Updated August 04, 2006

What to Expect at Your Eye Exam

by Harry G. Randall, M.D.

Cataract
When we are young, the lens of the eye is almost perfectly transparent, but during the normal course of aging, it gradually changes color and becomes cloudy. A clouded or opaque lens is called a cataract. There is no definite dividing line between normal aging changes and early cataract. Most people develop some cataract as they get older; people with diabetes are more likely than others to have cataract.

If a cataract gets bad enough to interfere with a person’s lifestyle and abilities, it can be removed with surgery and replaced with an intraocular lens, or implant. It used to be said that a cataract should be removed when it was “ripe,” but the decision to remove a cataract is really based on how much disability it causes a person. If it does not significantly impair your vision, it’s OK to wait. (It is possible to wait too long to have a cataract removed, but that is after the person can no longer see through it.) Cataract surgery is so quick and successful these days that there is no reason at all to dread or avoid it.

Retinal detachment
An eye problem that cannot wait to be treated is a retinal detachment. Most of eye’s interior is filled with vitreous, a gelatinous substance with fibers and cells that is firmly attached to the retina. Over time, the vitreous gradually becomes more liquid and less gelatinous. As the gelatin liquefies, the thin membrane at the back of the vitreous (the posterior vitreous membrane) can peel away from the retina and flap into the vitreous. This is called a posterior vitreous detachment, or PVD. It can occur without the person noticing it; alternatively, it can create dramatic flashes of light inside the eye, or brown or black floaters, which are actually the shadows cast on the retina either by the posterior vitreous membrane itself or by some leakage of blood into the vitreous.

While a PVD itself is not harmful, if part of the membrane is caught or has scarred to a spot on the retina, it can tear a hole in the retina as it peels away. If liquid vitreous then leaks through the hole and under the retina, the retina itself starts to separate from the outside of the eye. This is called a retinal detachment. Gradually, a person will lose sight in that eye, as if a curtain were slowly being drawn over it.

Most posterior vitreous detachments do not lead to retinal detachment, and many small retinal holes can be treated easily with a laser or even left alone. Because of the seriousness of a retinal detachment, however, anyone who notices new flashes and floaters needs to have an exam of the retina promptly. Fixing a retinal detachment requires complicated surgery; it is much better to treat it sooner rather than later.

Macular degeneration
The part of the retina responsible for central vision and fine visual acuity is the macula. Aging changes in the macula, called age-related macular degeneration, are one of the most common eye problems and the one that people seem to dread the most. Macular degeneration is caused by the breakdown of an insulating, outer layer of the retina. In the common, “dry” stage, the light-converting cells in the macula slowly deteriorate. In the less common but more serious “wet” form, harmful elements in the blood are able to reach the retina, damaging and scarring it.

Macular degeneration never causes total blindness, because it does not affect peripheral vision, but it makes images in the central vision appear extremely warped or blurry, and activities like driving a car or reading become difficult or impossible.

In most cases, there is no treatment for macular degeneration, although good nutrition, exercise, adequate zinc intake, and not smoking are thought to prevent or slow the progression of the condition. Still, many people with early macular degeneration continue to see well enough to lead a normal life, and there are now some laser treatments for the most severe kind of macular degeneration.

Dr. Randall is an ophthalmologist in private practice and Assistant Professor of Ophthalmology at the Johns Hopkins Medical Institutions.

More articles on Eyes & Vision

Statements and opinions expressed on this Web site are those of the authors and not necessarily those of the publishers or advertisers. The information provided on this Web site should not be construed as medical instruction. Consult appropriate health-care professionals before taking action based on this information.