Increased risk of advanced AMD after cataract surgery unfounded

At-risk patients, however, showed a higher rate of disease and should be monitored closely, study authors said.

Data from a large clinical trial showed no significant increased risk of advanced age-related macular degeneration after cataract surgery. However, at-risk patients require constant monitoring, the study authors said.

“We did not find an increased rate of accelerated progression to advanced AMD following cataract surgery,”

Emily Y. Chew, MD, said. “That’s the No. 1 message. The second message is that you better follow these patients who are at risk because the natural course is that they may develop advanced AMD.”

Results were from the Age-Related Eye Disease Study (AREDS), a multicenter, controlled, randomized clinical trial conducted between 1992 and 2005. The AREDS assessed the effect of antioxidant and mineral supplements on progression to advanced AMD and cataract formation.

The AREDS is the only large, prospective study to document the severity of AMD before and after cataract surgery with more than 5 years of follow-up, the study authors said.

“These data, which are contrary to that of previously reported results, may provide some reassurance to patients with AMD who are considering cataract surgery,” they said in Ophthalmology.

Long-term, frequent assessment

The cataract-AMD analysis included 8,050 eyes of 4,577 patients. Because of the large cohort and long-term, frequent assessment of AMD and cataract surgery, the AREDS had more statistical power than earlier population-based studies such as the Beaver Dam Eye Study and Blue Mountains Eye Study, Dr. Chew said.

“What’s curious about those studies is that they always looked at cataract surgery performed prior to baseline,” she said. “If they followed patients who had cataract extraction during the course of the study, they didn’t find the association with increased risk of neovascular AMD. This lack of agreement raised concern. The AREDS population may be a better cohort to follow. First of all, we had larger numbers of participants who developed disease, as well as having had cataract surgery.”

In the earlier studies, patients were evaluated at baseline and at 5-year intervals. The AREDS investigators assessed development of advanced AMD and history of cataract surgery every 6 months. They excluded eyes with cataract surgery or advanced AMD at baseline.

“Because they were population-based, they didn’t follow them on an annual basis,” Dr. Chew said. “They followed them at baseline and then 5 years, 10 years and 15 years. There were a lot of things that happened in between that they really couldn’t capture in this study design.”

Four risk categories

Investigators used separate statistical models that adjusted for various covariates to assess the rate of development of neovascular AMD, geographic atrophy and central geographic atrophy after cataract surgery. Patients were assigned to one of four AMD risk categories, determined according to size of drusen, retinal pigmentation abnormalities, presence of advanced AMD and visual acuity. Matched-pair analysis was conducted to determine whether cataract surgery accelerated the development of advanced AMD. At-risk eyes that underwent cataract surgery were matched with eyes that did not have cataract surgery.

Patients were matched according to age, race, gender, smoking history, AREDS treatment group and AMD severity. “We had excellent controls,” Dr. Chew said.

“We stood on our heads to do multiple analyses because everybody else showed something different,” she said.

The cataract surgery group had a mean age of 70 years; the noncataract surgery group had a mean age of 68 years. Mean follow-up was about 10 years.

Of 1,704 eyes that underwent cataract surgery, 95 eyes (6%) developed neovascular AMD. Of 6,448 eyes that did not undergo cataract surgery, 448 eyes (7%) developed neovascular AMD.

“The multiple statistical analyses showed no clear differences in the rates of development of advanced AMD, either neovascular or geographic atrophy, in those with or without cataract surgery,” Dr. Chew said.

Patients at greater risk, however, had markedly higher rates of advanced AMD. Those with intermediate AMD (bilateral large drusen) or unilateral advanced AMD have a 50% risk of developing advanced wet AMD or geographic atrophy within 5 years and should be followed vigilantly, she said, adding that further study with a different patient cohort is planned. – by Matt Hasson

Reference:

• Chew EY, Sperduto RD, Milton RC, et al. Risk of advanced age-related macular degeneration after cataract surgery in the Age-Related Eye Disease Study. Ophthalmology. 2009;116(2):297-303.

• Emily Y. Chew, MD, can be reached at National Eye Institute, 31 Center Drive, Bethesda, MD 20892-2510; 301-496-6583; fax: 301-496-2297; e-mail: echew@nei.nih.gov.