partial and total visual impairment and learning disabilities, donated State of the Art vision aids and electronic devices to the Low Vision Care Clinic, Sankara Nethralaya, the one of its kind comprehensive vision care facility in Asia. As a result of this generous and most thoughtful gesture a wide array of highly advanced first in the nation optical, non-optical, assistive devices and gadgets like Topaz, Pearl, Sara, Sapphire, Onyx and software programmes like Jaws, Magic and Open book developed exclusively for patients with low vision would now be available at Sankara Nethralaya’s Low Vision Clinic, as demonstration samples, where such patients could take a trial and choose the application most suitable for their eye impairment.

For further details on infrastructure and treatment options, visit


Thursday, December 20, 2012

‘Media and its role in Eliminating Avoidable Blindness”

It is said that a work well begun is half completed, the high profile and enthusiastic participation of a cross section of eminent personalities representing the government, NGO’s, Health care providers and senior members of the Press at the recently held seminar ‘Media and its role in Eliminating Avoidable Blindness” organized by the India chapter of Vision 2020, facilitated by Joseph Eye Hospital and hosted by Sankara Nethralaya was a clear indication of the beginning of a strong and strategic alliance with the media that would take awareness on eye care to the next level.

The one day function and deliberations held at the Sri VD.Swami Auditorium, Sankara Nethralaya, Chennai on 10th December 2012 provided the ideal platform to discuss the various issues pertaining to eye care and spreading awareness on the same. The observations made by the eminent participants both in their addresses and the spirited panel discussion that followed helped in bringing forth their view points, thrashing out differences and evolving a strong and collective strategy to combat blindness by spreading awareness on eye care and to mobilize support for such initiatives from corporate bodies and the general public.

The spontaneous response to the clarion call made by Vision 2020 and active participation by senior members of the media like Shri N.Ram, Former Editor-in-chief of ‘The Hindu’, Shri Arun Ram, Senior Editor, The Times of India, Shri Rangarajan, Senior Correspondent, Dinamani, Shrimathi Aarthi Dhar, Senior Assistant Editor, Delhi Bureau of ‘The Hindu’, Shri SN.Kulkarni, Former Editor, Sakaal and Advisor, Kesari, Maharashtra, Dr Neeraja Prabhakar, Programme Executive from the All India Radio and many more journalists was a clear indication that it was the beginning of a great new chapter in creating awareness on eye care with the tremendous reach and power of the Fourth Estate.

Monday, December 10, 2012

Double Vision

Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally (i.e. both vertically and horizontally) in relation to each other.[1] It is usually the result of impaired function of the extraocular muscles (EOM's), where both eyes are still functional but they cannot converge to target the desired object.[1] Problems with EOM's may be due to mechanical problems, disorders of the neuromuscular junction, disorders of the cranial nerves (III, IV, and VI) that stimulate the muscles, and occasionally disorders involving the supranuclear oculomotor pathways or ingestion of toxins.[2]
Diplopia is often one of the first signs of a systemic disease, particularly to a muscular or neurological process,[3] and it may disrupt a person’s balance, movement, and/or reading abilities.[1][4]
Contents [hide]
1 Classification
1.1 Binocular
1.2 Monocular
1.3 Temporary
1.4 Voluntary
2 Causes
3 Treatment
4 See also
5 References
6 External links

Binocular diplopia is double vision arising as a result of the misalignment of the two eyes relative to each other, such as occurs in esotropia or exotropia. In such a case while the fovea of one eye is directed at the object of regard, the fovea of the other is directed elsewhere, and the image of the object of regard falls on an extra-foveal area of the retina.
The brain calculates the 'visual direction' of an object based upon the position of its image relative to the fovea. Images falling on the fovea are seen as being directly ahead, while those falling on retina outside the fovea may be seen as above, below, right or left of straight ahead depending upon the area of retina stimulated. Thus, when the eyes are misaligned, the brain will perceive two images of one target object, as the target object simultaneously stimulates different, non-corresponding, retinal areas in either eye, thus producing double vision.
This correlation of particular areas of the retina in one eye with the same areas in the other is known as retinal correspondence. This relationship also gives rise to an associated phenomenon of binocular diplopia, although one that is rarely noted by those experiencing diplopia: Because the fovea of one eye corresponds to the fovea of the other, images falling on the two foveas are 'projected' to the same point in space. Thus, when the eyes are misaligned, the brain will 'project' two different images in the same visual direction. This phenomenon is known as 'confusion'.
The brain naturally guards against double vision. In an attempt to avoid double vision, the brain can sometimes ignore the image from one eye; a process known as suppression. The ability to suppress is to be found particularly in childhood when the brain is still developing. Thus, those with childhood strabismus almost never complain of diplopia while adults who develop strabismus almost always do. While this ability to suppress might seem an entirely positive adaptation to strabismus, in the developing child this can prevent the proper development of vision in the affected eye resulting in amblyopia. Some adults are also able to suppress their diplopia, but their suppression is rarely as deep or as effective and takes longer to establish, and thus they are not at risk of permanently compromising their vision. Hence, in some cases diplopia disappears without medical intervention, but in other cases the cause of the double vision may still be present.
More rarely, diplopia can also occur when viewing with only one eye; this is called monocular diplopia, or, where the patient perceives more than two images, monocular polyopia. In this case, the differential diagnosis of multiple image perception includes the consideration of such conditions as corneal surface keratoconus, subluxation of the lens, a structural defect within the eye, a lesion in the anterior visual cortex (rarely cause diplopia, more commonly polyopia or palinopsia) or non-organic conditions.
Temporary diplopia can be caused by alcohol intoxication or head injuries, such as concussion. If temporary double vision does not resolve quickly, one should see an ophthalmologist immediately. It can also be a side effect of the anti-epileptic drugs Phenytoin and Zonisamide, and the anti-convulsant drug Lamotrigine, as well as the hypnotic drug Zolpidem and the dissociative drugs Ketamine and Dextromethorphan. Temporary diplopia can also be caused by tired and/or strained eye muscles or voluntarily. If diplopia appears with other symptoms such as fatigue and acute or chronic pain, the patient should see an optometrist immediately.
Some people are able to consciously uncouple their eyes, either by over focussing closely (i.e. going cross eyed) or unfocusing. Also, while looking at one object behind another object, the foremost object's image is doubled (for example, placing one's finger in between one's face while reading text on a computer monitor). In this sense double vision is neither dangerous nor harmful, and may even be enjoyable. It makes viewing stereograms possible.[5]

Diplopia has a diverse range of ophthalmologic, infectious, autoimmune, neurological, and neoplastic causes.
Damage to the third, fourth, or sixth cranial nerves, which control eye movements.
Multiple sclerosis
Fluoroquinolone antibiotics[6]
Guillain-Barré syndrome
Brain tumor
Wernicke's syndrome
Graves disease
Orbital myositis
Myasthenia gravis[7]
Lyme Disease

The appropriate treatment for binocular diplopia will depend upon the cause of the condition producing the symptoms. Efforts must first be made to identify and treat the underlying cause of the problem. Treatment options include eye exercises,[1] wearing an eye patch on alternative eyes,[1] prism correction,[8] and in more extreme situations, surgery[4] or botulinum toxin.[9]
[edit]See also

Binocular vision

^ a b c d O'Sullivan, S.B & Schmitz, T.J. (2007). Physical Rehabilitation. Philadelphia, PA: Davis. ISBN 978-0-8036-1247-1.
^ Blumenfeld, Hal (2010). Neuroanatomy through Clinical Cases. Sunderland MA: Sinauer. ISBN 978-0-87893-058-6.
^ Rucker, JC. (2007). "Oculomotor disorders". Semin Neurol. 27 (3): 244–56.
^ a b Kernich, C.A. (2006). "Diplopia". The Neurologist 12 (4): 229–230.
^ http://www.focusillusion.com/Instructions/ Instructions on how to view stereograms such as magic eye
^ Fraunfelder FW, Fraunfelder FT (September 2009). "Diplopia and fluoroquinolones". Ophthalmology 116 (9): 1814–7. doi:10.1016/j.ophtha.2009.06.027. PMID 19643481.
^ http://www.merck.com/mmpe/sec09/ch098/ch098e.html
^ Phillips PH. (2007). "Treatment of diplopia". Semin Neurol. 27 (3): 288–98.
^ Taub, M.B. (2008). "Botulinum toxin represents a new approach to managing diplopia cases that do not resolve.". Journal of the American Optometric Association 79 (4): 174–175.
^ Cassin, B. & Solomon, S. (1990) Dictionary of Eye Terminology. Gainesville, Florida: Triad Publishing Company
[edit]External links

Pinhole Glasses

Pinhole glasses, also known as stenopeic glasses, are eyeglasses with a series of pinhole-sized perforations filling an opaque sheet of plastic in place of each lens. Similar to the workings of a pinhole camera, each perforation allows only a very narrow beam of light to enter the eye which reduces the size of the circle of confusion on the retina and increases depth of field. In eyes with refractive error, the result is claimed to be a clearer image. However, a second effect may appear at the common bridge between each two adjacent holes, whereby two different rays of light coming from the same object (but each passing through a different hole) are diffracted back toward the eye and onto different places on the retina. This leads to double vision (objects having doubled edges) around the rim of each hole the eye is not focussing on, which can make the overall image disturbing and tiring to look at for prolonged periods of time.
Unlike conventional prescription glasses, pinhole glasses produce an image without the pincushion effect around the edges (which makes straight lines appear curved). While pinhole glasses are claimed to be useful for people who are both near- and far-sighted, they are not recommended for people with over 6 diopters of myopia. Additionally, pinhole glasses reduce brightness and peripheral vision,[1][2] and thus should not be used for driving or when operating machinery.[3]
Merchants state that after prolonged use, the plastic grating should become easy to ignore. However, each time the user blinks, the horizontal lines of the grating will briefly appear to be thicker. This is because the eyelid moving over the pupil will reduce the amount of light falling onto the retina and thus will briefly remove the lateral inhibition effect which normally makes all the holes appear bigger (and the grating appear thinner). So, as long as the user keeps blinking, they will be constantly reminded of the dark grating covering their eyes.
Pinhole glasses have been marketed by various companies on the claim that—combined with certain eye exercises—they could permanently improve eyesight. Skeptics argue that no scientific evidence has been found to support them. Due to a lack of formal clinical studies to substantiate this type of claim by companies selling pinhole glasses, this type of claim is no longer allowed to be made in the United States under the terms of a legal settlement with the Federal Trade Commission.[4]
The pinhole occluder, a device used by ophthalmologists and optometrists for diagnosis of refractive errors, works on the same principles, but is not intended for use outside of diagnosis.
As viewing through a pinhole can much improve clarity of vision of people with refractive error, in an emergency a clear view can sometimes be obtained by looking through a single improvised pinhole.


