Stargardt Disease

What is Stargardt Disease?

Stargardt disease is the most common form of inherited juvenile macular degeneration. The progressive vision loss associated with Stargardt disease is caused by the death of photoreceptor cells in the central portion of the retina called the macula.

The retina is the delicate light-sensing tissue lining the back inside wall of the eye. Photoreceptor cells in the retina provide vision by conveying information from the visual field to the brain. The macula is responsible for sharp central vision — for tasks like reading, watching television, and looking at faces.

Decreased central vision is a hallmark of Stargardt disease. Side vision is usually preserved. Stargardt disease typically develops during childhood and adolescence. Also involved in Stargardt disease is a region beneath the macula called the retinal pigment epithelium.

What are the symptoms?

The symptom that brings most people to an eye doctor is a change in central vision. A doctor looking at the retina of a person with Stargardt disease will see characteristic yellowish flecks in and under the macula. The flecks might extend outward in a ring-like fashion.

The flecks are deposits of lipofuscin, a fatty byproduct of normal cell activity. In Stargardt disease, lipofuscin accumulates abnormally. The Foundation Fighting Blindness supports research studying lipofuscin build up and ways to prevent it.

A decrease in color perception also occurs in Stargardt disease. This is because photoreceptor cells involved in color perception are concentrated in the macula.

How quickly does vision fade?

The progression of symptoms in Stargardt disease is variable. Visual acuity (the ability to distinguish details and shape) may decrease slowly at first, accelerate, and then level off.
A study of 95 people with Stargardt disease showed that once a visual acuity of 20/40 is reached, there is often rapid progression of additional vision loss until it reaches 20/200. (Normal vision is 20/20. A person with 20/40 vision sees at 20 feet what someone with normal vision sees at 40 feet.) By age 50, approximately 50 percent of people in the study had visual acuities of 20/200 or worse.

Eventually, almost everyone with Stargardt disease has a visual acuity in the range of 20/200 to 20/400. The vision loss is not correctable with prescription eyeglasses, contact lenses, or refractive surgery.

Is it an inherited disease?

Stargardt disease is almost always inherited as an autosomal recessive trait. It is inherited when both parents, called carriers, have one gene for the disease paired with one normal gene. Each offspring has a 25 percent chance of inheriting two copies of the Stargardt gene (one from each parent) needed to cause the disease. Carrier parents are unaffected because they have only one copy of the gene.

Genetic counselors are an excellent resource for discussing inheritability, family planning, career choices, and other issues related to living with Stargardt disease.

In 1997, FFB-funded researchers found the gene for Stargardt disease, ABCA4, which normally causes the production of a protein involved in the visual cycle. Lipofuscin buildup appears to be related to a mutation in this gene, and the resulting production of a dysfunctional protein.

What treatment is available?

FFB is supporting several promising avenues of research, including gene and drug therapies. Researchers are planning a clinical study of a treatment that involves delivery of a healthy version of the ABCA4 gene into retinal cells to restore production of the normal protein. They are also optimistic about several drugs that may slow vision loss by reducing the buildup of lipofuscin.

Because there is some evidence that sunlight may influence lipofuscin accumulation in the retina, u-v blocking sunglasses are generally recommended for outdoors. For people who already have significant vision loss, low vision aides are available.

Are there any related diseases?

Stargardt disease is also known as Stargardt macular dystrophy or fundus flavimaculatus. In addition to recessive Stargardt disease, there are other rarer forms inherited as dominant rather than recessive traits.

Fundus Flavimaculatus

Stargardt disease, also known as fundus flavimaculatus, is usually diagnosed in individuals under the age of 20 when decreased central vision is first noticed. On examination, the retina of an affected individual shows a macular lesion surrounded by yellow-white flecks, or spots, with irregular shapes. The retina consists of layers of light-sensing cells that line the inner back wall of the eye and are important in normal vision. The macula is found in the center of the retina and is responsible for the fine, detailed central vision used in reading and color vision.

Stargardt - Risk Factors

Stargardt disease, an early-onset form of macular degeneration, is an inherited disease. The condition is programmed into your cells at conception. It is not caused by injury, infection or exposure to a toxic agent. Because Stargardt disease is an inherited condition, there is nothing that can be done to reduce the risk of developing the disease.

However, recent findings in rodent models of Stargardt disease find that unprotected, prolonged exposure to light can accelerate vision loss. Therefore, The Foundation Fighting Blindness strongly recommends that patients with Stargardt wear brimmed hats or visors and sunglasses when outdoors.

Stargardt disease is an autosomal recessive disease. In autosomal recessive diseases, unaffected parents, who are carriers, have one gene with a disease-causing mutation paired with one normal gene. Each of their children then has a 25 percent chance (or 1 chance in 4) of inheriting the two diseased genes (one from each parent) needed to cause the disorder. Carriers are unaffected because they have only one copy of the gene.

Usher Syndrome

What is Usher Syndrome?

Usher syndrome is an inherited condition characterized by hearing impairment and progressive vision loss. The vision loss is due to retinitis pigmentosa (RP), a degenerative condition of the retina, and usually appears during adolescence or early adulthood. Balance may also be affected. Symptoms vary from person to person and progress at different rates.

Researchers funded by The Foundation Fighting Blindness (FFB) are studying causes and potential treatments for Usher syndrome and other retinal degenerative diseases. Excellent progress in research has been made recently

What are the symptoms?

There are at least three different forms of Usher syndrome. People with Usher syndrome type 1 (USH1) are born completely deaf and experience problems with balance. The first signs of RP — night blindness and loss of peripheral vision — usually appear in early adolescence.

In Usher syndrome type 2 (USH2), newborns have moderate to severe hearing impairment. Symptoms of RP typically start shortly after adolescence. Visual problems progress less rapidly than in Usher type 1 and hearing loss usually remains stable.

