To learn more about factors that may reduce diabetic retinopathy (DR) risk, Laurence Shen Lim, MRCS, and colleagues at the Singapore National Eye Centre, studied how refractive error (vision worse than 20/20, without glasses) relates to the presence and severity of DR. Earlier, smaller studies had suggested a protective effect for nearsightedness (myopia), but were inconclusive.
Dr. Lim's study -- presented at the 2009 Joint Meeting of the American Academy of Ophthalmology (AAO) and the Pan-American Association of Ophthalmology (PAAO) -- is the first to include axial length (AL, measured from the front to back of the eye) in an analysis of the myopia-DR relationship. About 10 percent of people with diabetes develop DR, which damages the eye's retina, the specialized tissue where images are focused for relay to the brain's visual cortex. DR is a major cause of vision loss worldwide.
Reduced risk of DR, especially severe DR, was found in patients whose myopia resulted from two anatomical characteristics: longer axial length and deeper anterior eye chamber (anterior chamber depth, ACD). The findings held true for all degrees of refractive error in these patients. The 675 diabetics evaluated by Dr. Lim's team were drawn from the Singapore Malay Eye Study, a population based study of adults aged 40 to 80.
"This DR-protective effect may result from conditions often found in myopia, including atrophy of the retina, choroid, or vitreous," Dr. Lim said. Though these conditions can cause vision problems in other circumstances, they may lower DR risk by reducing retinal metabolic needs and/or improving oxygen circulation in the back of the eye. "Our findings add to our understanding of how DR develops and the assessment of DR risk in nearsighted patients," Dr. Lim added.
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