Orthoptics (from the Greek words ortho meaning "straight", and optikas meaning "vision" [1]) is a discipline dealing with the diagnosis and treatment of defective eye movement and coordination (such as nystagmus), binocular vision, and amblyopia by eye care professionals.[2] There are five areas of treatment for orthoptic problems:
corrective lenses (spherical, cylindrical lens, prismatic and Fresnel lenses)
strabismic-related orthoptics as an "eye exercise" is limited to the treatment of eye coordination problems by increasing the range of binocular fusion.[citation needed]
pharmaceuticals, such as cycloplegics
However the term orthoptics is sometimes used to refer simply to eye exercises which are a component of strabismic-related vision therapy.
Contents [hide]
1 Orthoptists
2 History
3 Current orthoptic practice
4 See also
5 References

Orthoptists are Eye care professionals who specialise in the diagnosis and management of binocular vision problems.[3][4] Orthoptists are represented worldwide by the International Orthoptic Association.
Orthoptics is usually studied as a primary or master's degree,[5] or as a 2 to 4 years post graduate training course. Orthoptists usually work in close cooperation with Ophthalmologists, pediatricians, and sometimes neurologists. Continuing professional development and registration is required in most countries.[6]

Orthoptists and ophthalmologists introduced a wide variety of techniques for the improvement of binocular function in the 1930s. The first pioneer was Mary Maddox, the daughter of an English ophthalmologist.[7]
The orthoptic health care profession evolved and specialised as scientific development increased in the diagnosis, management and pre/post-surgical care of patients with strabismus, binocular vision abnormalities and specific pediatric disorders.[8][9] Because of their lower prevalence and variational presentation, these were beyond the realm of a primary eyecare consultation at a spectacle shop (where most Optometrists work) and beyond the Ophthalmologists' demanding surgical workload and practice. Hence, Orthoptists began to specialize in hospitals with these problems throughout more than 20 countries.[9][10]
[edit]Current orthoptic practice

Orthoptists are mainly involved with diagnosing and managing patients with binocular vision disorders which relate to amblyopia, extraocular muscle balance such as with version, refractive errors, vergence, accommodation imbalances, (positive relative accommodation, negative relative accommodation) and pathological causes. They work closely with ophthalmologists to ensure that patients with eye muscle disorders are offered a full range of treatment options. According to the International Orthoptic Association, professional orthoptic practice involves the following[3]:
Primary activities
Ocular motility diagnosis & co-management[11]
Vision screening
Assessment of special needs[12]
Assessment and rehabilitation in neurological disorders[13]
Secondary activities
Low Vision assessment and management[14][15][16]
Glaucoma assessment & stable glaucoma management[17]
Biometry (includes sonography work)[18][19]
Fundus photography & screening[20]
Visual electrodiagnosis[21]
Retinoscopy and refraction, such as using a phoropter to assess refractive errors[22]
Further activities
Specific outpatient waiting list initiatives to reduce the delay for children referred to the eye clinic (filter screening)[23]
Joint multidisciplinary children’s vision screening clinics (orthoptics/optometry)[24]
Organisation/prioritisation of the strabismus surgical admissions list according to agreed criteria
Assistance with surgical procedures

Behavioural & Functional Optometry

Behavioral optometry also known as functional optometry is an expanded area of optometric practice that uses a holistic approach to the treatment of vision and vision information processing problems. The practice of behavioral optometry incorporates various vision therapy methods and has been characterized as a complementary alternative medicine practice.[1][2] The field has been subject to criticism because there is little scientific evidence of its effectiveness.[3] The American Optometric Association has published a clinical guideline for the practice of vision therapy, the methods and techniques utilised in behavioural optometry.[4]
Contents [hide]
1 History
2 Research
2.1 Case studies
3 See also
4 References
5 External links
5.1 National and international organizations

Behavioral optometry is considered by some optometrists to have its origins in orthoptic vision therapy. However, Vision therapy is differentiated between strabismic/orthoptic vision therapy (which Orthoptists and Ophthalmologists practice) and non-strabismic vision therapy.[5] A.M. Skeffington was an American optometrist known to some as "the father of behavioral optometry".[6] Skeffington has been credited as co-founding the Optometric Extension Program with E.B. Alexander in 1928.[6]
Part of behavioral vision care is concerned with impact of visual "skills" on performing visual tasks. Various behaviors and poor performance during visual tasks may suggest non-optimal visual skills. For example this could manifest as eyestrain symptoms experienced during visual tasks, or adopting poor posture (e.g. leaning in too close to visual material). Another example, could be difficulty understanding maps, difficulty recalling visual information, difficulty completing jigsaws and difficulty drawing/copying/interpreting visual information.[citation needed]
Claims have been made that behavioral optometry can aid with cognitive, behavioral or language disorders such as ADHD and dyslexia, although there is no evidence to support these claims.[citation needed] It is therefore popular among parents who may not want their children to be stigmatized by being labeled with a cognitive or language impairment, as it claims that poor vision is the "real" cause of their disorder.[7][not in citation given]

In 1944-1945 the Wilmer Eye Institute of Johns Hopkins Hospital in Baltimore undertook a study of the use of behavioral optometry in the treatment of myopia.[8] The training was undertaken by A. M. Skeffington and his associates, who traveled to Baltimore for the purpose, but who used a clinic outside the hospital, and were carefully kept apart from the staff in the Wilmer Institute who assessed their progress. The 103 candidates were school students and young adults with uncomplicated myopia. Independent examination before and after training was undertaken using Snellen charts, and use of a retinoscope after introduction of a cycloplegic agent. The examining physicians "were impressed by a psychologic improvement in a number of patients. Some patients while exhibiting no material change in their visual acuity, were nevertheless convinced that they saw better and that they used their eyes with greater satisfaction to themselves." The objective results were as follows. Of the 103 subjects:
30 showed some improvement on all measures
31 showed overall improvement, but not on all measures
32 showed no overall change
10 showed deterioration of vision
The report's author concludes "With the possible exception of educating some patients to interpret blurred retinal images more carefully and of convincing some others that they could see better even though there was no actual improvement, this study indicates that the visual training used on these patients was of no value for the treatment of myopia."
A review in 2000 concluded that there were insufficient controlled studies of the approach[9] and a 2008 review concluded that "a large majority of behavioural management approaches are not evidence-based, and thus cannot be advocated."[3]
[edit]Case studies
In 2006, neurologist Oliver Sacks published a case study about "Stereo Sue" (Susan R. Barry), a woman who was strabismic and stereoblind since early infancy and who developed stereo vision after undergoing vision therapy.[10] Barry, a professor of neurobiology, later published a memoir, Fixing My Gaze: a Scientist's Journey into Seeing in Three Dimensions,[11] describing the therapy, the science underlying it, and her experience with it.


Optometry is a health care profession concerned with the health of the eyes and related structures, as well as vision, visual systems, and vision information processing in humans. Optometrists are trained to prescribe and fit lenses to improve vision, and to diagnose and treat various eye diseases. In the United States and Canada optometrists are considered Doctors of Optometry[1][2][3][4][5][6] and are held to the same legal standards as any physician.[7][8] In all U.S. states optometrists are licensed to diagnose and treat diseases of the eye through topical diagnostic and therapeutic drugs,[9][10] and oral drugs in 47/50 states.[11] Doctors of Optometry are also able to perform certain types of laser surgery in some states. In other countries patients are referred to other healthcare professionals, such as ophthalmologists, neurologists and general medical practitioners for further treatment or investigation.
The term "optometry" comes from the Hellenic (Greek) words ὄψις (opsis; "view") and μέτρον (metron; "something used to measure", "measure", "rule"). The root word opto, is a shortened form derived from the Hellenic (Greek) word, ophthalmos, meaning, "eye." Like most professions, the practice of optometry education and certification is regulated in most countries. Optometrists and optometry-related organizations interact with governmental agencies, other health care professionals, and the community to deliver eye and vision care.
Contents [hide]
1 History
2 Licensing
2.1 Argentina
2.2 Australia
2.3 Brazil
2.4 Canada
2.5 Colombia
2.6 Europe
2.6.1 Ireland
2.6.2 Italy
2.6.3 United Kingdom
2.7 Ghana
2.8 India
2.9 Mozambique
2.10 Norway
2.11 Philippines
2.12 Russia
2.13 United States
3 See also
4 References
5 External links

