Understanding Stargardt's Disease
by
Richard L. Windsor, O.D.
Laura K. Windsor, O.D.
The Low Vision Centers of Indiana
General
Stargardt's Disease is a form of macular dystrophy that begins early in life. Dr. Stargardt first described this condition in 1909 giving it its name. It is one of the most common forms of a juvenile macular degeneration. Stargardt's disease may occur in one of every 20,000 children over the age of 6 and is usually diagnosed before the age of 20. Boys and girls are equally affected by this condition. Over 25,000 Americans have Stargardt's disease.
Stargardt's is usually a recessive inherited condition requiring the person to receive a gene from each parent to cause the disease. However, there have been a number of cases identified as dominant inheritance, requiring only one gene from either parent. Recently researchers have identified the gene, ABCR, now called abca4, which causes Stargardt's Disease. This brings hope that a treatment will eventually be available.
With Stargardt's Disease, the macula and surrounding retina are affected. The macula is the very center of our retina. The images we see are focused on the retina like the film in the camera. Unlike camera film where every part of the film is equally sensitive, our retina concentrates the most sensitive vision in the very center. Additionally, our best color vision resides in the macula. Thus, damage to the macula results in loss of visual acuity or sharpness of vision, decreased color vision and small blind spots.
Diagnosis:
Early in the disease, the macula may appear normal which may slow the initial diagnosis of Stargardt's. Children may be misdiagnosed with a psychological vision loss given as the diagnosis. In time, characteristic changes occur in the retinas that help facilitate diagnosis. Fluorescein angiography is a test in which a dye is injected into the arm and the flow of this dye as it enters the eye is studied. The damaged retina sits above a layer called the choroids which is rich in blood vessels that supply nutrients to the retina. During angiography in a patient with Stargardt's, the damage to the retina blocks the flow of light from the choroids causing a "dark choroid" and this may be used to help diagnosis. This test alone is not considered to be completely diagnostic of the disease.
In later stages of Stargardt's Disease, the classic appearance of the retina allows a much easier diagnosis. The appearance of a "beaten metal" macula combined with small yellowish-white flecks (fundus flavimaculatus) in the peripheral retina is typical of Stargardt's disease.
Emotional Impact:
Adolescent years are difficult for every child, but imagine suddenly learning that your vision is failing. The sudden awareness to the child and parents that the child is losing vision can be devastating. The family and the child need to learn immediately about low vision care. Knowledge of the options to help the child can help the family and child put the problem in perspective. Counseling may be needed to help the child through their fears. Support groups or interaction between the parents of other Stargardt's patients can be beneficial.
Decrease of Visual Acuity:
Stargardt's disease may first be detected by a mild loss of visual acuity or sharpness of vision. In the early stages, however, the vision may be near normal. Visual acuity measurements may also vary due to the effects of light exposure and one should not be alarmed if your visual acuity varies on each test. Most Stargardt's patients have visual acuities from 20/100 to 20/400. One study of Stargardt's patients found that all persons tested had decreased visual acuities of at least 20/200 within approximately nine years after onset.
Come and Go Vision:
As Stargardt's disease progresses, patients may experience small areas of vision loss or blind spots. As images fall upon the damaged areas of the retina, objects may disappear and reappear causing a come and go effect.
Eccentric Viewing:
Stargardt's disease creates central blindspots that increase in size as the disease progresses. Patients learn to turn their eyes in a specific direction to see around the blindspots. They must place the image on an area adjacent the macula. Family members and teachers need to understand that this is an adaptive step used to maximize their vision.
Photostress and Dark Adaptation:
Children with Stargardt's disease often complain of difficulty adapting to the dark after sunlight exposure. Light striking our retina causes chemical reactions to occur in the rods and the cones. Our retina must continuously create new photo-reactive chemicals and remove the waste products of these chemical reactions. When a Stargardt's patient is exposed to bright sunlight, the retina may become bleached by the light and the sharpness of vision may decrease and blind spots may become denser. These are temporary conditions, but can be prevented or lessened by use of sun filters and hats.
From laboratory studies in mice, it has been suggested that sun filters may lessen the formation of lipofuscin, which is the waste products of the rods and cones. Lipofuscin, if allowed to accumulate, may damage the retina. Mice, without the ABCR gene like patients with Stargardt's, do not accumulate these waste products when raised in darkness. Additionally, younger patients, under 26 years old, transmit more ultraviolet light to the retina due to the clarity of the crystalline lens which in theory may lead to more retinal damage in Stargardt's patients. More research is needed.
