August 24th, 2011
08:32 AM ET
Every weekday, a CNNHealth expert doctor answers a viewer question. On Wednesdays, it's Dr. Otis Brawley, chief medical officer at the American Cancer Society.
Question asked by Ann:
Is there a treatment for macular degeneration of the eye?
Age related macular degeneration is a disease of the central portion of the retina. This area is called the macula. The retina is the area of tissue in the back of the eyeball that senses light and is the key to vision. The macula or central area is the most important part of the retina as we use it to perform daily activities such as reading, watching television and driving.
Macular degeneration is one of the leading causes of blindness in the Western world. It is surpassed only by glaucoma and diabetic retinopathy.
AMD is a disease rarely seen in people under age 55. Some studies suggest that between 1% and 2% of adults over 55 have it and more than 5% of people over 75 have some form of it. Beyond age, risk factors include smoking, a history of the disease in one's family, a history of cardiovascular disease and heavy drinking. A diet rich in green leafy vegetables and fish products may reduce risk of AMD.
There are two kinds of AMD. There is "so called" dry AMD, which is also referred to as atrophic AMD, and there is wet AMD, which is also referred to as neovascular or exudative AMD. Dry AMD involves deposits of a material in the retina. Wet AMD involves blood vessels growing into the retina and leaking in the retina. Both forms of AMD lead to death of nerve cells. Wet AMD is far less common than dry. Dry AMD typically progresses slowly over many years and is less threatening to vision than wet AMD. It is possible and indeed common for someone with dry AMD to progress to wet AMD.
Both types of AMD can be diagnosed at their earliest stages by a trained clinician looking for signs of it at the back of the eye with an ophthalmoscope. Adults should have an eye examination on a regular basis, for this reason and as well as for early detection of other eye diseases such as glaucoma, diabetic retinopathy and cataract. Late-stage AMD is often diagnosed after the patient complains of loss of vision in the middle of the viewing field. It's often described as a ring of vision around a black hole.
There is no known effective therapy for dry AMD. Some have speculated that antioxidant vitamins such as vitamin C, vitamin E, beta carotene and zinc might be a helpful treatment. There is some limited clinical study to justify their use in mild AMD. Thankfully, dry AMD tends to progress toward blindness very slowly.
Aggressive treatment of early wet AMD can prevent blindness. Antioxidants are prescribed as treatment of mild wet disease. Several drugs that inhibit vascular growth factors have been shown beneficial in more severe wet AMD. These drugs, bevacizumab and the related ranibizumab, are injected into the eye on a monthly basis for a period of a year or more. Bevacizumab is also used as a treatment for some cancers under the brand name Avastin. The growth factor inhibitors have largely replaced laser therapy which used to be a mainstay of wet AMD treatment.
There are experimental therapies of both forms of AMD. They vary from antioxidant eyedrops to eyedrops that inhibit vascular growth factors to photodynamic therapy to even fetal cell transplantation.
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