Long-term trends in glaucoma-related blindness in Olmsted County, Minnesota

Abstract

Objective: To determine the longitudinal trends in the probability of blindness due to open-angle glaucoma (OAG) in Olmsted County, Minnesota, from 1965 to 2009.

Design: Retrospective, population-based cohort study.

Participants: All residents of Olmsted County, Minnesota (aged ≥ 40 years) who were diagnosed with OAG between January 1, 1965, and December 31, 2000.

Methods: All available medical records of every incident case of OAG were reviewed until December 31, 2009, to identify progression to blindness, defined as visual acuity ≤ 20/200 or visual field constriction to ≤ 20°. Kaplan-Meier analysis was used to estimate the cumulative probability of glaucoma-related blindness. Population incidence of blindness within 10 years of diagnosis was calculated using US Census data. Rates for subjects diagnosed in the period 1965-1980 were compared with rates for subjects diagnosed in the period 1981-2000 using log-rank tests and Poisson regression models.

Main outcome measures: Cumulative probability of OAG-related blindness and population incidence of blindness within 10 years of diagnosis.

Results: Probability of glaucoma-related blindness in at least 1 eye at 20 years decreased from 25.8% (95% confidence interval [CI], 18.5-32.5) for subjects diagnosed in 1965-1980 to 13.5% (95% CI, 8.8-17.9) for subjects diagnosed in 1981-2000 (P = 0.01). The population incidence of blindness within 10 years of the diagnosis decreased from 8.7 per 100,000 (95% CI, 5.9-11.5) for subjects diagnosed in 1965-1980 to 5.5 per 100,000 (95% CI, 3.9-7.2) for subjects diagnosed in 1981-2000 (P = 0.02). Higher age at diagnosis was associated with increased risk of progression to blindness (P < 0.001).

Conclusions: The 20-year probability and the population incidence of blindness due to OAG in at least 1 eye have decreased over a 45-year period from 1965 to 2009. However, a significant proportion of patients still progress to blindness despite recent diagnostic and therapeutic advancements.

Figure 1

Annual incidence of open angle glaucoma (including treated ocular hypertension) in 5 year time intervals per 100,000 population (>40 years) from 1965–2000. OAG = open-angle glaucoma

Figure 2

Kaplan–Meier cumulative probability of open angle glaucoma-related blindness (including treated ocular hypertension). Red lines: blindness in at least one eye by visual acuity (VA) criteria (≤20/200). Green lines: blindness in at least one eye by visual field (VF) criteria (constriction to 20° or less). Blue lines: blindness in at least one eye by either visual acuity criteria or visual field criteria. Solid lines: Current Study Period: 1981–2000; Dashed lines: Previous Study Period: 1965–1980.