Retinal Nerve Fiber Layer Thickness in Healthy Eyes of Black, Chinese, and Latino Americans A Population-Based Multiethnic Study

Purpose: To compare peripapillary retinal nerve fiber layer (RNFL) thickness among healthy adults by race and ethnicity and to identify determinants of RNFL thickness. Design: Population-based cross-sectional study. Participants: Data from 6133 individuals (11 585 eyes) from 3 population-based studies in Los Angeles County, California, 50 years of age or older and of self-described African, Chinese, or Latin American ancestry. Methods: We measured RNFL thickness and optic nerve head parameters using the Cirrus HD-OCT 4000. Multivariate linear mixed regression was used to evaluate factors associated with RNFL thickness among participants without ocular diseases. Main Outcome Measures: Determinants and modifiers of RNFL thickness. Results: The mean age of the participants was 60.1 years (standard deviation, 7.4 years). Black Americans showed the lowest RNFL thickness and smallest cup-to-disc ratio (CDR), and Chinese Americans showed the largest CDR and disc area after adjusting for age and gender (all P < 0.05). Per each 10-year older age group, the average RNFL thickness was 2.5 mu m (95% confidence interval [CI], 1.8-3.1 mu m), 2.8 mu m (95% CI, 2.3-3.3 mu m), and 3.5 mu m (95% CI, 2.9-4.1 mu m) thinner for Black, Chinese, and Latino Americans, respectively (age trend P < 0.05 and interaction P = 0.041). Black Americans compared with Chinese Americans, older age, male gender, hypertension, diabetes, greater axial length (AL), bigger disc area, and lower scan signal strength were associated with thinner average RNFL. Race, age, AL, disc area, and scan signal strength consistently were associated with RNFL thickness in all quadrants, whereas gender, hypertension, and diabetes were associated with RNFL thickness in select quadrants. Age and race explained the greatest proportion of variance of RNFL thickness. Conclusions: Clinically important differences in RNFL thickness are present in healthy adults 50 years of age or older from different racial and ethnic groups of the same age, with the thinnest measures observed in Black Americans. This difference remains after accounting for disc size and AL. Furthermore, age-related RNFL thinning differs by race and ethnicity. Longitudinal studies are needed to verify our findings and to assess the influence of race and ethnicity in the clinical application of RNFL thickness. (C) 2020 by the American Academy of Ophthalmology

Automated summary

This study compared peripapillary retinal nerve fiber layer (RNFL) thickness among healthy adults by race and ethnicity, and identified determinants of RNFL thickness. Significant differences in RNFL thickness were found among different racial and ethnic groups of healthy adults 50 years of age or older, with Black Americans showing the lowest RNFL thickness. Age and race were the main factors influencing RNFL thickness.