Diurnal Variation in Corneal Stromal and Epithelial Thickness in Fuchs Endothelial Corneal Dystrophy: With and Without Intensified Hypertonic Saline Eyedrop Application

Abstract

Purpose: The purpose of this study was to investigate diurnal fluctuations in corneal stromal and epithelial thickness in patients with Fuchs endothelial corneal dystrophy (FECD), with and without intensified hypertonic 5% saline eye drops, using anterior segment optical coherence tomography.

Methods: In this prospective observational study, patients with FECD were examined using anterior segment optical coherence tomography imaging (Anterion, Heidelberg Engineering) to measure corneal epithelial and stromal thickness at admission and on the following morning at 0-, 45-, 60-, and 90-minute postawakening. Eyes were divided into 3 groups: FECD without treatment, treated with hypertonic saline, and post-Descemet membrane endothelial keratoplasty. FECD treated with hypertonic saline eyes received 5 drops of 5% NaCl eye drops at 5-minute intervals after awakening. Corrected distance visual acuity and subjective visual clarity were assessed at admission and at 0, 60, and 90 minutes.A linear mixed-effects model was used to account for the inclusion of both eyes from the same patient, thereby addressing the nonindependence of data.

Results: A total of 48 eyes from 25 patients with FECD were analyzed. Overnight corneal swelling was predominantly due to stromal thickening (median increase of 21.0 μm, interquartile ranges 13.0), with a minimal change in the epithelial layer (median increase of 2.0 μm, interquartile ranges 4.75) in the whole cohort. Application of hypertonic saline eyedrops accelerated the physiological deswelling process, leading to almost double the reduction in corneal thickness within 60 minutes after waking compared with untreated eyes (median decrease of 13.0 μm vs. 7.0 μm; estimate -6.24 μm; 95% confidence interval, -9.58 to -2.90; P < 0.001), an effect primarily attributed to stromal thinning. No significant effects of pachymetric fluctuations on corrected distance visual acuity or subjective visual clarity were observed at any time point between the groups.

Conclusions: Diurnal fluctuations in corneal thickness in FECD are predominantly stromal. The intensified application protocol of hypertonic saline drops reduces morning corneal edema but does not result in improved vision.

Keywords: FECD; Fuchs endothelial corneal dystrophy; anterior segment optical coherence tomography; corneal edema; hyperosmolar saline eye drops; hypertonic saline eye drops.