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

SNK

SNK

Sunday, April 28, 2013

Kolkata Kutcheri – Thoughts by Venkataramanan Ramasethu

Around 30 years ago a popular joke among the middle class South Indian population, while talking about Kolkata was that if you land up in Howrah Station from Coromondol Express in the morning during breakfast time, you could be certain that by evening around tea time you would have a job in one of those firms run by Gujarati & Rajasthani businessmen. But things have taken a complete circle and today truly speaking the South Indian population is scarce. Greener pastures in abroad and other metropolis in terms of education and employment opportunities have lured the present generation and rightly so, since education and a respectable employment are the two things of utmost significance to an average Indian middle class and South Indians are no exception. Recently a news piece in a leading English Daily published from Kolkata, highlighted the significant drop in students opting for Tamil or any other South Indian language in some of the few schools in Kolkata that offer them.

Traditionally the South Indians in Kolkata are believed to be largely based in and around Lake Market and Rash Behari Avenue in South Kolkata, but a recent trend since the last five years have seen a steep migration of the population away from these areas and moving further towards Southern Suburbs, with Brahmapur, Patuli and Garia evolving as the new epicenter of South Indian population in Kolkata. Availability of Flats and independent housing systems has attracted the South Indian population to these localities largely. Also with the Metro Rail getting expanded with fairly large number of reputed schools and hospitals emerging in these localities have further enhanced the motivation levels to relocate from Lake Market and Rash Behari areas. Starting from Flower Market, Vegetable Market, Temples, Shops selling South Indian Masalas and South Indian Movies, give an impression that in future this might emerge as a Mini Mylapore.

For a long time Bharathi Tamil Sangam at Deshopriyo Park was the only place wherein the Literature Loving people could flock together. But a couple of years ago the Brahmapur Tamil Association was launched and it’s been rendering yeomen service to the needs of the South Indian population in the City of Joy. For those who are spiritually inclined the Sankara Hall at Southern Avenue, Veda Bhavan at Lake Avenue and Shri Thygaraja Hall of Sadguru Gnanananda Rasika Ranjana Sabha behind Lake Kali Bhari provide ample scope to splurge in South Indian serenity.

And of course the most sweet part is that in almost all celebrations be it the Pongal Celebration,Ugadi Celebration,Onam Celebration,Carnatic Classical Concerts or Bharathanatyam Concerts,the local Bengali population would always outnumber the South Indian population in terms of support,participation,encouragement and enthusiasm.

Might be that’s why still Calcutta is undeniably the “Cultural Capital” and “Cosmopolitan Cradle” of this nation.

Bhagwan Sri Sathya Sai Baba Aradhana Day on 24th April 2013 @ Sankara Nethralaya



Across the globe, cutting barriers of caste, creed, religion, race or color, Sri Sathya Sai Baba was “Bhagawan”, or “God” and a spiritual guru to scores of millions.

He remained an icon, throwing a positive influence unprecedented in the annals of education, creating mammoth medical institutions, super specialty hospitals and addressing water crisis in the drought hit areas of Ananthapuri, Medak, Mahbubnagar and suburban Chennai districts with revolutionary projects for providing safe drinking water, the services which the Government of India recognized by releasing a postal stamp in his honour.

Sri Sathya Sai Baba’s Aradhana day was observed at the I Floor, Mahyco Block, Sankara Nethralaya, with veneration and devotion to the lighting of Kuthu Vilakku, amidst chanting of Sai Bhajans by Consultants, staff and visitors to the hospital and paying rich floral tributes to the portrait of the towering and revered Atma.

Wednesday, April 24, 2013

Sri City Special Economic Zone and Sankara Nethralaya’s dream of providing quality ophthalmic care



Tamil New Year’s Day falling on 14th April 2013 marked the culmination of a Special Economic Zone’s dream to bring a human touch to its endeavour in bringing about a world class industrial facility and hub and marked yet another mile stone in the journey of a service oriented eye care institution towards providing quality eye care across boundaries. The day marked Sri City Special Economic Zone and Sankara Nethralaya’s dream of providing quality ophthalmic care to the employees of the various units in the zone and cost free care to the poor and needy villagers of the region.

The chanting of Vedas and mantras at the first floor of Sri City’s Central hospital marked the auspicious beginning to the inaugural function of the Sri City Sankara Nethralaya to function from this venue, this was followed by the ceremonial ribbon cutting by Dr.MYS.Prasad, Director, Satish Dhawan Space Centre, Sriharikota in the presence of the distinguished invitees, donors/supporters, well wishers, senior management and staff members of both organizations, vendors/contractors to the project and local villagers who would be benefiting out of the facility. After a quick honouring of the chief guest, guest of honour, the consultant who would be posted at the new facility and the internal and external teams involved in the project, the action moved to the Sri City business center.

The proceedings at the filled to capacity business center started with a warm welcome address by Srimati Akila Ganesan, Senior General Manager, Sankara Nethralaya and an invocation song to Gajanan the Lord of auspicious beginnings by Ms Sumana Vishnu Vahan, wife of Dr Vishnu Vahan, Consultant, Sri Srinivasa Sankara Nethralaya.

Speaking on the occasssion Shri Ravi Sanna Reddy, MD, Sri City Special Economic Zone remarked that it was both the toughest and happiest day in his life as the 45 day challenge was completed with clockwork precision, he expressed his profuse thanks to Dr SS.Badrinath, Chairman Emeritus, Sankara Nethralaya for consenting to his request for a joint eye care initiative and attributed its inception to his blessings. Shri Reddy closed his address with a note of thanks to the Chief Guest, Guest of honour Professor Mani Sundaram, the first Principal of the REC, Trichy and former Vice-Chancellor, Bharathidasan University, Shri Chandrasekhar formerly of L&T who brought about the alliance between the two organizations and Dr S.Bhaskaran, Chairman, Sankara Nethralaya.

Dr SS.Badrinath started his address on a vibrant note that if the Sri Srinivasa Sankara Nethralaya embodied Balaji service the Sri City Sankara Nethralaya would embody Sriharikota service, he complimented the teams involved for their ‘4 week magic’ denoting the short frame of time in which the project was completed. He added in lighter vein that the new facility would propel itself to glorious heights in record speed as it was inaugurated by the head of India’s premier rocket launch center. Dr Badrinath highlighted that the new facility would serve the staff members of industrial units in the zone, serve as a referral hospital for camp patients and as a cost free eye care center for the poor and needy villagers in the region. Dr SS.Badrinath declared that Nanobiotechnology and stem cell therapy would bring about sweeping changes in the clinical processes and treatment and Sankara Nethralaya as a pioneer in these fields would enter into a larger area beyond ophthalmology in the years to come.

Shri Chandrasekhar the man who acted as the bridge between the two institutions congratulated the two pioneers for coming together and making it happen in a short time. He made a surprise announcement that Dr Sathya Atluri, the world famous Mechanical and Aerospace Engineer from Phoenix, USA and recipient of the Padma Bhushan for 2013 has made a large contribution to the new facility and read out his greeting message for the inaugural function to the thunderous applause of the gathering. Dr Krishna Kumar, Principal Elite School of Optometry gave an interesting note on the pioneering role of Dr SS.Badrinath and Professor PP.Santanam in the development of occupational optometry, finding a place of importance for this field and its relevance in overall ophthalmic care. He added that as an eye care facility located in an industrial zone the Sri City Sankara Nethralaya would enable better vision to the employees of the diverse units to enable vision and better productivity through occupational optometry.

Delivering the Chief Guest’s address Dr .MYS Prasad, Director, Satish Dhawan Space Centre thanked the organizers for the honour, he remarked that it was age old wisdom that one should do a noble deed on New year’s day and there could not be anything more noble than starting a service oriented health care facility. He expressed his happiness and satisfaction that just like the Satish Dhawan Space Centre at Sri Harikota the Sri City Special Economic Zone also did not displace or disturb local villagers but made them an inclusive part of its growth. He expressed that as one grew old one had the tendency to look for torch bearers to carry forth one’s work and Sri Sanna Reddy was a great hope in this direction. The guest of honour Professor Manisundaram, the first Principal of the Regional Engineering College, Trichy and Vice-Chancellor of the Bharathidasan University had a high word of praise for his student Sri Ravi Sanna Reddy and added that the government should outsource its projects to dynamic people like him to ensure timely completion.

The high power function came to an end with acknowledgements for their contribution towards timely completion of the project and kick off to the Sankara Nethralaya and Sri City teams and vendors by Sri Suresh Kumar, Manager Projects, Sankara Nethralaya and a warm vote of thanks by Dr Eesh Nigam, Associate Consultant, who would be in-charge of the Sri City Sankara Nethralaya.

