What is Stargardt disease?
Stargardt disease is an inherited condition of the retina - the cells at the back of the eye which are light sensitive. The condition typically causes vision loss during adolescence or early childhood, although in some cases, this isn’t noticed until in later adulthood. It is rare for people with Stardardt to go completely blind, and in most cases, people progressively lose vision over time typically down to 20/200 (20/20 is normal).
Also known as Stargardt macular dystrophy, juvenile macular degeneration, or fundus flavimaculatus. The disease causes degeneration of the macular, a small area in the retina responsible for straight ahead vision. One of several genetic disorders that cause macular degeneration, it is believed 1in 8,000 people have the disease.
How is Stargardt inherited?
Genes are combined on structures called chromosomes. One chromosome each is passed by a parent at conception. The disease can come from either one parent's gene, or by a combination of both parents genes.
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.
What are the symptoms?
In its early stages, a person with Stargardt may have good visual acuity, but may have problems seeing or reading in low light. Other common symptoms include blurriness and distortion of vision.
People with the Stargardt may notice black, grey or hazy spots in their central visual field, or that it takes longer than usual for their eyes to adjust when moving from light to dark environments. Their eyes may be more sensitive to bright light. Some people also notice a developing colour blindness later in the disease.
How quickly does vision deteriorate?
The progression of symptoms in Stargardt disease is different for each person. People with an earlier onset of disease tend to have more rapid vision loss. Vision loss may decrease slowly at first, then worsen rapidly until it levels off.
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.)
How is Stargardt diagnosed?
A professional can make a positive diagnosis of Stargardt disease by examining the retina. Lipofuscin deposits can be seen on the macular as yellowish flecks. The flecks are irregular in shape and usually extend outward from the macula in a ring-like pattern. The number, size, colour, and appearance of these flecks are widely variable. A standard eye chart and other tests may be used to assess symptoms of vision loss in Stargardt disease, including:
Visual Field Test
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 test types none of which are 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 to press a button 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.
Colour Testing: There are several tests that can be used to detect loss of colour vision, which can occur late in Stargardt disease. Three tests are often used to get additional information: fundus photography combined with autofluorescence, electroretinography, and optical coherence tomography.
A fundus photo is a picture taken of the retina. These photos may reveal the presence of lipofuscin deposits. In fundus autofluorescence (FAF), a special filter is used to detect lipofuscin. Lipofuscin is naturally fluorescent (it glows in the dark) when a specific wavelength of light is shined into the eye. This test can detect lipofuscin that might not be visible with standard fundus photography, making it possible to diagnose Stargardt disease earlier.
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 in a similar fashion to ultrasound. Ultrasound captures images by bouncing sound waves off living tissues; OCT does it 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. During autofluorescence imaging your eyes may be photographed with a special camera that measures the fluorescence of cells in the back of your eye.
A specific pattern of autofluorescence imaging may be seen in patients with Stargardt disease.
There is no treatment for Stargardt disease currently available. Some ophthalmologists encourage people with Stargardt disease to wear dark glasses and hats when out in bright light to reduce the buildup of lipofuscin. Smoking cigarettes or second-hand smoke should be avoided.
Low vision aids, lighting and technology
A number of tools and devices can help people with Stargardt disease carry out daily activities and maintain their independence. Low Vision Aids can be helpful for many daily tasks and range from simple Magnifying Glasses with Lights to Electronic and Video Magnifiers.