AGE-RELATED
MACULAR DEGENERATION
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."
Retinal Physician, Issue: September 2006