Detection of Glaucoma Progression is Delayed in African Descent Compared to European Descent Subjects

Abstract

Purpose : African Descent (AD) individuals have been reported to be at higher risk for becoming visually impaired from glaucoma compared to European Descent (ED) subjects. It is possible that delayed detection of progression may lead to delayed intervention and increased risk of visual impairment. We investigated the time to detect visual field (VF) progression in a cohort of AD and ED glaucoma patients followed over time.

Methods : The study included 445 eyes of 322 ED subjects and 334 eyes of 233 AD subjects recruited from the African Descent and Glaucoma Evaluation Study (ADAGES). Eyes had glaucomatous VF loss on standard automated perimetry (SAP) at baseline and were followed for an average of 8.0 ± 3.4 years with an average of 12.4 ± 5.9 SAP tests. Ordinary least squares linear regression (OLS) was used to regress SAP mean deviation values over time. Residuals were extracted from OLS regression to represent expected variability estimates for levels of mean deviation (MD). Distributions of residuals for each level of MD were obtained for each racial group. These distributions allowed reconstruction of visual field trajectories over time by computer simulation, according to expected “true” rates of glaucoma progression. 50,000 VF were then simulated for each racial group under different assumptions about rate of change and frequency of testing. Empirical cumulative distribution functions were built to investigate the probability of detecting progression over time.

Results : When controlling for the fitted (“true”) MD level and age, absolute residuals on existing data were significantly larger in AD versus ED patients (mean difference: 0.15dB; P<0.001). A significant interaction between MD level and race was seen, suggesting that AD subjects had greater increase in variability with worsening disease as compared to ED (P=0.022). When simulations were performed assuming baseline MD of -5dB, true rate of progression of -0.25dB/year (average rate of change in the cohort) and 1-year testing interval, the median time to detect progression was significantly longer in AD versus ED (difference=4.76 years; P<0.05).

Conclusions : Our results suggest that, due to increased VF variability, detection of glaucoma progression may be significantly delayed in AD versus ED glaucoma patients. This could explain, at least in part, higher incidence of glaucoma-related visual impairment in AD compared to ED subjects.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.