Corneal collagen cross-linking in progressive keratoconus, pellucid marginal degeneration, and LASIK –induced ectasia : an observational single – centre study

Abstract

Purpose : We evaluated the efficacy, safety and outcome parameters before and after corneal collagen cross-linking (CXL).

Methods : We performed the following pre-operatively and at 1, 3, 6 and 12 months post operatively: logMAR best corrected visual acuity (BCVA) and best corrected spectacle visual acuity (BCSVA), corneal topography and tomography, manifest refraction and intraocular pressure. Central corneal thickness (CCT) with ultrasound, fundus exam, macular volume and endothelial cell density (ECD) were performed pre-operatively and at one year. Haze was assessed post -operatively at all time points. Statistical analysis included a paired t- test to look for change from baseline to 1 year after surgery, as well as a linear model examining the change from baseline to 12 months and an analysis of covariance, controlling for covariates of age, sex, allergies and ethnicity.

Results : Five hundred and seventy-seven (577) eyes that underwent CXL alone were followed. Mean (±SD) baseline values included age; 27±8, BCVA; 0.20(±0.23), BCSVA; 0.23 ±0.24, Maximum keratometry (Kmax); 56.0D (±8.5), CCT; 487um (±50), Minimum Corneal Thickness (MCT); 465um (± 49), ECD; 2876 cells/mm² (±187), manifest spherical equivalent (MRSE); -3.57D (±4.15) and cylinder; +3.19D (±2.07), corneal cylinder; 3.76(±3.51) and coma; 2.86um (±1.68). There was an improvement (p<0.0001) in both BCVA and BCSVA of 0.06 (95%CI 0.05, 0.08) with less effect with age. There was no significant change in Kmax, with some evidence that those with allergies show a greater increase at 1 year compared to those without. Corneal cylinder decreased (p<0.05) by 0.35D (CI 0.02, 0.67), coma was reduced (p=0.01) by 0.08um (CI 0.02, 0.15), MCT was thinner (p<0.0001) by 4.5um (CI 2.5,6.4), ECD was reduced (p=0.04) by 13.3um (CI 0.9, 25.8) and MRSE was more positive (p<0.0001) by 0.66D (CI 0.40, 0.92). There was no significant change in CCT or macular volume. Significant haze was seen in 1 subject at 1 year. Those who were African American/Canadian had a higher haze grade on average than those who were not.

Conclusions : Kmax showed no change at one year indicating corneal stabilization. Visual acuity improved by about half a line. Allergies, age, and ethnicity appear to influence the amount of change in outcomes. CXL has a favorable safety profile.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.