A rarer third type of Usher syndrome (USH3) was documented in 1995. Children with USH3 are usually born with good or only mild impairment of hearing. Their hearing and vision loss is progressive, starting around puberty. Balance may be affected.

Hearing loss in Usher syndrome is due to a genetic mutation (alteration) affecting nerve cells in the cochlea, a sound-transmitting structure of the inner ear. The same genetic defect also adversely affects photoreceptor cells in the retina, leading to vision loss. The retina is a delicate tissue in the back of the eye composed of light-sensing photoreceptor cells. These cells — also known as rods and cones — are responsible for converting light into electrical impulses that transfer messages to the brain.

How is Usher syndrome inherited?

Usher syndrome is passed from parents to their offspring through an autosomal recessive inheritance pattern. In this type of inheritance, two copies of a mutated gene, one from each parent, are required for the child to be affected. A person with only one copy of the gene is a “carrier” and rarely has any symptoms. Genetic counselors are excellent resources for discussing inheritability, family planning, genetic testing, and other related issues.

About 20,000 people in the U.S. have Usher syndrome. Worldwide, it is the leading cause of combined deafness and blindness. Approximately 30 percent of people with RP report some degree of hearing loss, and about half of them are diagnosed with Usher syndrome. Genetic testing may soon be available to help people define their condition and the risk of other family members or future offspring being affected.

What treatment is available?

Intensive research is under way to discover the causes of, and treatments for, all forms of RP. Researchers have found numerous genetic variations causing Usher syndrome, allowing for the designation of a variety of subtypes (i.e., 1A, 1B, IC, 1D, 1E, 1F, 1G, 2A, 2B, 2C, and 3A). Gene therapy to replace defective Usher genes is being studied in preclinical settings.

Researchers have also identified a nutritional therapy to slow the rate of vision loss in some RP patients. Although not a cure, they found that vitamin A palmitate can slow retinal degeneration in some people with RP and Usher syndrome type 2. They also showed that docosahexaenoic acid (DHA) — an omega-3 fatty acid — can enhance the effect of vitamin A. However, the enhanced benefit of DHA was realized only during the first two years of vitamin A therapy. (Only adult RP and USH2 patients were studied, so the effect in other patients with Ushers Syndrome is not known.) FFB can provide you with the recommendations of the study’s author.

A Phase II/lll human clinical trial is underway to test encapsulated cell technology (ECT) for delivery of a vision-preserving, therapeutic agent (ciliary neurotrophic factor or CNTF) to the retina. Preliminary results from the phase I study of the ECT-CNTF treatment were highly encouraging. Other therapeutic agents are showing promise in pre-clinical studies.

In addition, numerous researchers are experimenting with artificial retinal implants. The devices are placed on the surface of the retina and restore rudimentary, functional vision.

Researchers are also making excellent progress in gene therapy to treat Usher syndrome. With gene therapy, a normal gene is delivered to the retina to replace the mutated, disease-causing gene. The gene therapy may also be used to treat hearing loss.

Retinal cell transplantation is another area of growing interest. In these potential treatments, transplanted retinal cells would replace retinal cells lost to RP and other retinal degenerative diseases.

Are there any related diseases?

Other conditions, some of which are also inherited, can result in deafness and deaf-blindness but are not related to Usher syndrome. However, the RP associated with Usher syndrome shares most of its characteristics with other forms of RP. Researchers expect that advances in understanding and treating other forms of RP will directly benefit people with Usher syndrome, and vice versa.

Usher Syndrome - Risk Factors

Recent research findings suggest that in some forms of retinal degeneration, prolonged, unprotected exposure to sunlight may accelerate vision loss. Therefore, The Foundation recommends that patients wear sunglasses and brimmed hats or visors when outdoors.

Some women feel that their vision loss progressed more rapidly during pregnancy. However, the effect of pregnancy on Usher syndrome has not been clinically studied.

Usher syndrome is an inherited, genetic disease. It is caused by mutations in genes that are active in the retina and in the ear. Gene mutations are programmed into your cells at the time of conception. Usher syndrome is not caused by injury, infection or exposure to any toxic substance.

Usher syndrome is an autosomal recessive disease. In autosomal recessive diseases, unaffected parents, who are carriers, have one gene with a disease-causing mutation paired with one normal gene. Each of their children then has a 25 percent chance (or 1 chance in 4) of inheriting the two diseased genes (one from each parent) needed to cause the disorder. Carriers are unaffected because they have only one copy of the gene.

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(800) 683-5555 or info@FightBlindness.org

Retinitis Pigmentosa

What is Retinitis Pigmentosa?

Retinitis pigmentosa (RP) refers to a group of inherited diseases causing retinal degeneration. The cell-rich retina lines the back inside wall of the eye. It is responsible for capturing images from the visual field. People with RP experience a gradual decline in their vision because photoreceptor cells (rods and cones) die.

Forms of RP and related diseases include Usher syndrome, Leber’s congenital amaurosis, rod-cone disease, Bardet-Biedl syndrome, and Refsum disease, among others.

Normal vision

As seen by a person with retinitis pigmentosa

What are the symptoms?

Symptoms depend on whether rods or cones are initially involved. In most forms of RP, rods are affected first. Because rods are concentrated in the outer portions of the retina and are triggered by dim light, their degeneration affects peripheral and night vision. When the more centrally located cones — responsible for color and sharp central vision — become involved, the loss is in color perception and central vision.

Night blindness is one of the earliest and most frequent symptoms of RP. People with mainly cone degeneration, however, first experience decreased central vision and ability to discriminate color.

RP is typically diagnosed in adolescents and young adults. It is a progressive disorder. The rate of progression and degree of visual loss varies from person to person. Most people with RP are legally blind by age 40, with a central visual field of less than 20 degrees in diameter. It is a genetic disorder and, therefore, is almost always inherited.

How is RP inherited?

