Tag Archives: Blindness

Sense and Lens

When those born blind get their vision, they have difficulty correlating the real to the ‘felt’. T.V. Jayan on the outcome of a project for visually challenged children in rural India.

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The participants were asked to feel a building block and then match the object felt with two blocks, one square and the other circular.

Blind children from India’s hinterland have found themselves a place in history by helping researchers resolve a profound and long-standing problem that perplexed philosophers and neuroscientists for over three centuries.

Posed for the first time in 1688 by Irish scientist and politician William Molyneux, the question is elegantly simple: can a person who has been blind from birth but gained sight in adulthood visually discriminate between objects that were previously identifiable only by touch?

The answer seems to be a definite “no”. That’s the conclusion of a team of Indian and American scientists after their studies involving blind children in rural India whose eyesight was restored surgically. In other words, a person’s ability to learn the correspondence between how an object looks and how it feels is not innate; it needs to be learnt. The study appeared yesterday in Nature Neuroscience.

 

The five children, aged between eight and 17, who participated in the study are part of a project launched by Pawan Sinha, a brain and cognitive sciences professor at the Massachusetts Institute of Technology (MIT), the US.

The Molyneux question has been the subject of much debate in philosophy and neuroscience over the past three centuries, says MIT’s Richard Held, the first author of the paper. It’s important for two reasons, he says. Philosophically speaking, it touches upon the core of the “nature versus nurture” debate. It also addresses a deep scientific question: do the various senses of a living organism share an innate common space?

Though efforts to answer the question began not long after it was first posed, it had thus far remained unresolved. The primary reason for this is that in the West, a majority of curable congenital blindness cases are detected in infancy and treated as early as possible. But the scientists working with Project Prakash — which Sinha launched in 2004 — however, had an opportunity to take a fresh look at the problem. They had been working with children with vision disabilities in rural India as part of the humanitarian venture. The country is said to have the highest number of blind children in the world — more than one million.

Most cases of blindness in India are caused by vitamin A deficiency, cataracts, retinal or optical dystrophies, or microphthalmos (poorly developed eyes). About half the cases are treatable or preventable, but many never receive medical care, especially in rural areas.

Under the project, the scientists have so far screened more than 20,000 children in some of the most backward villages in Uttar Pradesh, Haryana, Rajasthan and Madhya Pradesh. “Over 700 children have been treated for conditions ranging from severe refractive error to congenital blindness,” says Sinha, a co-author of the study. The medical care was provided at New Delhi’s eye hospital, Shroff’s Charity Eye Hospital, a project partner.

For their study, the scientists chose five children who were blind from birth owing to a congenital cataract or an opaque cornea. After surgery — a cataract removal or a corneal transplant — the participants were asked to feel a building block and then match the object felt with one or two blocks (of two different shapes — one square and the other circular). The children were unable to match the blocks they felt with what they only saw. Significantly, their performance improved substantially five days later, although they didn’t receive any kind of training.

This rapid improvement was surprising, says Yuri Ostrovsky, another MIT researcher associated with the study. He points out that many visual tasks, such as face perception, can take six to 12 months to learn after sight is restored. “The outcome has been a surprise — one that has important implications for theories regarding how the brain learns to acquire a coherent account of the complex environment,” Held told KnowHow.

Sinha, who holds a BTech from the Indian Institute of Technology, Delhi, says the project has been an eye opener in more ways than one. It served a dual purpose: providing sight to blind children and advancing fundamental science. This, along with earlier findings from Project Prakash, shows that the human brain retains an impressive ability to launch programmes of visual learning well after the normal period of their deployment has passed.

“It has helped clear several myths regarding vision. Most eye doctors hesitate to treat older patients because they believe the brain is incapable of learning to see after age six or seven,” Sinha told KnowHow. “Our work has broken this dogma.”

The results of the study are significant for basic neuroscience as well as paediatric ophthalmology and implementation of later-stage blindness treatment programmes.

Here’s hoping there will be light for all.
You may click to see :Those Who Once Were Blind Can Learn To See, Study Shows

Source: The Telegraph ( Kolkata, India)

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New Surgery For AMD Patients

An innovative form of eye surgery is offering hope to the estimated three million sufferers of age-related macular degeneration (AMD), the most common cause of blindness in people over 55 in the UK.
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The technique, known as IOL VIP – Intra-Ocular Lenses for Visually Impaired People, is similar to cataract surgery. Developed in Milan by low-vision specialists and ophthalmologists, it was first made available in the UK about 18 months ago and is now performed in private hospitals, although it isn’t currently available on the NHS.

