Race, income impact variability in visual field testing
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Black patients experienced greater variability in visual field testing compared with white patients in the U.S., according to findings from a retrospective cohort study.
Also, the variability was strongly influenced by socioeconomic status and may partially explain racial disparities evident in glaucoma outcomes, according to Brian Stagg, MD, of the John A. Moran Eye Center at the University of Utah, and colleagues.
The difference between Black and white patients “was present even when adjusting for age, follow-up duration, number of visual fields performed and ZIP code level socioeconomic variables,” Stagg and colleagues wrote. “Simulation modeling showed that this increased variability could lead to a delay in identification of glaucomatous progression in Black patients.”
The researchers investigated racial differences in variability of longitudinal visual field testing in a clinical population by conducting an observational cohort study. They analyzed data from 751 white patients and 317 Black patients. Stagg and colleagues applied linear regression when comparing the two cohorts.
The majority of patients in both groups were women. The mean age among Black patients was 62.2 years and 66.7 years among white patients. The average follow-up for white patients was 8.1 years and 8.7 years for Black patients. The mean number of visual fields for white patients was 7.4 and 6.9 for Black patients. Also, the average rate of change among white patients was –0.25 dB/year and –0.2 dB/year for Black patients. Black patients experienced greater average residuals (1.53 dB) than white patients (1.25 dB). Moreover, the researchers observed significant interaction between race and disease severity with visual field variability. Income impacted variability, with lower incomes associated with greater differences between the two cohorts.
Stagg and colleagues recognized that other social factors not analyzed in this study could impact variability between white and Black patients.
“The underlying cause of greater visual field variability in Black patients compared with whites is not clear,” they wrote. However, “Previous research using national claims databases has also shown that Black patients receive visual field testing less frequently than white patients.”
Perspective
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Following disease diagnosis, staging, establishing target pressure range, and initiating therapy, “… the most important question becomes whether the disease is stable … or whether the disease is progressive and the therapy in relation to the life expectancy has to be intensified …” (World Glaucoma Association, 2011). This, however, is easier said than done, at least in part due to the variability of AVF analysis, which remains the primary means of assessing functional loss.
Using data from the “real world” Duke Glaucoma Registry, Stagg and colleagues demonstrated that Black patients showed more AVF variability than white patients. This led to significant delays in identifying disease progression, although time to detect change was improved across the board with more frequent testing, and this is a conclusion that all clinicians should pay close attention to.
Chauhan and colleagues have suggested that six AVF tests within the first 24 months post-diagnosis are necessary to detect rapid progression, yet surveys consistently show that testing frequency is woefully inadequate. Despite incredible advances in structural evaluation (and the fact that everyone loves to hate VF testing), we should be performing more, not fewer AVF tests for all patients with glaucoma.
Reference:
Chauhan BC, et al. Br J Ophthalmol. 2008;doi.org/10.1136/bjo.2007.135012.
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Stagg B, et al. Br J Ophthalmol. 2021;doi:10.1136/bjophthalmol-2020-318104.
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