An estimated 100,000 people in the U.S. have RP, mainly caused by mutated genes inherited from one or both parents. Mutated genes give the wrong instructions to photoreceptor cells, telling them to make an incorrect protein, or too little or too much protein. (Cells need the proper amount of particular
proteins in order to function properly.) Many different gene mutations exist in RP. In Usher syndrome, for example, at least 14 disease-causing genes have been identified.

Genetic mutations can be passed from parent to offspring through one of three genetic inheritance patterns — autosomal recessive, autosomal dominant, or X-linked. In autosomal recessive RP, parents who carry the gene but have no symptoms themselves could have some children who are affected and others who are not. Similarly, in autosomal dominant RP, an affected parent could have affected and unaffected children. In families with X-linked RP, only males are affected; females carry the genetic trait but do not experience serious vision loss.

If a family member is diagnosed with RP, it is strongly advised that other members of the family also have an eye exam by a physician who is specially trained to detect and treat retinal degenerative disorders. Discussing inheritance patterns and family planning with a genetic counselor can also be useful.

What treatments are available?

The Foundation Fighting Blindness (FFB) has funded many important RP research and clinical advances. A nutritional therapy using vitamin A and docosahexaenoic acid (DHA) has emerged as an effective treatment for many patients; gene therapies are progressing through preclinical trials; technologies for delivering therapeutic agents to rod and cone cells are being studied in Phase II/lll clinical studies; an implantable microchip to enhance retinal function is under development. Details are available on FFB’s Web site, www.FightBlindness.org, or by calling 1-800-683-5555.

Although not a treatment for RP, it is also important to know that low vision aids are useful for maintaining independence. Low vision specialists can make personalized recommendations for mechanical, optical, electronic, and computer-based low vision products.

What testing is available?

Genetic testing is available for RP. It helps assess the risk of passing the disorder from parent to offspring. It also helps with attaining an accurate diagnosis. A patient with an accurate diagnosis is in a better position to keep track of new findings, research developments, and treatment approaches.

However, not all RP-causing genes have been discovered. If a person chooses to get genetically tested, there is about a 50 percent chance that their disease-causing gene will be identified.

Retinitis Pigmentosa - Risk Factors

Recent research findings suggest that in some forms of Retinitis Pigmentosa, prolonged, unprotected exposure to sunlight may accelerate vision loss. Therefore, The Foundation recommends that patients wear sunglasses and visors when outdoors.

Some women feel that their vision loss progressed more rapidly during pregnancy. However, the effect of pregnancy on Retinitis Pigmentosa has not been clinically studied.

Retinitis Pigmentosa is an inherited, genetic disease. It is caused by mutations in genes that are active in retinal cells. Gene mutations are programmed into your cells at the time of conception. Retinitis Pigmentosa is not caused by injury, infection or exposure to any toxic substance.

There are three common inheritance patterns: autosomal dominant, autosomal recessive, and X-linked.

In autosomal dominant forms of Retinitis Pigmentosa, an affected person has one gene with a mutation causing the disease paired with one healthy, normal gene. When the affected person has children with an unaffected partner, there is a 50 percent chance that the affected parent will pass the disease-causing gene to each child. The unaffected partner will only pass normal genes. In dominant diseases, a child who does not have the disease gene will not have the disease and cannot pass the disease to his or her children.

In autosomal recessive forms of Retinitis Pigmentosa, unaffected parents, who are carriers, have one gene with a disease-causing mutation paired with one normal gene. Each of their children then has a 25 percent chance (or 1 chance in 4) of inheriting the two diseased genes (one from each parent) needed to cause the disorder. Carriers are unaffected because they have only one copy of the gene.

In X-linked forms of Retinitis Pigmentosa, the gene for the disease is located on the X chromosome. Females have two X chromosomes and can carry the disease gene on one of these X chromosomes. Because they have a healthy version of the gene on their other X chromosome, X-linked diseases typically do not affect females. Sometimes, however, when carrier females are examined, the retina shows minor signs of the disease.

Males have only one X chromosome paired with one Y chromosome and are therefore genetically susceptible to X-linked diseases. Males cannot be carriers of X-linked diseases. Males affected with an X-linked disease always pass the gene on the X chromosome to their daughters, who then become carriers. Affected males never pass an X-linked disease gene to their sons because fathers pass the Y chromosome to their sons.

Female carriers have a 50 percent chance (or 1 chance in 2) of passing the X-linked disease gene to their daughters, who become carriers, and a 50 percent chance of passing the gene to their sons, who are then affected by the disease.

It is important to remember that because Retinitis Pigmentosa is an inherited disorder, it commonly affects other members of a family. If someone in your family is diagnosed with a retinal degeneration, it is strongly advised that all members of the family contact an eye care professional.

Macular Degeneration

What is Age-Related Macular Degeneration?

Age-related macular degeneration (AMD) is a retinal degenerative disease that causes a progressive loss of central vision. AMD is the most common cause of vision loss in individuals over 55. An estimated nine million people in the U.S. either have AMD or are at substantial risk of developing it.

What are the symptoms?

The macula is a small region in the center of the retina, which enables a person to see fine detail. Light sensing cells in the macula, known as photoreceptors, convert light from the visual field into electrical impulses and then transfer the impulses to the brain via the optic nerve. Central vision loss from AMD occurs when photoreceptor cells in the macula degenerate.

People with AMD may first notice a blurring of central vision, especially during tasks such as reading or sewing. Also, straight lines may appear distorted or warped. As the disease progresses, blind spots may form within the central visual field. In most cases, if one eye has AMD, the other eye will develop the disease. The extent of central vision loss varies depending on the type of AMD — dry or wet.

Normal vision

Picture as seen by someone who has macular degeneration

What is dry AMD?