Optometric history is tied to the development of
vision science (related areas of medicine, microbiology, neurology, physiology, psychology, etc.)
optics, optical aids
optical instruments, imaging techniques
other eye care professions
The history of optometry can be traced back to the early studies on optics and image formation by the eye. The origins of optometric science (optics, as taught in a basic physics class) date back a few thousand years BC as evidence of the existence of lenses for decoration has been found. It is unknown when the first spectacles were made, but the British scientist and historian Sir Joseph Needham stated in his research that the ancient Chinese invented the earliest eyeglasses 1000 years ago and were also mentioned by the Venetian Marco Polo in his account of his travels in ancient China. Alternatively, research by David A. Goss in the United States, shows they may have originated independently in the late 13th century in Italy as stated in a manuscript from 1305 where a monk from Pisa named Rivalto stated "It is not yet 20 years since there was discovered the art of making eyeglasses".[12] Spectacles were manufactured in Italy, Germany, and the Netherlands by 1300.
Benito Daza de Valdes published the third book on optometry in 1623, where he mentioned the use and fitting of eyeglasses. In 1692, William Molyneux wrote a book on optics and lenses where he stated his ideas on myopia and problems related to close-up vision. The scientists Claudius Ptolemy and Johannes Kepler also contributed to the creation of optometry. Kepler discovered how the retina in the eye creates vision. From 1773 until around 1829, Thomas Young discovered the disability of astigmatism and it was George Biddell Airy who designed glasses to correct that problem that included spherocylindrical lens.[13]
Although the term optometry appeared in the 1759 book A Treatise on the Eye: The Manner and Phenomena of Vision by Scottish physician William Porterfield, it was not until the early twentieth century in the United States and Australia that it began to be used to describe the profession. By the late twentieth century however, marking the distinction with dispensing opticians, it had become the internationally accepted term.

Optometry is officially recognized in many jurisdictions.[14] Most have regulations concerning education and practice. Optometrists like many other health care professionals are required to participate in ongoing continuing education courses to stay current on the latest standards of care.
See also: List of optometry schools
In Argentina optometrists are required to register with the local Ministry of Public Information, but licensing is not required. Anyone holding a Bachelor's degree may register as an optometrist after completing a written exam. Fees for the exam are set by the provincial government and vary from province to province.
Australia currently has three recognised courses in optometry:
Bachelor of Optometry Bachelor of Science (BOptom BSc), University of New South Wales
Bachelor of Vision Science and Master of Optometry, Queensland University of Technology
Doctor of Optometry, Melbourne University (post-graduate)
These courses are developments of prior course offerings at these institutions that have been expanded along with the increased scope of practice for optometrists in Australia, specifically the ability to prescribe certain therapeutic agents.
New courses are being developed at Flinders University in South Australia, which accepted students in a science degree in 2010, to begin the post graduate component of the course in 2013. A second new course is expected at Deakin University in Geelong, Victoria at the beginning of 2012.
To support these courses the Australian College of Optometry provides clinical placements to undergraduate students from Australian Universities and abroad.
The Brazilian Government does not legally recognize optometry as a profession, and the Brazilian Council of Ophthalmology recommends against its official legal recognition.[15]
In Canada optometrists must complete at least 3 years of undergraduate education and a four-year Doctor of Optometry degree from one of two Schools of Optometry (one at the University of Waterloo and the other at Université de Montreal). Furthermore, they must pass board licensing examinations to demonstrate their professional skills and knowledge.
Optometrists in Canada are licensed to prescribe topical and oral medications, however, the exact medications that they are licensed to prescribe varies province by province.
In Colombia optometry education has been accredited by the Ministry of Health. The last official revision to the laws regarding health care standards in the country was issued in 1992 through the Law 30.[16] Currently there are eight official universities that are entitled by ICFES to grant the Optometrist certification. The first optometrists arrived in the country from North America and Europe circa 1914. These professionals specialized in optics and refraction. In 1933, under Decrees 449 and 1291, the Colombian Government officially set the rules for the formation of professionals in the field of optometry. In 1966 La Salle University opened its first Faculty of Optometry after recommendation from a group of professionals. At the present time optometrists are encouraged to keep up with new technologies through congresses and scholarships granted by the government or the private sector (such as Bausch & Lomb).
Currently, optometry education and licensing varies throughout Europe. For example, in Germany, optometric tasks are performed by ophthalmologists and professionally trained and certified opticians. In France, there is no regulatory framework and optometrists are sometimes trained by completing an apprenticeship at an ophthalmologists' private office.[17]
Since the formation of the European Union, "there exists a strong movement, headed by the Association of European Schools and Colleges of Optometry (AESCO), to unify the profession by creating a European-wide examination for optometry" and presumably also standardized practice and education guidelines within EU countries.[18] The first examinations of the new European Diploma in Optometry were held in 1998 and this was a landmark event for optometry in continental Europe.[19]
The profession of Optometry has been represented for over a century by the Association of Optometrists, Ireland [AOI]. In Ireland an optometrist must first complete a four-year degree in optometry at D.I.T. Kevin Street. Following successful completion of the a degree, an optometrist must then complete Professional Qualifying Examinations to enter the register of the Opticians Board [Bord na Radharcmhaistoiri]. Optometrists must be registered with the Board to practice in the Republic of Ireland.
The A.O.I. runs a comprehensive continuing education and professional development program on behalf of Irish optometrists. The legislation governing Optometry was drafted in 1956. Some feel that the legislation restricts optometrists from using their full range of skills, training and equipment for the benefit of the Irish public. The amendment to the Act in 2003 addressed one of the most significant restrictions: the use of cycloplegic drugs to examine children.
The Italian Government does not legally recognize optometry as a sanitar profession. There are seven university: Padua, Turin, Milan, Lecce, Florence, Naples and Rome. Also there are some optometry courses in private institution (near Firenze, in Bologna, in Milano to name few), none of these latter confer a degree; instead they offer advanced professional education for already qualified opticians.
[edit]United Kingdom
In the United Kingdom, optometrists have to complete a 3 or 4 (Scotland) year undergraduate honours degree followed by a minimum of a one-year "pre-registration period", (internship), where they complete clinical practice under the supervision of a qualified and experienced practitioner. During this year the pre-registration candidate is given a number of quarterly assessments, often including temporary posting at a hospital, and on successfully passing all of these assessments, a final one-day set of examinations (Examination details correct for candidates from 2006 onwards). Following successful completion of these assessments and having completed one year's supervised practice, the candidate is eligible to register as an optometrist with the General Optical Council (GOC) and, should they so wish, are entitled to membership of the College of Optometrists. Registration with the GOC is mandatory to practice in the UK. Members of the College of Optometrists (incorporated by a Royal Charter) may use the suffix MCOptom. Nine universities offer Optometry in the UK: Anglia Ruskin, Aston, Bradford, Cardiff, City, Glasgow Caledonian, Manchester, University of Ulster at Coleraine and University of Plymouth.
Additionally, the Institute of Optometry in London offers a post-graduate professional doctorate in optometry in partnership with London South Bank University.[20]
In Ghana the Ghana Optometric Association (GOA) regulates the practise of Optometry. After the six-year training at any of the two Universities offering the course, the O.D degree is awarded. The new Optometrist must write a qualifying exam, after which the optometrist is admitted as a member of the GOA, leading to the award of the certificate MGOA.
In 1958, two schools of optometry were established, one at Gandhi Eye Hospital, Aligarh in Uttar Pradesh and the other one at Sarojini Devi Eye Hospital, Hyderabad in Andhra Pradesh, under the second five-year plan by Director General of Health Services of Government of India. These schools offered Diploma in Optometry courses of two years duration. Subsequently four more schools were opened across India situated at Sitapur Eye Hospital, Sitapur in Uttar Pradesh, Chennai (formerly Madras) in Tamil Nadu, Bangaluru (formerly Bangalore) in Karnataka and Thiruvanthipuram (formerly Trivandrum) in Kerala.[21] Elite School of Optometry (ESO) was established in 1985 at Chennai and was the first to offer a four-year degree course.
The four-year degree courses are offered in well established schools and institutions including All India Institute of Medical Sciences - New Delhi; Elite School of Optometry attached to Shankar Netralaya - Chennai; Bausch and Lomb School attached to L. V. Prasad Eye Institute - Hyderabad; Bharati Vidyapeeth University Medical College - Pune; Manipal College of Allied Health Sciences, Manipal University, Manipal; Dr. D.Y. Patil Institute of Optometry - Pimpri, Pune; Lotus College of Optometry at Mumbai; Nethradhama school of optometry, Bangalore; Sankara College of Optometry in the state of Karnataka launched under the aegis of Rajiv Gandhi University of Health Sciences and Dr.Anand College of Optometry and Vision Science at Salem, Tamil Nadu in collaboration with Periyar University. Presently more colleges and schools of optometry in India are offering a four-year degree course based on the CMOC curriculum endorsed by the ASCO.-http://asco-india.org/
India needs approximately 115,000 optometrists. Currently India has approximately 9000 optometrists (four-year trained) and 40,000 eye care personnel (two-year trained).[22] In order to prevent blindness or visual impairment more well trained optometrists are required in India.[23] It should be noted that definition of optometry differs considerably in different countries of the world.[24] India needs more optometry schools offering four-year degree courses with a syllabus similar to that in force in those countries where optometry is very well established with an internationally accepted definition.
The first optometry course in Mozambique was started in 2009 at Universidade Lurio, Nampula. The course is part of the Mozambique Eyecare Project. University of Ulster, Dublin Institute of Technology and International Centre for Eyecare Education are supporting partners.
In Norway the optometric profession has been regulated as a healthcare profession since 1988. After a three-year bachelor program one can practice basic optometry. At least one year in clinical practice qualify for a post-degree half-year sandwich course in contact lens fitting, which is regulated as a healthcare specialty. A separate regulation for the use of diagnostic drugs in optometric practice was introduced in 2004.
Optometry is regulated by the Professional Regulation Commission of the Philippines. To be eligible for licensing, each candidate must have satisfactorily completed a Doctor of Optometry course at an accredited institution and demonstrate good moral character with no previous record of professional misconduct. Professional organizations of optometry in the Philippines include Optometric Association of the Philippines[25] and Integrated Philippine Association of Optometrists, Inc. (IPAO).
This section requires expansion. (October 2008)
In Russia optometry education has been accredited by the Federal Agency of Health and Social Development.[citation needed] There are only two educational institutions that teach optometry in Russia: Saint Petersburg Medical Technical College, formerly known as St. Petersburg College of Medical Electronics and Optics, and The Helmholz Research Institute for Eye Diseases. They both belong and are regulated by the Ministry of Health. The Optometry program is a four-year program. It includes one to two science foundation years, one year focused on clinical and proficiency skills, and one year of clinical rotations in hospitals. Graduates take college/state examinations and then receive a specialist diploma. This diploma is valid for only five years and must be renewed every five years after receiving additional training at state accredited programs.
The scope of practice for optometrists in Russia includes: refraction, contact lens fitting, spectacles construction and lens fitting (dispensing), Vermont, low vision aids, foreign body removal, referrals to other specialists after clinical condition diagnoses (management of diseases in the eye).
[edit]United States

