Age-related macular degeneration (AMD) is the most frequent cause of vision loss among people 50 years and older in developed countries. If only one eye is affected, patients may not even be aware that they have AMD. Other people may fail to report vision loss because they believe it to be an inevitable consequence of aging. Early diagnosis and treatment is very important to the outcome of macular degeneration. A significant delay can reduce the likelihood of any improvement in visual function.
AMD can be classified as either dry or wet. Dry AMD is characterized by the build up of drusen, which are small yellow deposits underneath the retina. Dry AMD often does not cause severe vision loss unless the retina and underlying layers begin to atrophy and die. It is important to monitor patients with dry AMD because it may progress to wet AMD, which can be treated. The wet form accounts for approximately 90% of severe vision loss in patients with AMD. Wet AMD is characterized by the presence of choroidal neovascularization, which is a term that describes abnormal new blood growth underneath the retina. The main symptoms of wet AMD are deterioration in central vision, blind spots, and distorted vision. Definitive diagnosis and classification of choroidal neovascularization requires fluorescein angiography, ocular coherence tomography, and color fundus photography of the retina. The location of neovascular lesions is an important factor in determining the risk of vision loss. Eyes with subfoveal lesions (those that extend under the center of the retina) are at the greatest risk of vision loss.
At present, no intervention has been proven to reduce the risk of developing dry AMD and there is no treatment that has been shown to reverse the condition. The Age-Related Eye Disease Study (AREDS) has shown, however, that some patients with dry AMD may benefit from supplementation with vitamin C 500 mg, vitamin E 400 IU, beta carotene 15 mg, zinc and copper to reduce the risk of vision loss arising from progression to advanced AMD.
One of the most common treatments for wet AMD is the intravitreal administration of medications that block the growth of abnormal blood vessels underneath the retina. They target a specific chemical messenger called Vascular Endothelial Growth Factor (VEGF). Two medications that are often used in this setting are ranibizumab (Lucentis) and bevacizumab (Avastin). Although the intraocular use of Avastin is “off-label,” many patients can be successfully managed with this medication. Lucentis and Avastin are injected directly into the vitreous cavity in the office. Treatments may be repeated as often as every month, and many injections may be required in order to keep the condition stable over the long term.
Photodynamic therapy with verteporfin (Visudyne) is another treatment option for wet AMD. With photodynamic therapy, verteporfin is administered by intravenous infusion. A non-thermal laser is then used to treat the target area in the eye. Laser light is applied 15 minutes after the start of the medication infusion. Treatments are generally given every 3 months. Patients should avoid exposure to direct sunlight or strong indoor light for 5 days following the procedure.
Another treatment option for wet AMD is the use of thermal laser, which may be considered in certain situations when the abnormal choroidal blood vessels do not extend directly underneath the fovea.