AMD damages the macula – the central part of the light-sensitive retina at the back of the eye – causing scarring, and preventing images being sent to the brain. This damage causes the gradual deterioration, or even loss, of central vision used for activities such as reading, writing, driving and recognising faces.
Eye

Hope: Treatment is now available for ‘dry’ AMD

There are two types of AMD: ‘dry’, the most common form, in which the cells of the macula disintegrate gradually; and the more aggressive ‘wet’ form. The latter is caused by the growth of new blood vessels behind the retina, which can leak, causing scarring and leading to loss of sight.

About ten per cent of people with AMD develop the ‘wet’ form, which can be treated with eye injections. But, until recently, there has been no effective treatment for the majority, who suffer from ‘dry’ AMD.

In the pioneering IOL VIP procedure, two artificial lenses are inserted into the eye. The natural lens behind the iris is removed and replaced with an artificial one, which diverts images from the scarred macula to healthy retinal tissue.

A second lens is then placed in front of the iris. Together, the two lenses act as a telescope, allowing the images to be focused and processed to the optic nerve and sent to the brain. The procedure can last as little as 30 minutes. It then takes approximately 12 weeks for sight to stabilise.

After the operation, computer vision training is vital to train the eye and get the best possible outcome.

Richard Newsom, a consultant ophthalmic surgeon, says: ‘The IOL VIP procedure is an exciting new innovation. It’s not appropriate for every patient with AMD and further studies are required but when it works, it works well and for some patients it can make a significant improvement to their vision.’

Brendan Moriarty, consultant eye surgeon at Leighton Hospital in Crewe, Cheshire, who was the first to perform the operation in the UK, says: ‘If you select patients correctly, the vast majority will at least double their near and distance vision.’

The Royal College of Ophthalmologists agrees further studies are required, stating that it is difficult to determine who will benefit and by how much.

The Macular Disease Society says it is not ‘a miracle cure’ and ‘has worked successfully for some but can’t be regarded as a regular new treatment for widespread use in MD patients’.

One patient who has benefited from the pioneering procedure, however, is 68-year-old Evelyn Dean.

Having suffered from ‘dry’ AMD for two-and-a-half years, Evelyn’s sight had deteriorated so much that she couldn’t read a book or newspaper-without a strong magnifying glass. To her dismay, it also got so bad she was told that she could no longer drive.

But, following an IOL VIP operation in November 2008 at Spire Hull and East Riding Hospital, Evelyn has been given the all-clear to get back behind the wheel.

She says: ‘ I can even read the labels on supermarket shelves properly, which I couldn’t before. I still wear glasses for long distances and reading but the best thing is being able to drive again after almost 15 months.

‘I feel like I have my freedom back.’

Sources: http://www.dailymail.co.uk/health/article-1200549/New-surgery-save-thousands-blindness.html#ixzz0LiXZkEUz

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Macular Degeneration (AMD OR ARMD)

Definition:
Macular degeneration is a medical condition usually of older adults which results in a loss of vision in the center of the visual field (the macula) because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness in the elderly (>50 years). Macular degeneration can make it difficult or impossible to read or recognize faces, although enough peripheral vision remains to allow other activities of daily life.

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Human eye cross section view

Macular degeneration doesn’t cause total blindness, but it worsens your quality of life by blurring or causing a blind spot in your central vision. Clear central vision is necessary for reading, driving, recognizing faces and doing detail work.

The deterioration occurs in the macula (MAK-u-luh), which is in the center of the retina — the layer of tissue on the inside back wall of your eyeball.

The inner layer of the eye is the retina, which contains nerves that communicate sight, and behind the retina is the choroid, which contains the blood supply to the retina. In the dry (nonexudative) form, cellular debris called drusen accumulate between the retina and the choroid, and the retina can become detached. In the wet (exudative) form, which is more severe, blood vessels grow up from the choroid behind the retina, and the retina can also become detached. It can be treated with laser coagulation, and with medication that stops and sometimes reverses the growth of blood vessels.

