Genetic condition causing loss of central vision - also known as Juvenile Macular Degeneration
Stargardt's disease (also known as fundus flavimaculitis) is a type of macular degeneration that typically surfaces before the age of 20. This disease causes a progressive loss of central vision of both eyes, but does not affect peripheral vision.
Patients with Stargardt's experience a gradual deterioration of the retina's cone receptor cells. Cones are concentrated in the macula, and are responsible for central vision and colour. Over time, these diseased cells cause a blackened hole to form in the central vision, and the ability to perceive colours is eventually affected.
This disease is usually an inherited, autosomal recessive disorder. In order to pass Stargardt's to their children, both parents must carry the recessive gene for the disease. If both patients are carriers, each of their children has a 25% chance of developing the disease. There is also a dominant form of Stargardt's.
Signs and symptoms
Stargardt's is a progressive disease. Initially, the symptoms may be mild, but worsen over time. The progression of Stargardt's varies with the individual. Studies show that after visual acuity decreases below 20/40, deterioration may be rapid until visual acuity reaches 20/200. At this level, the patient's vision typically becomes more stable.
• Blurred vision not correctable with glasses or contact lenses (this is one of the earliest symptoms)
• Difficulty adapting from bright sunlight to a dimmer room
• Progressive deterioration of central vision
• Missing areas of central vision
• Central blind spot
• Diminishing ability to perceive colours
Detection and Diagnosis
In the early stages of the disease, a child with Stargardt's may have vague complaints about his or her vision. At this point, the retina may still appear normal, making it difficult to diagnose with a routine examination.
Over time, signs of Stargardt's become more evident with ophthalmoscopy. Upon discovering the clinical signs of Stargardt's, some physicians may order electrodiagnostic tests to study macular function, and the patients ability to adapt to dim lighting. Visual acuity tests, colour vision testing, and the Amsler grid are all used to monitor vision.
If the patient develops leaking vessels in the macula, fluorescein angiography may be necessary to study the retina's circulatory system and determine if treatment is necessary.
Unfortunately, there is no known cure for Stargardt's. Some patients may require laser treatment to seal leaking blood vessels in the retina. Laser treatment is performed to reduce lost vision from leaking vessels; however, it cannot restore vision or halt the progression of the disease.
Low vision aids are recommended so patients can better utilize their peripheral and remaining central vision. These devices include: lamps, large print, special magnifiers and telescopes. Contact a local agency for the visually impaired for low vision and vocational counselling.
In 1997, scientists isolated the gene that causes Stargardt's. Mutations of this gene, known ABCR, result in degeneration of the retina's photoreceptor cells. Understanding the genetics of the disease is critical in developing new therapies and treatments.
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