Retinal nerve fibre layer thickness in a normal black South African population
Abstract Background The measurement of retinal nerve fibre layer (RNFL) thickness on spectral domain OCT (SD-OCT) are compared with built-in age— and gender—matched European normative databases and this difference is used to assist with glaucoma diagnosis. However, there are differences in RNFL thickness between population groups. Therefore, using the built in European normative database as a comparison across all population groups could lead to erroneous results, due to the basic assumption that the normative values for non-European populations are the same as their European counterparts. Methods Cross-sectional study of RNFL thickness in normal black South African patients. Results One hundred and thirty-two eyes of 132 patients were enroled in this study. The mean (SD) age of patients in this study was 41.3 (12.5) years. Males comprised 40.9% (n = 54; p = 0.0367). All RNFL sectors except the temporal sector were significantly thicker than the reference database. The RNFL sectors measured as follows: global (108.7 µm, p < 0.001), superotemporal (152.4 µm, p < 0.001), superonasal (132.6 µm, p < 0.001), inferotemporal (150.1 µm, p < 0.001), inferonasal (129.2 µm, p < 0.001), nasal (77.7 µm, p < 0.001), temporal 74.8 µm, p = 0.9534). Conclusion The RNFL thickness of normal black South Africans is significantly thicker than that of the European database on the Spectralis SD-OCT. This needs to be taken into account when performing RNFL thickness measurements on black patients.
A research report submitted in partial fulfilment of the requirements for the degree of Master of Medicine in Ophthalmology to the Faculty of Health Sciences, School of Clinical Medicine, University of the Witwatersrand, Johannesburg, 2020