Corneal epithelial permeability: Ethnic differences between Asians and non-Asians

Abstract

a b s t r a c tPurpose: To ascertain whether a difference in the permeability of the corneal epithelium to fluorescein (P dc ) exists between Asians and non-Asians. Methods: From a multi-study database we extracted 632 records of baseline, open-eye P dc measurements taken on both eyes of 176 subjects. Subjects were awake for a minimum of 4 h before measurement, and were free of ocular disease and central corneal staining. P dc was transformed by natural logarithm to better approximate normality for statistical tests. Results: The mean ln(P dc ) in the Asian group was significantly greater than in the non-Asian group [−2.34 ln(nm/s) vs. −2.58 ln(nm/s); p < 0.001]. Conclusions: Compared with non-Asians, Asians exhibited a less negative ln(P dc ), which translates to a higher P dc and a more permeable corneal epithelium. We speculate that this may be related to anatomic differences responsible for greater eyelid tension in Asians.

Accounting for Ethnicity-Related Differences in Ocular Surface Integrity as a Step Toward Understanding Contact Lens Discomfort

“…Therefore, variations in the permeability of this tissue can have significant impacts on the safety of contact lens wear 20 and the efficacy of topical medication delivery. 23 Previous studies have shown that Asians who have no history of contact lens wear and no apparent corneal staining with fluorescein dye have higher corneal epithelial permeability when compared with non-Asian subjects. 20,23 According to one study, the inherent ethnicity-related difference, on average, is 27.7%.…”

“…23 Previous studies have shown that Asians who have no history of contact lens wear and no apparent corneal staining with fluorescein dye have higher corneal epithelial permeability when compared with non-Asian subjects. 20,23 According to one study, the inherent ethnicity-related difference, on average, is 27.7%. 23 Anatomic and physiological differences in eyelid structure have been the most accepted explanations of this inherent difference.…”

“…These include obliqueness of eye shape, 22,23 smaller palpebral fissure and aperture, 24,25 a thicker brow fat pad, 26 and the presence of epicanthal folds 27 typical for Asians compared with non-Asians. The combination of a smaller palpebral fissure and thicker brow fat pad not only affects surgical techniques implemented on an Asian eyelid, 25 but also impacts contact lens performance.…”

“…The former method has its limitations, specifically poor repeatability and reproducibility. 23 Using the latter method with optical coherence tomography imaging, Tan et al 39 were able to show an accurate description of the CSJ with repeatable measurements. With their technique, the CSJ was reported to be significantly steeper or rougher, especially at the nasal quadrant.…”

“…20,23 According to one study, the inherent ethnicity-related difference, on average, is 27.7%. 23 Anatomic and physiological differences in eyelid structure have been the most accepted explanations of this inherent difference. Asian eyelids have a higher volume of orbital fat, smaller PAS, thinner postlens tear film, and tighter positioning of the lids, which may lead to increased shearing force across the ocular surface during blinking, resulting in increased permeability of the corneal epithelium.…”