What is Stargardt’s disease?
Stargardt’s disease affects the light sensing part of the eye called the retina – primarily the central retina that provides detailed vision, colour vision, recognising faces and reading vision. Early on in the disease people experience blurring of vision, mainly the ability to see fine details such as text. As the disease progresses there is increasing loss of colour vision. Some people also experience impairment of night vision at a later stage. How quickly vision deteriorates varies greatly between individuals but after years both fine and course detail may be difficult to see. The condition makes reading challenging, as well as impairing everyday tasks such as studying, working, driving and crossing a road safely.
What is the age of onset?
The disease is most commonly diagnosed in children and young adults, but it can also be diagnosed in middle age and less often in older patients.
How common is Stargardt’s disease?
The exact incidence is not known but about 1 in 10,000 of the population is affected. There are therefore approximately 6000 people with Stargardt disease in the UK.
What causes Stargardt’s disease?
Stargardt’s disease is a genetic condition with a recessive pattern of inheritance – which means that both parents of an affected person each carry a fault in the ABCA4 gene – the gene that causes Stargardt’s disease. This faulty gene does not cause disease in your parents because they have another copy of the ABCA4 gene, which does not carry a fault. One normal gene is enough to allow your eye to work normally. But if you inherit two faulty genes then this will cause Stargardt’s disease. There are >1000 genetic faults in the ABCA4 gene that cause Stargardt’s, which plays a major role in the very wide variation in the age at which the disease is diagnosed as well as affecting how rapidly visual impairment occurs.
The genetic faults lead to a faulty/deficient protein being produced in photoreceptor cells. This protein is like a door through which products that need to be recycled for normal vision and retinal health leave photoreceptors – the light sensitive cells in the retina. Because these products cannot leave via the faulty door efficiently, harmful waste accumulates over time and damages the retina.
What are the symptoms of Stargardt’s disease?
The disease causes a blurring of vision especially the ability to see fine detail. It may cause difficulty reading a book or newspaper for instance.
How is Stargardt’s disease diagnosed?
The diagnosis is made by taking a careful history of any visual changes, followed by a detailed examination and some tests. The examination and tests may give some idea of prognosis. There is often no family history of the disease unless you have an affected sibling.
Pupil dilation – It is likely that eye drops will be used to dilate your pupils before examination and some of the tests being performed.
Slit lamp examination – A standard way of your doctor looking at your retina using a microscope with light and some lenses.
Colour vision – A standard colour vision test book is often used.
Visual field test – This test measures the sensitivity of multiple areas of the retina and can be helpful both in diagnosis and monitoring change over time.
Optical coherence tomography (OCT) – This very sensitive investigation uses light to image the different layers of the retina. In Stargardt disease the outer layers are disrupted. Comparison of the images over time allows disease progression to be monitored.
Fundus autofluorescence imaging uses blue light to image the retinal pigment epithelial layer of the retina and also indirectly acquire information about photoreceptors. It can help to detect and monitor areas of retinal thinning over time.
Electroretinography (ERG) – This test records the electrical responses of the retina to various different light intensities and frequencies – both in the dark and light – with small contacts placed close to the eyes. It can provide information on the degree and extent of retinal functional reduction. It can help to better inform advice on prognosis.
Genetic testing – Many patients have a genetic test to determine the specific changes in the ABCA4 gene that causes Stargardt disease. Usually the gene from your father has a different mutation to that from your mother.
How is Stargardt disease treated?
Currently there are no treatments for Stargardt disease. Though it is wise to follow simple steps that may slow down the progression of the disease. These recommendations include avoiding excessive exposure to bright sunlight, including wearing good quality UV-blocking sunglasses and a wide brimmed hat. Have a healthy balanced diet rich in green vegetables and potentially consider taking lutein and omega-3 supplements. Do not take Vitamin A supplements. Do not smoke.
What research is being done?
Multiple research avenues are being explored in Stargardt’s disease – including gene therapy, stem cell therapy, and pharmacological approaches. More is in active / planned clinical trial for Stargardt’s disease than any other inherited retinal disease. Technological advances in visual aids and how we interact with our environment – and how it interacts with us – are also potentially valuable developments. There is cautious optimism for the future.
For further information, see the section on Stargardt’s research.
What is a genotype and phenotype?
The genotype describes the genes that you have inherited from your parents. It is a bit like a recipe that describes the ingredients of a cake and how to bake it.
The phenotype is the cake itself including how the cake looks and tastes. The genotype is found by using sophisticated laboratory tests. The phenotype is determined at the hospital clinic and involves examining the eye as well as specialised tests.
How can I help?
To find a cure or a treatment requires research. Research is expensive and ways you can help include fundraising, consider participating in research studies and trials, and help to raise awareness of inherited retinal diseases.
Thank you to Professor Michel Michaelides BSc MB BS MD FRCOphth FACs of UCL Institute of Ophthalmology and Moorfields Eye Hospital for reviewing the Stargardt’s F.A.Q. page.