The latest report from the Age-Related Eye Disease Study (AREDS) in the December issue of Ophthalmology, the journal of the American Academy of Ophthalmology, emphasizes the association of smoking and hypertension with development of macular degeneration. The study also calls for further investigation of the apparent association between antacid and thyroid hormone use and macular degeneration.
Academy spokesperson Paul Sternberg, Jr., MD, said, "This study is a
welcome addition to our growing understanding of macular degeneration, and it
suggests interesting avenues for further research in this increasingly
important area of ophthalmology."
Macular degeneration (AMD) occurs when the macula -- the small area at the back of the eye that allows central, detailed vision -- is damaged or breaks down. The two types of AMD are dry (or atrophic) and wet (or exudative), also called neovascular AMD. Approximately 90 percent of people with AMD have the dry form, which is caused by aging and thinning of the macula. There is no
known cure for dry AMD, although some researchers advocate a nutritional
approach, which AREDS will address in a subsequent report.
Although only ten percent of people with AMD have the wet form, it is this form that causes 90 percent of visual impairment from AMD. Wet AMD is
characterized by the growth of abnormal retinal blood vessels that leak blood
or fluid, causing rapid and severe central vision loss. Both types of AMD are
often indicated by the presence of drusen, white protein deposits on the
retina, and retinal pigment epithelial (RPE) abnormalities.
AREDS, supported by contracts from the National Eye Institute, is an
ongoing multi-center longitudinal study of risk factors for AMD and cataracts.
Eleven retinal specialty clinics studied 4,519 people, 60 to 80 years of age,
from 1992 to 1998. The major AREDS findings are:
- -- Smoking is associated with the more severe forms of AMD.
- -- Hypertension is associated with large drusen or neovascular AMD.
- -- Use of thyroid hormones and antacids is associated with geographic
atrophy (dry AMD). This finding needs more study.
- -- Use of hydrochlorothiazide diuretics or presence of arthritis is
associated with one or more large drusen or extensive intermediate
drusen. This finding needs more study.
- -- Hyperopic (farsighted) refractive error is associated with more
extensive drusen and neovascular AMD.
- -- Higher body mass index (BMI), a measure of obesity, is associated with
- -- Wet AMD occurs more frequently in whites than in nonwhites.
- -- Lens opcacity may be associated with large drusen or the presence of
- -- College graduates are significantly less likely to develop AMD than
those with a high school education or less.