Although some macular dystrophies affecting younger individuals are sometimes referred to as macular degeneration, the term generally refers to age-related macular degeneration (AMD or ARMD).

Signs:
Drusen
Pigmentary alterations
Exudative changes: hemorrhages in the eye, hard exudates, subretinal/sub-RPE/intraretinal fluid
Atrophy: incipient and geographic
Visual acuity drastically decreasing (two levels or more) ex: 20/20 to 20/80.

Symptoms:
Dry macular degeneration usually develops gradually and painlessly. You may notice these vision changes:

* The need for increasingly bright light when reading or doing close work
* Increasing difficulty adapting to low light levels, such as when entering a dimly lit restaurant
* Increasing blurriness of printed words
* A decrease in the intensity or brightness of colors
* Difficulty recognizing faces
* Gradual increase in the haziness of your overall vision
* Blurred or blind spot in the center of your visual field combined with a profound drop in the sharpness (acuity) of your central vision
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Normal Vision.……………………………...Vision with AMD

Your vision may falter in one eye while the other eye remains fine for years. You may not notice any or much change because your good eye compensates for the weak one. Your vision and lifestyle begin to be dramatically affected when this condition develops in both eyes.

Hallucinations

Additionally, some people with macular degeneration may experience visual hallucinations as their vision loss becomes more severe. These hallucinations may include unusual patterns, geometric figures, animals or even faces. You might be afraid to discuss these symptoms with your doctors or friends and family for fear you’ll be considered crazy. However, such hallucinations aren’t a sign of mental illness. In fact, they’re so common that there’s a name for this phenomenon — Charles Bonnet syndrome.

The Amsler Grid Test is one of the simplest and most effective methods for patients to monitor the health of the macula. The Amsler Grid is essentially a pattern of intersecting lines (identical to graph paper) with a black dot in the middle. The central black dot is used for fixation (a place for the eye to stare at). With normal vision, all lines surrounding the black dot will look straight and evenly spaced with no missing or odd looking areas when fixating on the grid’s central black dot. When there is disease affecting the macula, as in macular degeneration, the lines can look bent, distorted and/or missing. See a video on how to use an Amsler grid here:  and watch an animation showing the Amsler grid with macular degeneration here: .

Macular degeneration by itself will not lead to total blindness. For that matter, only a very small number of people with visual impairment are totally blind. In almost all cases, some vision remains. Other complicating conditions may possibly lead to such an acute condition (severe stroke or trauma, untreated glaucoma, etc.), but few macular degeneration patients experience total visual loss. The area of the macula comprises about 5% of the retina and is responsible for about 35% of the visual field. The remaining 65% (the peripheral field) remains unaffected by the disease

The loss of central vision profoundly affects visual functioning. It is not possible, for example, to read without central vision. Pictures which attempt to depict the central visual loss of macular degeneration with a black spot do not really do justice to the devastating nature of the visual loss. This can be demonstrated by printing letters 6 inches high on a piece of paper and attempting to identify them while looking straight ahead and holding the paper slightly to the side. Most people find this surprisingly difficult to do.

There is a loss off contrast sensitivity, so that contours, shadows and color vision are less vivid. The loss in contrast sensitivity can be quickly and easily measured by a contrast sensitivity test performed either at home or by an eye specialist.

Similar symptoms with a very different etiology and different treatment can be caused by Epiretinal membrane or macular pucker or leaking blood vessels in the eye..

When to see a doctor
See your eye doctor — particularly after age 50 — if:

* You notice changes in your central vision
* Your ability to see colors and fine detail becomes impaired

One way to monitor your eyes to determine if you may need to visit your eye doctor is to check your vision regularly using an Amsler grid. This simple test may help you detect changes in your sight that you otherwise may not notice.

Here’s how to perform the test:

* Hold the grid 14 inches (about 36 centimeters) in front of you in good light. Use your corrective glasses or reading glasses if you normally wear them.
* Cover one eye.
* Look directly at the center dot with your uncovered eye.
* While looking at this dot, determine whether all of the lines of the grid appear straight, uninterrupted and have the same contrast.
* Repeat the above steps with your other eye.
* If any part of the grid is missing or looks wavy, blurred or dark, contact your eye doctor immediately.