A Doctor of Optometry examining a patient with a slit lamp biomicroscope.
Doctors of Optometry in the United States are currently regulated by state boards that determine their scope of practice, which may vary from state to state. Within the healthcare system, optometrists function as primary eye care providers who are especially experienced in fitting contact lenses and glasses prescriptions.
Optometrists can also treat their patients that have eye diseases with:
-Oral medications [26] (such as antivirals, antibiotics, oral steroids and pain medications[27])
-Topical medications such as prescription eye drops to treat glaucoma[28] or red eye for example.
-Injectable medications.[29]
Optometrists may also be trained in some surgical techniques, including those for foreign body removal, corneal injury, eyelid & lacrimal disease, removal of "lumps and bumps" around the eyes[30] and others. In Oklahoma, the state optometry board also allows state-certified optometrists to perform surgeries limited to the anterior segment of the eye. In Kentucky, recent legislation permits Optometrists to perform a multitude of laser procedures. In many cases optometrists and ophthalmologists work together in the treatment and management of patients with various eye conditions. Opticians in America generally dispense corrective eye wear, and in some cases also construct the corrective eye wear. The scope of practice in optometry varies as it is regulated by each state.
The American Optometric Association (AOA) and the American Optometric Society (AOS) represent optometrists nationally in the USA. Prior to admittance into optometry school, optometrists typically complete four years of undergraduate study, culminating in a bachelor’s degree. Required undergraduate coursework for pre-optometry students covers a variety of health, science and mathematics courses. These courses include: four semesters of chemistry to include organic and biochemistry, two semesters of physics and biology, as well as one semester of calculus, statistics, physiology, anatomy, microbiology, and psychology. Additional requirements are imposed by specific institutions. Once completing these courses, admission to an optometry doctorate program requires that candidates score well on the O.A.T., Optometry Admission Tests. There are currently 20 optometry schools in the United States, and admission into these schools is highly competitive.
Optometrists are required to complete a four-year postgraduate degree program to earn their Doctor of Optometry (O.D. - Oculus Doctor) titles. The four-year program includes classroom and clinical training in geometric, physical, physiological and ophthalmic optics, ocular anatomy, ocular disease, ocular pharmacology, neuroanatomy and neurophysiology of the vision system, binocular vision, color, form, space, movement and vision perception, design and modification of the visual environment, and vision performance and vision screening. In addition, an optometric education also includes a thorough study of human anatomy, systemic diseases, general pharmacology, general pathology, microbiology, sensory and perceptual psychology, biochemistry, statistics and epidemiology. There are three new colleges of optometry (Midwestern University Arizona College of Optometry, University of the Incarnate Word School of Optometry, Western University of Health Sciences College of Optometry) that have received the pre-accreditation status of preliminary approval from the Accreditation Council on Optometric Education (ACOE). Programs with "Preliminary Approval" have shown that they are developing within the ACOE's standards. The programs have approval to begin recruiting and admitting students, and to begin offering the program.[31]
Upon completion of an accredited program in optometry, graduates hold the Doctor of Optometry degree. Optometrists must then pass a national examination administered by the National Board of Examiners in Optometry (NBEO).[32] The three-part exam includes basic science, clinical science and patient care. (The structure and format of the NBEO exams are subject to change beginning in 2008.) Some optometrists go on to complete one- to two-year residencies with training in a specific sub-specialty such as pediatric eyecare, geriatric eyecare, specialty contact lens, ocular disease or neuro-optometry. All optometrists are required to fulfill continuing education requirements to stay current regarding the latest standards of care.

Convergence Insufficiency

Convergence insufficiency or Convergence Disorder is a sensory and neuromuscular anomaly of the binocular vision system, characterized by an inability of the eyes to turn towards each other, or sustain convergence.
Contents [hide]
1 Symptoms
2 Diagnosis
3 Treatment
4 Prevalence
5 References
6 See also
7 External links

The symptoms and signs associated with convergence insufficiency are related to prolonged, visually demanding, near-centered tasks. They may include, but are not limited to, diplopia (double vision), asthenopia (eye strain), transient blurred vision, difficulty sustaining near-visual function, abnormal fatigue, headache, and abnormal postural adaptation, among others. Note that some Internet resources confuse convergence and divergence dysfunction, reversing them.

Diagnosis of convergence insufficiency is made by an eye care professional skilled in binocular vision dysfunctions to rule out any organic disease. Convergence insufficiency characterized by one or more of the following diagnostic findings: Patient symptoms, High exophoria at near, reduced accommodative convergence/accommodation ratio, receded near point of convergence, low fusional vergence ranges and/or facility. Some patients with convergence insufficiency have concurrent accommodative insufficiency -- accommodative amplitudes should therefore also be measured in symptomatic patients.

Convergence insufficiency may be treated with convergence exercises prescribed by an eyecare specialist trained in orthoptics or binocular vision anomalies. Some cases of convergence insufficiency are successfully managed by prescription of eyeglasses, sometimes with with therapeutic prisms.
In 2005, the Convergence Insufficiency Treatment Trial (CITT) published two randomized clinical studies. The first, published in Archives of Ophthalmology demonstrated that computer exercises when combined with in-office based vision therapy was more effective than "pencil pushups" or computer exercises alone for convergency insufficiency in 9 to 18 year old children.[1] The second found similar results for adults 19 to 30 years of age.[2]
Surgical correction options are also available, but the decision to proceed with surgery should be made with caution.
Bilateral medial rectus resection is usually the most effective operation for convergence insufficiency. However, the patient should be warned about the possibility of uncrossed diplopia at distance fixation after surgery. This typically resolves within 1-3 months postoperatively. The exophoria at near often recurs after several years, although most patients remain asymptomatic.

A British survey found that less than 1 in 300 patients receiving optometric eye examinations had convergence insufficiency[3] and a Spanish study found that nearly 1 in 100 (0.8%) of symptomatic patients in an optometric clinic had CI.[4] In contrast, studies conducted by the Southern California College of Optometry found that approximately 1 in 8 (13%) of fifth and six grade children examined during visual screenings had the disorder[5] as did nearly 1 in 5 (17.6%) of 8 to 12 year olds receiving examinations at optometry clinics.[6] A recent Romanian study revealed that roughly 3 in 5 (60.4%) of young adult patients complaining of blurred vision at near work suffered from convergence insufficiency.[7]

Duane Syndrome

Duane's syndrome (DS) is a rare, congenital eye movement disorder most commonly characterized by the inability of the eye to abduct or move outwards. It affects the neural pathways associated with the sixth cranial nerve and the parts of the brain associated with reason and taste[citation needed]. The syndrome was first described by Jakob Stilling (1887) and Siegmund Türk (1896), and subsequently named after Alexander Duane who discussed the disorder in more detail in 1905[1]
Other names for this condition include: Duane's Retraction Syndrome (or DR syndrome), Eye Retraction Syndrome, Sausage Eye, Retraction Syndrome, Congenital retraction syndrome and Stilling-Turk-Duane Syndrome.[2]
Contents [hide]
1 Characteristics
2 Causes
3 Epidemiology
4 Classification
4.1 Brown's classification
4.2 Huber's classification
5 Differential diagnosis
6 Treatment
7 Surgical approaches
8 See also
9 References
10 External links

Patient with Duane syndrome attempting to look far right. Notice the afflicted left eye faces straight and up, rather than following the right eye to the right.
As described by Duane, the characteristic features of the syndrome are:
Limitation of abduction (outward movement) of the affected eye.
Less marked limitation of adduction (inward movement) of the same eye.
Retraction of the eyeball into the socket on adduction, with associated narrowing of the palpebral fissure (eye closing)
Widening of the palpebral fissure on attempted abduction. (N.B. Mein and Trimble [3] point out that this is "probably of no significance" as the phenomenon also occurs in other conditions in which abduction is limited).
Poor convergence
A face turn to the side of the affected eye to compensate for the movement limitations of the eye(s) and to maintain binocular vision.
Eye is 45゚ to left or right, resulting in "correct movement", but wrong placing of eye. (i.e. when an unaffected eye looks to the right, the affected eye looks straight forward, and when the unaffected eye looks straight forward, the affected eye looks to the left)


DS is a miswiring of the eye muscles, causing some eye muscles to contract when they shouldn't and other eye muscles not to contract when they should.[2] Attachment to and affecting the neural pathways.
Alexandrakis G & Saunders RA [4] state that:
In most cases, the abducens nucleus and nerve are absent or hypoplastic, and the lateral rectus muscle is innervated by a branch of the oculomotor nerve. However, there may be contributing mechanical abnormalities
This view is supported by the earlier work of Hotchkiss et al.[5] who reported on the autopsy findings of two patients with Duanes syndrome. In both cases the sixth cranial nerve nucleus was absent, as was the sixth nerve, and the lateral rectus muscle was innervated by the inferior division of the third or oculomotor cranial nerve. This misdirection of nerve fibres results in opposing muscles being innervated by the same nerve. Thus, on attempted abduction, stimulation of the lateral rectus via the oculomotor nerve will be accompanied by stimulation of the opposing medial rectus via the same nerve; a muscle which works to adduct the eye. Thus, co-contraction of the muscles takes place, limiting the amount of movement achievable and also resulting in retraction of the eye into the socket.
The mechanical factors noted by Miller and Clark above are generally regarded as arising secondary to loss of innervation. During corrective surgery fibrous attachments have been found connecting the horizontal recti and the orbital walls and fibrosis of the lateral rectus has been confirmed by biopsy. This fibrosis can result in the lateral rectus being 'tight' and acting as a tether or leash. Co-contraction of the medial and lateral recti allows the globe to slip up or down under the tight lateral rectus producing the up and down shoots characteristic of the condition.

