Stargardt's disease (also known as fundus flavimaculatus and Stargardt's macular dystrophy) is the most common form of inherited juvenile macular degeneration. Inherited as an autosomal recessive trait, it is a severe form of MD that begins in late childhood, leading to legal blindness.
Stargardt's disease is symptomatically similar to age-related macular degeneration, and it affects approximately 1 in 20,000 children. Boys and girls are equally affected by this condition.
Stargardt's disease is thought to be passed along to children when both parents carry gene mutations causing the eye disease. Parents can carry recessive genetic traits responsible for Stargardt's, even though they themselves may not have the disease.
Researchers have found that about 5 percent of the human population carries gene mutations causing inherited retinal diseases such as Stargardt's and retinitis pigmentosa.
Children may be misdiagnosed with a psychological vision loss given as the diagnosis. The disease is often misdiagnosed, or not diagnosed in the first few years of onset, and this could be the result of little evidence being found during eye examinations.
Stargardt's disease is usually diagnosed in individuals under the age of twenty, when decreased central vision is first noticed. It causes a progressive loss of central vision and, in the early stages, patients may have good visual acuity, but they may experience difficulty with reading and seeing in dim lighting. Other common symptoms of Stargardt's disease include blurriness and distortion. On examination, the ophthalmological findings vary significantly with the progression of the disease. In fundus photos, patients with early Stargardt's disease appear to have simple macular degeneration. Children with the disease typically begin experiencing dark adaptation problems and central vision loss between six and twelve years of age, but symptoms may also first appear in adulthood.
As the disease progresses, lipid rich deposits accumulate in the retinal pigment epithelium (RPE) layer beneath the macula. This "lipofuscin" appears as yellowish-tinted flecks. The RPE is a layer of cells that lies between the retina and the choroid, where it serves the purpose of nourishing the photoreceptor cells. In advanced Stargardt's disease, the buildup of lipofuscin causes atrophy of the macula and the underlying RPE. The progression of vision loss is variable and can start with a visual acuity of 20/40 and decrease rapidly (especially in children) to 20/200 (legal blindness). By age 50, approximately 50% of all of those studied in clinical trials had visual acuities of 20/200 to 20/400. In late stages of this disease, there may also be color vision impairment.
Children with Stargardt’s disease often complain of difficulty adapting to the dark after sunlight exposure. Light striking our retina causes chemical reactions to occur in the rods and the cones. Our retina must continuously create new photo-reactive chemicals and remove the waste products of these chemical reactions. When a Stargardt’s patient is exposed to bright sunlight, the retina may become bleached by the light and the sharpness of vision may decrease and blind spots may become denser. These are temporary conditions, but can be prevented or lessened by use of sun filters and hats.
From laboratory studies in mice, it has been suggested that sun filters may lessen the formation of lipofuscin, which is the waste products of the rods and cones. Lipofuscin, if allowed to accumulate, may damage the retina. Mice, without the ABCR gene like patients with Stargardt’s, do not accumulate these waste products when raised in darkness. Additionally, younger patients, under 26 years old, transmit more ultraviolet light to the retina due to the clarity of the crystalline lens which in theory may lead to more retinal damage in Stargardt’s patients. More research is needed.
The damage to the retina also leads to greater internal reflection of light often causing an increase in light sensitivity (photophobia).
Currently, there is no effective treatment for Stargardt's disease. It is also important that the learning and working environment be adapted for people with Stargardt's disease. Appropriate low vision aids and lighting are two important considerations for helping both children and adults to function as normally as possible. |
