All About the Eye and Vision - Diseases - Wikipedia
An eye is an organ of vision that detects light. Different kinds of light-sensitive organs are found in a variety of organisms. The simplest eyes do nothing but detect whether the surroundings are light or dark, while more complex eyes can distinguish shapes and colors. Many animals, including some mammals, birds, reptiles and fish, have two eyes which may be placed on the same plane to be interpreted as a single three-dimensional "image" (binocular vision), as in humans; or on different planes producing two separate "images" (monocular vision), such as in rabbits and chameleons.
Scientists can tell date of birth by looking into eyes Telegraph.co.uk - February 26, 2008
Vision Loss Treatment For Age-related Macular Degeneration Looks Hopeful Science Daily - February 21, 2008
... a blinding eye disease that affects millions of people.
Macular Degeneration Wikipedia
New Contact Lenses Go Bionic Live Science - January 19, 2008
Gene therapy aimed at restoring sight for 30,000 people Guardian - May 2, 2007
Bionic Eyes Plug Directly into the Brain Live Science - April 27, 2007
Deep brain implants show bionic vision promise New Scientist - April 23, 2007
How irises 'reveal personality types BBC - February 20, 2007
How Do We See Red? Count the Ways NY Times - February 6, 2007
Genetics of eye colour unlocked BBC - December 20, 2006
Prosopagnosis: Inability to recognize faces BBC - July 27, 2006
Seeing double: brainwaves offer scientists key to unraveling how optical illusions trick the mind Scotsman.com - May 22, 2006
First Picture of Living Human Retina Reveals surprising variation from one person to the next Live Science - November 28, 2005
The Brain Sees What We Don't Live Science - November 1, 2005
Scientists prove blind people can 'see' with sixth sense Scotsman.com - November 1, 2005
New Book Explains Age-Old Mystery Of Geometrical Illusions Science Daily - October 3, 2005
Our eyes perceive only a fraction of the electromagnetic spectrum PhysOrg - September 26, 2005
Erotic images, gore cause temporary "blindness" PhysOrg - August 11, 2005
If your partner seems to be ignoring you after a flash of nudity
on the television screen, it might not be his or her fault.
How the Brain Learns to See PhysOrg - June 9, 2005
The Mystery Of Eye Evolution Science Daily - November 2004
How optical illusions have played with our perception Guardian - October 2004
New York: 7-month-old Is Youngest Recipient Of Artificial Corneal Transplant Science Daily - January 2004
The Genetics Of Blindness Science Daily - October 2003
Blind 'see with sound' BBC - October 2003
Human eyes can be in two places at once ABC - July 2003
The German study, which used a sophisticated computer version of the card game 'snap', asked the 15 subjects to concentrate on a point on a computer screen while four different symbols were also flashed on the screen. They had to press a button when they saw two symbols that matched.
Matthias Muller from the University of Leipzig, who led the study, found that the subjects were able to identify when there were two matching symbols on different parts of the screen.
This result helps to answer a long-standing controversy about whether the 'spotlight' of spatial attention only has one beam, or if it can be divided into several locations. The results are published in this week's issue of the journal, Nature. Previous results of many behavioural and electrophysical studies had supported the single spotlight view. But the new research shows that the brain can simultaneously focus on multiple regions, rather than just rapidly switching its attention between them.
The researchers eliminated the possibility of the subjects quickly alternating their vision between the two symbols by flashing the symbols at a rate of 181 milliseconds (thousands of a second). This is faster than humans can switch between two locations, which has previously been measured at between 200 and 500 milliseconds.
Each of the symbols was flickering at a different rate, which meant the researchers could distinguish symbols from one another using their measuring equipment. The subjects, who were linked up to 30 scalp electrodes on an elastic cap, were able to determine when there were two matching symbols - this demonstrates that human eyes are able to focus on two things at once.
"The present findings provide evidence that the spotlight may be divided for sustained periods. This would appear to be a highly efficient early selection mechanism for distributing attention optimally to dispersed stimuli in the visual surroundings," Muller concluded in his paper.
Eye Movement Studies To Help Diagnose Mental Illness Science Daily - June 2003
The Human Eye Can Self-correct Some Optical Faults Science Daily - February 2003
Futuristic System Brings Vision To Blind Science Daily - June 2002
A Japanese embryologist has grown and successfully transplanted artificial frogs' eyes using a type of stem cell
The photograph of the bridge, top, was translated into the middle outline and conveyed through music to a blind subject. The subject produced the bottom image of the bridge using the musical description.