Dry AMD accounts for about 90 percent of all cases, and normally affects vision less than wet AMD. Dry AMD is sometimes called atrophic, nonexudative, or drusenoid macular degeneration. A characteristic of dry AMD is the accumulation of tiny protein and fat-containing “drusen” deposits in a thin layer of cells beneath the photoreceptors in the retina called Bruch’s membrane. The origin of drusen is unknown, but they may be from waste products of various cells and tissues of the retina. Drusen may interfere with the health of the macula, causing progressive degeneration of the photoreceptor cells. Drusen deposits can, however, be present without vision loss.

Reduction in central vision from dry AMD occurs gradually over many years. Vision may even remain stable between eye examinations. People with dry AMD do not usually experience a total loss of central vision but tasks that require finely focused vision may become more difficult.

Research suggests that medium- and large-sized drusen present a greater risk for the progression of dry AMD to wet AMD. Wet AMD causes more severe vision loss. Although no standard therapies currently exist to treat dry AMD, several clinical research trials are evaluating methods, including laser treatments, to reduce their size.

What is wet AMD?

Wet AMD accounts for about 10 percent of all cases of macular degeneration. Wet AMD is also called choroidal neovascularization (CNV), subretinal neovascularization, or exudative or disciform degeneration. In wet AMD, abnormal blood vessels grow beneath the macula. These vessels leak blood and fluid into the macula that damage photoreceptor cells. Wet AMD often progresses rapidly and can cause substantial loss of central vision.

What treatments are available for wet AMD?

Excellent progress is being made in understanding, predicting, and treating wet AMD. Scientists have discovered new causes of the disorder — including genetic and environmental factors — as well as possible risk indicators. Numerous pharmaceutical companies are developing wet AMD treatments. Researchers are also studying cell transplantation to preserve and/or restore vision.

In June 2006, the FDA approved a drug called Lucentis for the treatment of wet AMD. Results from a large, two-year study showed that Lucentis halted vision loss in more than 90 percent of individuals with the wet form of age-related macular degeneration (AMD). In addition, Lucentis restored vision in 33 percent of those study participants. FFB has funded dozens of research projects to better understand the mechanisms that lead to vision-robbing blood vessel growth in wet AMD, giving companies like Genentech, maker of Lucentis, clear targets for the development of AMD treatments.

Numerous clinical research trials are being conducted to evaluate other promising treatments for wet AMD.

If you have been diagnosed with wet AMD, visit www.FightBlindness.org for a list of treatments and clinical trials. FFB recommends that patients always discuss study participation with a health care provider before enrolling.

How does nutrition affect AMD?

The Age-Related Eye Disease Study (AREDS), conducted by the National Eye Institute, revealed that a dietary supplement containing a combination of vitamins and minerals could help reduce the risk of advanced wet AMD and vision loss in people who are at greatest risk.

The AREDS study found that high levels of antioxidants and zinc can reduce the risk of developing advanced AMD by about 25 percent. The specific daily amounts of antioxidants and zinc used by the study researchers were 500 milligrams of vitamin C; 400 International Units of vitamin E; 15 milligrams of beta-carotene (often labeled as equivalent to 25,000 International Units of vitamin A); 80 milligrams of zinc as zinc oxide; and two milligrams of copper as cupric oxide. Copper was added to the AREDS formulations containing zinc to prevent copper deficiency anemia, a condition associated with high levels of zinc intake. Please visit www.nei.nih.gov/amd for more information about the AREDS recommendations.

AMD may also be related to dietary fat, according to scientists studying people with early- and intermediate-stage disease. They found that study subjects who reported eating lower amounts of vegetable and animal fat were less likely to develop advanced AMD.

However, fish and nuts can slow the progress of AMD. Studies have revealed that eating fish — which is high in healthful omega-3 fatty acids — has a protective effect. Though nuts are also protective, researchers did not determine which nuts, or how much of them, should be consumed.

Carotenoids are also possible protectors against AMD. Researchers found that the more dietary lutein and zeaxanthin — two carotenoids found in green and colorful vegetables — you eat, the lower the likelihood you have of developing advanced AMD. These carotenoids are highly concentrated in the macula and may be protecting it from damage.

What are the risk factors?

The exact causes of both dry and wet AMD are not completely understood. However, genetics, diet, cigarette smoking, bright sunlight, cardiovascular disease, and hypertension are considered to be possible risk factors for AMD.

Is AMD an inherited disease?

Researchers are discovering that genetics appears to be a major factor in more than half of the cases of AMD. In March 2005, three independent research groups — including one funded by FFB — discovered a gene called Complement Factor H (CFH) that appears to be linked to at least 50 percent of all cases of AMD. Prior to this landmark discovery, FFB-funded researchers discovered other genes that appeared to be linked to AMD, though these genes were implicated in a smaller number of cases than CFH.

What is the Amsler grid?

Along with regular examinations by an eye doctor, people can evaluate their eyesight for possible symptoms of AMD using a simple home testing device known as the Amsler grid. The Amsler grid, consisting of parallel and perpendicular lines, looks much like a sheet of graph paper. By focusing on a marked spot in the middle of the grid, it is quite easy to detect blurred or distorted vision. While the Amsler Grid is not a substitute for an expert medical diagnosis, it does allow people to check their eyesight regularly for possible symptoms of AMD. To receive a free Amsler Grid, please call the Foundation Fighting Blindness.

What low-vision aids are available?

As central vision declines, people with AMD may benefit from low-vision aids like magnifying glasses and special lenses, screens that enlarge small print, text-to-speech and speech-to-text computer software programs, and any number of other specialized technologies. Low-vision experts can also help individuals adapt daily living skills. Low-vision specialists are available through ophthalmology centers and physician referrals.

Common eye problems

Short sight (myopia) and long sight (hypermetropia) are common conditions, both caused by the cornea and lens not focusing properly on the retina.

Short sight is where the eyeball is elongated or the lens is too thick, causing the image to focus in front of the retina.

Short sight means that the image is focused in front of the retina

Long sight is where the eyeball is too short or the lens too thin, causing the image to focus behind the retina.