Causes:
The exact cause of dry macular degeneration is unknown, but the condition develops as the eye ages. The initial site of change is not in the light-sensitive cells of the macula, but in the retinal pigment epithelium (RPE), a single layer of cells located just behind the retina close to the back wall of your eye.

Your macula is an area about two-tenths of an inch (5 millimeters) in diameter at the center of your retina. This small part of your eye is responsible for clear vision, particularly in your direct line of sight.

The macula consists of millions of densely packed light-sensitive cells called cones and rods. Cones and rods have two segments: An inner segment controls cell functions and produces proteins responsive to light, and an outer segment stores and makes use of these proteins.

As they absorb light, outer segment proteins become degraded and eventually are shed as waste. Meanwhile, the inner segments continuously provide replacements for the outer segments. One function of the cells of the RPE is to remove the outer segments that are shed.

As the eye ages, cells in the RPE begin to deteriorate (atrophy) and lose their pigment. As a consequence, the RPE becomes less efficient in removing outer segment waste. When that happens, the normally uniform reddish color of the macula (as seen with an ophthalmoscope) takes on a mottled appearance. Drusen — yellow, fat-like deposits — begin to appear under the cones and rods. As the drusen and mottled pigmentation continue to develop, your vision gradually deteriorates.

Based on this progression, dry macular degeneration is categorized in three stages:

* Early stage. Several small drusen or a few medium-sized drusen are detected on the macula in one or both eyes. Generally, there’s no vision loss in the earliest stage.
* Intermediate stage. Many medium-sized drusen or one or more large drusen are detected in one or both eyes. At this stage, your central vision may start to blur and you may need extra light for reading or doing detail work.
* Advanced stage. Several large drusen, as well as extensive breakdown of light-sensitive cells in the macula, are detected. These features cause a well-defined spot of blurring in your central vision. The blurred area may become larger and more opaque over time.

Macular degeneration almost always starts out as the dry form. Dry macular degeneration may initially affect only one eye but, in most cases, both eyes eventually become involved.

Risk factors:
Contributing factors for development of macular degeneration include:

* Age. In the United States, macular degeneration is the leading cause of severe vision loss in people age 60 and older.
* Family history of macular degeneration. If someone in your family had macular degeneration, your odds of developing macular degeneration are higher. In recent years, researchers have identified some of the genes associated with macular degeneration. In the future, genetic screening tests may be helpful for assessing early risk of the disease.
* Race. Macular degeneration is more common in whites than it is in other groups, especially after age 75.
* Sex. Women are more likely than men to develop macular degeneration, and because they tend to live longer, women are more likely to experience the effects of severe vision loss from the disease.
* Cigarette smoking. Exposure to cigarette smoke doubles your risk of macular degeneration. Cigarette smoking is the single most preventable cause of macular degeneration.
*Stargardt’s disease (STGD, also known as Juvenile Macular Degeneration) is an autosomal recessive retinal disorder characterized by a juvenile-onset macular dystrophy, alterations of the peripheral retina, and subretinal deposition of lipofuscin-like material. A gene encoding an ATP-binding cassette (ABC) transporter was mapped to the 2-cM (centiMorgan) interval at 1p13-p21 previously shown by linkage analysis to harbor the STGD gene. This gene, ABCR, is expressed exclusively and at high levels in the retina, in rod but not cone photoreceptors, as detected by in situ hybridization. Mutational analysis of ABCR in STGD families revealed a total of 19 different mutations including homozygous mutations in two families with consanguineous parentage. These data indicate that ABCR is the causal gene of STGD/FFM.
*Drusen CMSD studies indicate that drusen are similar in molecular composition to plaques and deposits in other age-related diseases such as Alzheimer’s disease and atherosclerosis.
While there is a tendency for drusen to be blamed for the progressive loss of vision, drusen deposits can, however, be present in the retina without vision loss. Some patients with large deposits of drusen have normal visual acuity. If normal retinal reception and image transmission are sometimes possible in a retina when high concentrations of drusen are present, then even if drusen can be implicated in the loss of visual function, there must be at least one other factor that accounts for the loss of vision. Retinitis Pigmentosa (RP) is a genetically linked dysfunction of the retina and is related to mutation of the ATP Synthase Gene 63.
* Obesity. Being severely overweight increases the chance that early or intermediate macular degeneration will progress to the more severe form of the disease.
* Light-colored eyes. People with light-colored eyes appear to be at greater risk than do those with darker eyes.
* Exposure to sunlight. Although the retina is more sensitive to shorter wavelengths of light, including ultraviolet (UV) light, only a small percentage of ultraviolet light actually reaches the retina. Most ultraviolet light is filtered by the transparent outer surface of your eye (cornea) and the natural crystalline lens in your eye. Some experts believe that long-term exposure to ultraviolet light may increase your risk of developing macular degeneration, but this risk has not been proved and remains controversial.
* Low levels of nutrients. This includes low blood levels of minerals, such as zinc, and of antioxidant vitamins, such as A, C and E. Antioxidants may protect your cells from oxygen damage (oxidation), which may partially be responsible for the effects of aging and for the development of certain diseases such as macular degeneration.
* Cardiovascular diseases. These include high blood pressure, stroke, heart attack and coronary artery disease with chest pain (angina).
*High fat intake is associated with an increased risk of macular degeneration in both women and men. Fat provides about 42% of the food energy in the average American diet. A diet that derives closer to 20-25% of total food energy from fat is probably healthier. Reducing fat intake to this level means cutting down greatly on consumption of red meats and high-fat dairy products such as whole milk, cheese, and butter. Eating more cold-water fish (at least twice weekly), rather than red meats, and eating any type of nuts may help macular degeneration patients.
*Oxidative stress: It has been proposed that age related accumulation of low molecular weight, phototoxic, pro-oxidant melanin oligomers within lysosomes in the retinal pigment epithelium may be partly responsible for decreasing the digestive rate of photoreceptor outer rod segments (POS) by the RPE. A decrease in the digestive rate of POS has been shown to be associated with lipofuscin formation – a classic sign associated with macular degeneration.
*Fibulin-5 mutation Rare forms of the disease are caused by geneic defects in fibulin-5, in an autosomal dominant manner. In 2004 Stone et al. performed a screen on 402 AMD patients and revealed a statistically significant correlation between mutations in Fibulin-5 and incidence of the disease. Furthermore the point mutants were found in the Calcium binding sites of the cbEGF domains of the protein. there is no structural basis for the effects of the mutations.

