Stargardt disease is the most common form of inherited macular degeneration, affecting about 30,000 people in the U.S. The progressive vision loss associated with Stargardt disease is caused by the degeneration of photoreceptor cells in the central portion of the retina called the macula.
The retina is the delicate light-sensing tissue lining the inside wall of the back of the eye. Photoreceptor cells in the retina convert light into electrical signals, which are sent to the brain where they are processed to create the images we see. The macula, which is rich in cone photoreceptors, is responsible for sharp central vision — for tasks like reading, watching television, and looking at faces. Cones also provide vision in lighted settings and color perception.
Decreased central vision due to loss of photoreceptors in the macula is the hallmark of Stargardt disease. Some peripheral vision is usually preserved. Stargardt disease typically develops during childhood or adolescence, but the age of onset and rate of progression can vary. The retinal pigment epithelium (RPE), a layer of cells supporting photoreceptors, is also affected in people with Stargardt disease.
A loss or change in central vision is what usually leads to the initial diagnosis of Stargardt disease. A retinal doctor examining the retinas of a person with Stargardt disease will see characteristic yellowish flecks in the RPE. The flecks are deposits of lipofuscin, a byproduct of normal retinal cell activity. However, in Stargardt disease, lipofuscin accumulates abnormally.
The progression of vision loss in Stargardt disease is variable. Visual acuity (the ability to distinguish details and shape) may decrease slowly at first, accelerate, and then level off. Some peripheral vision is usually maintained.
Stargardt disease is usually an autosomal recessive condition caused by mutations in the gene ABCA4. It is inherited when both parents, called carriers, have one mutated copy of ABCA4 and a normal copy. Each child has a 25 percent chance of inheriting the two copies of ABCA4 (one from each parent) needed to cause the disease. Parents are unaffected carriers because they have only one mutated copy of ABCA4.
In a small percentage of cases, Stargardt disease is caused by mutations in the gene ELOVL4 and is passed on to children through the autosomal dominant inheritance pattern. In these cases, the parent has the disease and has a 50 percent chance of passing the mutated copy of ELOVL4 (and the disease) on to each child.
Living with the Disease
There are many services and accommodative and assistive resources available to people and families with Stargardt disease. Visit the Foundation’s Living and Thriving pages to learn about many of these resources. A low vision specialist can help recommend the resources that are right for you.
Genetic testing is available to help people definitively diagnose their condition and the risk of other family members or future offspring being affected. A genetic diagnosis can also help a person qualify for a clinical trial. Genetic counselors are excellent resources for discussing inheritability, family planning, genetic testing, and other related issues.