A guide to this article!
What is it?
Stargardt’s disorder (other names such as Stargardt’s macular dystrophy and fundus flavimaculatus) is a degenerative genetic disorder that affects the tissue in the back of the eye called the retina.
It causes progressive vision loss in patients as early as their adolescence. One in 10,000 people have this disorder. Oftentimes, Stargardt’s disorder does not lead to complete loss of sight. Some patients can get their night vision affected, some get affected by color vision. Like most diseases, the symptoms and effects vary from patient to patient. Stargardt’s disorder is introduced into a generation by mutation of the ABCA4 gene. It is transmitted to the next generation by autosomal recessive inheritance.
Symptoms
The symptoms of Stargardt’s disorder vary between every patient. The most common symptom is loss of central vision.
The affected person may start to see dark or hazy spots in the center of their vision, usually in both eyes. They may also notice that they become sensitive to a sudden change in surrounding light. Their eyes may take more than average time to adjust to a change in light. The early arrival of symptoms may lead to more rapid vision loss as the disease progresses. Most Stargardt’s patients end up with 20/200 vision. The normal vision is said to be only 20/20! As the patients get older, they may also experience loss of peripheral vision (side-view vision when looking straight).
The retina is a tissue in the back of the eye that contains light-sensitive cells which allow you to see. These cells are called photoreceptors and are of two types: cones and rods. Cone cells help with color vision and rod cells help with night/black and white vision. The macula is an area in the center of the retina that is responsible for clear and straight vision. It is packed with cone cells.
In Stargardt’s macular dystrophy, these photoreceptors die. However, due to unknown reasons, cone cells are more affected than rod cells.
We all know that Vitamin A (found in food) is essential for good eyesight. They are used to make photoreceptors in the retina.
Although, the process of making photoreceptors also leads to the formation of harmful byproducts. The ABCA4 gene in a cell produces proteins that eliminate these harmful products from the cell, but a mutation can cause it to work imperfectly.
This leads to excessive accumulation of a substance called lipofuscin in the cells.
Groups of lipofuscin accumulation in cells around the macula lead to impaired vision. Eventually, the photoreceptors in the area die.
Diagnosis
There are many ways to diagnose Stargardt’s disorder.
Primarily, the healthcare worker would do a retinal examination to try to see any lipofuscin deposits in the retina. If it were present, it would look like irregular, yellow, ring-like patches.
Alternatively, the professional might also choose to do a fundus photo-- which is a microscopic picture of the retina.
Other ways to diagnose are visual field testing and color blindness tests.
Visual field testing is a non-invasive method of diagnosis, which tests the coordination and response of the patient’s visual system to a stimulus. It can pinpoint the exact site of damage in central or peripheral vision. The colorblindness test does not confirm Stargardt’s disease but narrows down the possibilities for the healthcare professional to analyze. The late stages of Stargardt’s disorder involve loss of color vision.
There is currently no definitive cure for Stargardt’s disease, but there are many treatments that can slow the progression of the disease. Doctor’s advice wearing dark sunglasses when going out to protect your eyes from UVa and UVb rays, which will ultimately lead to lesser lipofuscin build-up.
Smoking is also not advised. Taking too many vitamin A supplement tablet has also proved to be ineffective.
Useful Devices & Therapies
There are also many devices that can help with the daily life activities of Stargardt’s patients. Low-vision aids can help with sight.
Occupational therapy and counseling are also recommended for handling emotional stress because losing eye vision in the early stages of life can be mentally draining.
Future endeavors
There is much ongoing research to find a cure for Stargardt’s disorder.
Embryonic stem cells are cells that can differentiate into any type of cell when induced appropriately. These stem cells can be used to make human photoreceptors, to replace the damaged ones in the retina already.
Gene therapy is also being researched, where they are trying to repair or replace the defective gene ABCA4 in the affected cells.
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