Stargardt disease is a genetic condition caused by a tiny alteration in a single gene. It is also known as fundus flavimaculatus and is the most common form of macular dystrophy.
Stargardt causes a wasting of a central area of the retina called the macula. This area is eventually surrounded by a ring of white or yellow spots. An important layer of the retina, the retinal pigment epithelium (RPE), is also affected by an accumulation of ‘waste’ material called lipofuscin.
Being diagnosed with Stargardt disease can be distressing, but with the right information and support, people can cope very well.
It’s important to remember that in the vast majority of cases, patients with Stargardt disease do not lose all their sight. Stargardt disease usually affects central vision only. Peripheral vision is not usually affected.
What is the macula?
The macula is part of the retina at the back of the eye. It is only about 5mm across but is responsible for our central vision, most of our colour vision and the fine detail of what we see.
The macula has a very high concentration of photoreceptor cells – the cells that detect light.
How is the disease inherited?
Genetic conditions are inherited as either a dominant or recessive form. Where a condition is caused by only one faulty gene from one parent, it is called a dominant form. In these cases the parent with the faulty gene will have the condition themselves and there is a 50% chance that they will pass the gene on to each child they have. This chance is the same for each child whether they are male or female, and regardless of the birth order.
Other forms are called recessive. This is where the faulty gene is inherited from both parents. In a recessive condition the parents probably won’t have the condition themselves, although they both carry the faulty gene. With recessive inheritance, there is a 25% (1 in 4) chance of each child inheriting the condition. This chance is the same for each child whether they are male or female, and regardless of the birth order.
Stargardt disease is most often inherited as the recessive form. The gene associated with this form of Stargardt disease is called ABCA4 on chromosome 1. Alterations in another gene called ELOVL4 cause a less common dominant form of the disease.
How common is Stargardt disease?
Stargardt disease affects approximately one in 10,000 people. It affects both males and females.
What are the symptoms?
In the early stages, people may have good visual acuity, but may experience difficulty reading or seeing in dim light. Other common symptoms of Stargardt disease include blurriness and distortion of vision.
Children often first experience symptoms between the ages of 6 and 12. They may begin to find it difficult to adapt from dark to light or light to dark surroundings (known as ‘dark-adaptation’). However, some do not have any symptoms until adulthood. Stargardt disease is usually diagnosed in people under the age of 20. There is a late onset form of the disease which can begin in people over the age of 50.
How quickly does vision deteriorate?
The progression of Stargardt disease varies. Visual acuity (the ability to distinguish details and shape) may decrease slowly at first.
Once visual acuity of 6/12 is reached, there is often rapid vision loss until it reaches 6/60. (‘Normal’ vision is 6/6. A person with 6/12 vision sees at 6 metres what someone with ‘normal’ vision sees at 12 metres.)
Eventually, almost everyone with Stargardt disease has a visual acuity in the range of 6/60 to 6/120. The vision loss is not correctable with prescription eyeglasses, contact lenses, or surgery.
How is Stargardt disease diagnosed?
An eye care professional can diagnose Stargardt disease by examining the retina. Lipofuscin deposits can be seen as yellowish flecks in the macula.
The flecks are irregular in shape and usually extend outward from the macula in a ring. The number, size, colour and appearance of these flecks varies from person to person.
A standard eye chart and other tests may be used to assess symptoms of vision loss in Stargardt disease, including:
Visual field testing
Visual field testing assesses the full horizontal and vertical range and sensitivity of a person’s vision, and detects blind spots (scotomas) which could be a sign of eye disease. There are several types of test but they are not painful or invasive.
The most common type of visual field test is often seen in local opticians. The patient sits at the machine with their chin on a rest and a patch over one eye. They have a button which they are asked to press when they see one or more flashing lights. This process results in a map of the person’s visual field, and can point to areas of the retina where there is vision loss.
ERG measures electrical signals produced by the retina following flashes of light. The test uses electrodes placed on the cheek under each eye. The patient looks at black and white checks moving across a TV screen and a lamp that flashes light into the eye three times per second.
The electrical responses are viewed and recorded on a monitor. Abnormal patterns of light response suggest the presence of Stargardt disease or other diseases that involve retinal degeneration.
Optical coherence tomography (OCT)
OCT is a scanning device that works a little like ultrasound. Ultrasound captures images by bouncing sound waves off living tissues; OCT does this with light waves.
The patient places his or her head on a chin rest and invisible, near-infrared light is focused on the retina. Cross-sectional pictures of the retina are analysed for any abnormalities which could indicate retinal degeneration. OCT is sometimes combined with infrared scanning
laser ophthalmoscopy (ISLO) to provide additional surface images of the retina.
The eyes may be photographed with a special camera that measures the fluorescence of cells in the back of the patient’s eye. A specific pattern of autofluorescence imaging may be seen in patients with Stargardt disease.
As part of the diagnosis, the patient may be invited to take a genetic test to learn more about their particular condition, and enable research scientists to learn more about the condition in general. Patients are not obliged to take a genetic test, but some people find it helpful to know more. In some cases, the tests don’t always return conclusive answers.
Some patients may find it helpful to talk with a genetic counsellor first. Usually part of the research team, the genetic counsellor will help a patient and their family understand how the condition has been inherited, and the implications for other family members and future generations. They will enable the patient to make informed decisions about testing and support them through the process. The consultant will be able to provide more information about genetic testing.
Being diagnosed can be stressful and highly emotional. Some patients benefit from working with a professional counsellor to understand their situation and find ways to manage their feelings. Our free telephone counselling service is provided by accredited counsellors who have extensive experience of working with people with sight loss. Please call 0300 3030 111 for a referral.
Support in Education
Children with sight loss are eligible for special educational needs (SEN) support in school. This can provide your child with the adaptations, equipment and support they need to fully access the curriculum.
In higher education, the Disabled Students’ Allowance (DSA) can fund equipment and support.
There is currently no treatment for Stargardt disease. However, there is a wide range of support available to help people with the condition, as well as their family and friends. If you or anyone in your family experiences any sudden changes in vision seek urgent medical advice from an eye hospital.
There is a great deal of research going on into potential treatments. We are finding out more about genetics, and gene-based therapies are being developed. Stem cell research is also encouraging.
What can I do to look after my eyes?
It is thought that people with Stargardt disease cannot process vitamin A properly, so it is important to avoid excess vitamin A. Also avoid bright light as it may accelerate the progress of the disease.
- Visit your optician at least every two years for a general eye test.
- Don’t smoke.
- Maintain a healthy weight and blood pressure.
- Wear lenses which block UV light, particularly in bright sunlight. Blue block filters also reduce glare.
- Wear a hat with a wide brim or visor to shade eyes from direct sunlight.
- Limit alcohol intake to recommended levels.
- Eat lots of fruit and green, leafy vegetables.
For information about living with an inherited macular dystrophy, call the Helpline on 0300 3030 111 or email email@example.com