October 29, 2000 - AP
Two blind people in England were able to imagine and draw pictures of cars, buildings, landscapes - even a painting by Cezanne - that were all described to them through music. B.K., a 52-year-old man, and M.S., a 49-year-old woman, both lost their sight over 20 years ago. And yet, by training their ear to listen for images encoded into music, they were able to "see" images in their imagination.
The technique works by using a computer to digitize images and then relay them numerically into musical form. The length of horizontal lines are conveyed by how long a single note is held. Vertical lines are made going up or down the musical scale. The subjects' ears are then trained to hear what a certain line sounded like. For instance, a horizontal line of a certain length that's rising sounds like this, and vert one sounds like that. "So for example, I had an X, two diagonal bars crossing each other, you'd hear notes going down and up at the same time. They reach a point where they're the same note and then they diverge," said co-author Krisha Persaud said.
The subjects picked up the musical clues very quickly, said John Cronly-Dillon, a neuroscientist at England's University of Manchester and lead author of the study. "Within five minutes they can do something simple, like a triangle," he said. The technique wouldn't work on people blind since birth, who have no appropriate reference points in their visual vocabulary.
Distilling complex visual scenes into simple shapes via sound has its origins in artificial intelligence. "Because you want a computer to recognize a scene, the image is fed into the computer and it creates an internal 'image,'" said neuropsychologist and artificial intelligence expert, Richard Gregory at England's University of Bristol. "It's not unlike what we do when our brains take in and interpret an image," he said Pernaud agrees and notes that translating rich, complex images into simple shapes doesn't necessarily limit their functional value.
"It's the same way Picasso did," he said. "Where you can draw a few lines and that could identify an object. So we're not conveying everything there is in vision to a blind person, but we're giving them enough information to actually deal with the world." The study will be published in the Nov. 7 issue of Proceedings B from Britain's Royal Society. "Where we're going with this is hooking it all up to video so they can visualize everything immediately," Cronly-Dillon This would involve attaching video cameras to blind people that would continuously emit sounds corresponding to objects in their environment, allowing them to navigate without help. For example, a manhole would sound like a circle and Christmas tree like a triangle. Right now, B.K. and M.S. are using the video systems to walk about - albeit very slowly with little shuffling steps, said co-author Krisha Persaud.
June 26, 2000 - AP
Scientists have identified the defective gene that causes a debilitating total color-blindness among many inhabitants of a tiny Pacific island. The neurologist Oliver Sacks described the condition in the 1997 book "The Island of the Colorblind." The afflicted islanders see the world as if watching it on a black-and-white television. The discovery of the defective gene ends a 30-year search. Researchers said it will not lead to a treatment immediately but might help find one eventually. It could also lead to a test to tell islanders with normal vision whether they carry a flawed copy of the gene that would raise their children's risk of color-blindness. The disorder appears only in people who inherit a flawed copy from each parent. The island, Pingelap, is part of the Federated States of Micronesia. Of the 3,000 Pingelapese, some of whom live on nearby islands, about one in 20 is totally colorblind. That compares with a worldwide rate of one in 50,000. The flawed gene has been traced back to one man, who was among 20 survivors of a typhoon on Pingelap around 1775 who went on to re-establish the population. The condition differs from the relatively common color-blindness in which people cannot distinguish certain colors. Affected people on the island cannot see colors at all. They lack the sharp vision most people use to read, and their eyes are overwhelmed by sunlight - a particularly severe problem in the tropics.
In his book, Sacks noted that some affected islanders found work fishing by night. "They're about as handicapped as you can be," said Dr. Irene Hussels Maumenee, a member of the research team that first formally described the condition on Pingelap in 1970. "They stay in the cabin all day. They just don't see when they go out in the sunlight," said Maumenee, a professor of ophthalmology and pediatrics at the Johns Hopkins University School of Medicine. Their difficulty in reading hampers their schoolwork, and "people consider them very much as an outcast," she said. She is senior author of the paper announcing the finding of the gene, which appears in the July issue of the journal Nature Genetics. Total color-blindness is called complete achromatopsia. One other flawed gene for the condition had been identified before, but it clearly was not responsible for the problem on Pingelap. The discovery is "a really exciting result," said Maureen Neitz, who studies the genetics of color-blindness at the Medical College of Wisconsin.