Photophobia:
The damage to the retina also leads to greater internal reflection of light often causing an increase in light sensitivity.
Color Vision:
Though new theories indicate the damage may begin in rod cells, our black and white vision, surrounding the macula, the condition eventually damages the macular area where cone or color vision cells are. Color vision declines as the disease progresses, but patients usually maintain a significant amount of color vision.
The Paradox of Peripheral Vision Sensitivity:
Patient may miss or see poorly objects that fall in their central vision, but the far peripheral vision remains intact with Stargardt's. It is not uncommon to not be able to see a face, but notice a piece of lint on the shoulder. Family members often mistake this ability as an indication that the patient can see better than he or she claims.
Phantom Vision / Charles Bonnet Syndrome:
In more severe stages of vision loss, patients may experience Phantom vision or visual hallucinations. These episodes are not usually related to underlying psychiatric problems, but rather are normal attempt by the brain to make sense of impaired sensory information. The brain may embellish the image making it very real just as it does in our dreams.
Depth Perception:
Depth perception is dependent on two good eyes. Anything that decreases vision in one or both eyes will cause an immediate drop in our depth perception.
The Good News:
Stargardt's never causes total vision loss. Peripheral vision is left intact. Central vision is usually in the range of 20/100 to 20/400 with younger patients usually showing less loss. Low vision care can help Stargardt's patients lead very normal lives. Following diagnosis every Stargardt's patient should have a low vision examination by a doctor skilled in low vision rehabilitation.
Low Vision Care:
Stargardt's patients respond well to magnification. Simple bifocals may be used in the early stages. In later stages, CCTV systems are helpful. It is important to maintain good cosmetic appearance for young patients. Mobility is usually minimally affected. Some Stargardt's patients can become bioptic drivers, but it may be for a limited time.
School Age Issues
In children and teens with Stargardt's disease, it is very important to have adequate low vision care. These students may have light and glare control problems in their classrooms. Adaptations including sitting away from the window or shutting the curtains may be necessary. Also, these students should be allowed to wear special sun filters when needed to decrease glare and light sensitivity.
Large print materials may be indicated for these children. This may include textbooks, worksheets, and tests. Due to their vision loss and difficulty reading, some students may require extended time on tests and quizzes.
Because the vision loss may progress over time, each student should have a Teacher of the Visually Impaired. A VI teacher will assess the classroom and educational plan for the child. With the low vision specialist's recommendations, the VI teacher makes adaptations including low vision devices, large print materials and other special services the child will need each year in school.
Because of the vision loss, there are also safety issues to look at in young active students. Eyewear with polycarbonate lenses should be worn for protection of the eyes from unexpected injury. Counseling should include safety issues in physical education. Sports like swimming and track are good options. Sports with fast moving projectiles may put young Stargardt's patients at risk. Protective face shields are essential if the patient is to play in such a sport. With the proper safety devices, patients have played hockey successfully.
Good Advise from a Stargardt's Patient:
"Don't listen to negative influences. Believe in yourself, and show others what you can do. Only "you" can find your potential."
Marla Runyan, US Olympian and Stargardt's patient and the first legally blind athlete to compete in the Olympics
About the Authors:
Drs. Richard and Laura Windsor are a father and daughter team of low vision specialists at the Low Vision Centers of Indiana. Dr. Laura Windsor was recently honored with the 2001 National Essilor Award. Her father is past recipient of the American Optometric Association's National Optometrist of the Year 1999. They have recently completed a new movie on bioptic driving. Their work and patients have been featured on Breakthroughs in Science and the CBS Evening News: Eye on America. You may reach them at:
Central Office:
Low Vision Centers of Indiana
P.O. Box 166
315 Huggins Drive
Hartford City, IN 47348
Tel: 765.348.2020
Website: http://www.eyeassociates.com
Other Offices:
Indianapolis: 844.0919 - 9002 N Meridian - Suite 208
Marion: 765.664.9637 - 711-A River Dr 46952
Ft. Wayne: 800.393.5555 or 260.432.0575 - 6708-B Constitution Dr 46804
Dr. Laura Windsor drlaura@eyeassociates.com
Dr. Richard Windsor richw@eyeassociates.com
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