Diagnosis:
Diagnostic tests for macular degeneration may include:

*An eye examination. One of the things your eye doctor looks for while examining the inside of your eye is the presence of drusen and mottled pigmentation in the macula. The eye examination includes a simple test of your central vision and may include testing with an Amsler grid. If you have macular degeneration, when you look at the grid some of the straight lines may seem faded, broken or distorted. By noting where the break or distortion occurs — usually on or near the center of the grid — your eye doctor can better determine the location and extent of your macular damage.

Regular screening examinations can detect early signs of macular degeneration before the disease leads to vision loss.
*Angiography. To evaluate the extent of the damage from macular degeneration, your eye doctor may use fluorescein angiography. In this procedure, fluorescein dye is injected into a vein in your arm and photographs are taken of the back of the eye as the dye passes through blood vessels in your retina and choroid. Your doctor then uses these photographs to detect changes in macular pigmentation or to identify small macular blood vessels.

Your doctor may also suggest a similar procedure called indocyanine green angiography. Instead of fluorescein, a dye called indocyanine green is used. This test provides information that complements the findings obtained through fluorescein angiography.
* Optical coherence tomography. This noninvasive imaging test helps identify and display areas of retinal thickening or thinning. Such changes are associated with macular degeneration. This test can also reveal the presence of abnormal fluid in and under the retina or the RPE. It’s often used to help monitor the response of the retina to macular degeneration treatments.

Treatment:
There’s no treatment available to reverse dry macular degeneration. But this doesn’t mean you’ll eventually lose all of your sight. Dry macular degeneration usually progresses slowly, and many people with the condition are able to live relatively normal, productive lives, especially if only one eye is affected. Dry macular degeneration can, however, develop into the more rapidly progressive wet type of macular degeneration at any time.

Taking a high-dose formulation of antioxidants and zinc may reduce progression of dry macular degeneration to advanced macular degeneration. The National Eye Institute-sponsored Age-Related Eye Disease Study (AREDS) showed that a daily supplement of 500 milligrams (mg) of vitamin C, 400 international units (IU) of vitamin E, 15 mg of beta carotene (often as vitamin A — up to 25,000 IU), 80 mg of zinc (as zinc oxide) and 2 mg of copper (as cupric oxide) reduced the risk of progressing to moderate or severe vision loss by up to 25 percent.

