Impact of Cataract Surgery on AMD Progression
Age-related Eye Disease Study provides ideal cohort to evaluate cataract/AMD relationship.
Age-related macular degeneration (AMD) patients in need of cataract surgery can be reassured of little to no increased risk of choroidal neovascularization (CNV) due to cataract surgery, according to Susan B. Bressler, MD, the Julia G. Levy PhD professor of ophthalmology, Johns Hopkins University School of Medicine, The Wilmer Eye Institute. "The age-related eye disease study (AREDS) Research Group has been able to show there is no clear-cut evidence of an adverse association between cataract surgery and progression to neovascular AMD in a cohort of people who are at risk for progression," Dr. Bressler reported at the 2006 Retinal Physician Symposium.
PROCEED WITH CAUTION
Although a literature review shows some evidence of increased CNV risk following cataract surgery, there are problems with using the final data from these studies, Dr. Bressler said. For instance, two population-based studies the Beaver Dam Eye Study and the Blue Mountains Eye Study (Australia) comprising approximately 12,000 eyes found that participants who were identified as pseudophakic/aphakic at baseline had an increased risk of developing CNV by the second assessment performed 5 years later. However, these studies pooled their subjects (minimum age 40s) to evaluate the connection between cataract surgery and AMD, though few participants had cataract surgery or neovascular AMD, and even fewer had both events.
Three other population-based studies showed another evaluation of the connection between cataract surgery and AMD progression. Patients who were pseudophakic or aphakic at their examination had nearly twice the risk of manifesting neovascular AMD or geographic atrophy.
"The problem with these studies is that it's impossible to ascertain which came first the cataract surgery or the advanced AMD," Dr. Bressler said. "Some ophthalmologists may be reluctant to perform cataract surgery on patients with AMD based on these findings. They may be withholding therapy from individuals who may derive vision benefit from cataract surgery."
RICH DATA SET
The AREDS study provides a cohort of approximately 5000 subjects monitored meticulously with annual fundus photographs for a neovascular AMD event. These subjects also are questioned frequently as to whether they have had cataract surgery. "Many of the AREDS participants have levels of AMD that put them at risk of progression to CNV, and many underwent cataract surgery while being observed in the study."
The AREDS design enabled the data to be adjusted for known predictors of neovascular AMD progression, including the level of non-neovascular AMD, which can be measured via a nine-point severity scale that evaluates and scores the eye's probability of progressing to CNV.
"By mining this rich data set from multiple analytic approaches, we've demonstrated no clear-cut evidence of an adverse association between cataract surgery and progression to neovascular AMD," Dr. Bressler said. "We're not suggesting that removing a cataract is beneficial or protective, but rather the data suggest a clear absence of harm between cataract surgery and AMD progression."