Thursday, April 11, 2013

When a good intention becomes a remarkable action, it is indeed impossible to describe



When a good-natured notion transforms into a valiant process, it is impossible to match. When a thoughtful idea turns into an insightful project, it is impossible to fathom. When a good intention becomes a remarkable action, it is indeed impossible to describe. It was exactly this that was done during the “Small Acts of Kindness-2013” performance for Sankara Nethralaya on March 30th, 2013 in Dallas, Texas.

As a sequel to the first “Small Acts of Kindness” program that took place in October 2011 in the Dallas-Fort Worth Metroplex, this year’s performance was targeted at a broader variety of people, hence the programme included songs in Malayalam, Tamil, and Hindi. A highly talented group of music lovers and performers –Prabhu Shankar, Manoj Krishnan, Shruthi Prabhu, Sahana Prabhu, Anjali Varghese, Sumithra Prabhu, Aarthi Giri, and Sankara Nethralaya OM Trustee – “Singer” Prabhu–joined together this time around to make this program a huge success. The singers were accompanied by yet another exceptional group of performing musicians–Joe, Shino (from Chicago), Isaac & Eugene—who truly entertained the ecstatic crowd of about 200 people who gave reviews that were never less than astounding.

Incorporating songs such as “Oru Murai,” from Mani Chitra Thaazhu, “Deewangi Deewangi,” from Om Shanthi Om, and “Nenjukulle,” from Kadal, the lively, bubbly crew put together an unforgettable performance that never failed to get the crowd on its feet, asking for more. The program was described by a plethora of spectators as “incredible,” “one of the best concerts of the year,” “astoundingly lively & interesting,” & “memorable.”

The “Small Acts of Kindness-2013” effort collected a net sum that could assist to the tune of about 65 free surgeries at Sankara Nethralaya- Chennai, India. There was a multitude of other magnanimous volunteers from the Metroplex that assisted in the smooth conduct of the event.

If anything is certain from this event, it is the fact that this will not be the last effort of this multitalented group of people. Dedication goes a long way, and most definitely, there will be many more wonderful performances in the months and years to come to entertain the DFW crowd and other cities to assist Sankara Nethralaya in Chennai.

“Education is not filling a pail, but the lighting of fire”



Welcoming the Chief guest, Honourable members from the DG Vaishnav College, awardees, the Members of Medical Research Foundation, Vision Research Foundation and the Sankara Nethralaya family, Ms.Sudha Mohan, Sr.Manager, HR, aptly quoted William Butler Yeats who said “Education is not filling a pail, but the lighting of fire”, to ignite the passion of learning and acquire knowledge. She complimented Lion Sri Haridas, Secretary, DG Vaishnav College and member Board of Governors, the Sankara Nethralaya Academy for his initiative in conducting a Basic Computer Training program for Sankara Nethralaya employees at the DG Vaishnav College.

Col.N.Raghavan, Projects, Sankara Nethralaya, Introduced the Chief Guest, Sri.V.R.Gopalakrishnan, Senior Journalist and profusely thanked him for gracing the occasion, he recalled his long and interesting association with the Ministry of Information and Broadcasting. He highlighted that a prolific writer and thinker, Sri.Gopalakrishnan was a man endowed with a rare quality that coupled scholarly education and politeness. He mentioned that the immensely popular Rama’s café at Kanchipuram belonged to Sri.Gopalakrishnan’s family and he has very magnanimously offered their Sri Rama buildings at Greams Road for the operation of the Jaslok Community Ophthalmology Center at a highly subsidized rent.

Starting off with a Prayer to Lord Ganesha, the Chief guest, Sri.V.R.Gopalakrishnan, said he felt diffident, but chose to attend the function because of the long association he had with Dr.SS.Badrinath dating to the early 70s. He highlighted the juxtaposition of events and called it divine persuasion when Dr.SS. Badrinath was called on to operate upon the Paramacharya and how he played host when the Badrinaths stayed for a week at Kanchipuram. Sri Gopalakrishnan hailed Dr.SS.Badrinath as an expert in treating vitreous haemorrage with the help of a Xenon laser, which was scarcely available in India then and how the veteran used this to advantage while treating him.

Shri Gopalakrishnan was torrential and inexorable in his anecdotes, exhaustively quoting scriptures of Thayumanavar, Appudhi Adigal, Koorathazwar and Adhi Sankara he touched upon Paramacharya’s astuteness which brought upon cosmic frequency in every aspect beyond his philosophy and doctrines. Sri Gopalkrishna deftly quoted Adi Shankara’s Bhaja Govindam, wherein the sage admonishes manhood as “Moodamathe”, that no matter how scholarly one were, liberation was only through wisdom and one must pursue that path through Karma, Bhakthi or Gnana and by being selfless in service like Dr.SS.Badrinath.

Dr.SS.Badrinath, Chairman Emeritus introducing Lion Shri P. Haridas, Secretary, DG Vaishnav College, said that he was a humane personality, a legal luminary and a charismatic man who founded many educational institutions. He was profusely thankful for the initiative that Shri Haridas had taken to train Sankara Nethralaya employees at the DG Vaishnav College. He showered encomiums for the steady support Shri Haridas rendered for the Television production of Sankara Nethralaya programs.

Distributing the certificates to employees who had undergone “Basic Training in Computer education”, Dr.S.Narasimhan, Principal, DG Vaishnav College and Dr.T.Santhanam, Head of the Computer Science Department, echoed that their institution traversed beyond the realm of education and training, to being resourceful in the interest of the community by prominently associating with NGOs for transcending education both to the public and engaging in projects such as “Green Club”.

A total of 67 certificates were distributed to Sankara Nethralaya employees who had successfully completed the basic training programme. The function also witnessed awarding of service recognition certificates to Sri.Suresh Kumar, Projects for his dedicated involvement in the Sri City Sankara Nethralaya project and Sri.Narasimhulu, House keeping department for his exemplary integrity shown in promptly handing over a lost wallet containing money.

The program concluded with a vote of thanks by Sri.Sampath Kumar, Head, IT and Systems, Sankara Nethralaya.

Elite School of Optometry,Imbibing the culture and value of “social accountability” from its alma mater Sankara Nethralaya



World Optometry Day has always been an occasion for the Elite School of Optometry (ESO-run by Sankara Nethralaya in collaboration with Birla Institute of Technology and Science, Pilani) to demonstrate its concern care for society. Right from its early days, ESO has taken small steps to create awareness about eye care among the public, through exhibitions, rallies, interactive sessions, competitions for schools and vision screening.

This year, in a different move to raise awareness among the public on various ocular problems like Diabetic Retinopathy and Glaucoma, a door to door campaign by the students of Optometry was arranged in the residential areas of Nanganallur on Sunday the 7th April 2013, between 9:00am and 11:30am. Student and faculty members of ESO went on a door to door and explained about Diabetic Retinopathy and Glaucoma, as the symptoms and critical implications of these conditions are yet to reach the public in large. They also distributed brochures, about these conditions, eye donation forms and conducted a “Glaucoma and Diabetic Retinopathy-Are you at risk?” survey.

Imbibing the culture and value of “social accountability” from its alma mater Sankara Nethralaya, the Elite School of Optometry with its 140 members as 15 teams, spread the light of eye care awareness among 1020 families in Nanganallur. The Elite School of Optometry and –Sankara Nethralaya conduct free eye camp for the public on the second Sunday of every month between 8.00 am. and 1.00 pm in the Nanganallur Anjaneya temple premises.