Long sight means that the image is focused behind the retina

How we see?

The images we see are made up of light reflected from the objects we look at. This light enters the eye through the cornea. Because this part of the eye is curved, it bends the light, creating an upside-down image on the retina (this is eventually put the right way up by the brain).

	Focusing on a nearby object	Focusing on a distant object

What happens when light reaches the retina?

The retina is a complex part of the eye, but only the very back of it is light-sensitive. This part of the retina has roughly the area of a 10p coin, and is packed with photosensitive cells called rods and cones. These allow us to see images in colour and detail, and to see at night.

Cones are the cells responsible for daylight vision. There are three kinds - each responding to a different wavelength of light: red, green and blue. The cones allow us to see in colour and detail.

Rods are responsible for night vision. They are sensitive to light but not to colour. In darkness, the cones do not function at all.

Focusing the image

The lens focuses the image. It can do this because it is adjustable - using muscles to change shape and help us focus on objects at different distances. The automatic focusing of the lens is a reflex response and is not controlled by the brain.

Sending the image to the brain

Once the image is clearly focused on the sensitive part of the retina, energy in the light that makes up that image creates an electrical signal. Nerve impulses can then carry information about that image to the brain through the optic nerve.

Low vision

What is low vision?

Specialist teacher Manju helps Sam Raj, who has low vision, at school © Fabienne Fossez / Sightsavers

Low vision is when, even after medical treatment, people have difficulty distinguishing objects and/or distances. People with low vision can be helped by changes made to their environment, such as painting the edges of stairs white so they can be seen more easily, or specially made devices.

Measuring low vision

Eye care specialists measure sight against a standard known as '20/20' vision. This based on what most people are able to see on a standard eye-test chart at a distance of 20 feet (in metres this is called 6/6 vision). If you can read the chart at 20 feet you have 20/20 or 'normal' vision.

The range of low vision:

• in mild cases of low vision, someone looking at a standard eye chart from 6 feet away will see what somebody with 'normal' or 20/20 vision sees from 18 feet away
• in extreme cases, low vision means that a person standing 3 feet from the eye chart will see the equivalent of what a person with 'normal' vision will see 60 feet away
• if someone's sight is any worse than this, they are classified as blind.

Low vision is officially defined as 'anybody who has an optimum corrected vision of less than 6/18 to 3/60 in their better eye'.

'Optimum corrected vision' means the 6/18 to 3/60 vision is enabled the aid of standard corrective visual devices - usually spectacles.

Many diagnosed with low vision can be helped by surgical treatment, and do not need low-vision aids. Even people with less than 3/60 vision can be helped.

Refractive error

A child has his eyes examined at school, Pakistan. © Jamshyd Masud / Sightsavers

Refractive error is an eye disorder meaning the shape of the eye does not bend light correctly, resulting in a blurred image. The disorder can be simply diagnosed, measured and corrected with spectacles, yet approximately 8.2 million people remain functionally blind due to uncorrected refractive error.

Sightsavers works in several ways to improve the vision of people with refractive error:

• screening: we identify individuals with poor vision which can be improved by spectacles or other optical devices. Last year we screened over 2 million people for refractive error.
• refraction: we evaluate the patient to determine what spectacles or device may be required.
• manufacture: we manufacture spectacles or an appropriate device and provide to those in need.

Common refractive errors:

• short sight (myopia)
• long sight (hypermetropia)
• Aging of the lens (presbyopia)
• Irregular curvature of the lens (astigmatism)
  

Low vision

Some people are still severely visually impaired even after correction, but their visual function can be greatly improved with the use of visual and non-visual aids.

Low vision aids

Visual aids

Visual aids for improving low vision work for those with visual capability of more than 1/60 (ie people who can see at a range of one foot what people with 'normal' vision would see at a range of 60 feet).

There are several types of low-vision device. Each works on particular form of low vision. Prescription is just the first step - it is also essential to motivate and train people to use the devices properly.

Visual aids include those that:

• help people seeing things close up. These are particularly useful for reading and to help children whose education would otherwise suffer. These include hand-held magnifying glasses and specially made, powerful spectacles.
• help people see things in the distance. These include telescopes.
• Technical enhancements such as closed circuit television, computer scanners and high tech image magnifiers.

Magnifiers

Some magnifiers can be made relatively easily and cheaply in optical workshops. Sometimes people in poorer countries use 'modified' plastic drainpipes fitted with a lens which acts as an effective reading aid.

Some studies show that over a third of children with low vision who cannot read would be able to with a simple magnifier.

Non-visual aids

Non-visual aids are often modifications to homes and everyday tools and equipment that make them low-vision friendly. These modifications are often quite cheap and easy to make.

Non-visual aids include:

• tilted desks for children, meaning they don't have to bend over flat desks to read text close-up.
• contrasting colours. A meal of rice and boiled fish can be difficult to distinguish for a low-vision person if served on a white plate. Certain colours and backgrounds can be combined to make text easier to read.
• size. Providing large felt tip pens or charcoal for children to write with, or using a photocopier to enlarge printed materials.
• lighting. Low-vision people needing more light can sit closer to windows or have better-positioned artificial light. People needing less light can benefit from dark glasses or large-brimmed hats.
• lines. A good way to aid mobility is through well-defined, contrasting-coloured lines to mark the edge of paths or steps.

Diabetic retinopathy

What is diabetic retinopathy?

Sinaida is being treated for diabetes at Mafinga District Hospital, Tanzania © Suzanne Porter / Sightsavers

Diabetic retinopathy is a complication of the eye cuased by diabetes.

What is diabetes?

Diabetes is a chronic disorder, meaning it is long-lasting or recurrent. It is characterized by a lack of insulin, or inability to use insulin effectively. This results in hyperglycaemia, an excess of glucose in the bloodstream. Over time, diabetes can also damage the heart, blood vessels, kidneys, and nerves, and increases the risk of cataract.

