Stargardt disease is an inherited form of macular degeneration. While it affects the same part of the central retinal, called the macula, as age-related macular degeneration (AMD), it is different from AMD.
Patients with Stargardt’s often develop symptoms including difficulty reading, black spots in their central vision, or changes in color perception between the ages of 10 and 40. The disease is also known as fundus flavimaculatus.
Stargardt’s can be diagnosed when an eye doctor sees elongated white, branching flecks in the retina during a dilated eye exam. A fluorescein angiogram may be performed to confirm the diagnosis. In this test, a dye (fluorescein) is injected into the arm and photos are taken of the retina. In patients with Stargardt’s, the camera’s view of the dye is blocked by material that builds up in the retina. This finding is called the “dark choroid.” This material, a fatty substance called lipofuscin, not only blocks to camera’s view of fluorescein in the choroid (a vascular tissue under the retina), but also constitutes the white flecks visible to an ophthalmologist viewing the retina with an ophthalmoscope.
Visual acuity may range from 20/20 to 20/200, but by age 50, about half of Stargardt patients will have acuity of 20/200 or worse. The disease primarily affects the macula, so peripheral vision is minimally affected.
The most common cause of Stargardt’s is an autosomal recessive mutation in a gene called ABCA4. This gene normally facilitates transport of a “used” form of vitamin A out of photoreceptors, the light sensitive cells in the retina. Without ABCA4, this material builds up in the retina and contributes to the formation of lipofuscin. Patients usually inherit Stargardt disease from parents who are unaffected carriers of the disease where one of the two copies of the ABCA4 gene in each parent carries a mutation. In such families, each child has a 25 percent chance of developing Stargardt’s disease and a 50 percent chance of being an unaffected carrier.
Rarely, Stargardt disease can be caused by an autosomal dominant mutation in a gene called ELOVL4. This gene is responsible for the synthesis of very long chain fatty acids. In families with this form of the disease, one parent has the disease and 50 percent of his/her children inherit one copy of a mutated version of the ELOVL4 gene and develop the disease.
There are currently no proven treatments for Stargardt disease. Sunglasses are thought to be somewhat protective when worn in bright light, but this has not been proven. Clinical trials are underway to test lipofuscin blocking drugs, and gene or stem-cell based therapies.
You can explore a list of open clinical trials for Stargardt’s disease on the clinicaltrials.gov website.