Sunday, April 7, 2013

Genome



In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of viruses, in RNA.[1] The genome includes both the genes and the non-coding sequences of the DNA/RNA

Origin of term

The term was adapted in 1920 by Hans Winkler,[3] professor of botany at the University of Hamburg, Germany. The Oxford English Dictionary suggests the name to be a blend of the words gene and chromosome. A few related -ome words already existed — such as biome, rhizome and, more recently, connectome — forming a vocabulary into which genome fits systematically.[4]
[edit]Overview

Some organisms have multiple copies of chromosomes: diploid, triploid, tetraploid and so on. In classical genetics, in a sexually reproducing organism (typically eukarya) the gamete has half the number of chromosomes of the somatic cell and the genome is a full set of chromosomes in a gamete. In haploid organisms, including cells of bacteria, archaea, and in organelles including mitochondria and chloroplasts, or viruses, that similarly contain genes, the single or set of circular and/or linear chains of DNA (or RNA for some viruses), likewise constitute the genome. The term genome can be applied specifically to mean that stored on a complete set of nuclear DNA (i.e., the "nuclear genome") but can also be applied to that stored within organelles that contain their own DNA, as with the "mitochondrial genome" or the "chloroplast genome". Additionally, the genome can comprise nonchromosomal genetic elements such as viruses, plasmids, and transposable elements.[5]
When people say that the genome of a sexually reproducing species has been "sequenced", typically they are referring to a determination of the sequences of one set of autosomes and one of each type of sex chromosome, which together represent both of the possible sexes. Even in species that exist in only one sex, what is described as a "genome sequence" may be a composite read from the chromosomes of various individuals. Colloquially, the phrase "genetic makeup" is sometimes used to signify the genome of a particular individual or organism. The study of the global properties of genomes of related organisms is usually referred to as genomics, which distinguishes it from genetics which generally studies the properties of single genes or groups of genes.
Both the number of base pairs and the number of genes vary widely from one species to another, and there is only a rough correlation between the two (an observation known as the C-value paradox). At present, the highest known number of genes is around 60,000, for the protozoan causing trichomoniasis (see List of sequenced eukaryotic genomes), almost three times as many as in the human genome.
An analogy to the human genome stored on DNA is that of instructions stored in a book:
The book (genome) would contain 23 chapters (chromosomes);
Each chapter contains 48 to 250 million letters (A,C,G,T) without spaces;
Hence, the book contains over 3.2 billion letters total;
The book fits into a cell nucleus the size of a pinpoint;
At least one copy of the book (all 23 chapters) is contained in most cells of our body. The only exception in humans is found in mature red blood cells which become enucleated during development and therefore lack a genome.
[edit]Sequencing and mapping

For more details on this topic, see Genome project.
In 1976, Walter Fiers at the University of Ghent (Belgium) was the first to establish the complete nucleotide sequence of a viral RNA-genome (bacteriophage MS2). The next year, Phage Φ-X174, with only 5386 base pairs, became the first DNA-genome project to be completed, by Fred Sanger. The first complete genome sequences for representatives from all 3 domains of life were released within a short period during the mid-1990s. The first bacterial genome to be sequenced was that of Haemophilus influenzae, completed by a team at The Institute for Genomic Research in 1995. A few months later, the first eukaryotic genome was completed, with the 16 chromosomes of budding yeast Saccharomyces cerevisiae being released as the result of a European-led effort begun in the mid-1980s. Shortly afterward, in 1996, the first genome sequence for an archaeon, Methanococcus jannaschii, was completed, again by The Institute for Genomic Research.
The development of new technologies has made it dramatically easier and cheaper to do sequencing, and the number of complete genome sequences is growing rapidly. The US National Institutes of Health maintains one of several comprehensive databases of genomic information.[6] Among the thousands of completed genome sequencing projects include those for mouse, rice, the plant Arabidopsis thaliana, the puffer fish, and bacteria like E. coli.
New sequencing technologies, such as massive parallel sequencing have also opened up the prospect of personal genome sequencing as an important diagnostic tool, as pioneered by Manteia Predictive Medicine. A major step toward that goal was the completion in 2007 of the full genome of James D. Watson, one of the co-discoverers of the structure of DNA.[7]
Whereas a genome sequence lists the order of every DNA base in a genome, a genome map identifies the landmarks. A genome map is less detailed than a genome sequence and aids in navigating around the genome. The Human Genome Project was organized to map and to sequence the human genome. A fundamental step in the project was the release of a detailed genomic map by Jean Weissenbach and his team at the Genoscope in Paris.[8][9]
[edit]Genome compositions

Genome composition is used to describe the make up of contents of a haploid genome, which should include genome size, proportions of non-repetitive DNA and repetitive DNA in details. By comparing the genome compositions between genomes, scientists can better understand the evolutionary history of a given genome.
When talking about genome composition, one should distinguish between prokaryotes and eukaryotes as the big differences on contents structure they have. In prokaryotes, most of the genome (85-90%) is non-repetitive DNA, which means coding DNA mainly forms it, while non-coding regions only take a small part.[10] On the contrary, eukaryotes have the feature of exon-intron organization of protein coding genes; the variation of repetitive DNA content in eukaryotes is also extremely high. When refer to mammalians and plants, the major part of genome is composed by repetitive DNA.[11]
Most biological entities that are more complex than a virus sometimes or always carry additional genetic material besides that which resides in their chromosomes. In some contexts, such as sequencing the genome of a pathogenic microbe, "genome" is meant to include information stored on this auxiliary material, which is carried in plasmids. In such circumstances then, "genome" describes all of the genes and information on non-coding DNA that have the potential to be present.
In eukaryotes such as plants, protozoa and animals, however, "genome" carries the typical connotation of only information on chromosomal DNA. So although these organisms contain chloroplasts and/or mitochondria that have their own DNA, the genetic information contained by DNA within these organelles is not considered part of the genome. In fact, mitochondria are sometimes said to have their own genome often referred to as the "mitochondrial genome". The DNA found within the chloroplast may be referred to as the "plastome".
[edit]Genome size


Log-log plot of the total number of annotated proteins in genomes submitted to GenBank as a function of genome size.[12]
Genome size is the total number of DNA base pairs in one copy of a haploid genome. The genome size is positively correlated with the morphological complexity among prokaryotes and lower eukaryotes; however, after mollusks and all the other higher eukaryotes above, this correlation is no longer effective.[11][13] This phenomenon also indicates the mighty influence coming from repetitive DNA act on the genomes.
Since genomes are very complex, one research strategy is to reduce the number of genes in a genome to the bare minimum and still have the organism in question survive. There is experimental work being done on minimal genomes for single cell organisms as well as minimal genomes for multicellular organisms (see Developmental biology). The work is both in vivo and in silico.[14][15]

Proportion of non-repetitive DNA
The proportion of non-repetitive DNA is calculated by using length of non-repetitive DNA divided by genome size. Protein-coding genes and RNA-coding genes are generally non-repetitive DNA.[47] Bigger genome does not mean more genes, and the proportion of non-repetitive DNA decreases along with the increase of genome size in higher eukaryotes.[11]
It had been found that the proportion of non-repetitive DNA can vary a lot between species. Some E. coli as prokaryotes only have non-repetitive DNA, lower eukaryotes such as C. elegans and fruit fly, still possess more non-repetitive DNA than repetitive DNA.[11][48] Higher eukaryotes tend to have more repetitive DNA than non-repetitive one. In some plants and amphibians, the proportion of non-repetitive DNA is no more than 20%, becoming a minority component.[11]
[edit]Proportion of repetitive DNA
The proportion of repetitive DNA is calculated by using length of repetitive DNA divide by genome size. There are two categories of repetitive DNA in genome: tandem repeats and interspersed repeats.[49]
[edit]Tandem repeats
Tandem repeats are usually caused by slippage during replication, unequal crossing-over and gene conversion,[50] satellite DNA and microsatellites are forms of tandem repeats in the genome.[51] Although tandem repeats count for a significant proportion in genome, the largest proportion in mammalian is the other type, interspersed repeats.
[edit]Interspersed repeats
Interspersed repeats mainly come from transposable elements (TEs), but they also include some protein coding gene families and pseudogenes. Transposable elements are able to integrate into the genome at another site within the cell.[10][52] It is believed that TEs are an important driving force on genome evolution of higher eukaryotes.[53] TEs can be classified into two categories, Class 1 (retrotransposons) and Class 2 (DNA transposons).[52]
[edit]Retrotransposons
Retrotransposons can be transcribed into RNA, which are then duplicated at another site into the genome.[54] Retrotransposons can be divided into Long terminal repeats (LTRs) and Non-Long Terminal Repeats (Non-LTR).[53]
Long Terminal Repeats (LTRs)
similar to retroviruses, which have both gag and pol genes to make cDNA from RNA and proteins to insert into genome, but LTRs can only act within the cell as they lack the env gene in retroviruses.[52] It has been reported that LTRs consist of the largest fraction in most plant genome and might account for the huge variation in genome size.[55]
Non-Long Terminal Repeats (Non-LTRs)
can be divided into long interspersed elements (LINEs), short interspersed elements (SINEs) and Penelope-like elements. In Dictyostelium discoideum, there is another DIRS-like elements belong to Non-LTRs. Non-LTRs are widely spread in eukaryotic genomes.[56]
Long interspersed elements (LINEs)
are able to encode two Open Reading Frames (ORFs) to generate transcriptase and endonuclease, which are essential in retrotransposition. The human genome has around 500,000 LINEs, taking around 17% of the genome.[57]
Short interspersed elements (SINEs)
are usually less than 500 base pairs and need to co-opt with the LINEs machinery to function as nonautonomous retrotransposons.[58] The Alu element is the most common SINEs found in primates, it has a length of about 350 base pairs and takes about 11% of the human genome with around 1,500,000 copies.[53]
[edit]DNA transposons
DNA transposons generally move by "cut and paste" in the genome, but duplication has also been observed. Class 2 TEs do not use RNA as intermediate and are popular in bacteria, in metazoan it has also been found.[53]
[edit]Genome evolution