Types of diabetes

• Type 1 is rare and the onset is usually rapid and before the age of 20. It is caused by the pancreas not producing enough insulin, and is controlled by insulin injections. The cause is not known.

• Type 2 accounts for at least 90% of diabetes in the world today, and is often bought about by poor diet, obesity and a lack of exercise, or a genetic predisposition. It develops more slowly, and is caused by inadequate amounts of insulin, or the body being unable to use its supply of insulin effectively.

• Gestational diabetes is a third type, which affects pregnant women. It is thought that the hormones produced during pregnancy reduce a woman's receptivity to insulin, resulting in high blood sugar.

Facts about diabetes

• The World Health Organization estimates that 180 million people worldwide have diabetes
• This is likely to double by 2030
• Up to 50% do not know they have the condition
• Diabetes increases the risk of blindness x 25 times

New blood vessels growing from the optic disc © London School of Hygiene and Tropical Medicine

How diabetes affects the eye

Diabetes can affect retinal blood vessels in two ways: they can become leaky, or they can become blocked. If blood vessels near the central area of the retina leak, sight loss can result.

The small blood vessels in the retina can also become blocked, which can lead to loss of vision. If peripheral blood vessels become blocked this can stimulate the growth of new, abnormal ones ("proliferative retinopathy") which in turn can bleed, or lead to detachment of the retina.

As a general rule, the risk of retinopathy increases the longer the person has had diabetes. However, not all diabetics will develop retinopathy.

Diagnosis and treatment

Ramenathan is an optometrist at Sankara Hospital, India, who spreads awareness about diabetic retinopathy at screening camps © Fabienne Fossez / Sightsavers

When it comes to diagnosing type 2 diabetes, common symptoms include:

• excessive urination
• constant thirst and/or hunger
• weight loss
• fatigue

Some people do not realise they have diabetes, and the first they know about it is when they develop complications with their eyesight.

Diabetic retinopathy often has no symptoms at the early stages and the vision can be quite normal. Symptoms of diabetic retinopathy include gradual or sudden painless loss of vision in one or both eyes.

Prevention

To help prevent type 2 diabetes, people should:

• Achieve and maintain a healthy body weight
• Be physically active - at least 30 minutes of regular, moderate-intensity activity on most days

To help reduce the risk of retinopathy for people who already have diabetes, people should:

• Have good control of blood sugar (using the treatment they have been prescribed, in combination with a low carbohydrate diet)

• Even when patients are screened it can be difficult to detect early stages of diabetic retinopathy © Suzanne Porter / Sightsavers

  Have good control of blood pressure
• Reduce factors that are known to damage blood vessels, such as smoking
• To help reduce the risk of visual loss from diabetic retinopathy, diabetics should have regular eye examinations even if their vision is normal.

Treatment

At the moment the mainstay of treatment for diabetic retinopathy is laser treatment, which can reduce leaking from retinal blood vessels. Laser treatment is also effective at treating proliferative retinopathy, when abnormal blood vessels have formed. This treatment is more effective at preserving sight if the retinopathy is detected and treated early.

In severe proliferative retinopathy, some people need an operation called a vitrectomy to restore vision.

TRACHOMA

Trachoma (a repeated conjunctivitis infection) is found worldwide. Though eradicated in most developed countries, it remains a significant public health problem in parts of the developing world. It is closely linked to poverty.

There are currently 590 million people at risk from blinding trachoma, and Sightsavers is making it a priority eye care issue.

The facts about trachoma:

• 150 million people have active trachoma
• 10.6 million people have trichiasis (scarring of the eyelid as a result of infection and ingrowing eyelashes that scratch the cornea)
• 5.9 million people have irreversible blindness caused by trachoma - two thirds are women
• trachoma is the second most common cause of blindness after cataract.

Where is it found?

Trachoma is found in hot and dusty parts of the world. It is often endemic in rural areas without basic sanitation, where washing hands and faces is difficult. Trachoma spreads rapidly in crowded households or neighbourhoods.

Children and trachoma

Demographically, active trachoma is most prevalent in children, although the scarring doesn't usually become visible until the early 20s. For those who have suffered since childhood, trichiasis normally sets in during their 40s - or even earlier in the worst-affected areas.

Women and trachoma

Women are much more susceptible to trachoma than men because they spend far more time in contact with children, providing childcare.

Causes of trachoma

Trachoma, one of the most common causes of blindness in the developing world, is linked to extreme poverty and poor sanitation. It is triggered by bacteria that cause repeated conjunctivitis, irritating the eyes and creating a mucous discharge. Although the conjunctivitis clears up after a month or so, it is easily spread. This is particularly the case in places where there is little water for people to wash their hands and faces regularly.

How trachoma causes corneal damage:

• reducing the amount of tears produced
• making it difficult to close the eyelids (which lubricate the eye and help flush away dust and dirt)
• triggering trichiasis, where the eyelid and eyelashes turn in on the eye.

How does it spread?

The discharge from infected eyes attracts flies that then land on other people's skin. People in crowded households or neighbourhoods are particularly vulnerable.

Trichiasis

Each infection of trachoma leads to a small amount of scarring on the cornea and conjunctiva. This scarring builds up over years of repeated infection until trichiasis sets in.

Trichiasis is when this scarring causes the eyelid to turn inwards, making eyelashes scratch the eyeball. Each time the eyelashes are lowered to blink, the cornea - which enables the eye to focus - is put at risk. Eventually it becomes opaque, causing poor vision and eventual irreversible blindness.

People often try to pull out the eyelashes themselves, put powder on their eyelids, or use tight headscarves to pull up the skin around the eye to restrict blinking. None of these provides a long-term solution.

