Stargardt Disease

 

Stargardt disease (also called Stargardt dystrophy or fundus flavimaculatus) is a genetic eye disease, and the most common childhood (juvenile) macular condition. It is caused by over 1000 different types of mutations (faults) in a single gene and affects about 1 in 10,000 people.

 

It usually first appears between the ages of 10 to 20, although visual impairment may not be apparent until as late as 40 to 50 years of age in the late-onset forms of the disease.

 

Stargardt disease affects the function of the macula (central part of the retina), leading to problems with detailed central vision and colour perception, and in more severe types may also affect side (peripheral) vision and night vision. 

 

Stargardt disease is caused by a faulty (mutated) gene. Genes are a set of instructions on how the body should develop. We all inherit two sets of genes, one set from each of our parents, and we each pass on one of those sets of genes to our children. These sets of genes 'lie' in pairs (one from each parent) and they determine our traits - the many things which make us individuals, such as hair or eye colour, or whether we get certain genetic conditions. 

 

The most common pattern of inheritance of Stargardt disease is autosomal recessive. This means that when two carriers of this faulty gene have a child, there is a 1 in 4 (25%) chance of the child having Stargardt disease. If an individual with Stargardt disease has a child with a partner who is a carrier, the child would have a 1 in 2 (50%) chance of having the disease. The most common gene associated with Stargardt disease is called ABCA4.

 

Special tests are available to determine which mutation and gene is causing the disease in many cases. Blood or saliva samples from both parents or one or more siblings are also necessary to confirm the diagnosis. Genetic testing to confirm the diagnosis as well as genetic counselling services to help better understand and cope with the condition are available in most states across Australia. 

 

People with Stargardt disease may also wish to register with the Australian Inherited Retinal Disease Register and DNA Bank, located at Sir Charles Gairdner Hospital in Perth. Through this national registry, researchers can gain more insight into the prevalence and varied presentation of Stargardt disease across Australia and identify suitable patients when new treatments become available. Call (08) 6457 2866 for more information.

 

In Stargardt disease, a waste product called lipofuscin slowly builds up in the retinal pigment epithelium (RPE), a special layer of the retina. The cells of the RPE normally clear away waste products like lipofuscin, however in someone with Stargardt disease, the ‘faulty’ (mutated) gene gives incorrect instructions which prevent the removal of these waste products. The waste products gradually build up, damaging the cells in the macula and sometimes in the rest of the retina. 

 

Stargardt disease affects the macula, making central vision unclear and sometimes distorted or blurred. As the disease progresses, a dark patch may appear in the centre of vision which often enlarges slowly over several decades. In some individuals, this can eventually extend out to the periphery and affect side vision, but for the majority of people, side vision is not affected. Most people with vision loss from Stargardt disease can manage to move about independently and use their side vision to view objects. Many people with Stargardt disease are able to manage very well with visual aids and adaptive technologies.

 

Stargardt disease can also cause problems such as glare and difficulties adapting to changing light conditions. 

 

In rare cases, Stargardt disease can be complicated by new, leaky blood vessels forming under the retina (neovascularisation), leading to sudden further loss of central vision. 

 

There is currently no cure for Stargardt disease. Symptoms of light sensitivity can be reduced by wearing sunglasses and a wide brimmed hat. 

 

For rare cases where Stargardt disease is complicated by new, leaky blood vessels forming under the retina, treatment with anti-VEGF injections into the eye can help stabilise and maintain best functional vision for as long as possible.

 

In general, the same dietary recommendations that are made for age-related form of macular degeneration (AMD) can apply to people with Stargardt disease. Supplements based on the Age-Related Eye Disease Studies (AREDS) are not indicated for people with Stargardt disease, as these are only for people with certain stages of AMD. 

 

Significant research is being conducted to understand the different genetic changes (mutations) associated with the disease. The trigger for the onset of the disease and the factors that alter the rate of progression during the lifetime of an individual with Stargardt disease are also being investigated. 

 

Gene therapies are being developed to treat genetic eye conditions such as Stargardt disease, which work by delivering a ‘normal’ copy of the faulty gene to the retina, which takes over the function of the defective gene. In addition, a substantial amount of research is taking place using human stem cells to better understand how the disease develops, screen or test new drugs that can reverse the abnormal processing of the gene, and to replace damaged cells in the retina.

 

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