Genomes are more than the sum of an organism's genes and have traits that may be measured and studied without reference to the details of any particular genes and their products. Researchers compare traits such as chromosome number (karyotype), genome size, gene order, codon usage bias, and GC-content to determine what mechanisms could have produced the great variety of genomes that exist today (for recent overviews, see Brown 2002; Saccone and Pesole 2003; Benfey and Protopapas 2004; Gibson and Muse 2004; Reese 2004; Gregory 2005).
Duplications play a major role in shaping the genome. Duplications may range from extension of short tandem repeats, to duplication of a cluster of genes, and all the way to duplications of entire chromosomes or even entire genomes. Such duplications are probably fundamental to the creation of genetic novelty.
Horizontal gene transfer is invoked to explain how there is often extreme similarity between small portions of the genomes of two organisms that are otherwise very distantly related. Horizontal gene transfer seems to be common among many microbes. Also, eukaryotic cells seem to have experienced a transfer of some genetic material from their chloroplast and mitochondrial genomes to their nuclear chromosomes.

Molecular Biology



Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell, including the interactions between the different types of DNA, RNA and protein biosynthesis as well as learning how these interactions are regulated.
Writing in Nature in 1961, William Astbury described molecular biology as
"...not so much a technique as an approach, an approach from the viewpoint of the so-called basic sciences with the leading idea of searching below the large-scale manifestations of classical biology for the corresponding molecular plan. It is concerned particularly with the forms of biological molecules and [...] is predominantly three-dimensional and structural—which does not mean, however, that it is merely a refinement of morphology. It must at the same time inquire into genesis and function."[1]
Relationship to other biological sciences

Schematic relationship between biochemistry, genetics, and molecular biology
Researchers in molecular biology use specific techniques native to molecular biology but increasingly combine these with techniques and ideas from genetics and biochemistry. There is not a defined line between these disciplines. The figure above is a schematic that depicts one possible view of the relationship between the fields:
Biochemistry is the study of the chemical substances and vital processes occurring in living organisms. Biochemists focus heavily on the role, function, and structure of biomolecules. The study of the chemistry behind biological processes and the synthesis of biologically active molecules are examples of biochemistry.
Genetics is the study of the effect of genetic differences on organisms. This can often be inferred by the absence of a normal component (e.g. one gene). The study of "mutants" – organisms which lack one or more functional components with respect to the so-called "wild type" or normal phenotype. Genetic interactions (epistasis) can often confound simple interpretations of such "knock-out" studies.
Molecular biology is the study of molecular underpinnings of the processes of replication, transcription, translation, and cell function. The central dogma of molecular biology where genetic material is transcribed into RNA and then translated into protein, despite being an oversimplified picture of molecular biology, still provides a good starting point for understanding the field. This picture, however, is undergoing revision in light of emerging novel roles for RNA.
Much of the work in molecular biology is quantitative, and recently much work has been done at the interface of molecular biology and computer science in bioinformatics and computational biology. As of the early 2000s, the study of gene structure and function, molecular genetics, has been among the most prominent sub-field of molecular biology.
Increasingly many other loops of biology focus on molecules, either directly studying their interactions in their own right such as in cell biology and developmental biology, or indirectly, where the techniques of molecular biology are used to infer historical attributes of populations or species, as in fields in evolutionary biology such as population genetics and phylogenetics. There is also a long tradition of studying biomolecules "from the ground up" in biophysics.
[edit]Techniques of molecular biology

Since the late 1950s and early 1960s, molecular biologists have learned to characterize, isolate, and manipulate the molecular components of cells and organisms. These components include DNA, the repository of genetic information; RNA, a close relative of DNA whose functions range from serving as a temporary working copy of DNA to actual structural and enzymatic functions as well as a functional and structural part of the translational apparatus; and proteins, the major structural and enzymatic type of molecule in cells.
For more extensive list on protein methods, see protein methods. For more extensive list on nucleic acid methods, see nucleic acid methods.
[edit]Expression cloning
Main article: Expression cloning
One of the most basic techniques of molecular biology to study protein function is expression cloning. In this technique, DNA coding for a protein of interest is cloned (using PCR and/or restriction enzymes) into a plasmid (known as an expression vector). A vector has 3 distinctive features: an origin of replication, a multiple cloning site (MCS), and a selective marker (usually antibiotic resistance). The origin of replication will have promoter regions upstream from the replication/transcription start site.
This plasmid can be inserted into either bacterial or animal cells. Introducing DNA into bacterial cells can be done by transformation (via uptake of naked DNA), conjugation (via cell-cell contact) or by transduction (via viral vector). Introducing DNA into eukaryotic cells, such as animal cells, by physical or chemical means is called transfection. Several different transfection techniques are available, such as calcium phosphate transfection, electroporation, microinjection and liposome transfection. DNA can also be introduced into eukaryotic cells using viruses or bacteria as carriers, the latter is sometimes called bactofection and in particular uses Agrobacterium tumefaciens. The plasmid may be integrated into the genome, resulting in a stable transfection, or may remain independent of the genome, called transient transfection.
In either case, DNA coding for a protein of interest is now inside a cell, and the protein can now be expressed. A variety of systems, such as inducible promoters and specific cell-signaling factors, are available to help express the protein of interest at high levels. Large quantities of a protein can then be extracted from the bacterial or eukaryotic cell. The protein can be tested for enzymatic activity under a variety of situations, the protein may be crystallized so its tertiary structure can be studied, or, in the pharmaceutical industry, the activity of new drugs against the protein can be studied.
[edit]Polymerase chain reaction (PCR)
Main article: Polymerase chain reaction
The polymerase chain reaction is an extremely versatile technique for copying DNA. In brief, PCR allows a single DNA sequence to be copied (millions of times), or altered in predetermined ways. For example, PCR can be used to introduce restriction enzyme sites, or to mutate (change) particular bases of DNA, the latter is a method referred to as "Quick change". PCR can also be used to determine whether a particular DNA fragment is found in a cDNA library. PCR has many variations, like reverse transcription PCR (RT-PCR) for amplification of RNA, and, more recently, real-time PCR (QPCR) which allow for quantitative measurement of DNA or RNA molecules.
[edit]Gel electrophoresis
Main article: Gel electrophoresis
Gel electrophoresis is one of the principal tools of molecular biology. The basic principle is that DNA, RNA, and proteins can all be separated by means of an electric field. In agarose gel electrophoresis, DNA and RNA can be separated on the basis of size by running the DNA through an agarose gel. Proteins can be separated on the basis of size by using an SDS-PAGE gel, or on the basis of size and their electric charge by using what is known as a 2D gel electrophoresis.
[edit]Macromolecule blotting and probing
The terms northern, western and eastern blotting are derived from what initially was a molecular biology joke that played on the term Southern blotting, after the technique described by Edwin Southern for the hybridisation of blotted DNA. Patricia Thomas, developer of the RNA blot which then became known as the northern blot actually didn't use the term.[2] Further combinations of these techniques produced such terms as southwesterns (protein-DNA hybridizations), northwesterns (to detect protein-RNA interactions) and farwesterns (protein-protein interactions), all of which are presently found in the literature.
[edit]Southern blotting
Main article: Southern blot
Named after its inventor, biologist Edwin Southern, the Southern blot is a method for probing for the presence of a specific DNA sequence within a DNA sample. DNA samples before or after restriction enzyme digestion are separated by gel electrophoresis and then transferred to a membrane by blotting via capillary action. The membrane is then exposed to a labeled DNA probe that has a complement base sequence to the sequence on the DNA of interest. Most original protocols used radioactive labels, however non-radioactive alternatives are now available. Southern blotting is less commonly used in laboratory science due to the capacity of other techniques, such as PCR, to detect specific DNA sequences from DNA samples. These blots are still used for some applications, however, such as measuring transgene copy number in transgenic mice, or in the engineering of gene knockout embryonic stem cell lines.
[edit]Northern blotting
Main article: northern blot
The northern blot is used to study the expression patterns of a specific type of RNA molecule as relative comparison among a set of different samples of RNA. It is essentially a combination of denaturing RNA gel electrophoresis, and a blot. In this process RNA is separated based on size and is then transferred to a membrane that is then probed with a labeled complement of a sequence of interest. The results may be visualized through a variety of ways depending on the label used; however, most result in the revelation of bands representing the sizes of the RNA detected in sample. The intensity of these bands is related to the amount of the target RNA in the samples analyzed. The procedure is commonly used to study when and how much gene expression is occurring by measuring how much of that RNA is present in different samples. It is one of the most basic tools for determining at what time, and under what conditions, certain genes are expressed in living tissues.
[edit]Western blotting
Main article: western blot
Antibodies to most proteins can be created by injecting small amounts of the protein into an animal such as a mouse, rabbit, sheep, or donkey (polyclonal antibodies) or produced in cell culture (monoclonal antibodies). These antibodies can be used for a variety of analytical and preparative techniques.
In western blotting, proteins are first separated by size, in a thin gel sandwiched between two glass plates in a technique known as SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis). The proteins in the gel are then transferred to a PVDF, nitrocellulose, nylon or other support membrane. This membrane can then be probed with solutions of antibodies. Antibodies that specifically bind to the protein of interest can then be visualized by a variety of techniques, including colored products, chemiluminescence, or autoradiography. Often, the antibodies are labeled with enzymes. When a chemiluminescent substrate is exposed to the enzyme it allows detection. Using western blotting techniques allows not only detection but also quantitative analysis.
Analogous methods to western blotting can be used to directly stain specific proteins in live cells or tissue sections. However, these immunostaining methods, such as FISH, are used more often in cell biology research.
[edit]Eastern blotting
Main article: Eastern blotting
Eastern blotting technique is to detect post-translational modification of proteins.[3] Proteins blotted on to the PVDF or nitrocellulose membrane are probed for modifications using specific substrates.
[edit]Arrays
Main article: DNA microarray
A DNA array is a collection of spots attached to a solid support such as a microscope slide where each spot contains one or more single-stranded DNA oligonucleotide fragment. Arrays make it possible to put down large quantities of very small (100 micrometre diameter) spots on a single slide. Each spot has a DNA fragment molecule that is complementary to a single DNA sequence (similar to Southern blotting). A variation of this technique allows the gene expression of an organism at a particular stage in development to be qualified (expression profiling). In this technique the RNA in a tissue is isolated and converted to labeled cDNA. This cDNA is then hybridized to the fragments on the array and visualization of the hybridization can be done. Since multiple arrays can be made with exactly the same position of fragments they are particularly useful for comparing the gene expression of two different tissues, such as a healthy and cancerous tissue. Also, one can measure what genes are expressed and how that expression changes with time or with other factors. For instance, the common baker's yeast, Saccharomyces cerevisiae, contains about 7000 genes; with a microarray, one can measure qualitatively how each gene is expressed, and how that expression changes, for example, with a change in temperature. There are many different ways to fabricate microarrays; the most common are silicon chips, microscope slides with spots of ~ 100 micrometre diameter, custom arrays, and arrays with larger spots on porous membranes (macroarrays). There can be anywhere from 100 spots to more than 10,000 on a given array.
Arrays can also be made with molecules other than DNA. For example, an antibody array can be used to determine what proteins or bacteria are present in a blood sample.
[edit]Allele-specific oligonucleotide
Allele-specific oligonucleotide (ASO) is a technique that allows detection of single base mutations without the need for PCR or gel electrophoresis. Short (20-25 nucleotides in length), labeled probes are exposed to the non-fragmented target DNA. Hybridization occurs with high specificity due to the short length of the probes and even a single base change will hinder hybridization. The target DNA is then washed and the labeled probes that didn't hybridize are removed. The target DNA is then analyzed for the presence of the probe via radioactivity or fluorescence. In this experiment, as in most molecular biology techniques, a control must be used to ensure successful experimentation. The Illumina Methylation Assay is an example of a method that takes advantage of the ASO technique to measure one base pair differences in sequence.[citation needed]
[edit]Antiquated technologies
In molecular biology, procedures and technologies are continually being developed and older technologies abandoned. For example, before the advent of DNA gel electrophoresis (agarose or polyacrylamide), the size of DNA molecules was typically determined by rate sedimentation in sucrose gradients, a slow and labor-intensive technique requiring expensive instrumentation; prior to sucrose gradients, viscometry was used.
Aside from their historical interest, it is often worth knowing about older technology, as it is occasionally useful to solve another new problem for which the newer technique is inappropriate.
[edit]History

