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David Musch, Leslie Niziol, Brenda Gillespie; Factors associated with the onset of treatment in fellow eyes in the Collaborative Initial Glaucoma Treatment Study. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3484.
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To describe the natural history of initially un-treated fellow eyes of the Collaborative Initial Glaucoma Treatment Study (CIGTS) participants and develop a predictive model for the initiation of treatment for open-angle glaucoma (OAG) in such eyes.
607 subjects with a new diagnosis of OAG in one or both eyes were enrolled in the CIGTS. Although a study eye was designated at baseline and randomized to receive either medical or surgical treatment for OAG, fellow eyes were also closely monitored and treated along with the study eye when protocol requirements for treatment eligibility were met. Kaplan-Meier analyses were used to estimate the time-related probability of fellow eye treatment for OAG, and Cox regression was used to investigate predictive factors of this same outcome.
A total of 291 fellow eyes (48%) were initially treated along with the study eye at baseline. Fellow eyes that were initially treated had significantly worse baseline mean deviation (MD), higher IOP, and were more likely to be from black participants than fellow eyes not initially treated at baseline. Of the 316 fellow eyes not initially treated, 193 (61%) never received treatment and 123 were eventually treated for OAG. In the 316 initially untreated eyes, the probability of fellow eye treatment for OAG at 1, 3, 5, and 7 years after randomization was 0.17, 0.25, 0.33, and 0.39, respectively. Baseline characteristics of these 316 fellow eyes that were significantly associated with an increased hazard of treatment included older age, glaucoma that failed to meet treatment criteria (vs. no glaucoma diagnosis), higher IOP, and worse MD. Some of these effects either decreased (glaucoma diagnosis and baseline MD) or increased (age) in the strength of their predictive association with increasing time from randomization.
Fellow eye treatment for OAG in the CIGTS was common, with nearly half of eyes being treated at baseline and 68% by 7 years of follow-up. This is consistent with the bilateral nature of OAG. Likewise, the observed predictors of fellow eye treatment are consistent with known predictors for OAG. Even within the confines of a strict treatment protocol, it is clear that initially untreated fellow eyes warrant close follow-up, and many will require treatment with extended follow-up.
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