Abstract
PurposeTo evaluate predictors for success in corneal crosslinking (CXL) for keratoconus in a large cohort and extended follow-up.DesignA retrospective study based on a prospectively built database.MethodsParticipants underwent CXL for keratoconus from 2007 to 2018. Statistical analysis was performed for patients with at least 1-year follow-up. We analyzed effects of CXL type (Epithelium-on or Epithelium-off and Accelerated (9mW/cm2@10min) or Standard (3mW/cm2@30min)) and pre-operative factors including age, gender, baseline LogMAR visual acuity (LogMARpre), maximal corneal power (Kmaxpre), pachymetry, refractive and topographic cylinders, spherical equivalent (SEpre), mean corneal power (MeanK) and follow-up time on outcome measures. The outcome measures were the final change of Kmax (Delta Kmax) and the final change in LogMAR visual acuity (Delta LogMAR). A more negative Delta Kmax or Delta LogMAR represents a favorable effect of crosslinking.Results517 eyes had Kmax results, and 385 eyes had LogMAR results with more than one year follow-up. These eyes were included in the study. The mean follow-up time was 2.29 years. Mean Kmax decreased from 54.07±5.99 diopters to 52.84±5.66 diopters (p<0.001), and Mean LogMAR decreased from 0.28±0.20 to 0.25±0.21 (p<0.001). Non-accelerated epithelium-off CXL resulted in greater flattening of Kmax when compared with other protocols. Visual acuity improvement was similar when comparing different CXL protocols. Multivariate analysis showed four factors associated with negative Delta Kmax: high Kmaxpre, high SEpre, high MeanKpre, and non-accelerated procedure. Multivariate analysis showed three factors associated with negative Delta LogMAR: high LogMARpre, high SEpre, and Low MeanKpre. After excluding corneas with Kmaxpre >65 D or Pachymetry<400 microns, multivariate analysis showed that high Kmaxpre, high SEpre, and non-accelerated CXL were associated with negative Delta Kmax while high LogMARpre and high SEpre were associated with negative Delta LogMAR.ConclusionCXL for keratoconus is a highly effective treatment, as evident by its effects on the outcome measures: Delta Kmax and Delta LogMAR. CXL was more successful in eyes with high Kmaxpre, high SEpre, and high LogMARpre, which express disease severity. The non-accelerated epithelium-off protocol was associated with greater flattening of corneal curvature but did not show a better effect on visual acuity as compared to the other CXL protocols.
Highlights
Keratoconus (KC) is a bilateral, progressive corneal ectasia characterized by progressive central or paracentral thinning, protrusion, and irregular astigmatism with a potential for severe visual loss
Multivariate analysis showed four factors associated with negative Delta Kmax: high maximal corneal curvature before crosslinking (Kmaxpre), high SEpre, high MeanKpre, and non-accelerated procedure
Multivariate analysis showed three factors associated with negative Delta LogMAR: high LogMARpre, high SEpre, and Low MeanKpre
Summary
Keratoconus (KC) is a bilateral, progressive corneal ectasia characterized by progressive central or paracentral thinning, protrusion, and irregular astigmatism with a potential for severe visual loss. Corneal collagen crosslinking (CXL) is a procedure used to strengthen the corneal tissue by creating new covalent bonds within and between amino acid residues in the collagen fibers of the cornea. This increases the biomechanical strength of the keratoconic cornea and halts the progression of ectasia. A meta-analysis of 49 trials, including four randomized controlled trials, reported a mean decrease of 1 diopter in Kmax two years following CXL and improvement in best-corrected distance visual acuity one year following CXL [7]. In another meta-analysis of 75 trials, CXL was demonstrated to be effective with a mean decrease of 0.19 in LogMAR of uncorrected distance visual acuity two years following treatment [4]
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