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.
See also: Age related macular degeneration.