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January 1, 2008

Participants and Methods in AREDS Report No. 8—Reply

Arch Ophthalmol. 2008;126(1):147. doi:10.1001/archophthalmol.2007.15

In reply

Hawkins suggests that AREDS analyses should be adjusted to control for possible confounding from cataract surgery. To be a confounder, a variable must both affect the outcome under study (cataract surgery must be associated with a change in risk for the development of advanced AMD) and be unequally represented in the various treatment groups. In AREDS, there was no apparent imbalance of cataract surgery within treatment groups. There are published articles linking AMD and cataract surgery, and these have been mostly population-based studies (eg, Hawkins' references 2-5). AREDS differs from these reported studies in important ways, including by using the following: clinic-based, large numbers of AMD events, regular periodic follow-up, and knowledge of the temporal relation between an AMD event and cataract surgery. In preliminary reports within AREDS, we find no clear evidence to support an association between cataract surgery and the development of neovascular AMD or geographic atrophy.1,2

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