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Macular degeneration
Macular degeneration is a medical condition where the light sensing
cells in the macula malfunction and over time cease to work. According to
the American Academy of Ophthalmology, it is the leading cause of central
vision loss (blindness) in the United States today for those over the age
of fifty. There are two basic types of the disease: Standard Macular Degeneration
(MD) and Age Related Macular Degeneration (AMD), with AMD being the most
common form of the condition. Macular degeneration that is not age related
is most commonly caused by an inherited condition. These forms are sometimes
called Juvenile macular degeneration (JMD). In macular degeneration the
final form results in missing or blurred vision in the central, reading
part of vision. The outer, peripheral part of the vision remains intact.
Age related macular degeneration
AMD is further divided into a "dry," or nonexudative,
form and a "wet," or exudative, form. Eighty five to ninety
percent of cases are categorized as "dry" macular degeneration
where fatty tissue, known as drusen, will slowly build up behind the retina.
Ten to fifteen percent of cases involve the growth of abnormal blood vessels
under the retina. These cases are called "wet" macular degeneration
due to the leakage of blood and other fluid from behind the retina into
the eye. Wet macular degeneration usually begins as the dry form. If allowed
to continue without treatment it will completely destroy the macula. Medical,
photodynamic, laser photocoagulation and laser treatment of wet macular
degeneration are available.
Signs
- Drusen
- Pigmentary alterations
- Exudative changes:
hemorrhages, hard exudates, subretinal/sub-RPE/intraretinal fluid
- Atrophy: incipient
and geographic
- Visual acuity drastically
decreasing (two levels or more) ex: 20/20 to 20/80.
Diagnosis
Fluorescein angiography allows for the identification and localization
of abnormal vascular processes.
Treatment
During the early stages of the disease, the neural layers of the
retina remain relatively unaffected. This fact makes it a possible target
for treatment with a retinal prosthesis, which are currently under development.
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