Treating trachoma

Surgery:

• stops the trichiasis from getting worse
• improves vision in the short term
• makes it much more comfortable for people
• reduces the levels of eye discharge

Find out more about our work on treating trachoma, or go back to the previous page, or find out how to make a donation

Antibiotics

Sightsavers provides two types of antibiotic to treat trachoma:

• tetracycline - ointment applied directly to the eye over a period of six weeks. Done properly, it has a success rate of 60-80%.
• oral azithromycin - this is just as medically effective as tetracycline, but because it is taken orally it is far more successful.

Problems with antibiotics

• antibiotics have side effects
• overuse can make people immune to them. For this reason they should only be part of trachoma treatment, used with infection-reduction methods such as facial cleanliness and good sanitation.
• treatment takes a long time and is difficult to administer in rural areas.

Facial cleanliness

Children with dirty faces may be up to two times more likely to contract the trachoma virus than those without. One of the best ways to prevent the transmission of trachoma is by encouraging face and hand washing - not easy where water is scarce.
Sightsavers' local partners are encouraging facial cleanliness through:

• training health workers to conduct health promotion sessions in local communities, explaining the benefits of face and hand washing
• promoting the use of the 'leaky tin', a cheap and easy method of face and hand washing where water is scarce
• improving access to water
• improving availability of soap.
  Find out more about our work on treating trachoma, or go back to the previous page, or find out how to make a donation

Environmental change

The transmission of trachoma by flies can be tackled by reducing the number of flies with which people come into contact. Sightsavers' local partners helps communities to achieve this by setting up local sanitation commitees to:

• Build covered latrines and encourage facial cleanliness
• Discourage people from sleeping close to their livestock, a common practice in Africa and Asia.
• Encourage villagers to collect and burn rubbish on a regular basis

River blindness

River blindness (onchocerciasis) is caused by a worm that breeds in fast-flowing rivers. It is a major cause of blindness in west and central Africa. Sightsavers is combating it with the drug Mectizan®.

Symptoms of river blindness

As well as causing blindness, river blindness creates nodules on the skin and severe itching. This results in damage to the pigment and over time the skin becomes mottled. This causes further problems because the de-pigmented spots are more susceptible to skin cancer.

Impact of river blindness

River blindness is endemic in certain areas. This has two important social implications:

• children miss out on education because they are staying at home to act as full-time carers for older relatives who have become blind
• people flee areas where the level of infection has hit hard, leaving 'ghost villages' behind. Unfortunately these infected areas are the ones with the most fertile land, closest to the river.

Causes of river blindness

River blindness is caused by a parasitical worm, onchocerca volvulus. The worm larvae are spread by the black simulium fly, which breeds in the high-oxygen water of fast-flowing rivers. The fly transmits the disease when it bites people, making those who live or work near the rivers vulnerable. Sightsavers is combating river blindness with the drug Mectizan®.

How river blindness spreads

When a black simulium fly becomes infected, the worm larvae spread to its saliva glands. When it bites a human, these pass into the skin. Here they develop into adults and form nodules under the skin. These adults then breed, producing thousands of larvae which spread throughout the whole body - including the eyes. This causes intense itching.

Impact on vision

A bite from an infected black simulium fly creates vulnerability to eye conditions such as glaucoma and cataract. But the biggest problem is when the worms die. The reaction of the person's immune system causes inflammation. If this happens in the eye it can cause blindness.
If infected at birth with river blindness it is common for people to have become blind by the time they have reached their 40s

Controlling river blindness

River blindness - caused by a parasitical worm that spreads through the body - is transmitted to humans by the black simulium fly which breeds in fast-flowing rivers. Sightsavers is combating it with the drug Mectizan®.

Ways to break the cycle of infection:

• reducing the number of flies by spraying affected areas with insecticide - an expensive and short-term solution
• slowing fast-flowing rivers, making them unattractive as breeding grounds - expensive and not always practical
• reducing exposure to flies by using protective garments - impractical because of the temperatures in affected countries
• killing the adult worms by removing the worm 'nodules' - difficult because infected villages are often very remote and poor, making accessible surgery difficult
• providing a yearly dose of the drug Mectizan® in affected areas.

Using Mectizan®

Mectizan® is an effective way to make the adult female worm temporarily infertile, killing larvae. If an uninfected simulium fly bites an infected person who has taken the drug, it will not itself become infected or infectious.

Problems with Mectizan®

Mectizan® is the best and most cost-effective way of tackling river blindness. But it is not without problems:

• it needs to be administered regularly and across a whole community, not a simple task in remote area
• with 125 million people at risk, training staff to distribute the drug is a major challenge for Sightsavers and our partners.

Childhood blindness

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Blindness is more common in poor countries than in rich ones. Children in low-income countries such as Sierra Leone are four times more likely to be blind than those born in high-income ones such as the UK. The main cause - corneal scarring - is rooted in poor diet (lack of Vitamin A) and inadequate sanitation. Sightsavers is working to address both.

Why is childhood blindness a priority?

There are several reasons why Sightsavers believes eliminating childhood blindness is a priority:

• there are an estimated 500,000 new cases each year of childhood blindness - roughly one per minute
• blindness in children is often preventable if communities and parents become aware of the causes
• without early intervention for cataract blindness children may go blind permanently
• blinding conditions increase child mortality - 50 per cent of children who become blind die within two years
• 90 per cent of children who are blind don't go to school
• eliminating childhood blindness will lead to a greater reduction in the number of 'blind years' experienced by adults.

Causes of childhood blindness

Childhood blindness has many causes. In poor countries the main ones are corneal scarring and cataract. If not treated in childhood, trachoma and river blindness may affect sight in later life. Some blindness is hereditary.

Global figures show:

• roughly 57 per cent of childhood blindness is unavoidable
• 28 per cent is preventable
• 15 per cent is treatable

The proportion of children suffering non-preventable blindness in wealthy and poor countries is comparable, but preventable blindness is much more prevalent in the developing world.