Main article: History of molecular biology
While molecular biology was established in the 1930s, the term was coined by Warren Weaver in 1938. Warren was the director of Natural Sciences for the Rockefeller Foundation at the time and believed that biology was about to undergo a period of significant change given recent advances in fields such as X-ray crystallography. He therefore channeled significant amounts of (Rockefeller Institute) money into biological fields.
[edit]Clinical significance

Clinical research and medical therapies arising from molecular biology are partly covered under gene therapy[citation needed]. The use of molecular biology or molecular cell biology approaches in medicine is now called molecular medicine. Molecular biology also plays important role in understanding formations, actions, regulations of various parts of cells which can be used efficiently for targeting new drugs, diagnosis of disease, physiology of Cell.

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.
The visual system in humans and animals allows individuals to assimilate information from the surroundings. 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.
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.
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) is believed to be 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.
[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[8] in picture viewing[9] and later in visual problem solving[10] and when headset-cameras became available, also during driving.[11]
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.[12]
[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.[13]
[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.[14] 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?" [15]
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.[16]
[edit]Transduction

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.[17]
[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.[17]
[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.

Emission theory (vision)

Emission theory or extramission theory is the proposal that visual perception is accomplished by rays of light emitted by the eyes. This theory has been replaced by intromission theory, which states that visual perception comes from something representative of the object (later established to be rays of light reflected from it) entering the eyes. Modern physics has confirmed that light is physically transmitted by photons, from a light source such as the sun, to visible objects, and finishing with the detector, such as a human eye or camera.
In the fifth century BCE, Empedocles postulated that everything was composed of four elements; fire, air, earth and water. He believed that Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible. If this were true, then one could see during the night just as well as during the day, so Empedocles postulated an interaction between rays from the eyes and rays from a source such as the sun.
Around 400 BCE, emission theory was held by Plato.[1]
In about 300 BCE, Euclid wrote Optica, in which he studied the properties of light. Euclid postulated that light travelled in straight lines and he described the laws of reflection and studied them mathematically. He questioned that sight is the result of a beam from the eye, for he asked how one sees the stars immediately, if one closes one's eyes, then opens them at night. Of course if the beam from the eye travels infinitely fast this is not a problem.
In 55 BCE, Lucretius, a Roman who carried on the ideas of earlier Greek atomists, wrote:
The light and heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove. – On the nature of the Universe
Despite being similar to later particle theories, Lucretius's views were not generally accepted and light was still theorized as emanating from the eye.
Ptolemy (c. 2nd century) wrote about the refraction of light, and developed a theory of vision that objects are seen by rays of light emanating from the eyes.
The dispute over the emission and Aristotelian intromission theories of vision began to settle during 11th century when the experiments of the Arabian physicist, Ibn al-Haytham (Alhazen, 965-1039) lent support to the intromissionist theory in his Book of Optics.
Adherents of emission theory cited at least two lines of evidence for it.
The custom of saluting is said by some to stem from the habit of Greek soldiers putting their hands up in front of their eyes to "shade" their eyes from the powerful "light" shining from the eyes of their commanders. The light from the eyes of some animals (such as cats, which modern science has determined merely have highly reflective eyes) could also be seen in "darkness". Adherents of intromission theory countered by saying that if emission theory were true, then someone with weak eyes should have his or her vision improved when someone with good eyes looks at the same objects.[2]
Most argue that Euclid's version of emission theory was purely metaphorical, highlighting only the geometrical relations between eyes and objects. The geometry of classical optics is equivalent no matter which direction light is considered to be moving in, since light is modeled by its path, not as a moving object. (Direction of propagation is important, however, in the modern theory of special relativity.)
Measuring the speed of light was one line of evidence that spelled the end of emission theory as anything other than a metaphor.
Winer et al. (2002) have found recent evidence that as many as 50% of American college students believe in emission theory.[3]
Modern computer graphics programs that use ray tracing often trace lines of sight from "eyes" to objects and thence to light sources to determine the colour and luminance of pixels in a simulated scene. This avoids the extra computation that would be required to trace rays which do not intersect with "eyes", and which by definition do not contribute to the simulated image.