Life Style & Home Remedies:
Macular degeneration doesn’t affect your side (peripheral) vision and usually doesn’t cause total blindness. But it can rob you of your central vision — which is important for driving, reading and recognizing people’s faces. A low-vision center may be able to assess your visual capabilities and suggest certain optical and household devices that can be helpful for some near-vision tasks. Ask your eye doctor if there are any low-vision centers in your area.

There are ways to cope with impaired vision. Below are a few suggestions:

* Use caution when driving. First, check with your doctor to see if driving is still safe based on your current visual acuity. When you do drive, there are certain situations to avoid. For example, don’t drive at night, in heavy traffic or in bad weather.
* Seek help traveling. Use public transportation or ask family members to help, especially with night driving.
* Travel with others. Contact your local area agency on aging for a list of vans and shuttles, volunteer driving networks or ride shares.
* Get good glasses. Optimize the vision you have with the right glasses, and keep an extra pair in the car.
* Use magnifiers. Large-print books and magazines can help you read more easily.
* View with large type on the Internet. Look for Web sites that use large-sized type fonts, or change the font size on your display.
* Obtain specialized appliances. Some clocks, radios, telephones and other appliances have extra-large numbers.
* Have proper light in your home. This will help with reading and other activities.
* Remove home hazards. Eliminate throw rugs and other possible tripping hazards in your home.
* Ask friends and family members for help. Tell them about your vision problems so that they can help you perform certain tasks and help you recognize people.
* Don’t become socially isolated. A common frustration of people with macular degeneration is the inability to recognize other people and greet them by name. If this happens to you, try asking people you know to say hi and tell you their names when you meet them on the street or in other situations so that you can greet them back.
* Take advantage of online networks. The Internet is a good source for support groups and resources for people with macular degeneration.

Alternative Medicine:
Some people have turned to complementary or alternative therapies, such as bilberry, ginkgo and shark cartilage, in the belief that they can help prevent the progression of macular degeneration.

However, there’s no conclusive evidence that any of these products are effective for macular degeneration, and some may interact with other medications you’re taking. Check with your doctor before taking any dietary or herbal supplement.

Prevention
The Age-Related Eye Disease Study showed that a combination of high-dose beta-carotene, vitamin C, vitamin E, and zinc can reduce the risk of progressing from early to advanced AMD by about 25 percent.  Studies are underway with the goal of reducing lipofuscin accumulation.

Studies have found that Lutein and zeaxanthin (Carotenoid nutrients found in green vegetables such as Kale, Spinach, Collards, spices such as Saffron, and egg yolk) protect against and possibly reverse macular degeneration and Retinitis pigmentosa.  Studies found that antioxidants disrupt the link of two processes that cause macular degeneration and extend the lifetime of irreplaceable photoreceptors and other retinal cells (Lutein is known to have antioxidant properties).

Eating spinach or collard greens five times a week decreases the risk of AMD by 43%

Studies reported in the British Journal of Ophthalmology suggest that while beneficial for those in advanced stages, antioxidant supplements can be counterproductive for people with early stages of AMD as antioxidants can potentially negate the beneficial effects of Omega-3 fats. It has been found that Omega-3 fatty acids can prevent or even halt the progress of degeneration. However, moderation of oily fishes in patients’ diets is suggested as they can lead to a build up of pollutants such fishes may contain.

The following measures may help you avoid macular degeneration:
*Eat foods containing antioxidants.
*Take antioxidant and zinc supplements.
* Eat fish.
*Stop smoking.
*Manage your other diseases.
*Get regular eye exams.
*Screen your vision regularly.

If you have some vision loss because of macular degeneration, your eye doctor can prescribe optical devices called low-vision aids that will help you see better for close-up work. Or your doctor may refer you to a low-vision specialist. In addition, a wide variety of support services and rehabilitation programs are available that may help you adjust your lifestyle.
Impact:
Macular degeneration can advance to legal blindness and inability to drive. It can also result in difficulty or inability to read or see faces.

