Macular degeneration
Key points
- Macular degeneration is a disorder that affects the macula (the central part of the retina of the eye) causing decreased visual acuity and possible loss of central vision.
- The macula is the part of the retina that allows the eye to see fine details at the center of the field of vision.
- There is no specific treatment for dry macular degeneration, although zinc supplementation may slow the progression of the disease (see zinc in diet).
- AMD Alliance International is a nonprofit organization committed to raising the awareness level of Age-related Macular Degeneration (AMD).
Alternative names
Age-related macular degeneration (ARMD or AMD); Senile macular degeneration (SMD)
Definition
Macular degeneration is a disorder that affects the macula (the central part of the retina of the eye) causing decreased visual acuity and possible loss of central vision.
Causes, incidence, and risk factors
The macula is the part of the retina that allows the eye to see fine details at the center of the field of vision. Degeneration results from a partial breakdown of the retinal pigment epithelium (RPE).
The RPE is the insulating layer between the retina and the choroid (the layer of blood vessels behind the retina). The RPE acts as a selective filter to determine what nutrients reach the retina from the choroid. Many components of blood are harmful to the retina and are kept away from the retina by normal RPE.
Breakdown of the RPE interferes with the metabolism of the retina, causing thinning of the retina (the "dry" phase of macular degeneration). These harmful elements may also promote new blood vessel formation and fluid leakage (the "wet" phase of macular degeneration).
This disorder results in the loss of central vision only - peripheral fields are always maintained. Although loss of ability to read and drive may be caused by macular degeneration, the disease does not lead to complete blindness.
The disease becomes increasingly common among people in each succeeding decade over 50. By age 75, almost 15% of people have this condition. Other risk factors are family history, cigarette smoking, and being Caucasian.
Symptoms
- Blurred, distorted, dim, or absent central vision
Signs and tests
Tests to evaluate the retina may include:
- Visual acuity
- Refraction test
- Pupillary reflex response
- Slit lamp examination
- Retinal examination by various techniques
- Retinal photography
- Fluorescein angiography, and sometimes indocyanine green angiography
- Amsler grid
Treatment
There is no specific treatment for dry macular degeneration, although zinc supplementation may slow the progression of the disease (see zinc in diet).
Laser photocoagulation (laser surgery to coagulate leaking choroidal blood vessels) may be useful in the early stages of the wet form of the disease. It involves the use of a thermal laser, which burns the abnormal, leaky blood vessels and stops them from spreading.
Written and revised by
David Cohen, M.D.
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