Factors associated with central corneal thickness changes after crosslinking combined with photorefractive keratectomy

Abstract

Purpose : The purpose of this study is to investigate changes in epithelial thickness (ET) and total corneal thickness (TCT) one year after crosslinking surgery combined with photorefractive keratectomy (CXL+PRK) and whether these changes are related to post-operative visual and refractive outcomes.

Methods : 10 eyes with keratoconus from 10 subjects were imaged with a Scheimpflug topographer and a research grade swept-source optical coherence tomographer (SS-OCT) no more than one month prior to receiving CXL+PRK surgery and again one year later. The pre-operative thicknesses of the cornea and epithelial layer at the point of minimum total corneal thickness were acquired from the SS-OCT images using custom processing software. Regression analysis was used to explore associations with corneal thickness changes and visual and refractive outcomes one year after surgery.

Results : The mean pre-operative corneal ET (54.5 ± 3.4µm) was not significantly different than the ET at the one year follow-up (54.3 ± 5.0µm; p=0.46). The average pre-operative TCT (478.0 ± 33.2µm) was significantly greater than the same measurement one year later (438.5 ± 15.4µm; p=0.00065). Individual data demonstrated both increases and decreases in ET and TCT measurements, with changes up to 17% for some participants. Changes in ET were significantly associated with changes in best corrected spectacle acuity (R²=0.42; p=0.043) and coma (R²=0.75; p=0.0012), but not changes in refractive error (p>0.05). Changes in TCT were not significantly associated with changes in VA, coma or refractive error (p>0.05 for all).

Conclusions : Mean central TCT measurements were significantly less at the one year follow up but ET did not show a significant change. Both increases and decreases in individual thickness data were observed. Only changes in ET were significantly correlated with changes in VA and coma such that thickness changes were inversely proportional to VA changes and directly proportional to changes in coma.

This is a 2021 ARVO Annual Meeting abstract.