June 14, 2000 - AP
Heredity plays a far larger role in the development of cataracts than widely blamed lifestyle factors such as smoking, according to a study. The finding could lead researchers to seek genes linked to cataracts and develop genetic tests to identify those most at risk. "I think this is a real breakthrough study," said Sheila West, a Johns Hopkins University cataract researcher. "I think this is exactly what we've needed to reorient our research on the genetic side."
Cataracts, which are a progressive clouding of the eye's lens, would develop in virtually all people if they lived to be 120 years old. But smoking and steroid drugs are seen as risk factors, while quality of diet and exposure to sunlight have also been implicated. A British team of researchers for the first time quantified the genetic component of age-related cataracts in a study published in Thursday's New England Journal of Medicine. The team studied 506 sets of identical or fraternal female twins ages 50 to 79. Identical twins, who develop from the same egg, are especially useful for such research because they are genetically the same. The researchers worked up an overall cloudiness score for patients' eyes and statistically analyzed the participants' age, heredity, lifestyles and environmental factors. They found that age explained 38 percent of cloudiness, but heredity accounted for even more at 48 percent. The other factors combined for just 14 percent. "It is not just your age that is the cause," said Dr. Christopher Hammond of St. Thomas' Hospital in London, who led the study.
At the same time, researchers cautioned that even 14 percent makes other factors very important, since cataracts are so common. Surgeon routinely operate on cataracts and replace the clouded-over lens with plastic. Congenital and disease-related cataracts are blamed on different causes than age-related cataracts. Another Hammond colleague, Dr. Clare Gilbert, said if future genetic tests identify who is most susceptible to cataracts, those people can then limit their exposure to the risks.
April 27, 2000 - BBC
An "artificial eye" which would allow blind people to see is due to be implanted in a patient within the next few months. The device taps directly into the optic nerve and could restore some measure of sight to people whose retinas have been damaged or destroyed. Visual sensations beamed from a video camera are created in the brain by the artificial eye, developed by a team at the Catholic University of Louvain, in Belgium, directly stimulating different parts of the optic nerve. Other implants being developed stimulate the ganglia cells on the retina or the visual cortex of the brain itself. But the Louvain team, led by Claude Veraart, says these other techniques require large number of electrodes to create images which are recognisable. His device uses a coil to wrap round the optic nerve with only four points of electrical contact.
A video camera, positioned externally, transmits via a radio transmitter and microchip to an implant behind the ear. This is connected to the electrodes on the optic nerve. Different parts of the optic nerve are stimulated by altering the signals, similar to the way in which the electron guns in TVs are aimed at different parts of the screen. Veraart and his colleagues have spent the past two years experimenting with a volunteer who has the electrode implanted, with wires leading out of her body to the signal processor. By asking her to point in response to various stimuli, Veraart and his colleague Charles Trullemans have been able to map camera pixels onto the corresponding parts of her visual field. This was possible, said Veraart in New Scientist magazine, because the subject was once sighted and knows what it means to "look at" something. The researchers hope the device will at least allow blind people to avoid obstacles, though more tests are necessary before the device is implanted. Most critical is the time it takes to realise they are approaching an object. "If it takes her 30 seconds to recognise an obstacle it will be of little use," said Veraart. But if the reaction time is fast, the team plan to implant at least three more patients, starting in August. Rebecca Griffith, health promotion officer for the Royal National Institute for the Blind, in the UK, welcomed the advance but sounded a word of caution.
The photograph of the bridge, top, was translated into the middle outline and conveyed through music to a blind subject. The subject produced the bottom image of the bridge using the musical description.
October 29, 2000 - AP
Two blind people in England were able to imagine and draw pictures of cars, buildings, landscapes - even a painting by Cezanne - that were all described to them through music.
B.K., a 52-year-old man, and M.S., a 49-year-old woman, both lost their sight over 20 years ago. And yet, by training their ear to listen for images encoded into music, they were able to "see" images in their imagination.
The technique works by using a computer to digitize images and then relay them numerically into musical form. The length of horizontal lines are conveyed by how long a single note is held. Vertical lines are made going up or down the musical scale. The subjects' ears are then trained to hear what a certain line sounded like. For instance, a horizontal line of a certain length that's rising sounds like this, and vert one sounds like that.
