Long-term Tomographic, Refractive, and Visual Analysis of Keratoconus Eyes With Extreme Corneal Flattening After Corneal Cross-linking.

Abstract

Purpose: To evaluate the long-term tomographic, refractive, and visual characteristics of eyes with extreme corneal flattening after corneal cross-linking (CXL) for progressive keratoconus.

Methods: A retrospective observational study included eyes that underwent corneal CXL with epithelial removal between June 2006 and March 2017 and had extreme keratometric flattening [greater than 5 diopters (D)] and a minimum follow-up of 5 years. Visual, tomographic, pachymetric, and refractive characteristics were evaluated.

Results: Mean follow-up time was 7.6 ± 2.6 years (range 5-13 years). Fifteen eyes were included in the study. Mean maximum keratometric (Kmax) flattening was -7.58 ± 2.63 D [range 5.0-12.2 D, (P <0.001)]. Approximately 56.25% (9/15) of the eyes experienced progressive flattening over the years. And 40% (6/15) presented an improvement of one or more lines of corrected distance visual acuity (CDVA), and 26.6% (5/16) of the eyes showed a worsening of CDVA. Logistic regression analysis revealed that postoperative Kmax flattening greater than 2 D at the first year postop (odds ratio 17.7, 95% confidence interval, 4.4-71.2) and preoperative Kmax greater than 55 D (odds ratio 8.8, 95% confidence interval, 2.7-28.3) were significant risk factors for extreme postop keratometric flattening.

Conclusions: Progressive extreme corneal flattening when accompanied with a decrease of CDVA was a late complication of CXL that may have required corneal transplantation for visual rehabilitation. Preoperative steeper corneas and keratometric flattening greater than 2 D at the first year postoperative period were risk factors associated with long-term extreme postoperative corneal flattening.