Loss to Follow-Up and Risk of Incident Blindness among Patients with Glaucoma in the IRIS® Registry

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 2 visual acuity (VA) measurements documented in the IRIS® Registry (Intelligent Research in Sight) in both 2014 and 2019.

Methods: Loss to follow-up was defined as a calendar year or more without an encounter. Univariable and multivariable robust log-Poisson regression models were used to estimate the risk of incident blindness, 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 1 or both eyes (VA ≤ 20/200) in 2019 among patients who were not blind in 2014.

Results: Among the 149 172 patients, incident monocular blindness occurred in 6338 (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/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 relative risk [aRR] = 1.19, 95% confidence interval [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/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 White patients (aRR = 1.93, 95% CI: 1.37-2.73). No effect modifications were identified by other baseline variables.

Conclusions: Loss to follow-up 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.

Financial disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords: Glaucoma blindness; Health disparities; Lapses in care; Loss to follow-up.