Macular Degeneration

Macular degeneration is the leading cause of visual loss among persons over the age of 60 in the United States. Because it usually affects only the "central" sight, it virtually never leads to complete blindness. However, it can be very disabling because of the loss of reading and driving and other central visual functions.

The retina is an extension of the brain. It is an extremely thin layer of nerve tissue lying on the back of the eye, like the film in a camera. It connects to the brain by way of the optic nerve. The central "fine vision" area, responsible for reading and color vision is the macula. This area is about 3 millimeters in diameter and is packed tightly with cells called cones. As you can imagine they work very hard with an extremely high rate of metabolism. Trillions of chemical reactions occurring daily, using large amounts of oxygen and nutrients. The cones are inserted into a layer of cells called the pigment epithelium, which work hand-in-glove to assist the function of the cones.

The peripheral or side vision is provided by the cells that make up the rest of the retina, called rods. They perceive movement and form better, and one can read only larger sized print with difficulty, with these cells.

Some people, often later in life (so the term; age-related) experience blurring of their reading (fine central vision). Upon examination they are found to show signs of degeneration (wearing out) of the cells that make up the macula. The exact cause is not known. We don't even know what causes us to age! It usually, but not always, is age-related and is progressive.

 

TYPES

Age-related macular degeneration usually occurs in two forms. The first type or dry form is characterized by a slow loss of visual function. Your ophthalmologist or optometrist can evaluate the visible breakdown of the tissue in the macula (the cones and pigment epithelium). This is by far the most common form and laser treatment is not helpful.

The second type or wet form is caused by abnormal blood vessels that grow beneath the pigment epithelium and the retina that leak fluid or may bleed and cause rapid destruction of the overlying retina and loss of visual function, blurring and distortion of vision. There may be a rapid catastrophic loss of central vision in a matter of days. Fluorescein angiography is performed by an injection of fluorescent dye into the vein in the arm. After several seconds the fluorescein dye travels to the eyes. Photographs of the retina are taken as the dye passes through the vessels showing the areas of new vessel formation and leakage of blood or serum. Fortunately this usually more destructive form is far less common than the dry form.

Your ophthalmologist may use an Amsler grid, a standard central testing grid, to help detect the distortion in an earlier stage and may be used after laser photocoagulation to pick up a recurrence.

Appearance of Amsler grid to a person with macular degeneration.

 

TREATMENT

The wet form may be helped by coagulation of the offending vessels by laser light. This would be dependent on the discovery of a "treatable leak" found on the fluorescein angiogram. The vessels may be large and directly beneath the macula, and treatment with laser destroys the overlying retina causing a permanent scotoma (blind spot). The treatment by laser in these instances may be successful only by limiting the area of blindness and stopping the progression of the disease. Surgery with removal of a blood clot and vessel membrane, dissolution of the clot and other treatment has been tried.

You recall that the macula is made up of tightly packed cones, inserted into pockets of retinal pigment epithelial cells. The cells are performing prodigious amounts of work, with trillions of chemical reactions occurring daily, as well as massive exposure to irradiation in the form of light. Because there are some imperfect chemical reactions creating so called "free radicals" (chemical compounds that are highly unstable and reactive and interfere with normal cellular function) which accumulate in the tissue causing breakdown, death of the cells, and eventual loss of function. This theory may partly explain aging and other degenerative conditions, such as cataract formation.

"Dry" macular degeneration, having a slow atrophic course, may in part be explained by the "free radical" theory because of the progressive age-related nature of the degeneration. Because it can be detected and suspected earlier, treatment in the form of antioxidants may be considered. Antioxidants occur naturally in the body to combat the accumulation of "free radicals" or may occur in nature, concentrated in foods such as green leafy vegetables (eg., spinach, collard greens). Because of the inability of our body to produce enough natural antioxidants, especially as we age, or to ingest sufficient quantities of green leafy vegetables, we may find it helpful to take supplements. Some of the better known supplements are fat soluble Vitamin E (with the "help-mineral", Selenium), water soluble Vitamin C, and Beta carotene (Vitamin A precursor). There are many compounds that have shown usefulness as antioxidants or as adjuncts to enzyme systems that support antioxidation. There is an increasing body of scientific information that supports this theory, although because of the complexity of the disease and the long and varied course, it is difficult to provide conclusive proof of their efficacy.

 

SUMMARY

Age-related macular degeneration is a progressive disease effecting the central vision, occurring in different forms. The more common dry form is slowly progressive, but may be retarded or prevented by the judicious use of antioxidants and related compounds and minerals, especially if taken early in the course and in sufficient quantities and persistence. We have advised some form of antioxidant therapy for many years and feel that with increasing scientific evidence that it may be beneficial to continue the use of these substances.