"So for example, I had an X, two diagonal bars crossing each other, you'd hear notes going down and up at the same time. They reach a point where they're the same note and then they diverge," said co-author Krisha Persaud said.
The subjects picked up the musical clues very quickly, said John Cronly-Dillon, a neuroscientist at England's University of Manchester and lead author of the study.
"Within five minutes they can do something simple, like a triangle," he said.
The technique wouldn't work on people blind since birth, who have no appropriate reference points in their visual vocabulary.
Distilling complex visual scenes into simple shapes via sound has its origins in artificial intelligence.
"Because you want a computer to recognize a scene, the image is fed into the computer and it creates an internal 'image,'" said neuropsychologist and artificial intelligence expert, Richard Gregory at England's University of Bristol.
"It's not unlike what we do when our brains take in and interpret an image," he said
Pernaud agrees and notes that translating rich, complex images into simple shapes doesn't necessarily limit their functional value.
"It's the same way Picasso did," he said. "Where you can draw a few lines and that could identify an object. So we're not conveying everything there is in vision to a blind person, but we're giving them enough information to actually deal with the world."
The study will be published in the Nov. 7 issue of Proceedings B from Britain's Royal Society.
"Where we're going with this is hooking it all up to video so they can visualize everything immediately," Cronly-Dillon
This would involve attaching video cameras to blind people that would continuously emit sounds corresponding to objects in their environment, allowing them to navigate without help. For example, a manhole would sound like a circle and Christmas tree like a triangle.
Right now, B.K. and M.S. are using the video systems to walk about - albeit very slowly with little shuffling steps, said co-author Krisha Persaud.
June 26, 2000 - AP
Scientists have identified the defective gene that causes a debilitating total color-blindness among many inhabitants of a tiny Pacific island.
The neurologist Oliver Sacks described the condition in the 1997 book "The Island of the Colorblind." The afflicted islanders see the world as if watching it on a black-and-white television.
The discovery of the defective gene ends a 30-year search. Researchers said it will not lead to a treatment immediately but might help find one eventually.
It could also lead to a test to tell islanders with normal vision whether they carry a flawed copy of the gene that would raise their children's risk of color-blindness. The disorder appears only in people who inherit a flawed copy from each parent.
The island, Pingelap, is part of the Federated States of Micronesia. Of the 3,000 Pingelapese, some of whom live on nearby islands, about one in 20 is totally colorblind. That compares with a worldwide rate of one in 50,000.
The flawed gene has been traced back to one man, who was among 20 survivors of a typhoon on Pingelap around 1775 who went on to re-establish the population.
The condition differs from the relatively common color-blindness in which people cannot distinguish certain colors. Affected people on the island cannot see colors at all. They lack the sharp vision most people use to read, and their eyes are overwhelmed by sunlight - a particularly severe problem in the tropics.
In his book, Sacks noted that some affected islanders found work fishing by night.
"They're about as handicapped as you can be," said Dr. Irene Hussels Maumenee, a member of the research team that first formally described the condition on Pingelap in 1970.
"They stay in the cabin all day. They just don't see when they go out in the sunlight," said Maumenee, a professor of ophthalmology and pediatrics at the Johns Hopkins University School of Medicine.
Their difficulty in reading hampers their schoolwork, and "people consider them very much as an outcast," she said.
She is senior author of the paper announcing the finding of the gene, which appears in the July issue of the journal Nature Genetics.
Total color-blindness is called complete achromatopsia. One other flawed gene for the condition had been identified before, but it clearly was not responsible for the problem on Pingelap.
The discovery is "a really exciting result," said Maureen Neitz, who studies the genetics of color-blindness at the Medical College of Wisconsin.
June 14, 2000 - AP
Heredity plays a far larger role in the development of cataracts than widely blamed lifestyle factors such as smoking, according to a study.
The finding could lead researchers to seek genes linked to cataracts and develop genetic tests to identify those most at risk.
"I think this is a real breakthrough study," said Sheila West, a Johns Hopkins University cataract researcher. "I think this is exactly what we've needed to reorient our research on the genetic side."
Cataracts, which are a progressive clouding of the eye's lens, would develop in virtually all people if they lived to be 120 years old. But smoking and steroid drugs are seen as risk factors, while quality of diet and exposure to sunlight have also been implicated.
