Stargardt Disease

Oct 13, 2018

Stargardt disease, also known as Stargardt macular dystrophy or juvenile macular degeneration, is a condition that involves the retina of the eye. The retina is the layer of the eye which is responsible for sensing light. Most people with Stargardt disease have some loss of vision at a young age, either as a child or an adolescent, although some people may retain good vision until adulthood. It is estimated that about 1 in 10,000 people has Stargardt disease.

It is a progressive condition, and the vision gradually gets worse over time to 20/200 or poorer. However, complete blindness rarely occurs in affected people.

Signs and Symptoms

The most common symptom of Stargardt disease is the slow, progressive loss of vision in the center of the focal point of sight in both eyes. Initially, affected individuals may report slight disturbances, such as a gray or hazy spot in the center of the visual field. Eventually, this may become a dark black spot that completely blocks sight in the center of the visual field.

Other signs and symptoms may include:

Sensitivity to bright light
Increased time of adjustment to changes in the environmental light
Color blindness

The rate of progression in Stargardt disease is highly variable. In general, patients with an early onset of disease tend to experience more rapid vision loss than those who develop the initial symptoms later in life. Most people eventually develop poor visual acuity of 20/200 or worse. They may also lose some peripheral vision in later stages of the disease.

Pathophysiology

Vision loss in Stargardt disease occurs due to the degeneration of the macula. The macula is a small area in the middle of the retina that allows clear, sharp vision when an individual looks straight ahead at an object.

Stargadt disease is an inherited disorder, usually caused by a mutation in the ABCA4 gene. This gene usually helps to remove toxic by-products in the reaction of vitamin A inside the photoreceptor cells. These sensory cells are responsible for the detection of light and conversion into electrical signals.

For people with Stargardt disease, this removal of by-products does not occur as usual, and there is a build-up of lipofuscin as a result. Lipofuscin is a fatty substance that can form yellowish clumps around the macula. The accumulation of this degradation product has the potential to impair vision. In severe cases, this can lead to necrosis of the photoreceptors.

Inheritance Pattern

The gene mutation responsible for causing Stargardt disease is usually inherited in an autosomal recessive pattern. This means that both parents must be genetic carriers for a child to get the disease. If both parents are carriers each child has a:

25% chance of having Stargardt disease
50% chance of being a carrier of the Stargardt disease gene
25% chance of being unaffected

However, some other gene mutations account for approximately 1 in 20 cases of Stargardt disease. These are inherited in an autosomal dominant pattern. In this case, if one parent is a carrier, each child has a 50% chance of having the disease.

Diagnosis

Diagnosis of Stargardt disease may include:

Retinal examination for evidence of yellow specks (lipofuscin deposits)
Visual field testing
Color testing
Fundus photo of the retina
Electroretinography (ERG)
Optical coherence tomography (OCT)

Management

There is no known cure for Stargardt disease. Some recommendations made on the basis of available but limited evidence include:

Wearing dark glasses when outside, to reduce exposure to bright light, which may be associated with lipofuscin build-up
Avoiding cigarette smoke
Avoiding high doses of vitamin A in supplements