MACULAR DEGENERATION

What is Macular Degeneration?

Age-related macular degeneration is the most common cause of irreversible blindness in people over the age of 65. It is a slow progressive disease that affects the central area of the retina called the macula. This is the location of the retina responsible for central vision or the vision which gives us the greatest detail in our sight.

The exact cause of macular degeneration is not known but the earliest changes occur in the choroid (vascular layer of the eye) and pigmented retinal epithelium. These changes begin as thickening of Bruch's membrane which is the layer of the choroid next to the retina. These thickened areas become raised and have the appearance of warts. These changes produce loss of pigment and cell death of the functioning layers of the retina. It eventually leads to fluid accumulation, hemorrhage and scar tissue. Loss of central vision occurs but this rarely produces total blindness because the peripheral vision is preserved.

The disease commonly occurs over the age of 65 years but there are several hereditary conditions which can lead to this disorder at a much earlier age. Patients usually complain of blurred vision and difficulty with close work. They can also develop wavy lines and distortion of linear targets. There is loss of color sense and the development of scotomas (small areas of blindness).

There is a higher incidence of macular degeneration with hypertension, arteriosclerotic vascular disease and diabetes.

There are several types of macular degeneration. The two common types described are the dry and wet types. The dry or areolar type consists of degeneration of the retinal pigment cells resulting in drusen (small wart like growth) hyper and hypopigmented areas in the retina with loss of rods and cones and generalized atrophy. The wet type or exudative type presents as vascular leakage with exudates and a detachment of the retina with loss of vision. A small percentage of these cases can be treated successfully with the argon laser.

There is another type of macular degeneration which occurs in the diabetic. This results from leakage of small blood vessels which leads to fluid accumulation under the retina and loss of central vision.