A British team of researchers for the first time quantified the genetic component of age-related cataracts in a study published in Thursday's New England Journal of Medicine.
The team studied 506 sets of identical or fraternal female twins ages 50 to 79. Identical twins, who develop from the same egg, are especially useful for such research because they are genetically the same.
The researchers worked up an overall cloudiness score for patients' eyes and statistically analyzed the participants' age, heredity, lifestyles and environmental factors.
They found that age explained 38 percent of cloudiness, but heredity accounted for even more at 48 percent. The other factors combined for just 14 percent.
"It is not just your age that is the cause," said Dr. Christopher Hammond of St. Thomas' Hospital in London, who led the study.
At the same time, researchers cautioned that even 14 percent makes other factors very important, since cataracts are so common.
Surgeon routinely operate on cataracts and replace the clouded-over lens with plastic.
Congenital and disease-related cataracts are blamed on different causes than age-related cataracts.
Another Hammond colleague, Dr. Clare Gilbert, said if future genetic tests identify who is most susceptible to cataracts, those people can then limit their exposure to the risks.
April 27, 2000 - BBC
An "artificial eye" which would allow blind people to see is due to be implanted in a patient within the next few months.
The device taps directly into the optic nerve and could restore some measure of sight to people whose retinas have been damaged or destroyed.
Visual sensations beamed from a video camera are created in the brain by the artificial eye, developed by a team at the Catholic University of Louvain, in Belgium, directly stimulating different parts of the optic nerve.
Other implants being developed stimulate the ganglia cells on the retina or the visual cortex of the brain itself.
But the Louvain team, led by Claude Veraart, says these other techniques require large number of electrodes to create images which are recognisable.
His device uses a coil to wrap round the optic nerve with only four points of electrical contact.
Stimulated
A video camera, positioned externally, transmits via a radio transmitter and microchip to an implant behind the ear. This is connected to the electrodes on the optic nerve.
Different parts of the optic nerve are stimulated by altering the signals, similar to the way in which the electron guns in TVs are aimed at different parts of the screen.
Veraart and his colleagues have spent the past two years experimenting with a volunteer who has the electrode implanted, with wires leading out of her body to the signal processor.
By asking her to point in response to various stimuli, Veraart and his colleague Charles Trullemans have been able to map camera pixels onto the corresponding parts of her visual field.
This was possible, said Veraart in New Scientist magazine, because the subject was once sighted and knows what it means to "look at" something.
The researchers hope the device will at least allow blind people to avoid obstacles, though more tests are necessary before the device is implanted.
Most critical is the time it takes to realise they are approaching an object.
"If it takes her 30 seconds to recognise an obstacle it will be of little use," said Veraart. But if the reaction time is fast, the team plan to implant at least three more patients, starting in August.
Rebecca Griffith, health promotion officer for the Royal National Institute for the Blind, in the UK, welcomed the advance but sounded a word of caution.
January 17, 2000 - Reuters - Washington
A New York researcher said on Monday he had helped a blind man see again using electrodes implanted into his brain and connected to a tiny television camera mounted on a pair of glasses.
Although he does not ``see'' in the conventional sense, he can make out the outlines of objects, large letters and numbers on a contrasting background, and can use the direct digital input to operate a computer.
``If he is he walking down a hall, the doorway appears as a white frame on a dark background,'' William Dobelle, of the Dobelle Institute and Columbia-Presbyterian Medical Center in New York, said in a telephone interview.
His ``Dobelle Eye,'' consists of a tiny television camera and an ultrasonic distance sensor mounted on a pair of eyeglasses. A cable runs to a dictionary-sized computer, worn in a belt pack.
After processing the information from the camera, the computer sends a signal to the user's brain via 68 platinum electrodes. ``Each electrode on the surface of the brain produces dots of light when stimulated that resemble stars in the sky,'' Dobelle told Reuters Television in an interview. These dots are known as phosphenes.
He demonstrated with Jerry, a 62-year-old patient who lost his vision at the age of 36 after a blow to the head.
``On a black background, he gets white phosphenes. With small numbers of phosphenes you have (the equivalent of) a time and temperature sign at a bank,'' Dobelle said. ``As you get larger and larger numbers of phosphenes, you go up to having a sports stadium scoreboard.''
