Macular Degeneration

Vision with AMD

Age-related Macular Degeneration or AMD is the leading cause of irreversible visual loss in people over the age of 65 in the US. Approximately 10-20% of patients with AMD develop choroidal neovascularization (CNV). In the US, 100,000 to 200,000 people develop CNV every year. The population at risk will double in size over the next 30-40 years in the Western world. AMD results in a tremendous burden to the individual and society. The individual often loses central vision in one eye, and is extremely anxious about losing the vision in the fellow eye. There is loss of the ability to work, loss of recreation, socialization and increased dependence on others. These patients comprise about 40% of many retinal practices.

The causes are not completely understood, but it seems that age and family history are the greatest risk factors. AMD increases in frequency with age and the advanced form affects approximately 8% of the population over the age of 75. Smoking history, diet, cardiovascular health and possibly lifetime sun exposure are other risk factors. Smokers have a two to three fold increased risk of developing this disease; patients exposed to second hand smoke may also be at increased risk. Nutritional factors appear to play a role; a large prospective carefully designed study has demonstrated the protective effect of certain supplements. Other nutrients like lutein, zeaxanthin and omega-3 fatty acids may also be beneficial. Ongoing studies (AREDS 2) are investigating this.

The retina is a thin, light sensitive layer that lines the inside of the back of the eye. It is similar to the film in a camera. The macula or center of the retina only covers about 5% of the retina, but is responsible for the most sensitive central vision and the remainder of the retina is for side vision. AMD causes progressive damage to the macula. When the macula is not functioning properly, one may experience blurring, distortion, or darkness in the center of the field of vision. Near vision such as reading is affected more than distance vision. AMD almost never causes total blindness.

There are two types of AMD, the dry or atrophic variety and the wet or exudative type. Dry AMD is much more common and accounts for 90% of all AMD. It cannot be treated with medication or surgery, but many patients can function well with magnifying and telescopic lenses. Most patients with Dry AMD do not progress to the Wet form.

Fluorescein angiography is a technique that is used to evaluate the macula. A dye is injected into a vein in the arm and photos are taken as the dye circulates through the retinal blood vessels. This helps to determine the type and location of the CNV. Sometimes indocyanine green angiography is used as well when the CNV is more difficult to visualize than with conventional fluorescein angiography. To help discern and characterize the location and extent of fluid in the macular an Optical Coherence Tomogram (OCT) will be performed. An OCT is a quick, non invasive scan that uses light to generate a detailed cross section of the macula.

Wet AMD is less common, but typically more severe than the Dry form. It accounts for 10% of all cases of AMD, but 90% of the blindness from the disease. Wet AMD is characterized by abnormal blood vessels that grow under the retina called choroidal neovascularization, or CNV. These abnormal blood vessels leak fluid and may bleed, which leads to scarring under the center of the macula and results in profound loss of central vision. The untreated course or natural history is bleak, with most patients losing central vision over a 2 year period. Conventional laser treatment, the mainstay of treatment a decade ago, is now reserved for a small minority of patients with Wet AMD that does not yet extend to the central macula.

PDT is a non-thermal ("cold") laser that is a novel treatment that uses a laser to activate a photosensitive drug called Verteporfin. Although still used in specific situations it has been supplanted as the primary monotherapy for Wet AMD.

A major breakthrough in the treatment of Wet macular degeneration has been the availability of anitiangiogenic medications. This class of drug, which includes Lucentis and Avastin are now the primary therapy of AMD. They work chemically to block a naturally occurring compound in the eye called Vascular Endothelial Growth Factor (VEGF). A major factor that leads to Wet AMD is the over abundance of VEGF in the eye. By blocking VEGF most patients are stabilized or even improved. Unfortunately these treatments may need to be repeated multiple times to preserve vision.

Treatment approaches are specific to individual patients. Therefore a detailed discussion is required with your retinal specialist to clarify what your optimal treatment may be. It is important to remember that the earlier the diagnosis the more likely the treatment is to be successful. Check your vision in each eye every day, preferably with an Amsler grid card, consider smoking cessation and use of appropriate nutritional supplements; notify your doctor if there is any change, especially distortion or blurriness.

« Back to Retina Disease List