Cataract surgery: characteristics and opinions of patients with monocular versus binocular vision

[Cataract surgery: characteristics and opinions of patients with monocular versus binocular vision].
[Article in Portuguese]
Marback RF, Temporini ER, Kara Júnior N.
Source
Hospital das Clínicas, Universidade de São Paulo, SP, Brasil. robertamarback@uol.com.br
Abstract
PURPOSE:
To verify in two groups of patients: monocular (group 1) and binocular vision (group 2) to be submitted to cataract surgery at an University Hospital, opinions, expectances and emotional reactions related to the ocular problem, to the quality of vision and to cataract surgery.
METHODS:
A transversal comparative and consecutive study was performed using a structured questionnaire applied by patients interview. The questionnaire was elaborated from a previous exploratory study; visual acuity and cause of the visual loss were evaluated.
RESULTS:
The sample was constituted by 96 persons of group 1 (50.0% male; 50.0% female, ages ranging from 41 to 91 years; average 69.3 years ± 10.4 years) and 110 persons of group 2 (40.9% male; 59.1% female, ages ranging from 40 to 89 years; average 68.2 years ± 10.2 years). The majority of persons of both groups presented low educational level. There was no statistically significant difference between the groups in relation to gender (p=0.191), age (p=0.702) and educational level (p=0.245). No work activity was mentioned in 95.8% of the persons of group 1 and 83.6% of group 2 (p=0.005) and 30.4% of group 1 informed the impossibility to work due the visual impairment. Visual acuity of the eye to be operated was less than 0.05 in 40.6% (group 1) and in 33,6% (group 2), presented visual acuity ranging from 0.05 to 0.25. Almost the totality of the persons of both groups informed difficulties to perform activities of daily life and qualified as insufficient their visual acuities; 71.9% of the patients of group 1 and 71.6% of group 2 informed to know the reason of low vision; among these, 87.1% of group 1 and 83.3% of group 2 mentioned cataract as the reason of low visual acuity.
CONCLUSION:
It was concluded that the patients of both groups were submitted to cataract surgery with visual acuities less than the visual acuity ideally indicated; the patients with monocular vision showed visual acuities significantly less in relation to the patients with binocular vision; the majority of the patients of both groups mentioned difficulties to perform daily activities as a consequence of low vision; patients with monocular vision mentioned doubts in relation to the surgical results as compared with the patients with binocular vision; many patients of both groups did not know the cause of the visual difficulty or explained the visual difficulty by other cause than the cataract.

Encoding visual information in retinal ganglion cells with prosthetic stimulation

Encoding visual information in retinal ganglion cells with prosthetic stimulation.
Freeman DK, Rizzo JF 3rd, Fried SI.
Source
Center for Innovative Visual Rehabilitation, Boston VA Healthcare System, 150 South Huntington Ave, Boston, MA 02130, USA. dfreeman@mit.edu
Abstract
Retinal prostheses aim to restore functional vision to those blinded by outer retinal diseases using electric stimulation of surviving retinal neurons. The ability to replicate the spatiotemporal pattern of ganglion cell spike trains present under normal viewing conditions is presumably an important factor for restoring high-quality vision. In order to replicate such activity with a retinal prosthesis, it is important to consider both how visual information is encoded in ganglion cell spike trains, and how retinal neurons respond to electric stimulation. The goal of the current review is to bring together these two concepts in order to guide the development of more effective stimulation strategies. We review the experiments to date that have studied how retinal neurons respond to electric stimulation and discuss these findings in the context of known retinal signaling strategies. The results from such in vitro studies reveal the advantages and disadvantages of activating the ganglion cell directly with the electric stimulus (direct activation) as compared to activation of neurons that are presynaptic to the ganglion cell (indirect activation). While direct activation allows high temporal but low spatial resolution, indirect activation yields improved spatial resolution but poor temporal resolution. Finally, we use knowledge gained from in vitro experiments to infer the patterns of elicited activity in ongoing human trials, providing insights into some of the factors limiting the quality of prosthetic vision.

Determinants of social participation of visually impaired older adults

Determinants of social participation of visually impaired older adults.
Alma MA, Van der Mei SF, Groothoff JW, Suurmeijer TP.
Source
Department of Health Sciences, University Medical Center Groningen, University of Groningen, PO Box 196, 9700 AD Groningen, The Netherlands. m.a.alma@med.umcg.nl
Abstract
PURPOSE:
To assess determinants of social participation among visually impaired older adults.
METHODS:
This cross-sectional study included visually impaired persons (≥55 years; n = 173) who were referred to a low-vision rehabilitation center. Determinants (i.e., sociodemographic, physical, social and psychological factors, and personal values) of participation were identified in four domains of participation: (1) domestic life; (2) interpersonal interactions and relationships; (3) major life areas; and (4) community, social, and civic life. Study participants completed telephone interviews.
RESULTS:
Age, physical fitness, and helplessness were determinants of participation in domestic life. Social network size was associated with participation in major life areas. The personal value attached to participation (i.e., perceived importance) was a determinant of participation in interpersonal interactions and relationships, major life areas, and community, social and civic life. Vision-related characteristics (i.e., self-perceived vision and degree of visual impairment) were not associated with participation.
CONCLUSIONS:
Across the participation domains, perceived importance is a major determinant of social participation among visually impaired older adults. Physical health along with social and psychological status, also affect participation. Knowing how participation is determined can be used to develop rehabilitation interventions to enhance participation of visually impaired older adults.

What does Neural Plasticity Tell us about Role of Primary Visual Cortex (V1) in Visual Awareness?

What does Neural Plasticity Tell us about Role of Primary Visual Cortex (V1) in Visual Awareness?
Silvanto J, Rees G.
Source
Brain Research Unit, Low Temperature Laboratory and Advanced Magnetic Imaging Centre, School of Science and Technology, Aalto University Espoo, Finland.
Abstract
The complete loss of visual awareness resulting from a lesion to the primary visual cortex (V1) suggests that this region is indispensable for conscious visual perception. There are however a number cases of conscious perception in the absence of V1 which appear to challenge this conclusion. These include reports of patients with bilateral V1 lesions sustained at an early age whose conscious vision has spontaneously recovered, as well as stroke patients who have recovered some conscious vision with the help of rehabilitation programs. In addition, the phenomenon of hemianopic completion and percepts induced by brain stimulation suggest that V1 may not be necessary for conscious perception in all circumstances. Furthermore, that the visual abilities in the cat are associated with the recovery of normal extrastriate tuning properties rather than emulation of V1 functions suggests that there is nothing unique about the functional properties of this region in visual awareness. Rather, the dramatic effect of a V1 lesion on visual awareness may be due to its role in providing the majority of extrastriate visual input, the loss of which abolishes normal neural responsiveness throughout the visual cortex.

Abandonment of low-vision devices in an outpatient population

Abandonment of low-vision devices in an outpatient population.
Dougherty BE, Kehler KB, Jamara R, Patterson N, Valenti D, Vera-Diaz FA.
Source
The Ohio State University College of Optometry, Columbus, Ohio 43210, USA. bdougherty@optometry.osu.edu
Abstract
PURPOSE:
To investigate abandonment rate of prescribed low-vision devices for near tasks and factors associated with abandonment in a U.S. outpatient population.
METHODS:
A telephone survey was administered to 88 patients with low vision from four clinical sites about 1 year after examination and prescription of devices. Patients were surveyed on timing and frequency of use and reasons for abandonment of devices. The main outcome measure (abandonment) was defined as patient report of no use of prescribed device in the previous 3 months. Multivariate logistic regression was used to investigate significant vision and demographic factors related to abandonment.
RESULTS:
Of 119 prescribed devices, 19% (95% CI, 12 to 26) had not been used within the previous 3 months. Mean (±SD) better eye visual acuity at examination was 0.61 ± 0.29 logMAR, and mean age was 77 ± 17 years. Mean time between device prescription and survey was 11 ± 3 months. Device abandonment was not associated with age (p = 0.863), time since prescription (p = 0.125), visual acuity (p = 0.804), or category of magnification device (spectacle, handheld, stand, or video) (p = 0.412). There was a significant association between documented non-central visual field loss and abandonment of magnification device (p = 0.046). Repeat administration of the survey resulted in the same abandonment classification in 15 of 15 patients (100%).
CONCLUSIONS:
Abandonment rate was similar for this outpatient population to those previously reported in the U.S. veteran inpatient population and in other countries. Patients with visual field loss may be more likely to abandon prescribed devices.

