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Diseases Affecting the Retina

The retina lies in the posterior portion of the eye. It is the film in your camera. The retina contains cells (cones & rods) that record your visual images and, after a series of cell connections, send the visual images to the brain. The visual center of the retina is called the macula. It is a relatively small area but is responsible for recording your acute vision. It is the area in the normal eyeball that is responsible for seeing the 20/20 line on the eye chart. Beyond the edge of the macula, visual capability quickly drops to 20/200, the big “E” on the eye chart. The remainder of the retina is responsible for peripheral vision. While the actual visual acuity of the retina beyond the macula is poor it plays a very vital part in your visual function. An individual with constricted peripheral vision would be severely handicapped (could not drive) even though the actual acuity may be recorded as near normal. The actual visual cells are called rods & cones. Cones are responsible for central, acute vision as well as color vision and rods are important in night and peripheral vision.

The following is a discussion of several common diseases that affect the retina and consequently have a major impact on vision.

Age-Related Macular Degeneration

Macular degeneration is a disease that affects that portion of the retina that is responsible for recording acute vision. Degeneration is a process in which cells deteriorate by a process that is not related to inflammation or trauma. The causes of degeneration often are unknown. Hereditary, dietary and other factors such as hypertension and smoking may play a role. While these factors may plan a role, the basic cause for macular degeneration remains unknown. As our population ages, the incidence of macular degeneration will increase.

As the term applies, age-related macular degeneration affects individuals in the 6th decade and beyond. It is the most common disease among Americans that results in legal blindness. It is divided into two forms: dry and wet.

Dry Macular Degeneration: Eighty percent of age-related macular degeneration is of the dry form. It is a slowly progressive deterioration of the pigment cells in the retina which eventually results in death of the overlying cone cells. Vision may not be affected early in the process but eventually it begins to deteriorate. This may take many, many years and is highly individualized! Sometimes the process seems to remain stationary in some individuals and accelerate in others. If vision declines, magnifying and telescopic devices may be of assistance. Peripheral vision usually remains intact and therefore even the most severely affected patients are not totally blind. However, at some point an individual may not meet the legal requirements for driving.

Wet Macular Degeneration: Usually wet macular degeneration develops in an eye that already has been affected by the dry type. It is referred to as “wet” because there is a sudden influx of new blood vessels into the macular area. New blood vessels tend to bleed and leak fluid and this will result in a sudden distortion of vision or a sudden decrease of vision in one eye.

Treatment: Patients with macular degeneration should be seen at least once a year, more frequently if vision is noticeably declining. Patients should monitor their vision by looking at an Amsler Grid, a card with multiple horizontal and vertical lines that create small squares. A distortion of these lines or absence of squares could indicate a change from the dry form to the wet form of macular degeneration. This also can be accomplished by looking at a newspaper first with one eye and then the other and noticing if there has been any change in the vision. If a change occurs, your ophthalmologist should be contacted immediately.

Unfortunately, there is no cure for macular degeneration. A recent study by the National Eye Institute found that the progression of dry macular degeneration could be slowed in 24% by taking a specific combination of vitamins on a regular basis. The wet form of macular degeneration can be treated with laser, which destroys the net of new blood vessels that has developed. However, laser works by destroying tissue and best results are achieved with this treatment if the “net” is located outside the very central area of vision. Patients must be carefully monitored for recurrences.

Macular Degeneration is a very common and serious disease of the eye. A great deal of research effort is being devoted to this disease but a cure has remained elusive.