Loss to follow-up and risk of incident blindness among patients with glaucoma in the IRIS® Registry (Intelligent Research in Sight).

Abstract

Purpose: To assess the association between loss to follow-up (LTFU) and risk of incident blindness among a national registry cohort of patients with primary open-angle glaucoma (POAG).

Design: Retrospective longitudinal cohort study.

Participants: Patients with a POAG diagnosis who had at least two visual acuity (VA) measures documented in the IRIS Registry (Intelligent Research in Sight) in both 2014 and 2019.

Methods: LTFU was defined as a calendar year or more without an encounter. Univariable and multivariable robust log-Poisson regression models were used to estimate the relative risk (RR) and 95% confidence interval (CIs) of incident blindness associated with intervals of LTFU as the primary exposure of interest. Effect modification by baseline characteristics on the association between LTFU and incident blindness was also assessed.

Main outcome measures: Incident blindness in one or both eyes (VA ≤20/200) in 2019 among patients who were not blind in 2014.

Results: Among 149,172 patients, incident monocular blindness occurred in 6,338 (4.2%) and incident binocular blindness occurred in 691 (0.5%) over the 6-year period. While most patients maintained follow up every year (90%), 8.8% were LTFU for 1-2 years, and 1.1% were LTFU for 3-4 years. Patients with LTFU had greater risk of blindness. In an adjusted model that accounted for age, sex, race and ethnicity, insurance, smoking status, glaucoma severity, baseline intraocular pressure, baseline cup-to-disc ratio, and history of glaucoma surgery, risk of incident monocular blindness was greater among patients with a lapse of 1-2 years (adjusted RR [aRR]=1.19, 95% CI: 1.05-1.35) or a lapse of 3-4 years (aRR=2.17, 95% CI: 1.66-2.78) compared to patients with no lapse in care. Race and ethnicity demonstrated a significant effect modification in the association between the longest lapse between encounters and the risk of blindness (P=0.02). The risk of incident blindness after a lapse of 3-4 years (compared to no lapse) was higher among Black patients (aRR=3.12, 95% CI: 2.06-4.76) than among White patients (aRR=1.93, 95% CI: 1.37-2.73). No effect modifications were identified by other baseline variables.

Conclusions: LTFU is an independent risk factor for incident blindness among patients with POAG. Lapses in care are particularly consequential for Black patients. Efforts to reduce LTFU may mitigate preventable glaucoma blindness.