Corneal Epithelium Thickness Profile in Normal Adults

Abstract

Aim To characterize the corneal epithelial thickness (ET) and corneal thickness (CT) profiles in normal eyes of Syrian adults, and to investigate associated factors with central epithelial thickness (CET). Method ET and CT were measured by Cirrus high-definition optical coherence tomography (HD-OCT) device in 208 eyes of 104 healthy adults aged 18 to 40 years. The average ET and CT were calculated in 25 (9 mm circle) zones and 17 (7 mm circle) zones, respectively. Correlations of CET with age, refractive errors, keratometry, and central corneal thickness (CCT) were calculated. Results The average ET was thicker in the central 2 mm than the paracentral, midperipheral and peripheral zones (50.42 ± 3.51 µm, 49.29 ± 3.61 µm, 47.80 ± 3.54 µm, and 46.74 ± 3.47 µm, respectively), whereas the average CT was thinnest in the centre. While Males have thicker ET than females in all zones (p < 0.05, all), CT did not significantly differ (p > 0.05, all). ET was thinner in the superior area than in the inferior, with the highest difference registered in the peripheral zone (-6 ± 5 µm). We found a positive significant correlation between CET and sphere (r = 0.25, p = 0.0022), and a negative significant correlation between CET and flat keratometry (r = -0.148, p = 0.043). CET was not correlated with age, cylinder or steep keratometry. Conclusion We present a comprehensive study in healthy, normal eyes using Cirrus HD-OCT to map the corneal epithelium with a 9 mm diameter. The epithelium was thinner centrally than peripherally and superiorly than inferiorly. Myopic eyes tend to have thinner corneal epithelium than hyperopic eyes. This may help in refractive procedures and in the prediction of corneal diseases.