Most patients are diagnosed by the age of 10 years and DS is more common in girls (60 percent of the cases) than boys (40 percent of the cases). A recent French study [6] reports the following findings:
The incidence of this syndrome in the population of strabismic patients was 1.9%. The number of women affected was 83 (53.5%). The syndrome was unilateral in 121 cases (78.1%). The left eye (71.9%) was affected more frequently than the right.
Around 10–20% of cases are familial; these are more likely to be bilateral than non-familial Duane syndrome. Duane syndrome has no particular race predilection. While usually isolated to the eye abnormalities, Duane syndrome can be associated with extraocular problems (so-called "Duane's Plus"), including cervical spine abnormalities (Klippel-Feil syndrome), Goldenhar syndrome, autism, heterochromia, and thalidomide-induced embryopathy.

Two different classification systems have been proposed, by Brown[7] and by Huber,[8] of which Brown's remains in more common clinical use.
[edit]Brown's classification
Brown classified the condition using the following three sub-types, based upon clinical observations:
Type A: Limited abduction and less limited adduction (as described originally by Duane).
Type B: Limited abduction but normal adduction, and
Type C: In which limitation of adduction is greater than limitation of abduction, giving rise to a divergent deviation and a head posture in which the face is turned away from the side of the affected eye.
[edit]Huber's classification
Huber's classification system was based upon electromyographical examinations:
Type I: Marked limitation of abduction (corresponds to Brown's Type B) explicable by maximum innervation reaching the lateral rectus only when the affected eye is adducted.
Type II: Limitation of adduction (corresponds to Brown's Type C)which Hubel explains as being caused by co-innervation of both medial and lateral recti on attempted adduction, and
Type III: Limitation of both adduction and abduction (corresponds to Brown's Type A) which Hubel explains as due to co-contraction, accompanied by a loss of innervation to the lateral rectus on attempted abduction.
[edit]Differential diagnosis

Disorders similar in presentation to Duane syndrome can be acquired as a result of trauma, or following localised infection of the orbit leading to inflammation and consequent mechanical restrictions of eye movement. In such cases a full case history will usually help in distinguishing between these conditions. In the clinical setting, the principal difficulties in differential diagnosis arise as a consequence of the very early age at which patients with this condition first present. The clinician must be persistent in examining abduction and adduction, and in looking for any associated palpebral fissure changes or head postures, when attempting to determine whether what often presents as a common childhood squint is in fact Duane syndrome. Fissure changes, and the other associated characteristics of Duane's such as up or down shoots and globe retraction, are also vital when deciding whether any abduction limitation is the result of Duane's and not a consequence of VI or abducens cranial nerve palsy.

The majority of patients remain symptom free and able to maintain binocularity with only a slight face turn. Amblyopia is uncommon and, where present, rarely dense. This can be treated with occlusion, and any refractive error can also be corrected.
Duane syndrome cannot be cured, as the "missing" cranial nerve cannot be replaced, and traditionally there has been no expectation that surgery will result in any increase in the range of eye movement. Surgical intervention, therefore, has only been recommended where the patient is unable to maintain binocularity, where they are experiencing symptoms, or where they are forced to adopt a cosmetically unsightly or uncomfortable head posture in order to maintain binocularity. The aims of surgery are to place the eye in a more central position and, thus, place the field of binocularity more centrally also, and to overcome or reduce the need for the adoption of an abnormal head posture. Occasionally surgery is not needed during childhood, but becomes appropriate later in life, as head position changes (presumably due to progressive muscle contracture).
[edit]Surgical approaches

In types A and B the most commonly adopted approach remains the recession of the medial recti of the affected eye, or of both eyes where the condition is bilateral. In type C, recession of the lateral recti is the method of choice.
The late Dr. Arthur Rosenbaum at UCLA championed the use of Vertical Rectus Transposition surgery.[9] He reported significant increases in lateral eye movements in many cases. The VRT realigned muscles work with the good medial muscle to provide a "tripod" of musculature for the eye; the newly moved muscles provide torque and tension against the medial muscle, which is what allows for the central alignment. And, because they are "working" muscles, they also may allow for some range of lateral movement in their new positions. [Anecdotal comment: this finding is 100% confirmed by the results with my daughter, who Dr. Rosenbaum operated on for Duane Syndrome in 1995.] Morad et al.[10] report the use of a similar approach in Duane's Type C.
Prominent down- or upshoots may be treated with a special form of muscle surgery, a "Y-splitting" procedure, often combined with a recession.


Strabismus (/strəˈbɪzməs/; Modern Latin, from Greek στραβισμός strabismos; cf. στραβίζειν strabizein "to squint", στραβός strabos "squinting, squint-eyed"[1]),[2] is a condition in which the eyes are not properly aligned with each other.[3] It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely affect depth perception. Strabismus can present as manifest (heterotropia), apparent, latent (heterophoria) varieties. Strabismus can be either a disorder of the brain in coordinating the eyes, or of one or more of the relevant muscles' power or direction of motion. Difficult strabismus problems are usually co-managed between eye doctors.
Contents [hide]
1 Classification
1.1 Paralytic strabismus
1.2 Other strabismus
2 Signs and symptoms
3 Pathophysiology
4 Diagnosis
4.1 Laterality
4.2 Onset
4.3 Differential diagnosis
5 Management
6 Prognosis
7 See also
8 References
9 External links

Apparent squint or pseudostrabismus
Latent squint (heterophoria)
Manifest squint (heteropia)
Concomitant squint
Convergent squint
Divergent squint
Vertical squint
Incomitant squint
Paralytic strabismus
A and V pattern heteropias
Restrictive squint
[edit]Paralytic strabismus
Forms of paralytic strabismus include
Third (oculomotor) nerve palsy
Fourth (trochlear) nerve palsy
Congenital fourth nerve palsy
Sixth (abducent) nerve palsy
Total (external) ophthalmoplegia
Progressive external ophthalmoplegia
Kearns-Sayre syndrome
[edit]Other strabismus
Other forms of strabismus include:
Convergent concomitant/Divergent concomitant
Vertical strabismus
Other and unspecified heterotropia
Monofixation syndrome
Mechanical strabismus
Brown's sheath syndrome
Duane syndrome
[edit]Signs and symptoms

A Maine Coon Cat affected by Strabismus.
Accommodation and vergence

Aligned vergence and accommodation. How one ideally views objects.

"Cross-eyed" vergence. Arrow indicates accommodation.

"Wall-eyed" ("parallel") vergence. (accommodation reflex)
One eye moves normally, while the other points in (esotropia or "crossed eyes"), out (exotropia), up (hypertropia) or down (hypotropia).
Strabismus is often referred to as "lazy eye", or known as amblyopia. In fact, amblyopia refers to the brain's ignoring input from one eye, which itself can result from discordance in the images provided by the eyes such as occurs in constant unilateral strabismus. It is also referred to as "crossed eyes", “wandering eyes”, or having a “cast”.[4]
"Cross-eyed" means that when a person with strabismus looks at an object, one eye fixes on the object and the other fixes with a convergence angle less than zero; the optic axes overconverge. "Wall-eyed" means that when a person with strabismus looks at an object, one eye fixes on the object and the other fixes with a convergence angle greater than zero; that is, the optic axes diverge from parallel.

Strabismus can be caused when the cranial nerves III (oculomotor), IV (trochlear) or VI (abducens) have a lesion. A strabismus caused by a lesion in either of these nerves results in the lack of innervation to eye muscles and results in a change of eye position. A strabismus may be a sign of increased intracranial pressure, as CN VI is particularly vulnerable to damage from brain swelling, as it runs between the clivus and brain stem.
More commonly however, squints are termed concominant (i.e. non paralytic). This means the squint is not caused by a lesion reducing innervation. The squint in this example is caused by a refractive error in one or both eyes. This refractive error causes poor vision in one eye and so stops the brain from being able to use both eyes together.

