Diurnal variation of corneal and corneal epithelial thickness measured using optical coherence tomography

To determine the feasibility of optical coherence tomography (OCT) measurem ent of overnight corneal swelling and deswelling and, specifically, to exam ine overnight changes in the corneal epithelium and recovery during the day . Methods. Ten healthy volunteers were recruited. Corneal OCT imaging was p erformed at 10:00 PM (baseline), 8:30 AM, and every 2 hours thereafter unti l 4:30 PM. Either the right or left eye was taped shut (using a gauze pad a nd surgical tape) until the 8:30 AM session of the next day. Measurements w ere made along a l-mm strip centered on the visual axis. Results. At baseli ne, there were no differences in corneal or epithelial thickness between co ntrol and experimental eyes (all p > 0.05). Immediately after patch removal , corneal and epithelial thicknesses of patched eyes were higher than the b aseline (all p < 0.05). In patched eyes, the cornea and epi thelium swelled 5.5% and 8.1% overnight, respectively (p > 0.05). Two hours later, the epi thelial thickness of the experimental eyes recovered to baseline level (p > 0.05), but corneal thickness did not reach to baseline level until 4 hours after patch removal. For control eyes, there were no differences compared with baseline (all p > 0.05). Conclusion. Both cornea and corneal epitheliu m experience proportionately similar amounts of overnight swelling. Recover y of overnight swelling may be slower for the cornea than for the epitheliu m. OCT provides valuable information about anterior segment morphometry.