Stargardt
Stargardt disease is the most common form of inherited juvenile macular degeneration. It is characterized by a reduction of central vision with a preservation of peripheral (side) vision.
Clinical Description
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.
The progression of visual loss is variable. One study of 95 individuals with Stargardt disease showed that once a visual acuity of 20/40 was reached, there was often rapid progression of additional visual loss until acuity was reduced to 20/200 (legal blindness). By age 50, approximately 50 percent of all those studied had visual acuities of 20/200 or worse. Eventually, almost all individuals with Stargardt disease are expected to have visual acuities in the range of 20/200 to 20/400. The reduced visual acuity due to Stargardt disease cannot be corrected with prescription eyeglasses or contact lenses. In late stages of the disease, there may also be noticeable impairment of color vision.
Inheritance
Stargardt disease is almost always inherited as an autosomal recessive disorder. It is inherited when both parents, called carriers, have one gene for the disease paired with one normal gene. Each of their children then has a 25 percent chance of inheriting the two copies of the Stargardt gene (one from each parent) needed to cause the disease. Carriers are unaffected because they have only one copy of the gene. At this time, and until the disease gene is identified, it is impossible to determine who is a carrier for Stargardt disease until after an affected child is diagnosed.
Treatment
In 1997, Foundation researchers isolated the gene for Stargardt disease. The ABCR gene produces a protein involved in energy transport to and from photoreceptor cells in the retina. Mutations in the ABCR gene, which cause Stargardt disease, produce a dysfunctional protein that cannot perform its transport function. As a result, photoreceptor cells degenerate and vision loss occurs. The discovery of the ABCR gene now allows researchers to study the underlying biochemical interactions that result from mutations in this gene. Understanding how genetic mutations lead to retinal degeneration is critical for the development of experimental therapies. Although there is currently no treatment for Stargardt disease, individuals may benefit from the use of low vision aids and orientation and mobility training.
2007 Foundation Fighting Blindness. All rights reserved.
