Distribution of corneal thickness measured using optical coherence tomography in South African young adults

Abstract

Background: Corneal thickness measurements have various diagnostic and therapeutic applications. Studies have reported on the distribution of corneal thickness measurements in Caucasian and Asian subpopulations with limited focus on African subpopulations.

Aim: The goal of this study was to examine the distribution of corneal thickness measured using optical coherence tomography in a South African young adult population.

Setting: The study was conducted at the eye clinic at the University of KwaZulu-Natal.

Methods: The study used a quantitative cross-sectional research design and participants were recruited using two-stage random sampling. Seven hundred participants consisting of 50% South African blacks and 50% South African Indians aged between 17 and 30 years were included. The sample included an equal distribution of male (n = 350) and female (n = 350) participants. Corneal thickness was measured using the Fourier-domain Optovue iVue100 optical coherence tomographer. As the data from the right and left eyes showed high levels of interocular symmetry, data from only the right eyes were analysed using descriptive and inferential statistics.

Results: The mean age of the sample was 20.42 ± 1.80 years. Corneal thickness measurements resembled Gaussian curves (p ≥ 0.095) and the mean central corneal thickness (CCT) was 501.91 µm. Corneal thickness at the thinnest point was 495.73 µm and 1.23% thinner than the mean CCT measurement (p < 0.001). Males had slightly higher corneal thickness measurements than females but these differences (0.35 µm – 3.93 µm) were not significant (p ≥ 0.137). Corneal thickness varied significantly with refractive error and was lowest in emmetropes followed by myopes and then hyperopes.

Conclusion: Corneal thickness measurements are normally distributed in South African young adults. The mean CCT is different from that reported in other populations and lower than the calibrated CCT measurement for Goldmann applanation tonometry. Eye care personnel should consider the characteristics of corneal thickness measurements and its implications on intraocular pressure measurements when examining South African individuals.