Adaptive devices can help people read. These include magnifying glasses, special eyeglass lenses, desktop and portable electronic devices, and computer screen readers such as JAWS for Windows.

Composer Josef Tal checks a manuscript (2006)Accessible publishing also aims to provide a variety of fonts and formats for published books to make reading easier. This includes much larger fonts for printed books, patterns to make tracking easier, audiobooks and DAISY books with both text and audio.

Because the peripheral vision is not affected, people with macular degeneration can learn to use their remaining vision to continue most activities. Assistance and resources are available in every country and every state in the U.S. Classes for “independent living” are given and some technology can be obtained from a state department of rehabilitation. You can also search for macular degeneration on the internet and contact one of the non-profit organizations for assistance.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.
Resources:
http://www.mayoclinic.com/health/macular-degeneration/DS00284
http://en.wikipedia.org/wiki/Macular_degeneration

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Oily Fish ‘Cuts Eye Disease Risk’

Eating food rich in omega-3, such as oily fish, could help some people avoid one of the most common causes of vision loss, a research review suggests.

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AMD causes a progressive loss of sight

The Annals of Ophthalmology review suggests omega-3 may cut the risk of age-related macular degeneration (AMD) by a third.

However, the Australian researchers stop short of encouraging everyone to eat more omega-3 for this reason alone.

An estimated 500,000 people in the UK suffer from AMD in some form.

“Prevention of this condition remains a major public health concern”….Spokesman, RNIB

it is a progressive and irreversible condition caused by thinning and bleeding around the macula – the central portion of the retina.

People with AMD, mostly over the age of 60, lose the ability to see fine detail, and, in severe cases, can choose to become registered blind, even though they still have some peripheral vision left.

Studies have already linked omega-3 fatty acids with a variety of health benefits, the most significant being suggestions that it can help people with heart disease.

The University of Melbourne study added up the results of nine previous studies on omega-3 and AMD, a total of 88,974 participants, including more than 3,000 with AMD.

 

Doing this gives the results more statistical strength – making it less likely than in the original nine studies that the findings are simply due to chance or some other confounding factor.

Eating fish twice a week was linked to a reduced risk of AMD, and a 38% reduction in risk was found when those eating the most omega-3 were compared with those eating the least.

‘Raise awareness’

Dr Elaine Chong, who led the research, said that omega-3 fatty acids were a vital component of the retina, and it was possible that a shortage of the chemical could “initiate” the disease as retinal cells were constantly shed and renewed.

However, she was cautious about recommending a change in diet, as little of the research analysed was set up to provide solid evidence.

“Although this meta-analysis suggests that consumption of fish and foods rich in omega-3 fatty acids may be associated with a lower risk of AMD, there is insufficient evidence from the current literature, with few prospective studies and no randomised clinical trials, to support their routine consumption for AMD prevention.”

A spokesman for the vision charity RNIB said that, given the high cost of treatment for one type of AMD, and the lack of treatment for the other, prevention was a “major public health concern”.

“The analysis of the existing evidence confirms that smoking is the only proven avoidable risk factor for AMD.

“We would welcome randomised controlled trials on the role that omega-3 fatty acids and fish consumption may be able to play in preventing AMD.

“In the interim we would encourage the government to do more to raise awareness of the link between smoking and blindness.”

Sources: BBC NEWS: 10Th. June, ’08

Scotoma

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Definition:A scotoma (Greek: darkness; plural: “scotomas” or “scotomata”) is an area or island of loss or impairment of visual acuity surrounded by a field of normal or relatively well-preserved vision.
Every normal mammalian eye has a scotoma in its field of vision, usually termed its blind spot. This is a location with no photoreceptors, where the retinal ganglion cell axons that comprise the optic nerve exit the retina. This location is called the optic disc. The blindspot does not intrude into consciousness because the corresponding visual field locations of the optic discs in the two eyes differ: The visual signals that are absent in one eye are sent to the cortex by signals from the other eye.

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The presence of the scotoma can be demonstrated subjectively by covering one eye, carefully holding fixation with the open eye, and placing an object (such as your thumb) in the lateral and horizontal visual field, about 15 degrees from fixation (see the blind spot article). The size of the monocular scotoma is surprisingly large – 5×7 deg of visual angle.

