Macular Degeneration

Age-related macular degeneration (AMD) is a chronic eye condition that typically affects people age 50 and older, and is the leading cause of severe vision loss in those over 60. A part of the retina (the tissue at the back of the eye) called the macula specifically allows central vision, which is critical for reading and recognizing faces. When a person has macular degeneration, the macula begins to deteriorate, causing anything from blurred or slightly distorted central vision to a blind spot in the center of the visual field. There are two stages of macular degeneration: dry and wet.


DIAGNOSIS

The diagnosis of macular degeneration is made based on a thorough eye exam. Following diagnosis, additional tests may be performed to determine the location and extent of the disease.

Eye Exam
The doctor looks for presence of abnormalities in the macula, such as deposits called drusen. In addition, the appearance of the macula is important to sharp central vision — if the pigmentation is mottled or uneven, instead of its normal even reddish color, macular degeneration is usually the cause.

Amsler grid test
As a part of the eye examination, the physician may evaluate the patient's vision using a printed grid. If macular degeneration is present, the lines of the grid may seem faded, broken or distorted. By noting where the distortion occurs (usually near the center of the grid), the doctor can better determine the location and extent of macular damage.

Fluorescein angiography
After diagnosis, the physician may perform this test to determine the extent of the damage from macular degeneration. First, the doctor injects dye into a vein in the patient's arm. As the dye circulates through the bloodstream and eventually to the eye, the blood vessels in the retina stand out as bright yellow when observed with a special blue light. A camera takes flash photographs of the eye every few seconds for several minutes, which help the doctor determine pigmentation changes or abnormal blood vessels.

Indocyanine green angiography (ICGA)
Another type of angiography of the vessels in the eye is ICG. ICG is a dye that lights up when exposed to infrared light. Infrared light is used to take pictures of the back of the eye visualizing retinal blood vessels, and the deeper, harder to see choroidal blood vessels.


TREATMENT

The goal of treatment is to stop further vision loss. In most cases, the damage that has already occurred cannot be reversed, making early detection very important for vision preservation.

Dry Macular Degeneration
There is no treatment currently available to reverse dry macular degeneration. This condition normally progresses slowly, and many people are able to live relatively normal lives, especially if vision is affected only minimally.

The good news is that the progression can be slowed by taking high doses of vitamins A, C, E and the mineral Zinc. Patients should discuss with their regular doctor (see also prevention of AMD).

Wet Macular Degeneration
In wet macular degeneration, new abnormal blood vessels behind the retina begin forming at a rapid rate. These vessels begin to leak blood and fluid, causing damage to the macula, the region of the retina responsible for central vision. The doctor will prescribe treatment based on the location and extent of the abnormal blood vessels.

Anti-angiogenic medicine
After the ophthalmologist numbs the eye with an anesthetic, the drug, called pegaptanib sodium (Macugen®) is injected into the affected eye. The medicine stops or slows the blood vessels from growing, leaking and bleeding. The treatment is given every six weeks to prevent the blood vessels from causing more vision loss. This therapy causes less damage to the retina than the laser treatments described below.

Photocoagulation
Also known as laser treatment, photocoagulation uses a high-energy laser beam to create small burns in areas of the retina with abnormal blood vessels. This treatment is used when the abnormal blood vessels are not yet under the area of central vision (fovea). Because it is uncommon for the blood vessels to spare the fovea, only a small number of patients are candidates for the procedure. The doctor determines who may benefit from the treatment based on the location and appearance of the blood vessels, the amount of blood leakage, and the overall health of the macula.

Photodynamic Therapy
The location of the abnormal blood vessels often determines which treatment is selected. The macula is the central portion of the retina responsible for central vision, and the fovea is directly in the center of the macula and is responsible for the sharpest vision. If the abnormal vessels are located directly under the fovea, hot laser treatment (photocoagulation) would damage the fovea and decrease central vision. In these cases, photodynamic therapy may be an excellent option.

In this treatment, a drug called verteporfin (Visudyne®) is injected into the bloodstream. The drug concentrates in the abnormal blood vessels under the macula. The doctor then focuses cold-laser light at the macula, which activates the drug and leads to the closing off of the abnormal vessels without damage to the macula.

Macular Translocation Surgery
Although the procedure is used in rare circumstances, patients with recent visual loss associated with wet macular degeneration and who still have healthy tissue around the fovea may be candidates for macular translocation. The procedure is especially useful when there is a large amount of bleeding under the macula (an uncommon complication of wet macular degeneration).

In this procedure, the surgeon detaches the retina, shifts the fovea away from the abnormal blood vessels and relocates it over healthy tissue. With the abnormal vessels exposed (previously under the fovea), the surgeon can remove them with tiny instruments. Since the fovea has been shifted to a new location, it can function without interference from the macular degeneration changes.