During eye examinations, orthoptists, ophthalmologists and optometrists typically use a cover test to aid in the diagnosis of strabismus. If the eye being tested is the strabismic eye, then it will fixate on the object after the "straight" eye is covered, as long as the vision in this eye is good enough. If the "straight" eye is being tested, there will be no change in fixation, as it is already fixated. Depending on the direction that the strabismic eye deviates, the direction of deviation may be assessed. Exotropic is outwards (away from the midline) and esotropic is inwards (towards the nose); these are types of horizontal strabismus. "Hypertropia" is upward, and "Hypotropia" is downward; these are types of vertical strabismus, which are less common.
A simple screening test for strabismus is the Hirschberg test. A flashlight is shone in the patient's eye. When the patient is looking at the light, a reflection can be seen on the front surface of the pupil. If the eyes are properly aligned with one another, then the reflection will be in the same spot of each eye. Therefore, if the reflection is not in the same place in each eye, then the eyes are not properly aligned.
Strabismus may be classified as unilateral if the same eye consistently 'wanders', or alternating if either of the eyes can be seen to 'wander'. Alternation of the strabismus may occur spontaneously, with or without subjective awareness of the alternation. Alternation may also be seen following the cover test, with the previously 'wandering' eye remaining straight while the previously straight eye is now seen to be 'wandering' on removal of the cover. The cover-uncover test is used to diagnose the type of strabismus (also known as tropia) present.[3]
Strabismus may also be classified based on time of onset, either congenital, acquired or secondary to another pathological process, such as cataract.[3] Many infants are born with their eyes slightly misaligned. The best time for physicians to assess this is between ages 3 and 6 months.[5]
[edit]Differential diagnosis
Pseudostrabismus is the false appearance of strabismus. It generally occurs in infants and toddlers whose bridge of the nose is wide and flat, causing the appearance of strabismus. With age, the bridge of the child's nose narrows and the folds in the corner of the eyes go away. To detect the difference between pseudostrabismus and strabismus, a Hirschberg test may be used.

Surgery to correct strabismus on an eight-month-old Nicaraguan infant.
As with other binocular vision disorders, the primary therapeutic goal for those with strabismus is comfortable, single, clear, normal binocular vision at all distances and directions of gaze.[6]
Whereas amblyopia (lazy eye), if minor and detected early, can often be corrected with use of an eyepatch on the dominant eye and/or vision therapy, the use of eyepatches is unlikely to change the angle of strabismus. Advanced strabismus is usually treated with a combination of eyeglasses or prisms, vision therapy, and surgery, depending on the underlying reason for the misalignment. Surgery does not change the vision; it attempts to align the eyes by shortening, lengthening, or changing the position of one or more of the extraocular eye muscles and is frequently the only way to achieve cosmetic improvement. The procedure can typically be performed in about an hour, and requires about a week for recovery. Double vision can result, and occasionally vision loss can occur. Glasses affect the position by changing the person's reaction to focusing. Prisms change the way light, and therefore images, strike the eye, simulating a change in the eye position.
Early treatment of strabismus and/or amblyopia in infancy can reduce the chance of developing amblyopia and depth perception problems. Most children eventually recover from amblyopia by around age 10, if they have had the benefit of patches and corrective glasses.[5]
Eyes that remain misaligned can still develop visual problems. Although not a cure for strabismus, prism lenses can also be used to provide some comfort for sufferers and to prevent double vision from occurring.
Botulinum Toxin (Botox) may also be used in the treatment of strabismus, to improve cosmetic appearance. Most commonly used in adults, the toxin is injected in the stronger muscle, causing temporary paralysis. The treatment may need to be repeated 3–4 months later once the paralysis wears off. Common side effects are double vision, droopy eyelid, over correction and no effect. The side effects will resolve fairly quickly.
In adults with previously normal alignment, the onset of strabismus usually results in double vision (diplopia).

When strabismus is congenital or develops in infancy, it can cause amblyopia, in which the brain ignores input from the deviated eye. The appearance of strabismus may also be a cosmetic problem. One study reported that 85% of adult strabismus patients "reported that they had problems with work, school and sports because of their strabismus." The same study also reported that 70% said strabismus "had a negative effect on their self-image."[7]

Visual perception

Visual perception is the ability to interpret the surrounding environment by processing information that is contained in visible light. The resulting perception is also known as eyesight, sight, or vision (adjectival form: visual, optical, or ocular). The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in psychology, cognitive science, neuroscience, and molecular biology.
Contents [hide]
1 Visual system
2 Study of visual perception
2.1 Early studies
2.2 Unconscious inference
2.3 Gestalt theory
2.4 Analysis of eye movement
2.5 Face and Object Recognition
3 The cognitive and computational approaches
4 Transduction
5 Opponent Process
6 Artificial visual perception
7 See also
7.1 Disorders/dysfunctions
7.2 Related disciplines
8 References
9 External links
[edit]Visual system

Main article: Visual system
The visual system in humans and animals allows individuals to assimilate information from the environment. The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive membrane in the back of the eye, called the retina. The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of patterns of light into neuronal signals. The lens of the eye focuses light on the photoreceptive cells of the retina, which detect the photons of light and respond by producing neural impulses. These signals are processed in a hierarchical fashion by different parts of the brain, from the retina upstream to central ganglia in the brain.
Note that up until now much of the above paragraph could apply to octopi, molluscs, worms, insects and things more primitive; anything with a more concentrated nervous system and better eyes than say a jellyfish. However, the following applies to mammals generally and birds (in modified form): The retina in these more complex animals sends fibers (the optic nerve) to the lateral geniculate nucleus, to the primary and secondary visual cortex of the brain. Signals from the retina can also travel directly from the retina to the superior colliculus.
[edit]Study of visual perception

The major problem in visual perception is that what people see is not simply a translation of retinal stimuli (i.e., the image on the retina). Thus people interested in perception have long struggled to explain what visual processing does to create what is actually seen.
[edit]Early studies

The visual dorsal stream (green) and ventral stream (purple) are shown. Much of the human cerebral cortex is involved in vision.
There were two major ancient Greek schools, providing a primitive explanation of how vision is carried out in the body.
The first was the "emission theory" which maintained that vision occurs when rays emanate from the eyes and are intercepted by visual objects. If an object was seen directly it was by 'means of rays' coming out of the eyes and again falling on the object. A refracted image was, however, seen by 'means of rays' as well, which came out of the eyes, traversed through the air, and after refraction, fell on the visible object which was sighted as the result of the movement of the rays from the eye. This theory was championed by scholars like Euclid and Ptolemy and their followers.
The second school advocated the so-called 'intro-mission' approach which sees vision as coming from something entering the eyes representative of the object. With its main propagators Aristotle, Galen and their followers, this theory seems to have some contact with modern theories of what vision really is, but it remained only a speculation lacking any experimental foundation.
Both schools of thought relied upon the principle that "like is only known by like", and thus upon the notion that the eye was composed of some "internal fire" which interacted with the "external fire" of visible light and made vision possible. Plato makes this assertion in his dialogue Timaeus, as does Aristotle, in his De Sensu.[1]

Leonardo DaVinci: The eye has a central line and everything that reaches the eye through this central line can be seen distinctly.
Alhazen (965 – c. 1040) carried out many investigations and experiments on visual perception, extended the work of Ptolemy on binocular vision, and commented on the anatomical works of Galen.[2][3]
Leonardo DaVinci (1452–1519) was the first to recognize the special optical qualities of the eye. He wrote "The function of the human eye ... was described by a large number of authors in a certain way. But I found it to be completely different." His main experimental finding was that there is only a distinct and clear vision at the line of sight, the optical line that ends at the fovea. Although he did not use these words literally he actually is the father of the modern distinction between foveal and peripheral vision.[citation needed]
[edit]Unconscious inference
Hermann von Helmholtz is often credited with the first study of visual perception in modern times. Helmholtz examined the human eye and concluded that it was, optically, rather poor. The poor-quality information gathered via the eye seemed to him to make vision impossible. He therefore concluded that vision could only be the result of some form of unconscious inferences: a matter of making assumptions and conclusions from incomplete data, based on previous experiences.
Inference requires prior experience of the world.
Examples of well-known assumptions, based on visual experience, are:
light comes from above
objects are normally not viewed from below
faces are seen (and recognized) upright.[4]
closer objects can block the view of more distant objects, but not vice versa
The study of visual illusions (cases when the inference process goes wrong) has yielded much insight into what sort of assumptions the visual system makes.
Another type of the unconscious inference hypothesis (based on probabilities) has recently been revived in so-called Bayesian studies of visual perception.[5] Proponents of this approach consider that the visual system performs some form of Bayesian inference to derive a perception from sensory data. Models based on this idea have been used to describe various visual subsystems, such as the perception of motion or the perception of depth.[6][7] The "wholly empirical theory of perception" is a related and newer approach that rationalizes visual perception without explicitly invoking Bayesian formalisms.[8]
[edit]Gestalt theory
Main article: Gestalt psychology
Gestalt psychologists working primarily in the 1930s and 1940s raised many of the research questions that are studied by vision scientists today.
The Gestalt Laws of Organization have guided the study of how people perceive visual components as organized patterns or wholes, instead of many different parts. Gestalt is a German word that partially translates to "configuration or pattern" along with "whole or emergent structure." According to this theory, there are six main factors that determine how the visual system automatically groups elements into patterns: Proximity, Similarity, Closure, Symmetry, Common Fate (i.e. common motion), and Continuity.
[edit]Analysis of eye movement

Eye movement first 2 seconds (Yarbus, 1967)
During the 1960s, technical development permitted the continuous registration of eye movement during reading[9] in picture viewing[10] and later in visual problem solving[11] and when headset-cameras became available, also during driving.[12]
The picture to the left shows what may happen during the first two seconds of visual inspection. While the background is out of focus, representing the peripheral vision, the first eye movement goes to the boots of the man (just because they are very near the starting fixation and have a reasonable contrast).
The following fixations jump from face to face. They might even permit comparisons between faces.
It may be concluded that the icon face is a very attractive search icon within the peripheral field of vision. The foveal vision adds detailed information to the peripheral first impression.
It can also be noted that there are three different types of eye movements: vergence movements, saccadic movements and pursuit movements. Vergence movements involve the cooperation of both eyes to allow for an image to fall on the same area of both retinas. This results in a single focused image. Saccadic movements is the type of eye movement that is used to rapidly scan a particular scene/image. Lastly, pursuit movement is used to follow objects in motion.[13]
[edit]Face and Object Recognition
There is some evidence (including disorders such as prosopagnosia) that face recognition is distinct from object recognition in terms of visual processing. For example, newborns show a preference for following moving faces within the first 30 minutes of life. However, some studies have shown that visual processing of complex non-face shapes happens in the same area of the brain as facial recognition. This implies it may be complexity, rather than the face per se, that influences visual processing in a distinct way.[14]
[edit]The cognitive and computational approaches

