Race-adjusted interpretation of data from Cirrus high-definition optical coherence tomography (HD-OCT) devices is not standard practice. The aim of this study is to evaluate differences in peripapillary retinal nerve fiber layer (RNFL) thickness between healthy African Americans and the Cirrus HD-OCT normative database.
This is a cross-sectional observational study using control patients recruited from the greater Philadelphia, Pennsylvania area.
A total of 466 eyes were included in this study. Subjects were retrospectively identified from the control cohort of the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study.
Using an age-stratified or linear regression method, we reclassified white-green-yellow-red color probability codes for RNFL thicknesses by quadrant.
The distribution of reclassified color codes was compared to the expected 5%-90%-4%-1% percentiles and to the original color codes by the Cirrus machine.
Average RNFL thickness in the POAAGG control cohort was thinner than the Cirrus normative database in all except the nasal quadrant. The original color codes of the POAAGG cohort did not fall into the expected distributions, with more RNFL measurements assigned as white and red codes than expected (9.5% and 1.7%) and fewer measurements assigned as green and yellow codes than expected (85.3% and 3.5%) (p<0.001). Compared to the original Cirrus machine, reclassification using linear regression produced color codes closest to the expected distributions (p=0.09). The proportion of abnormal results shifted closer to the expected 5% in the nasal (1.3%, p<0.001 vs. 3.0%, p=0.048) and temporal (8.2%, p=0.002 vs. 3.6%, p=0.18) quadrants.
Results further establish the presence of structural differences in the RNFL of African American patients. Color code reclassification suggests that the existing Cirrus database may not be accurately evaluating glaucomatous nerves in patients of African descent. To the best of our knowledge, this represents the first study assessing Cirrus HD-OCT color probability codes in an African American population.

Copyright © 2021. Published by Elsevier Inc.