Age-related macular degeneration (AMD) is a condition characterized by the progressive degeneration of the macula, the part of the retina responsible for clear central vision. Hence, AMD often leads to loss of central vision in the form of blurriness, dark areas, and distortion. This vision loss can make ordinary activities such as reading, driving and recognizing faces difficult or even impossible. AMD is the leading cause of severe vision loss in the developed world and affects approximately 1 million Canadians.
The exact cause for AMD is unknown, however common risk factors for this disease include:
Macular degeneration is classified as either dry (non-neovascular) or wet (neovascular). Neovascular, or neovascularization, is a term used to describe the growth of new blood vessels in an area where they should not be.
Dry AMD is the early stage of macular degeneration, and is the result of thinning of the macular tissues, accumulation of pigment in the macula, or a combination of the two. The central vision loss that may occur in dry AMD is typically gradual and much less severe than the symptoms of wet AMD; however, dry AMD has the capability of progressing to geographic atrophy, the gradual deterioration of retinal cells that can also lead to severe central vision loss.
In approximately 10 percent of cases, dry AMD progresses to wet AMD. Wet AMD is the more advanced and serious form of the disease, and is characterized by neovascularization in the macular area. These new vessels are prone to leakage, and this leakage causes permanent damage to the associated retinal cells and thus blind spots in central vision.
AMD can be detected during the course of a routine eye exam. Drusen, small yellow deposits under the retina, are one of the most common early signs of the disease. An Amsler Grid, a pattern that resembles a checkerboard, may be used to see if there is any central vision distortion. Distortion or absence of some of the straight lines may indicate the presence of AMD.
If there is concern about AMD, a digital retinal photograph of your retina, and a special scan called an OCT, may be performed. An OCT produces a 3D photograph of the retina and also allows a cross-sectional view of the retina. Your optometrist will likely dilate your pupils to allow for a better view of the area in question.
Early detection of AMD is important as there are therapies that can delay or decrease the severity of the disease.
There is no definitive cure for AMD, but there are measures that can be taken to delay its progression. Nutritional supplementation is typically advised to prevent dry AMD from progressing to wet AMD.
For wet AMD, surgical intervention aimed at preventing the abnormal blood vessel growth and stabilizing vision is usually advised.
The best way to protect the eyes from developing dry AMD is to wear sunglasses in order to protect the eyes from the sun, maintain a healthy diet, avoid or stop smoking, and manage any other associated conditions like hypertension and diabetes.
Treatments for macular degeneration depend on whether the disease is in its early-stage, dry form or in the more advanced, wet form that can lead to serious vision loss. No FDA-approved treatments exist yet for dry macular degeneration, although nutritional intervention may help prevent its progression to the wet form.
For wet AMD, treatments aimed at stopping abnormal blood vessel growth include FDA-approved drugs called Lucentis, Eylea, Macugen and Visudyne used with Photodynamic Therapy or PDT. Lucentis has been shown to improve vision in a significant number of people with macular degeneration. For more details, read our article about macular degeneration treatments.