Comparison of Outcomes Between Standard and Accelerated Corneal Cross-linking Protocols in Patients with Progressive Keratoconus

Abstract

Purpose : To compare changes in corneal shape after corneal cross-linking (CXL) using the standard protocol vs. two accelerated protocols with differing total irradiance in patients with progressive keratoconus.

Methods : Retrospective data analysis of three groups of patients at two institutions receiving either standard CXL (3mW/cm², 30 minutes, 5.4 mJ/cm² irradiance) protocol (3mW) or one of two accelerated protocols: 9mW/cm², 10 minutes, 5.4 mJ/cm² irradiance (9mW) or 30mW/cm², 4 minutes, 7.2 mJ/cm² irradiance (30mW). Data was gathered using a Scheimpflug based device (Pentacam HR, Oculus, Inc.) prior to and 12 months following treatment. Group comparisons included changes in refractive astigmatism, pachymetric, topometric, keratometric, and densitometric indices. Only patients with pre-operative KMax Zonal Mean 3mm. within 45D-65D were included in the analysis in order to better equalize baseline values.

Results : The 3mW/30min group had significant decreases at 12 months in pachymetry (min.), CKI, IHD, IVA, KI, ISV, KMax Sagittal (front), KMax Zonal Mean (3, 4, and 5mm.), and IS-Value. The 9mW/10min group had significant decreases at 12 months in KMax Sagittal (front) only, while the 30mW/3min group had significant decreases at 12 months in pachymetry (apex, pupil, and min.), CKI, KMax Sagittal (front), and KMax Zonal Mean (3, 4, and 5mm.). There was no significant difference in observed changes at 12 months between the 9mW and 30mW groups for any variable. The 3mW group had a significantly greater decrease at 12 months for IVA[3mW -0.14±0.26 vs. 30mW 0.0±0.08 (p=0.01)], KI [3mW -0.39±0.07 vs. 9mW 0.0±0.04 (p=0.02)], ISV [3mW -11.39±16 vs. 9mW -2.17±10 (p=0.04) vs. 30mW -1.36±5.8 (p=0.01)], and IS-Value [3mW -1.2±2.0 vs. 9mW -0.10±1.0 (p=0.03) vs. 30mW -0.07±0.6 (p=0.01)].

Conclusions : All three protocols were effective at halting disease progression and improving overall outcomes. The 30mW group had significant improvements in more variables than the 9mW group, but there was no difference between the two when quantifying the changes at 12 months. Patients receiving CXL in the 3mW group had more statistically significant improvements in outcome indices, although the group had significantly higher baseline values for KI, IHA, IHD, and IS-Value.

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