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Laser treatment does not prevent vision loss

BioPhotonics
Jan 2007
Age-related macular degeneration is a disease that leads to vision loss. The presence of multiple large drusen -- yellow deposits under the retina -- is associated with an increased risk of developing advanced macular degeneration. Laser treatment of the retina has been used to reduce drusen. However, Dr. Stuart L. Fine and his colleagues from the University of Pennsylvania School of Medicine in Philadelphia recently found that low-intensity laser treatment is ineffective in preventing complications of the disease.

In a randomized study sponsored by the National Eye Institute, the researchers tested 1052 participants from 22 clinical centers across the country and observed them over a five-year period. All of them had bilateral large drusen. One eye of each participant was selected for the laser treatment, and the other was assigned to observation. The laser treatment consisted of forming a grid pattern comprising 60 burns using a 100-μm spot size with a 1-s duration about 1500 to 2500 μm from the foveal center. Argon green (514 nm) was the preferred wavelength. Additional laser treatment was performed at 12 months on 856 patients who had 10 or more drusen that were 125 μm in diameter.

As reported in the November issue of Ophthalmology, the researchers discovered that, after five years, 20.5 percent of the treated eyes and 20.5 percent of the untreated eyes had lost three or more lines of visual acuity; 13.3 percent of treated eyes and 13.3 percent of untreated eyes had choroidal neovascularization (abnormal growth of new blood vessels in the choroid); and 7.4 percent of treated eyes and 7.8 percent of untreated eyes developed geographic atrophy. They also found a similarly insignificant difference between treated and untreated eyes for contrast threshold -- the amount of contrast needed to read letters on a chart -- and critical print size -- the print size needed to read a document.

The investigators concluded that low-intensity laser treatment does not significantly improve vision in people with bilateral large drusen.


GLOSSARY
retina
1. The photosensitive membrane on the inside of the human eye. 2. A scanning mechanism in optical character generation.
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