Diurnal variation of corneal epithelium and stroma measured by optical coherence tomography

The purpose of the study is to evaluate whether there is a significant diurnal variation in the thickness of corneal epithelium and stroma, in healthy volunteers, using corneal optical coherence tomography (OCT). During sleep, closing the eyelids impairs the diffusion of oxygen through the corneal epithelium, resulting in the production of lactic acid, which can interfere with corneal thickness in the 1st min of wakefulness. OCT is an objective and noninvasive accurate method for evaluating corneal epithelium and storm thickness. A prospective and analytical study investigated the thickness and regularity of the cornea and its epithelium in the eyes (n = 30) of individuals without comorbidities. The volunteers underwent corneal OCT examination in two different periods: between 30 and 60 min after waking up and in the late afternoon of the same day. The study was carried out at Médicos de Olhos S.A, Curitiba, Brazil, between August and October 2023. For statistical analysis, the T-Student test was used, considering P < 0.0001 as statistically significant. Epithelium variability index, in OD (P = 0.965) and in OS (P = 0.516), did not present a statistically significant difference. The difference in thickness between epithelium minimum and maximum, OD (P = 0.880) and OS (P = 1.0), also did not show a statistically significant difference. It was possible to verify that the epithelial and stromal thickness of the cornea did not show significant diurnal variations. Furthermore, the regularity of epithelial thickness remained constant, as indicated by the epithelial variability index value.