Jerry, who does not want his last name used, demonstrated by walking across a room to pull a woolly hat off a wall where it had been taped, took a few steps to a mannequin and correctly put the hat on its head.
A reproduction of what Jerry sees showed crosses on a video screen that changed from black to white when the edge of an object passed behind them on the screen.
``When an object passes by the television camera ... I see dots of light. Or when I pass by it,'' Jerry said.
The system works by detecting the edges of objects or letters. Jerry, currently the only user of the latest system, must move his head slightly to scan what he is looking at.
Writing in the ASAIO Journal (the journal of the American Society of Artificial Internal Organs), Dobelle said Jerry has the equivalent of 20/400 vision -- about the same as a severely nearsighted person -- in a narrow field.
``Although the relatively small electrode array produces tunnel vision, the patient is also able to navigate in unfamiliar environments including the New York City subway system,'' Dobelle said in a statement.
Jerry can read two-inch tall letters at a distance of five feet. And he can use a computer, thanks, Dobelle said, to some input from his 8-year-old son Marty.
``He was with us this summer and he said, 'you guys are out of date. Why don't you take digital signals straight from the TV or computer?''' It worked. Jerry must scan these images, using a joystick for a computer game, but he is learning to use a computer and is eager to try some on-line stock trading. ``He's hot for that,'' Dobelle said.
Dobelle said he thought being able to use a computer would ultimately prove more important for blind users of the system than the mobility it offers them.
Jerry and one other patient have had the electrodes implanted in their brains since 1978, said Dobelle, who specializes in various neural-stimulating implants.
He said only recently was he able to get the computer small enough to be portable. ``The original electronics package was 10 feet long, 5 feet high and 3 feet wide,'' (3 m long, 1.6 m high and 1 m wide) he said.
``It weighed 2,000 pounds (800 kg). The present system weighs 10 pounds (5 kg) and is 500 times faster. The semiconductor technology that we needed to implement active stimulation has changed dramatically and that was the last technology piece. The chips became available less than a year ago.''
One other patient who has tried the new system cannot ''see'' anything with it. Dobelle said the man was blinded at the age of 5, 60 years ago, and his brain may have ``forgotten'' how to use its visual cortex.
He added that he does not know whether the system will work for people who were born blind.
August 17, 1999 - National Academy of Sciences
Scientists peering deep into the eyes of rats have discovered a new target for treating glaucoma: Blocking a chemical called nitric oxide may slow, if not prevent, the blindness. So far, it has worked only in rats. But the research is so promising that the Missouri scientists are talking with pharmaceutical companies about trying to create a drug glaucoma patients could one day use.
The discovery is "a completely different way of treating the disease," explained lead researcher Arthur Neufeld, an ophthalmology professor at Washington University School of Medicine in St. Louis.
The work "will likely be considered classic in years to come," University of Wisconsin ophthalmologist Paul Kaufman declared in reviewing the research, published in this week's Proceedings of the National Academy of Sciences.
Glaucoma is the second leading cause of irreversible vision loss in the United States, and the most common cause among black Americans. An estimated 3 million Americans have glaucoma, and 120,000 are blind as a result.
In glaucoma, pressure inside the eyeball increases to high levels because eye fluid doesn't drain properly. Eventually, that pressure damages the optic nerve and progressively eats away vision.
Until now, all treatment has been aimed at easing that pressure, either with medicated eye drops or surgery. But "even with very effective lowering, there are a significant number of people who continue to lose vision," said Dr. Carl Kupfer, director of the National Eye Institute. "The exciting thing about ... (the new discovery) is that it represents an entirely new and different way" of fighting glaucoma.
Neufeld knew other scientists had discovered that excessive levels of a body chemical called nitric oxide can be toxic to certain tissues. What if nitric oxide, he wondered, also was toxic to eye tissue?
That question led off a chain of discoveries.
First, Neufeld examined human eye tissue from glaucoma patients, and discovered an enzyme called NOS-2 that makes excessive - destructive - amounts of nitric oxide.
"I knew that nitric oxide must be at very high levels" in patients' eyes, Neufeld said.
But did it cause the glaucoma, or was it merely a byproduct of dying cells in the retina?
So Neufeld turned to an animal model of glaucoma, clogging up rats' eyes until their optic pressure built enough to begin destroying their sight. Sure enough, their eyes harbored NOS-2, also.