The major problem with the Gestalt laws (and the Gestalt school generally) is that they are descriptive not explanatory. For example, one cannot explain how humans see continuous contours by simply stating that the brain "prefers good continuity". Computational models of vision have had more success in explaining visual phenomena and have largely superseded Gestalt theory. More recently, the computational models of visual perception have been developed for Virtual Reality systems — these are closer to real life situation as they account for motion and activities which are prevalent in the real world.[15] Regarding Gestalt influence on the study of visual perception, Bruce, Green & Georgeson conclude:
"The physiological theory of the Gestaltists has fallen by the wayside, leaving us with a set of descriptive principles, but without a model of perceptual processing. Indeed, some of their "laws" of perceptual organisation today sound vague and inadequate. What is meant by a "good" or "simple" shape, for example?" [16]
In the 1970s David Marr developed a multi-level theory of vision, which analysed the process of vision at different levels of abstraction. In order to focus on the understanding of specific problems in vision, he identified three levels of analysis: the computational, algorithmic and implementational levels. Many vision scientists, including Tomaso Poggio, have embraced these levels of analysis and employed them to further characterize vision from a computational perspective.[citation needed]
The computational level addresses, at a high level of abstraction, the problems that the visual system must overcome. The algorithmic level attempts to identify the strategy that may be used to solve these problems. Finally, the implementational level attempts to explain how solutions to these problems are realized in neural circuitry.
Marr suggested that it is possible to investigate vision at any of these levels independently. Marr described vision as proceeding from a two-dimensional visual array (on the retina) to a three-dimensional description of the world as output. His stages of vision include:
a 2D or primal sketch of the scene, based on feature extraction of fundamental components of the scene, including edges, regions, etc. Note the similarity in concept to a pencil sketch drawn quickly by an artist as an impression.
a 2½ D sketch of the scene, where textures are acknowledged, etc. Note the similarity in concept to the stage in drawing where an artist highlights or shades areas of a scene, to provide depth.
a 3 D model, where the scene is visualized in a continuous, 3-dimensional map.[17]

Main article: Visual phototransduction
Transduction is the process through which energy from environmental stimuli is converted to neural activity for the brain to understand and process. The back of the eye contains three different cell layers; Photoreceptor layer, Bipolar cell layer and Ganglion cell layer. The photoreceptor layer is at the very back and contains rod photoreceptors and cone photoreceptors. Cones are responsible for colour perception. There are three different cones: red, green and blue. Photoreceptors contain within them photopigments, composed of two molecules. There are 3 specific photopigments (each with their own colour) that respond to specific wavelengths of light. When the appropriate wavelength of light hits the photoreceptor, its photopigment splits into two, which sends a message to the bipolar cell layer, which in turn sends a message to the ganglion cells, which then send the information through the optic nerve to the brain. If the appropriate photopigment is not in the proper photoreceptor (for example, a green photopigment inside a red cone), a condition called colour blindness will occur.[18]
[edit]Opponent Process

Transduction involves chemical messages sent from the photoreceptors to the bipolar cells to the ganglion cells. Several photoreceptors may send their information to one ganglion cell. There are two types of ganglion cells: red / green and yellow/blue. These neuron cells consistently fire – even when not stimulated. The brain interprets different colours (and with a lot of information, an image) when the rate of firing of these neurons alters. Red light stimulates the red cone, which in turn stimulates the red/green ganglion cell. Likewise, green light stimulates the green cone, which stimulates the red/green ganglion cell and blue light stimulates the blue cone which stimulates the yellow/blue ganglion cell. The rate of firing of the ganglion cells is increased when it is signalled by one cone and decreased (inhibited) when it is signalled by the other cone. The first colour in the name if the ganglion cell is the colour that excites it and the second is the colour that inhibits it. I.e.: A red cone would excite the red/green ganglion cell and the green cone would inhibit the red/green ganglion cell. This is an opponent process. If the rate of firing of a red/green ganglion cell is increased, the brain would know that the light was red, if the rate was decreased, the brain would know that the colour of the light was green.[18]
[edit]Artificial visual perception

Theories and observations of visual perception have been the main source of inspiration for computer vision (also called machine vision, or computational vision). Special hardware structures and software algorithms provide machines with the capability to interpret the images coming from a camera or a sensor. Artificial Visual Perception has long been used in the industry and is now entering the domains of automotive and robotics.

Vision therapy

Vision therapy, also known as vision training, is used to improve vision skills such as eye movement control, eye focusing and coordination, and the teamwork of the two eyes. It involves a series of procedures carried out under professional supervision, usually by a specially-trained optometrist.
Vision therapy can be prescribed when a comprehensive eye examination indicates that it is an appropriate treatment option for the patient. The specific program of therapy is based on the results of standardized tests, the needs of the patient, and the patient's signs and symptoms. Programs typically involve eye exercises and the use of lenses, prisms, filters, occluders, specialized instruments, and computer programs. The course of therapy, which may take from several weeks to several months, is closely monitored by the therapist.[1][2]
Contents [hide]
1 Historical development
2 Current definitions in clinical practice
3 Orthoptic visual therapy
4 Behavioural visual therapy
4.1 Efficacy of behavioural visual therapy
5 Eye exercises
5.1 Other forms
6 See also
7 References
[edit]Historical development

Various forms of visual therapy have been used for centuries.[3] The concept of vision therapy was introduced in the late nineteenth century for the non-surgical treatment of strabismus. This early and traditional form of vision therapy was the foundation of what is now known as orthoptics.[4]
In the first half of the twentieth century, orthoptists, working with ophthalmologists, introduced a variety of training techniques mainly designed to improve binocular function. In the second half of the twentieth century, vision therapy began to be used by optometrists and paramedical personnel to treat conditions ranging from uncomfortable vision to poor reading and academic performance. It has also been used specifically to improve eyesight, and even to improve athletic performance.[3]
At the beginning of the twenty-first century, most vision therapy is done by optometrists. Based on assessments of claims and studies of published data, ophthalmologists claim that, except for near point of convergence exercises, vision therapy lacks documented evidence of effectiveness.[3]
[edit]Current definitions in clinical practice

This section needs additional citations for verification. (May 2012)
Vision Therapy encompasses a wide variety of non-surgical methods[5][broken citation] which some[by whom?] have divided into two broad categories based on their clinical acceptance and general practice by eyecare professionals:
1) Orthoptic Vision Therapy, also known as orthoptics.
It may be prescribed to patients with problems of visual related skills required for reading, eye strain, visually induced headaches, strabismus and/or diplopia[citation needed] It is commonly practiced by optometrists and behavioral optometrists - however, more specialized problems are co-managed between orthoptists and ophthalmologist[6][not in citation given]
2) Behavioral Vision Therapy, or Visual Integration Vision Therapy (also known as behavioral or developmental optometry).[7]
Behavioural Vision Therapy does not limit itself to disorders of the visual system. For example, Behavioral Optometrists hold that the sensitivity of a professional athlete's peripheral vision on the playing field may have enhanced responsiveness to fast moving objects with vision therapy, beyond the normal realm general improvement with practicing their sport.[citation needed] Ophthalmologists and orthoptists do not endorse these exercises as having clinically significant validity for improvements in vision.[citation needed] Furthermore, absent of any visual pathology they view perceptual-motor deficiencies as being in the sphere of either speech therapy, occupational therapy or physical therapy.[citation needed]
3) Perception (motor) Therapy
Although the problems may have visual consequences, the visual system itself may be intact. Common management of dyslexia and sensory processing disorders by Speech Pathologists and Occupational Therapists for pathological or neurological conditions such as hemispatial neglect is viewed as outside of the realm of what is classified here as 'behavioural vision therapy'. This differentiation is primarily based on these disorders having widespread and independent efficacy of treatment.[citation needed]
[edit]Orthoptic visual therapy

for more detail, see also Orthoptics.
Orthoptics aims to treat binocular vision disorders such as strabismus, and diplopia. Key factors involved include: Eye Movement Control, Simultaneous Focus at Far, Sustaining Focus at Far, Simultaneous Focus at Near, Sustaining Focus at Near, Simultaneous Alignment at Far, Sustaining Alignment at Far, Simultaneous Alignment at Near, Sustaining Alignment at Near, Central Vision (Visual Acuity) and Depth Awareness.[8]
Some of the exercises used are:
Near point of convergence exercises (i.e. "pencil push-ups"),
Base-out prism reading, stereogram cards, computerized training programs are used to improve fusional vergence.[9]
The wearing of convex lenses
The wearing of concave lenses
"Cawthorne Cooksey Exercises" also employ various eye exercises, however, these are designed to alleviate vestibular disorders, such as dizziness, rather than eye problems.[10]
Antisuppression exercises - this is being less commonly practiced, although occasionally it may be used.
There is widespread acceptance of orthoptic therapy indications for:
Convergence insufficiency. Patients who experience eyestrain, "tired" eyes, or diplopia (double vision) while reading or performing other near work, and who have convergence insufficiency may benefit from orthoptic treatment. Patients whose outward drift occurs at distance rather than at near distance are less ideal candidates for treatment.
Intermittent exotropia.[11] This is often linked to convergence insufficiency.
Convergence insufficiency is a common binocular vision disorder characterized by asthenopia, eye fatigue and discomfort.[12] Asthenopia may be aggravated by close work and is thought by some to contribute to reading inefficiency.[7] In 2005, the Convergence Insufficiency Treatment Trial (CITT) published two large, randomized clinical studies examining the efficacy of orthoptic vision therapy in the treatment of symptomatic convergence insufficiency. Although neither study examined reading efficiency or comprehension, both demonstrated that in-office vision therapy was more effective than "pencil pushups" (a commonly prescribed home-based treatment) for improving the symptoms of asthenopia and the convergence ability of the eyes.[13][14] The design and results of at least one of these studies has been met with some reservation, questioning the conclusion as to whether intensive office-based treatment programs are truly more efficacious than a properly implemented home-based regimen.[15] The CITT has since published articles validating its research and treatment protocols.[16][17] Its most recent publication suggested that home-based computer therapy [2] combined with office based vision therapy is more effective than pencil pushups or home-based computerised therapy alone for the treatment of symptomatic convergence insufficiency.[18]
[edit]Behavioural visual therapy

