Are differences in visual function between people of African and European descent with healthy eyes due to early glaucoma?

Abstract

Purpose : Differences in visual function between the healthy eyes of people of European descent (ED) and African descent (AD) have been previously reported (Racette et al, 2010). The purpose of this study is to determine whether these differences are found in the same regional distribution as early glaucomatous visual field loss and thus may be indicative of subclinical pathology.

Methods : 760 participants (393 AD and 367 ED) with healthy eyes were selected from the Diagnostic Innovations in Glaucoma Study and from the African Descent and Glaucoma Evaluation Study. Healthy eyes had normal appearing optic discs and no history of elevated IOP. We compared the threshold, total deviation (TD) and pattern deviation (PD) values at 52 locations on standard automated perimetry (SAP) and short-wavelength automated perimetry (SWAP) between AD and ED. We hypothesized that if the previously reported racial differences were due to early glaucoma, differences would be observed in visual field locations that are commonly affected by glaucoma (e.g. arcuate area). If these differences were distributed randomly across the visual field, then it was unlikely they were due to early glaucoma. Fisher’s exact test was used for patient-specific categorical variables and the generalized estimating equation was used to adjust for inter-eye correlation. A subset of 41 AD and 41 ED eyes with normal SAP results at baseline and 3 years of longitudinal data were assessed to determine whether a higher proportion of people of AD with healthy eyes would develop visual field defects over time.

Results : On the PD plot, the AD group had 19 locations that were significantly worse than the ED group (p <0.05) on both SAP and SWAP. All were in the arcuate and nasal step regions (all p<0.05). Similar findings were found for the threshold, TD and PD values, as well as in a subset that excluded eyes with abnormal visual fields. After 3 years, a significantly higher proportion of AD (16.1%) with normal baseline visual field developed a repeatable visual field defect compared to the ED group (6.8%) (p<0.01).

Conclusions : These results suggest that the previously reported differences between AD and ED eyes may be due to early glaucoma. Clinicians may choose to carefully monitor AD eyes, even in the absence of visual field loss, as very early loss may be present before abnormalities are triggered on the visual field tests.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.