Neufeld never treated the pressure in any of the rats' eyes. Instead, he put into some of the rats' drinking water an experimental drug called aminoguanidine that can inhibit NOS-2.
Six months later, the rats who didn't drink any medicine had lost 36 percent of their retinal cells - but the medicated rats had lost less than 10 percent of those crucial vision cells, even though their eye pressure had never been lowered.
"By blocking the nitric oxide, we protected the optic nerve," Neufeld explained.
That suggests both that nitric oxide buildup is a cause of glaucoma, and that lowering the chemical might prove an important treatment.
There are no nitric oxide-lowering drugs sold today, Neufeld cautioned, and it will take at least five years to test experimental glaucoma drugs.
Unlike the experimental medicine Neufeld fed rats, developing a nitric oxide-blocking eyedrop would be better for people, Kupfer said. That way, it could be tested in just one eye of each patient - so if potential drugs fail or prove harmful, the other eye would be untouched.
Because nitric oxide is a target in other diseases, pharmaceutical companies already were hotly researching nitric oxide blockers, and Neufeld said he's already in discussions about creating a glaucoma drug.
By Lauran Neergaard
Rockville, Md. -January 12, 1999
Tiny rings implanted onto the cornea may help correct nearsightedness that plagues 20 million Americans, offering an alternative to popular but irreversible laser surgery. The key to KeraVision Inc.'s Intacs implants: If the patient doesn't like the result or suffers a side effect such as glare, doctors can remove the ring with a good chance of returning the patient's eye to its condition before surgery.
"People who know about the ring can't be talked into having the laser" surgery, said Dr. David Schanzlin of the University of California, San Diego, who led KeraVision's clinical trials. "It's the idea that if this doesn't work, you can take it out." Advisers to the Food and Drug Administration voted unanimously Tuesday that the implants - two crescents about the thickness of a contact lens that form a ring around the cornea's edge - should be sold. But the panel stressed that Intacs can cause side effects. Removing the implant will often, but not always, relieve the problem. "It's largely reversible," said panel chairman Dr. James McCulley of the University of Texas Southwestern Medical Center. But he stressed, "It's not an absolute certainty."
The FDA is not bound by its advisers' recommendations but typically follows them. Nearsightedness occurs when a person's cornea, the membrane covering the front of the eye, is too steeply curved. Flattening the cornea can help correct nearsightedness. Hundreds of thousands of Americans have sought radial keratotomy, where surgeons slice the cornea with a knife, or laser surgery that shaves the cornea to do that.
But those surgeries can be risky, sometimes causing problems with night vision, glare, seeing halos or blurry vision. Patients occasionally cannot see as well after surgery as before. Thus, most patients who choose these operations do so only because they are severely nearsighted. With Intacs, the implants' slight weight flattens the cornea without the permanence of cutting the tissue.
KeraVision hopes to attract some 20 million mildly to moderately nearsighted Americans - those whose vision ranges from 20/40, where it's OK to drive but a movie is blurry without glasses, to 20/200, where patients can barely see the big "E" atop eye charts.
In a yearlong study of the surgery on 449 eyes, 97 percent could see 20/40 or better without glasses or contact lenses after the implant. About 74 percent had 20/20 or better vision without glasses, and 53 percent could see 20/16 - the sharper vision Schanzlin said is required of combat pilots. Most patients achieved good vision a day after surgery. Intacs isn't risk-free: Some 7 percent to 17 percent of patients suffered side effects similar to laser surgery, including glare, halos and problems with night vision. About 5 percent of patients had their implants removed. That included 14 patients dissatisfied with their vision correction and 16 who had visual side effects. Removing the implant corrected over 80 percent of hose side effects, the company said.
The operation itself is "very easy to master," said Schanzlin. Patients get anesthetic eye drops to numb the eye, but remain awake. The doctor clamps the eyelid open, cuts a tiny pocket into the cornea and uses a special device to slip the crescents onto the cornea. The implants are made of the same material as the lenses implanted into cataract surgery patients. A single stitch closes the wound. It takes about 15 minutes. About 15 percent of patients report some pain; as with any surgery, infection also is a risk. The procedure will cost about $2,200 an eye, about the same as laser surgery - and includes removal if the patient is not satisfied, KeraVision said. The FDA is reviewing three sizes of Intacs. The company is testing thicker versions for more severely nearsighted patients.
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