Stargardt macular dystrophy
What is Stargardt macular dystrophy?Stargardt macular dystrophy (or Stargardt disease) is a genetic eye condition that causes progressive central sight loss. Affecting a person’s fine detailed vision, the condition is estimated to affect between one in 8,000 to 10,000 people in the UK.
Stargardt disease is a consequence of progressive damage to the macula, which is a small area in the centre of the retina, the specialised light-sensitive layer that lines the back of the eye. The macula is responsible for our sharp, straight-ahead vision that we rely on for many activities – such as reading, recognising faces or watching TV.
Once the condition develops, a person’s symptoms will get slowly worse over time. As they will usually maintain their peripheral (side) vision, it is rare for someone to become completely blind. However, most people with Stargardt disease will experience severe sight loss that affects their daily lives.
What causes Stargardt macular dystrophy?Stargardt disease is caused by faults in a gene known as ABCA4. This gene provides the instructions for making an important protein that usually removes toxic by-products out of the light-sensing cells in the retina, at the back of the eye.. But when this protein is missing or faulty, these substances build up and form a fatty waste product – called lipofuscin – in and around the macula that start to affect the person’s central vision. And eventually this causes the progressive sight loss that is characteristic of Stargardt disease.
When faults in the ABCA4 gene are the cause of the condition, a child will inherit one faulty copy of the gene from each parent. Their parents will typically each carry one copy of the faulty gene but will not have the disease themselves.
Although having faults in ABCA4 is the most common cause of Stargardt disease, a minority of patients have faults in other genes – ELOVL4, PROM1 and RDS (also known as PRPH2).
What are the signs and symptoms of Stargardt macular dystrophy?The signs and symptoms of Stargardt disease typically start in late childhood or adolescence and will gradually get worse over time. However, the age that the first symptoms develop, and the speed of the disease progression varies widely from person to person. For some people, sight loss may not begin until later in adulthood.
At first a person will usually experience unclear or blurry vision. As their condition progresses, things may start to appear distorted or wavy and some people may also develop blind spots. In addition to problems affecting their central vision, sometimes a person may experience problems with light, such as sensitivity and difficulties adapting to low light levels - and some may have issues with colour perception.
As Stargardt disease doesn’t normally affect other parts of the retina outside of the macula, a person will usually maintain their side vision and won’t become completely blind.
How is Stargardt macular dystrophy diagnosed?A loss or change in central vision will usually lead to a person being diagnosed with Stargardt disease. An ophthalmologist (hospital eye doctor) will examine the retina at the back of the eye to look for characteristic yellowish flecks – lipofuscin deposits – positioned in and around their macula, which can help them to diagnose the condition. These can vary widely in their size, number, colour and appearance. But as the disease progresses, the flecks usually extend outward from the macula in a ring-like pattern.
A person may also be asked to read standard eye charts as well as other tests to assess sight loss, such as:
- visual field testing – to check their central and side vision
- colour testing – to detect any loss of colour vision
- fundus photo – to look at their retina in detail
- electroretinography (ERG) – to test their retinal function
- optical coherence tomography (OCT) – to look for structural abnormalities in the layers of their retina
How is Stargardt macular dystrophy treated?Unfortunately, there is currently no cure for Stargardt disease – and very little can be done to slow down its progression. However, there is a lot of ongoing research into potential new treatments – including gene, stem and drug therapies.
Wearing protective sunglasses outdoors may help to protect vision by reducing exposure to ultraviolet (UV) light which can potentially cause further retinal damage. Some evidence suggests that people with the condition should avoid taking vitamin A supplements as this may help promote the accumulation of lipofuscin.
What research is underway into Stargardt macular dystrophy?Researchers are exploring potential new treatments that can slow down or stop sight loss from Stargardt disease, which they hope will lead to new effective therapies in the future.
Gene therapy is a promising avenue of research, which aims to repair or replace the faulty ABCA4 gene in the affected eye cells. Following initial research funded by Fight for Sight for another inherited eye condition, scientists at the University of Oxford have developed a new technology that is currently being used to test a potential treatment for Stargardt disease, using a harmless virus to carry the correct genetic information into cells.
Stem cell-based therapies offer another potentially exciting approach. Stem cells are a special type of cell that can be encouraged to develop into many other cell types. The hope is that transplanting these cells into the eye will be an effective way to replace the damaged cells in the macula.
Another avenue involves the use of ‘designer drugs’ that are specially engineered to override the genetic fault in Stargardt disease, with a recent laboratory study showing potential benefits from a synthetic form of vitamin A that isn’t readily turned into lipofuscin.
Scientists are also continuing to investigate the biology and genetics of the disease – to gain vital new insight to understand the way lipofuscin builds up and identify new ways for how to reduce it.
What can I do?There are lots of things available that can help a person with Stargardt disease to make the most of their remaining vision. An assessment with a low vision specialist can help find ways to maximise their sight using things like magnifiers to make things bigger, brighter lighting, using colour to make things clearer to see. They may also benefit from a range of assistive technologies, such as text to speech software.
If you are concerned about how having Stargardt disease may affect other family members, you can access genetic testing along with support from a genetic counsellor who can help you to make informed medical and personal decisions.
Have your eyes tested every two years even if you think your vision is fine. An eye test can spot some eye conditions and, if caught early, treatment may prevent further deterioration.
At Fight for Sight we are working with families of people with Stargardt disease to provide information and expertise on the latest research and to help raise funds for more research into this condition. If you are interested in more information please contact us.
Last updated June 2019
Approved by Prof Andrew Webster, Moorfields Eye Hospital
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