Disparities in awareness and use of low-vision rehabilitation

Disparities in awareness and use of low-vision rehabilitation.
Mwilambwe A, Wittich W, Freeman EE.
Source
Department of Ophthalmology, University of Montreal, Montreal, QC.
Abstract
OBJECTIVE:
To describe the demographic, visual, health, and psychological variables associated with awareness and use of low-vision rehabilitation services in Montreal, Que.
STUDY DESIGN:
Hospital-based cross-sectional study.
PARTICIPANTS:
Four hundred forty-eight patients with best-corrected visual acuity worse than 20/70 in their better eye recruited from 4 ophthalmology departments.
METHODS:
Patients answered questions about their awareness and use of low-vision services. Visual acuity was recorded and patients answered the Brief Cope and Center for Epidemiologic Studies - Depression Scale questionnaires and provided information on demographics and health status. Multiple logistic regression was used to identify independent predictors of awareness and use of low-vision rehabilitation services.
RESULTS:
A majority of patients in the sample (71%) were aware of low-vision rehabilitation. Of those who were aware, 81% reported participating in low-vision rehabilitation. Black patients, those whose first language was French, those with less severe visual acuity loss, and those who reported less acceptance on the Brief Cope questionnaire were less likely to know about low-vision services (p < 0.05). Of those who knew about low-vision services, those with less severe visual acuity loss were less likely to have participated in low-vision services (p < 0.05).
CONCLUSIONS:
It is important that all those who qualify for low-vision rehabilitation services can access them. Although the patients in this Montreal area study showed a high rate of awareness and use of low-vision rehabilitation, awareness and use could be improved in certain demographic populations and in those with less severe vision loss.

Barriers to low vision rehabilitation: the Montreal Barriers Study

Barriers to low vision rehabilitation: the Montreal Barriers Study.
Overbury O, Wittich W.
Source
School of Optometry, University of Montreal, Montreal, Quebec, Canada. olga.overbury@umontreal.ca
Abstract
PURPOSE:
One objective of the Montreal Barriers Study was to examine demographic characteristics of people with vision impairment that may hinder their referral or decision to access rehabilitation services.
METHODS:
Data collection was conducted in three phases, whereby during phase I, patients in ophthalmology department waiting rooms underwent a structured interview to ascertain demographic variables that may be related to their utilization of the rehabilitation process. Phase II examined variables recorded in the rehabilitation agency file of those who had made the choice to access services. Phase III examined the rehabilitation access behavior of those participants who were referred as part of phase I.
RESULTS:
In phase I, 54% of the 702 participants had been referred to and received rehabilitation services. An additional 13% were aware of these services but chose not to access them, whereas 33% were unaware of their existence. The variables associated with positive access choice were education, diagnosis, race, acuity at the time of interview, and living situation. In phase II, it was found that acuity at agency intake was markedly better than at the study interview. Of the participants who were referred to rehabilitation services as part of the phase I protocol, it was found in phase III that only 56% had engaged in rehabilitation services.
CONCLUSIONS:
It seems that even under ideal referral situations, there remain barriers to vision rehabilitation services that have not been specifically identified in the present study. Further research is necessary on the psychological and psychosocial contributors to this process.

Rehabilitation of vision disorder and improved quality of life in patients with primary open angle glaucoma

Rehabilitation of vision disorder and improved quality of life in patients with primary open angle glaucoma.
Luo RJ, Liu SR, Tian Z, Zhu WH, Zhuo YH, Liao RD.
Source
Department of Ophthalmology, First Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510080, China.
Abstract
BACKGROUND:
Primary open angle glaucoma (POAG) is a common cause of irreversible blindness. The variable etiology of POAG poses significant challenges for treatment and rehabilitation. We analyzed a large POAG patient cohort during treatment to reveal possible causes of vision disorder, assess vision-related quality of life (VRQL), and to evaluate the efficacy of rehabilitative treatments.
METHODS:
We analyzed the visional disturbances in 500 POAG patients (890 eyes) by regular ophthalmic examination and visual field examination using Humphrey 30° perimetry. Appropriate rehabilitative treatments for POAG were prescribed based on results of clinical examination and included correction of ametropia, health education, counseling, and the fitting of typoscopes. VRQL was assessed before and after treatment by a VRQL self-assessment questionnaire.
RESULTS:
Scores on the VRQL self-assessment were significantly lower compared to healthy controls. The primary cause of the vision disturbances was ametropia (97.99%), and 51.61% of the ametropia eyes had not received appropriate correction. The secondary causes of visual impairment were glaucomatous neurodegeneration (26.29%), complicated cataract, or other accompanying eye diseases. The causes of the clinical low vision (44 patients) were glaucomatous neurodegeneration (32 eyes), fundus diseases (23 eyes), keratopathy (11 eyes), and other eye diseases (10 eyes). The VRQL scores of patients improved significantly after rehabilitation and the correction of ametropia (P < 0.01). Twenty-five patients with low vision were provided with typoscopes, and 21 (84%) experienced significant functional recovery, while the remaining low vision patients could see letter lines two or more levels lower (smaller) on visual charts in a near vision test.
CONCLUSIONS:
Vision disorders in POAG patients are common and severe. Appropriate rehabilitation, especially the correction of ametropia, can significantly improve VRQL as revealed by the self-assessment of POAG patients.

Reducing crowding by weakening inhibitory lateral interactions in the periphery with perceptual learning

Reducing crowding by weakening inhibitory lateral interactions in the periphery with perceptual learning.
Maniglia M, Pavan A, Cuturi LF, Campana G, Sato G, Casco C.
Source
Department of General Psychology, University of Padua, Padua, Italy. marcello.maniglia@studenti.unipd.it
Abstract
We investigated whether lateral masking in the near-periphery, due to inhibitory lateral interactions at an early level of central visual processing, could be weakened by perceptual learning and whether learning transferred to an untrained, higher-level lateral masking known as crowding. The trained task was contrast detection of a Gabor target presented in the near periphery (4°) in the presence of co-oriented and co-aligned high contrast Gabor flankers, which featured different target-to-flankers separations along the vertical axis that varied from 2λ to 8λ. We found both suppressive and facilitatory lateral interactions at target-to-flankers distances (2λ - 4λ and 8λ, respectively) that were larger than those found in the fovea. Training reduces suppression but does not increase facilitation. Most importantly, we found that learning reduces crowding and improves contrast sensitivity, but has no effect on visual acuity (VA). These results suggest a different pattern of connectivity in the periphery with respect to the fovea as well as a different modulation of this connectivity via perceptual learning that not only reduces low-level lateral masking but also reduces crowding. These results have important implications for the rehabilitation of low-vision patients who must use peripheral vision to perform tasks, such as reading and refined figure-ground segmentation, which normal sighted subjects perform in the fovea.

Attentional demands of movement observation as tested by a dual task approach

Attentional demands of movement observation as tested by a dual task approach.
Saucedo Marquez CM, Ceux T, Wenderoth N.
Source
Group Biomedical Sciences, Department of Biomedical Kinesiology, Research Centre for Motor Control and Neuroplasticity, KULeuven, Heverlee, Belgium.
Abstract
Movement observation (MO) has been shown to activate the motor cortex of the observer as indicated by an increase of corticomotor excitability for muscles involved in the observed actions. Moreover, behavioral work has strongly suggested that this process occurs in a near-automatic manner. Here we further tested this proposal by applying transcranial magnetic stimulation (TMS) when subjects observed how an actor lifted objects of different weights as a single or a dual task. The secondary task was either an auditory discrimination task (experiment 1) or a visual discrimination task (experiment 2). In experiment 1, we found that corticomotor excitability reflected the force requirements indicated in the observed movies (i.e. higher responses when the actor had to apply higher forces). Interestingly, this effect was found irrespective of whether MO was performed as a single or a dual task. By contrast, no such systematic modulations of corticomotor excitability were observed in experiment 2 when visual distracters were present. We conclude that interference effects might arise when MO is performed while competing visual stimuli are present. However, when a secondary task is situated in a different modality, neural responses are in line with the notion that the observers motor system responds in a near-automatic manner. This suggests that MO is a task with very low cognitive demands which might be a valuable supplement for rehabilitation training, particularly, in the acute phase after the incident or in patients suffering from attention deficits. However, it is important to keep in mind that visual distracters might interfere with the neural response in M1.