It is a common type of vision loss post stroke or traumatic brain injury, a scotoma is an island of visual field loss (blindness) or impaired vision surrounded by relatively normal vision. The eyes of mammals naturally have a small scotoma (blind spot) that we normally don’t detect. However, a wide range of diseases and injuries can cause a pathological scotoma. For example, a scotoma can be a sign of optic nerve damage sustained during a stroke or brain injury. Previously considered untreatable, new research has led to exciting developments in treating scotoma.

Types of Scotoma: After a stroke or brain injury, a scotoma may occur in any shape or size, and it may affect any portion of the visual field. In some cases, a scotoma will include and enlarge the blind spot occurring naturally in a person’s eye. The main types of scotomas include:

* Central scotoma: an area of decreased or lost vision that interferes with central vision (likely to affect daily life)...CLICK & SEE
* Hemianopic scotoma: an area of decreased or lost vision that affects half of the central visual field….CLICK & SEE
* Peripheral scotoma: an area of decreased or lost vision toward the edge of the visual field (less likely to affect daily life)...CLICK & SEE

Symptoms: The main symptom of scotoma is one or more dark, light, or blurred areas in the field of vision. Those affected by visual field loss may also experience a need for greater illumination and contrast when reading, and may have difficulty perceiving certain colors.

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Symptom-producing or pathological scotomata may be due to a wide range of disease processes, affecting either the retina (in particular its most sensitive portion, the macula) or the optic nerve itself. A pathological scotoma may involve any part of the visual field and may be of any shape or size. A scotoma may include and enlarge the normal blind spot. Even a small scotoma that happens to affect central or macular vision will produce a severe visual handicap, whereas a large scotoma in the more peripheral part of a visual field may go unnoticed by the bearer due to the normal reduced visual resolution in the peripheral visual field.

Causes:Common causes of scotomata include demyelinating disease such as multiple sclerosis (retrobulbar neuritis), toxic substances such as methyl alcohol, ethambutol and quinine, nutritional deficiencies, and vascular blockages either in the retina or in the optic nerve. Scintillating scotoma is a common visual aura in migraine.   Less common, but important because sometimes reversible or curable by surgery, are scotomata due to tumors such as those arising from the pituitary gland, which may compress the optic nerve or interfere with its blood supply.

Rarely, scotomata are bilateral. One important variety of bilateral scotoma may occur when a pituitary tumour begins to compress the optic chiasm (as distinct from a single optic nerve) and produces a bi-temporal hemicentral scotomatous hemianopia. This type of visual field defect tends to be very eloquent symptom-wise but often evades early objective diagnosis, as it is more difficult to detect by cursory clinical examination than the classical or text-book bi-temporal peripheral hemianopia and may even elude sophisticated electronic modes of visual field assessment.

In a pregnant woman, scotomata can present as a symptom of severe preeclampsia, a form of pregnancy-induced hypertension.

Click To learn about Detection:->

* Amsler grid…..CLICK & SEE
* Perimetry……..CLICK & SEE
* Visual field test….CLICK & SEE

Treatment: There is no treatment for scotomas.

When they are in the peripheral areas and are not large, they usually do not cause severe problems in general visual functioning. If the scotomas are large or numerous, mobility may be affected.

Central scotomas are another situation entirely. Functional acuity is severely affected and educational adjustments are indicated. Magnification or large print may be indicated. Higher levels of illumination and good contrast in reading materials may also be useful. Color perception may be affected.

Vision loss post stroke or brain injury, which may include scotoma, hemianopia / quadrantanopia, and diffuse field defect / low vision, can drastically impact a person’s quality of life. In the past, these vision defects were considered untreatable. However, cutting-edge research into neuroplasticity, the brain’s ability to grow and heal throughout adulthood, has led to effective methods of vision rehabilitation.

Developed by NovaVision, one such method of vision rehab, called Vision Restoration Therapy, works by stimulating the brain in precise, consistent ways. Studies show that 70 percent of patients who complete Vision Restoration Therapy experience significant improvements in their vision, which improves their quality of life. Today, the therapy is available at premier institutions and medical centers across the United States.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose

Resources:
http://www.helpforvisionloss.com/vision-loss/scotoma/#types
http://en.wikipedia.org/wiki/Scotoma
http://www.spedex.com/resource/documents/veb/scotoma.html

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