Association of Fellow Eye With Study Eye Disease Trajectories and Need for Fellow Eye Treatment in Collaborative Initial Glaucoma Treatment Study (CIGTS) Participants

Abstract

Clinicians would benefit from knowing the association of glaucomatous change in 2 eyes of the same patient. To estimate the time between initial glaucoma treatment of the study eye (SE) and the need for treatment of the fellow eye (FE) and to ascertain the concordance between rates of progression in SEs and FEs. In this post hoc analysis of participants from the Collaborative Initial Glaucoma Treatment Study, 607 participants with newly diagnosed open-angle glaucoma in 1 or both eyes were followed up for up to 11 years. An SE was designated at baseline and randomized to medical or surgical treatment. By protocol, FEs were treated when eligible or at physician discretion. Survival analysis methods were used to estimate the probability of FE treatment over time and to test baseline and time-dependent predictors of treatment. Disease trajectory was calculated with linear regression as the patient eye-specific slopes of mean deviation (MD) and intraocular pressure (IOP) over time, and correlations between SE and FE trajectories were calculated. Data were collected from October 1993 to December 2004. Data were analyzed from September 2012 to May 2018. Time to FE treatment and slopes over time of MD and IOP in SEs and FEs. Of the 607 included patients, 334 (55.0%) were male and 337 (55.5%) were white, and the mean (SD) age was 58.0 (10.9) years. A total of 291 FEs (47.9%) were treated at baseline, 123 (20.3%) were eventually treated, and 193 (31.8%) never received treatment. The probability of FE treatment for open-angle glaucoma was 0.57 at 1 year and 0.68 at 7 years after randomization. Characteristics significantly associated with an increased hazard of FE treatment included older age (hazard ratio [HR], 1.33; 95% CI, 1.08-1.64; P = .007), hypertension (HR, 1.76; 95% CI, 1.16-2.67; P = .008), higher IOP (HR, 1.24; 95% CI, 1.20-1.29; P < .001), large cup-disc ratio (HR, 1.40; 95% CI, 1.23-1.58; P < .001), and worse MD. Correlations in MD slopes between SEs and FEs initially, eventually, and never treated were 0.73, 0.71, and 0.34, respectively. Comparable correlations in IOP slopes were 0.57, 0.24, and 0, respectively. Among patients with newly diagnosed open-angle glaucoma, almost half had initial treatment of both eyes. After 7 years, approximately two-thirds of patients had bilateral treatment. Of the variables predictive of FE treatment, modifiable factors included hypertension and IOP. Slopes of MD were similar between SEs and treated FEs. This implies that SE change is a harbinger of FE change and therefore warrants close surveillance.