The impact of low vision on activities of daily living, symptoms of depression, feelings of anxiety and social support in community-living older adults seeking vision rehabilitation services

The impact of low vision on activities of daily living, symptoms of depression, feelings of anxiety and social support in community-living older adults seeking vision rehabilitation services.
Kempen GI, Ballemans J, Ranchor AV, van Rens GH, Zijlstra GA.
Source
Department of Health Services Research, and CAPHRI School for Public Health and Primary Care, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. G.Kempen@maastrichtuniversity.nl
Erratum in
Qual Life Res. 2012 Oct;21(8):1413.
Abstract
PURPOSE:
Previous studies showed that older persons with vision loss generally reported low levels of health-related quality of life, although study outcomes with respect to feelings of anxiety and social support were inconsistent. The objective of this study was to examine the impact of low vision on health-related quality of life, including feelings of anxiety and social support, among community-living older adults seeking vision rehabilitation services.
METHODS:
Differences of activities of daily living (Groningen Activity Restriction Scale-GARS), symptoms of depression and feelings of anxiety (Hospital Anxiety and Depression Scales-HADS) and social support (Social Support Scale Interactions-SSL12-I) between 148 older persons ≥57 years with low vision and a reference population (N = 4,792) including eight patient groups with different chronic conditions were tested with Student's t tests.
RESULTS:
Older persons with vision loss reported poorer levels of functioning with respect to activities of daily living, symptoms of depression and feelings of anxiety as compared to the general older population as well as compared to older patients with different chronic conditions. In contrast, older persons with vision loss reported higher levels of social support.
CONCLUSIONS:
Vision loss has a substantial impact on activities of daily living, symptoms of depression and feelings of anxiety. Professionals working at vision rehabilitation services may improve their quality of care as they take such information into account in their intervention work.

A study of eccentric viewing training for low vision rehabilitation

A study of eccentric viewing training for low vision rehabilitation.
Jeong JH, Moon NJ.
Source
Department of Ophthalmology, Chung-Ang University College of Medicine, Seoul, Korea.
Abstract
PURPOSE:
The definition of eccentric viewing (EV) is using non-foveal preferred retinal loci (PRL) for viewing. The purpose of the present study was to investigate the clinical effect of EV training for low vision rehabilitation in patients with central scotomas.
METHODS:
The direction of EV was monitored in 30 low vision patients with central scotomas by moving the patient's view. The PRL was found by using a direct ophthalmoscope and retinal camera; the preserved visual field was identified using a kinetic visual field analyzer. The relationships between EV, PRL, and visual field were evaluated. The patients and their guardians were educated regarding EV. After 2 weeks of self-training, maintenance of EV was checked and changes in best-corrected visual acuity (BCVA), reading speed, and satisfaction questionnaire were evaluated.
RESULTS:
A relationship between EV, PRL, and visual field was in accordance in half of the patients. There were no significant differences in demographics and basic visual characteristics in patients where the relationship was not in accordance. EV was maintained in two-thirds of the patients, but there were no significant differences in demographics and basic visual characteristics in patients who discontinued EV. There were no significant improvements in BCVA; however, reading speed and the satisfaction scores increased significantly with EV.
CONCLUSIONS:
The direction of EV was effectively detected by convenient access using an inexpensive method. Functional vision and satisfaction significantly improved following EV training. EV training can be used as an effective method for low vision rehabilitation in patients with central scotomas.

Effect of depression on actual and perceived effects of reading rehabilitation for people with central vision loss

Effect of depression on actual and perceived effects of reading rehabilitation for people with central vision loss.
Grant P, Seiple W, Szlyk JP.
Source
The Chicago Lighthouse for People Who Are Blind or Visually Impaired, Low Vision Research Laboratory, 1850 W. Roosevelt Rd, Chicago, IL 60616, USA. patricia.grant@chicagolighthouse.org
Abstract
To investigate the relationship between depression and quantitative measures of visual function, we recruited 18 subjects with central scotomas from macular degeneration who were enrolled in a reading rehabilitation program. Psychological batteries and reading assessments were administered prior to rehabilitation; reading assessments and a measure of adaptation to vision loss were administered following rehabilitation. We investigated relationships between reported levels of depressive symptoms and reading and adaptation outcome measures by using Pearson product moment correlation analysis. Results revealed a significant relationship between depression levels and reading acuity difference scores (r(16) = 0.54, p = 0.02) and changes in adaptation to vision loss levels (r(16) = 0.62, p = 0.01), suggesting that those who reported greater depressive symptoms did not respond as well functionally to reading rehabilitation but reported greater improvement in levels of adaptation to vision loss following rehabilitation. Future research should focus on defining standard methods to assess and remediate depression as part of the rehabilitation process.

Implantation and explantation of an active epiretinal visual prosthesis: 2-year follow-up data from the EPIRET3 prospective clinical trial

Implantation and explantation of an active epiretinal visual prosthesis: 2-year follow-up data from the EPIRET3 prospective clinical trial.
Menzel-Severing J, Laube T, Brockmann C, Bornfeld N, Mokwa W, Mazinani B, Walter P, Roessler G.
Source
Department of Ophthalmology, RWTH Aachen University, Aachen, Germany. johannes.menzelsevering@uk-erlangen.de
Abstract
PURPOSE:
The EPIRET3 retinal prosthesis was implanted in six volunteers legally blind from retinitis pigmentosa (RP) and removed after 4 weeks. Two years later, these subjects were re-examined to investigate ocular side effects and potential changes to quality of life.
METHODS:
Vision-related quality of life was recorded using the NEI-VFQ-25 questionnaire. Clinical data including interval history, visual acuity, and intraocular pressure were obtained. Anterior and posterior segments of the study eyes were examined and photographed; this included fluorescein angiography and optical coherence tomography (OCT).
RESULTS:
Data from five patients could be analysed. Life-quality score was consistent with results obtained at baseline. No unexpected structural alteration could be found in the study eyes. A moderate epiretinal gliosis was present in areas where the epiretinal stimulator had been fixated using retinal tacks. Angiography revealed no leakage or neovascularisation; OCT showed no generalised increase of central retinal thickness.
CONCLUSIONS:
Vision-related quality of life is low in patients suffering from end-stage RP. No further deterioration of life quality could however be detected within our monitoring period. Surgery was well tolerated by both patients and their eyes, without adverse events occurring during the follow-up period. Epiretinal gliosis is known to occur with retinal tacks, but seems of no major concern to the integrity of the study eyes. However, it may potentially interfere with functional aspects of active implants. Hence, alternative, possibly biochemical, fixation methods merit further research.

Methods for automated identification of informative behaviors in natural bioptic driving

Methods for automated identification of informative behaviors in natural bioptic driving.
Luo G, Peli E.
Source
Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, MA 02114, USA. gang.luo@schepens.harvard.edu
Abstract
Visually impaired people may legally drive if wearing bioptic telescopes in some developed countries. To address the controversial safety issue of the practice, we have developed a low-cost in-car recording system that can be installed in study participants' own vehicles to record their daily driving activities. We also developed a set of automated identification techniques of informative behaviors to facilitate efficient manual review of important segments submerged in the vast amount of uncontrolled data. Here, we present the methods and quantitative results of the detection performance for six types of driving maneuvers and behaviors that are important for bioptic driving: bioptic telescope use, turns, curves, intersections, weaving, and rapid stops. The testing data were collected from one normally sighted and two visually impaired subjects across multiple days. The detection rates ranged from 82% up to 100%, and the false discovery rates ranged from 0% to 13%. In addition, two human observers were able to interpret about 80% of targets viewed through the telescope. These results indicate that with appropriate data processing the low-cost system is able to provide reliable data for natural bioptic driving studies.

Comorbid cognitive impairment and functional trajectories in low vision rehabilitation for macular disease

Comorbid cognitive impairment and functional trajectories in low vision rehabilitation for macular disease.
Whitson HE, Ansah D, Sanders LL, Whitaker D, Potter GG, Cousins SW, Steffens DC, Landerman LR, Pieper CF, Cohen HJ.
Source
Aging Center, Duke University Medical Center, DUMC 3003, Durham, NC 27710, USA. heather.whitson@duke.edu
Abstract
BACKGROUND AND AIMS:
Comorbid cognitive impairment is common among visually impaired older adults. This study investigated whether baseline cognitive status predicts functional trajectories among older adults in low vision rehabilitation (LVR) for macular disease.
METHODS:
The Telephone Interview for Cognitive Status - modified (TICS-m) was administered to macular disease patients aged ≥ 65 years receiving outpatient LVR. Mixed models assessed the rate of change in instrumental activities of daily living and visual function measures over a mean follow-up of 115 days.
RESULTS:
Of 91 participants, 17 (18.7%) had cognitive impairment (TICS-m score ≤ 27) and 23 (25.3%) had marginal impairment (TICS-m scores 28 to 30). Controlling for age and gender, baseline cognitive status did not predict most functional outcomes. However, participants with marginal cognitive impairment experienced worse functional trajectories in ability to prepare meals (p=0.03) and activities that require distance vision (p=0.05).
CONCLUSION:
Patients with mild to moderate cognitive impairment should not be excluded from LVR, but programs should be prepared to detect and accommodate a range of cognitive ability.