Behavioural VT aims to treat problems including difficulties of visual attention and concentration, which behavioral optometrists classify as visual information processing weaknesses. These manifest themselves as an inability to sustain focus or to shift focus from one area of space to another.[citation needed] Some assert that poor eye tracking affects reading skills, and that improving tracking can improve reading.[19]
This includes vision therapy for: Peripheral Vision, Color Perception, Gross Visual-Motor, Fine Visual-Motor, and Visual Perception.[8]
Some of the exercises involve the use of:
Marsden balls
Rotation trainers
Balance board/beams
Saccadic fixators
Directional sequencers
Behavioral vision therapy is practiced primarily by optometrists after doing extra studies in this area. Major optometric organizations, including the American Optometric Association, the American Academy of Optometry, the College of Optometrists in Vision Development, and the Optometric Extension Program, support the assertion that non-strabismic visual therapy does not directly treat learning disorders, but rather addresses underlying visual problems which are claimed to affect learning potential.[20]
Major organizations, including the International Orthoptic Association and the American Academy of Ophthalmology have alternatively so far concluded that there is no current validity for clinically significant improvements in vision with Behavioural Vision Therapy, therefore they do not practice it.
[edit]Efficacy of behavioural visual therapy
In 1988, a review of 238 scientific articles was published in the Journal of the American Optometric Association widely defined vision therapy as "a clinical approach for correcting and ameliorating the effects of eye movement disorders, non-strabismic binocular dysfunctions, focusing disorders, strabismus, amblyopia, nystagmus, and certain visual perceptual (information processing) disorders." - and thereby did not discriminate between orthoptic and behavioural visual therapy. The paper was positive about vision therapy generally: "It is evident from the research that there is scientific support for the efficacy of vision therapy in modifying and improving oculomotor, accommodative, and binocular system disorders, as measured by standardized clinical and laboratory testing methods for patients of all ages for whom it is properly undertaken and employed."[21]
A more recent (2005) review concluded less positively that: "Less robust, but believable, evidence indicates visual training may be useful in developing fine stereoscopic skills and improving visual field remnants after brain damage. As yet there is no clear scientific evidence published in the mainstream literature supporting the use of eye exercises in the remainder of the areas reviewed, and their use therefore remains controversial."[22]
In 2006, noted neurologist Oliver Sacks published a case study about "Stereo Sue", a woman who had regained her stereo vision, absent for 48 years, after undergoing vision therapy. The article was published in The New Yorker magazine, which is fact-checked but not peer-reviewed, very few details were given of the exact therapies used and the article discussed only one case of stereo rehabilitation.[23] However, the woman described by Sacks, Susan Barry, a neurobiology professor at Mt. Holyoke College, subsequently published a book, "Fixing My Gaze." The book discusses multiple case histories and details the therapy procedures and the science underlying them.
A systematic review of the literature on the effects of vision therapy on visual field defects published in 2007 concluded that it was unclear to what extent patients benefited from vision restoration therapy (VRT) as "no study has given a satisfactory answer." The authors concluded that scanning compensatory therapy (SCT) seemed to provide a more successful rehabilitation, and simpler training techniques, therefore they recommended SCT until the effects of VRT could be defined.[24]
A 2008 review of the literature concluded that "there is a continued paucity of controlled trials in the literature to support behavioural optometry approaches. Although there are areas where the available evidence is consistent with claims made by behavioural optometrists ... a large majority of behavioural management approaches are not evidence-based, and thus cannot be advocated."[25]
Other than for strabismus (such as intermittent exotropia[11]) and convergence insufficiency, the consensus among ophthalmologists, orthoptists and pediatricians is that non-strabismic visual therapy lacks documented evidence of effectiveness.[3][22] In 1998, the American Academy of Pediatrics, American Academy of Ophthalmology, and American Association for Pediatric Ophthalmology and Strabismus issued a policy statement regarding the use of vision therapy specifically for the treatment of learning problems and dyslexia. According to the statement: "No scientific evidence exists for the efficacy of eye exercises ('vision therapy')... in the remediation of these complex pediatric neurological conditions."[26] More recently, in 2004, the American Academy of Ophthalmology released a position statement asserting that there is no evidence that vision therapy retards the progression of myopia, no evidence that it improves visual function in those with hyperopia or astigmatism, or that it improves vision lost through disease processes.[27] This was also supported by the International Orthoptic Association.[28]
The Joint Statement mentioned above[26] was criticised at the time by Merrill Bowan, a vision therapy enthusiast, for being biased, with the author of a rebuttal concluding "The AAP/AAO/AAPOS paper contains errors and internal inconsistencies. Through highly selective reference choices, it misrepresents the great body of evidence from the literature that supports a relationship between visual and perceptual problems as they contribute to classroom difficulties.".[29] The author also states that the Joint Statement presents an unsupported opinion by implication that Optometrists claim that vision therapy cures the learning problem. A similar criticism could be levelled at the 2004 American Academy of Ophthalmology paper which implies that vision therapy is claimed to treat "vision lost through disease processes". There is a common theme that critics of vision therapy seem to do by placing vision therapy under the same banner with alternative therapies. By implication, the lack of evidence for the alternative therapies is cited as a lack of evidence for vision therapy. No supporting evidence is given that vision therapy is actually used to treat eye disease or vision lost through disease processes.[citation needed]
Some optometrists take a slightly different view. In 1999 a joint statement by the American Academy of Optometry, the American Optometric Association, the College of Optometrists in Vision Development and Optometric Extension Program Foundation reported: "Many visual conditions can be treated effectively with spectacles or contact lenses alone; however, some are most effectively treated with vision therapy....Research has demonstrated that vision therapy can be an effective treatment option for ocular motility problems, non-strabismic binocular disorders, strabismus, amblyopia, accommodative disorders (and) visual information processing disorders."[30]
Practitioners in Behavioral optometry (also known as functional optometrists or optometric vision therapists) practice methods that have been characterized as a complementary alternative medicine practice.[31] A review in 2000 concluded that there were insufficient controlled studies of the approach[32] and a 2008 review concluded that "a large majority of behavioural management approaches are not evidence-based, and thus cannot be advocated."[25]
The consensus among Ophthalmologists, Orthoptists and Pediatricians is that "visual training" in non-strabismic Behavioural Vision therapy lacks documented scientific evidence of effectiveness.[3][33] Although Ophthalmologists and Orthoptists believe that exercises can improve binocular vision control, they believe it does not purely improve monocular visual acuity such as that in amblyopia (rather, occlusion is the therapy of choice),[34] change a person's refractive error, improve general physical fitness or agility or improve intelligence. It is probable that they do not change the accommodative/convergence ratio or enable someone to develop the ability for stereopsis. It is likely that they do not change the amplitude of accommodation to postpone or delay presbyopia.[35]
[edit]Eye exercises

This section needs additional citations for verification. (May 2012)
The eye exercises used in vision therapy can generally be divided into two groups; those employed for "strabismic" outcomes and those employed for "non-strabismic" outcomes, to improve eye health.
Some of the exercises used are
Near point of convergence training, or the ability for both eyes to focus on a single point in space,
Base-out prism reading, stereogram cards, computerized training programs are used to improve fusional vergence.[9][not in citation given]
The wearing of convex lenses
The wearing of concave lenses
"Cawthorne Cooksey Exercises" also employ various eye exercises, however, these are designed to alleviate vestibular disorders, such as dizziness, rather than eye problems.[36]
Antisuppression exercises - this is no longer commonly practiced, although occasionally it may be used.
The eye exercises used in Behavioural Vision Therapy, also known as Developmental Optometry is practiced primarily by Behavioural Optometrists. Behavioural Vision Therapy therapy aims to treat problems including difficulties of visual attention and concentration, which may manifest themselves as an inability to sustain focus or to shift focus from one area of space to another.
Some of the exercises used are:
Marsden balls
Rotation trainers
Balance board/beams
Saccadic fixators
Directional sequencers
Ophthalmologists and orthoptists do not endorse these exercises as having clinically significant validity for improvements in vision. Usually they see these perceptual-motor activities being in the sphere of either speech therapy or occupational therapy.
Fusional Amplitude and Relative Fusional Amplitude training
Designed to alleviate convergence insufficiency. The CITT study (Convergence Insufficiency Treatment Trial) was is a randomized, double blind multi-centre trial (high level of reliability) indicates that Orthoptic Vision Therapy is an effective method of treatment of convergence insufficiency (CI). Both optometry and ophthalmology were co-authors of this study.
Designed to alleviate intermittent exotropia[37] or other less common forms of strabismus.
[edit]Other forms
Do-it-yourself eye exercises are claimed by some to improve visual acuity by reducing or eliminating refractive errors. Such claims rely mainly on anecdotal evidence, and are not generally endorsed by orthoptists, ophthalmologists or optometrists.[38][39]