AMD not accelerated by cataract surgery

This study was prompted by the results of the Beaver Dam Eye Study and the Blue Mountain Eye Study, which, in a combined analysis, showed that there was about a five times increased risk of neovascularization in aphakic patients who were followed for 5 years; the Baltimore Eye Survey and the Proyecto VER similarly showed a increase in risk of about two times of the development of AMD, according to Dr. Ferris, director of the Division of Epidemiology and Clinical Research, National Eye, National Institutes of Health, Bethesda, MD.

Dr. Ferris explained that population-based studies, while large, may not contain reliable information on the preoperative status of the patients' retinas. It may be especially difficult in these studies to eliminate the possibility that early retinal changes that cause some vision loss were not the reason for the cataract surgery.

To surmount the problems encountered with population-based studies, the investigators studied the effects of cataract surgery in these patients using four statistical approaches to determine if there was an association between surgery and development of AMD: a Cox proportional hazards model using cataract surgery as a time-dependent covariate, repeated measures regression analysis, ordinary logistic regression analysis, and a matched case/ control approach, he said.

The covariates that were analyzed included smoking, gender, age, race, the AREDS treatment to which the patient was randomly assigned, and the current classification of the severity of AMD on a nine-point scale.

The median follow-up in this study was more than 6 years. The median patient age at baseline was 70 years, and 55% of patients were women.

Dr. Ferris reported that none of the statistical approaches indicated that having undergone cataract surgery placed the patients at a significant increased risk of developing neovascular AMD.

"About 73% of eyes had neither progression to advanced AMD nor cataract surgery; 19% had cataract surgery only; 5% had progression to advanced AMD only, and 2% of eyes had both events," he said. "Matched case/control analysis, Cox proportional hazards analysis, and regression analysis adjusted (or matched) for age, treatment assignment, baseline AMD status, and length of follow-up showed that cataract surgery did not significantly accelerate or was not associated with progression to neovascular AMD."

In all the analyses, the relative risks were approximately 1.0, indicating that there is little or no association of cataract extraction with the development of neovascular AMD.

"We did not think that there was clear evidence of an association between cataract surgery and the development of neovascular AMD," Dr. Ferris said. "We think that some of the discrepancies between our results and those of the population-based studies may be due to the methods of our study, in which we examined patients every 6 months, and the fact that in our study retina specialists participated in the decision about cataract surgery.

"Generally, we think that patients who need cataract surgery should not be unnecessarily worried that they are going to increase their risk of AMD," Dr. Ferris concluded.