The main causes:

• corneal scarring (the drying out and scarring of the outer eye because of vitamin A deficiency) is the most common cause of childhood blindness. It has caused irreversible sight loss for around 230,000 children.
• cataract (the clouding of the eye's lens) causes an estimated 39 per cent of all childhood blindness. It affects around 200,000 children worldwide.
• trachoma is a repeated infection, causing scarring of the upper eyelid, turning it inwards and making the eyelashes scratch the eye and cause blindness. Although this tends to blinds adults, after repeated infections, trachoma is often first suffered in childhood.
• river blindness (caused by a parasitic worm and spread by flies) rarely blinds before the age of 15, but must be prevented by taking Mectizan® to avoid blindness in later life.

Cataract

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Cataract is a clouding of the eye's lens - the part of the eye responsible for focusing light and producing clear, sharp images.

The lens is made up mainly of water and protein. Over time, protein can build up, clouding the light passing through the eye and making sight blurred or fuzzy. For most people, cataracts are a natural result of ageing.

Often cataracts develop in both eyes at the same time. The symptoms vary, but include a gradual blurring of vision, halos around lights, glare and double vision. The very worst cataracts - where the iris appears almost entirely clouded over - can cause a total loss of vision.

Treating cataract is simple. In 2004 Sightsavers performed more than 95,000 operations to restore the sight of cataract sufferers through simple but effective treatments.

There is no single cause of cataract (the clouding of the eye's lens). A number of risk factors seem to have an impact. There are some risks that can be reduced by a change in lifestyle, and some that can't.

Risks that can be reduced:

• cigarette smoking
• drugs: some eye drops used to treat eye problems contain steroids. If unsupervised and taken over a long time, they can cause cataracts.
• diabetes: proper treatment can reduce the risk of cataract
• dehydration: people who have suffered severe dehydration seem more likely to suffer from cataract. This can result from severe illness (such as cholera), acute heat stroke or even from local customs such as withholding water from women during labour and immediately after giving birth.

Risks that can't be reduced:

• ageing - the single-most important cause of cataract
• genetic predisposition- in 25-50 per cent of cases there is a family history of cataract
• eye conditions such as short sightedness and inflammation in the eye seem to be linked to cataract. Severe trauma to the eye can also be a cause.
• environmental factors - cataract occurs more often and at an earlier age in developing countries
• daylight - some controversially believe ultraviolet light worsens cataract. This is unproven and impossible to combat if true.

Removing cataract (the clouding of the eye's lens) is a relatively simple surgical procedure. It is common and easily accessible in developed countries. But in the countries where Sightsavers works, many people with cataracts are yet to benefit.

Why is this?

• lack of awareness in some areas about the number of people with cataracts, and how best to diagnose them
• lack of staff and equipment to significantly reduce the growing backlog of cataract operations needed.
  

There are also reasons why prospective patients may be wary of an operation:

• they may not know that the operation is simple and safe
• they may have heard of someone who had a bad experience while having an operation
• they may live far from towns, and getting to hospital may involve a lot of travel and expense. This is never easy for a blind person.
• as well as the travel costs, people will not be able to work immediately after the operation and will lose income
• people sometimes expect to go blind as a natural part of ageing and are unaware of how simple it is to have their sight restored

Glaukoma

Glaucoma is the third biggest cause of blindness worldwide. It affects around 60 million people, of whom about 4.5 million have become blind. It is common in both developed and developing countries.

Glaucoma is when the nerve, known as the optic nerve, that carries images from the eye to the brain is damaged. This is caused by clogged drainage channels within the eye which cause pressure in the eyeball. The result is loss of vision. It develops gradually, and people may not realise they have it. On reaching an advanced stage glaucoma is extremely difficult and expensive to treat.

Glaucoma is often associated with ageing, though it is not confined to the elderly. People with glaucoma in their family history are far more likely to be at risk. It is more prevalent among African and Asian people.

The main types:

• primary open angle glaucoma is the most common glaucoma. It happens when blockages deep in the eye's drainage channels cause the inner pressure of the eye to build because not enough fluid is drained. This causes a gradual loss of vision.
• angle closure glaucoma (or acute or narrow angle glaucoma) is less common, but develops swiftly. It is caused by a build up in fluid - the result of blockages at the entrance to the eye's drainage channels. Symptoms include headaches, eye pain and blurred vision.
• secondary glaucoma is generally caused by eye injury, tumour or advanced cataract. It can also be a side-effect of certain drugs - particularly steroids.
• normal tension glaucoma causes damage to the optic nerve even though there is no notable increase in the pressure of the eyeball. The causes are subject to debate.
• pigmentary glaucoma occurs when pigmentary granules from the iris break up and spread into the fluid of the eyeball. These then block eye drainage channels.

Treatments

In western countries, the key to reducing the incidence of glaucoma is early diagnosis. This is done by ensuring that a glaucoma check is part of a routine eye test. It measures eye pressure using a jet of air, and examines the inner eye for symptoms.

In Asia and Africa, where eye tests are not as common, checking for glaucoma isn't easy. This makes the impact of the disease far greater as it is caught much later on, when it is difficult to treat.

Treatments for glaucoma

Treating open angle glaucoma is done by lowering the inner-eye pressure through:

• reducing the amount of aqueous humour produced using medication
• increasing the amount drained from the eyeball using surgery or laser treatment.

For closed angle glaucoma, surgery is the only treatment with noticeable benefits.

Medication

Medication normally comes in the form of eye drops, which often need to be administered every day, for life. As with other forms of long-term medication, this can prove difficult in places where 'western' approaches to medication are not common practice. In poor countries, eye drops are also often either not available or very expensive.

Laser treatment

Laser treatment is very costly and provides only a temporary lowering of pressure.

Surgery

Surgery is the prime treatment for glaucoma in the developing world. It involves creating an artificial drainage hole in the eye, allowing the excess aqueous humor to drain from the eyeball. But surgery has its problems - it may fail, and it increases the risk of cataract.