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Management |
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In the ten years between 1980 and 1990, the Macular Photocoagulation Study (MPS) defined the criteria which are still used in the management of "wet" AMD. Once the diagnosis is confirmed by clinical examination, the patient is subjected to a special study known as fluorescein angiography. In this study, rapid sequence photographs of the macula are made by an eye photography camera while a dye known as fluorescein is injected intravenously. Either on film or digitally, the blood vessel area behind the macula can be visualized in order to find the abnormal blood vessel. Some improvement in the results of this test can be obtained in selected patients with a similar procedure using indocyanine dye (ICG) and infrared light. These procedures are not difficult or usually painful, and are carried out in all offices of the Retina Group of Washington.
In a few patients, the injection of fluorescein can cause transient nausea and to a lesser degree, hives. Although it is extremely rare, more severe reactions have been reported and the dye is not used in patients with severe cardiac disease or active asthma. Indocyanine green contains iodine, like dyes used in radiology. A history of allergy to the radiographic dyes or allergies to fish would contraindicate the use of this dye. No dye is used during pregnancy.
The purpose of the photography is to identify the character and position of the abnormal subretinal blood vessels. These are generally found in two forms, classic and occult. A classic subretinal blood vessel can be sharply delineated and laser treatment to destroy the blood vessel may be possible. Unfortunately, the classic membrane is much less frequent than the untreatable occult membrane. In the occult membrane, the borders are poorly defined and laser treatment is rarely possible. It has been found that laser photocoagulation is of limited benefit.
After treatment, careful follow up is necessary with repeated fluorescein angiograms because of the persistence or recurrence of these membranes and the further risk of bleeding. It is critically important that patients monitor their own vision carefully once AMD is diagnosed.
The American Academy of Ophthalmology advises:
- Treatment will reduce but not eliminate the risk of severe visual loss.
- Treatment will produce a permanent spot in vision from the damage induced by the laser.
- There is a high risk of subretinal neovascular membrane persistence or recurrence that could require more laser treatment. The risk is greatest during the first year.
- Multiple fluorescein angiograms are necessary for appropriate post-laser follow up.
- For most patients in whom the subretinal blood vessel membrane is located directly under the fovea and who have better than 20/200 vision, there will be a recognized loss of acuity following laser therapy but it is anticipated that long term stabilization may occur thereafter.
Finally, many patients with AMD can benefit from what are called low vision services. These services range from counseling to special optical magnifying devices, lighting, television and computer devices and many other services. In the Retina Group of Washington, Dr. Suleiman Alibhai runs our Low Vision Service for which he is eminently qualified. We encourage you to benefit from his experience.
he American Academy of Ophthalmology recommends a comprehensive dilated eye examination every 2-4 years for patients between 40-64 and every 1-2 years for patients 65 years and older. If patients have evidence of "dry" macular degeneration found on these examinations, even if they are still asymptomatic, they are usually given a straight-line grid to examine one eye at a time. The first symptom of "wet" macular degeneration is often curvature or distortion of the straight lines. If this occurs it should be reported immediately. The grid given out in the eye doctor’s office is referred to as an Amsler grid but any straight-line object will do. For example, a crossword puzzle, a venetian blind or the corner of a window. MD is the leading cause of irreversible legal blindness (less than 20/200 in both eyes) in patients over 65 years of age and is the commonest cause of blindness in the Western world. More than three million Americans are visually disabled by AMD, with that figure to triple by the year 2020. Every year, an estimated 400,000 people in the U.S. develop a severe form of the disease, with 16,000 cases of legal blindness per year. Although more common in the older population, the disease has been reported to be the second leading (diabetes being first) cause of legal blindness in the 45-64 year age group. |
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