Macular degeneration is a disease that can cause severe loss of central vision. The macula, located in the center of the retina, is the light-sensitive part of the eye that sends nerve signals to the brain. According to the National Eye Institute, age-related macular degeneration (ARMD) is the leading cause of vision loss in Americans 60 years of age and older. Early detection is critical since treatment can prevent, or delay, further vision loss.
Dry Form of Age-Related Macular Degeneration
ARMD always begins with the dry form, which is much more common than the wet form. It usually affects both eyes, although one may appear to be unaffected. A doctor may detect an early sign of the disease, which are yellow deposits called "drusen" under the retina, during a dilated eye exam. At this early stage the patient usually does not yet show vision loss. However, the doctor will typically do a visual acuity test with an eye chart and ask the patient to look at an amsler grid, which is a pattern of straight lines that resembles a checkerboard. Seeing lines that look wavy, or seem to be missing, is an early sign of the dry form of macular degeneration.
Wet Form of Age-Related Macular Degeneration
The wet form of ARMD is so named because abnormal blood vessels behind the retina tend to leak blood and fluid. The patient may start to see dark spots in his central vision caused by the leakage. ARMD always begins as the dry form and can suddenly turn into the wet form at any time without warning. Wet ARMD is always an advanced form. However, early warning signs of the wet form can help doctors proceed with treatment options such as laser surgery or photodynamic therapy. Patients with the dry form should use an amsler grid everyday, checking each eye separately. A printable chart is available on the Examinations website (see Resources). If the lines start to appear increasingly wavy, a thorough examination is necessary.
Stargardt's Disease
Stargardt's disease is a form of juvenile macular degeneration that is inherited and usually diagnosed before age 20. According to optometrists Richard L. Windsor and Laura K. Windsor, the macula may appear to be normal early in the disease, delaying a diagnosis. In fact, the disease is characterized by rapid visual acuity loss, making it difficult to diagnose until it has reached an advanced stage.
References
- "Age-Related Macular Degeneration; What You Should Know"; National Eye Institute; 2003
- "Coping with Vision Loss"; Bill Chapman; 2001
- Understanding Stargardt's Disease
- "Foundations of Low Vision; Anne L. Corn and Alan J. Koenig; 2004
- "Low vision Rehabilitation"; Mitchell Scheiman, Maxine Scheiman and Stephen G. Whittaker; 2007
