Macular Degeneration

Your eye works like a camera. Light is focused by the cornea and the crystalline lens (which functions like a camera lens) and forms an image on the retina, the "film system" of the eye. The image is then sent by the retina through the optic nerve to your brain.

The largest portion of the retina is the peripheral retina which provides your peripheral, or side vision. The central portion is the macula which, though tiny, is one hundred times more sensitive to detail than the peripheral retina. The macula provides the central detailed vision you need for activities such as reading fine print or road signs. Macular degeneration is a disorder in which the central portion of the retina becomes damaged.

The main cause of macular degeneration is the aging process. As we grow older, many of us will develop spots on the retina called drusen. Drusen are the earliest sign of macular degeneration. Most patients with drusen will never have a serious loss of vision. However, in a small group of people with drusen, visual loss and the more serious forms of macular degeneration can develop.

Research suggests that long term exposure to light damages the retina and contributes to the development of macular degeneration, particularly blue and ultraviolet light. Low blood levels of antioxidant vitamins and minerals have also been associated with a higher incidence of macular degeneration. Other risk factors include heredity, light eye coloration (i.e. blue eyes), cigarette smoking and gender. Women appear to be at somewhat higher risk than men.

What are the symptoms?

Most people who develop macular degeneration begin to notice problems with eyesight after age 50. Typically, only one eye is affected initially so you may not immediately be aware of changes. It may become a little harder to see with the affected eye; you may experience blurring when reading, or difficulty with distance vision may occur. Distortion is a common symptom - a tree or a telephone pole may appear bent or crooked. You may also have a dark spot in your vision similar to the after-effect of a flash bulb. Objects may appear a different size in each eye and colors may look different in each eye.

Obtaining regular eye exams is the best way to detect early changes that may benefit from treatment. The Amsler grid test is an effective way of alerting you to any changes in your vision. When changes develop, a prompt eye exam with your optometrist can help to determine whether macular degeneration is responsible, and what can be done about it.

Types of Macular Degeneration

There are two main types of macular degeneration, a dry form and a wet form.

• Dry form of Macular Degeneration
  The dry form of macular degeneration accounts for roughly 90% of macular degeneration cases. Dry macular degeneration can progress to the wet form, resulting in more rapid and severe visual loss. Therefore, early detection and monitoring of the dry form is important to help preserve vision. Any change in vision or distortion which develops in people with the dry form can be a sign of the development of wet macular degeneration, and should be evaluated immediately.

• Wet form of Macular Degeneration
  The wet form of macular degeneration is less common, accounting for approximately 10% of the cases. This form is potentially more damaging, and can be treated in its early stages. It involves the growth of abnormal blood vessels behind the retina which may rupture and leak blood or fluid, causing the retina to lift or separate from the eye. This abnormal growth of blood vessels is called a subretinal neovascular membrane. Visual loss occurs rapidly as the blood vessels grow into the area of central vision. When a subretinal neovascular membrane is diagnosed in its early stages, treatment with an ophthalmic laser may help to preserve vision. On rare occasion a hemorrhage develops when a subretinal neovascular membrane bleeds. This is called a subretinal hemorrhage and results in a sudden loss of vision.

Prevention

There is at present no surgical or medical cure for the dry form of macular degeneration. Research suggests that sunglasses which block ultraviolet and blue light may help to prevent progression. Antioxidant vitamins A, C, E and the minerals selenium and zinc also appear to be beneficial. These vitamins are found in most dark green vegetables, such as spinach and kale. Most commercially available multivitamins with minerals are also satisfactory. In people who can't take these multivitamins for medical reasons, the use of an antioxidant complex formulated specifically for the eye (i.e.: I-Caps, Ocutabs, or Ocuvite) is an alternative.

Your doctor may recommend the use of sunglasses and dietary changes, and/or antioxidant vitamins to attempt to reduce the rate of progression of macular degeneration. Sunglasses specially designed to help minimize your exposure to the sun's damaging rays are recommended. Because macular degeneration is hereditary, it is suggested that your children and grandchildren take similar precautions to reduce their risk of developing macular degeneration.

Evaluation

At our office, some of the latest diagnostic equipment is available to evaluate your retina. If I find an abnormality which suggests the presence of wet macular degeneration, I will refer you to a specialist for a test called an angiogram. There are two types of angiograms, fluorescein angiograms; and indocyanine green angiograms (ICG). Both involve the injection of a dye into your arm, which then travels throughout the body to the eye. As the dye passes through the eye, photographs are taken which allow the specialist to detect the presence of treatable macular degeneration. In most instances a fluorescein angiogram is done first, and will enable your doctor to determine whether you will benefit from laser or surgical treatment. If the fluorescein angiogram shows certain problems requiring further evaluation, an indocyanine green angiogram may be ordered. ICG is a new technique which allows for the treatment of up to 40% of patients who were not previously eligible for treatment.

Laser treatment

When abnormal blood vessel growth is discovered early, laser treatment may prevent more severe vision loss. The laser's high energy light beam seals the abnormal blood vessels, preventing further bleeding and providing a deterrent to future growth. The procedure, performed in a specialist's office under local anesthetic, takes only minutes and is virtually painless. The treated eye may be patched for the rest of the day and patients resume normal activities almost immediately, except for strenuous physical activity.

The Optometrist's Role

Our duty is to ensure that your eyes are healthy. When you come in for your routine exam, we will perform a thorough inspection of all ocular structures so that any potential abnormality of your eyes is detected. If there is a problem, then it is our responsibility to either treat you, or refer you to a professional who specializes in treating the condition in question.

All we ask of you is that you do your part by faithfully coming in for your scheduled exams, and adhere to the treatment plan that we advise. You have our promise that we will keep you thoroughly informed at all times, and any questions you may have are strongly encouraged. Please don't hesitate to ask. By working together, we can keep your eyes healthy for many years to come.