Outcomes of Epi-On Collagen Cross-Linkage Procedure Assessed in Progressive Keratoconus Patients

Introduction: Keratoconus is a corneal ectasia that causes astigmatism and reduced vision. Conventional treatment to stop the progression of ectasia involves debridement of corneal epithelium, followed by ultraviolet light and riboflavin drops to reinforce the collagen covalent bonds, called collagen cross-linkage (CXL). Epi-on (epithelium-on) is a modified technique without epithelial debridement and associated complications of pain, infection, and damage to the cornea. However, despite a good safety index and efficacy, Epi-on has not completely replaced the conventional Epi-off (epithelium-off) CXL. We aim to report our five-year experience and outcomes with Epi-on CXL Methods: In this five-year retrospective clinical audit, we included all patients who underwent Epi-on CXL from December 2014 to June 2020 at the Aga Khan University Hospital. Outcomes were based on best-corrected visual acuity (BCVA) and topographic indicators such as keratometry-max (K-max), keratometry mean (K-mean), pachymetry apex (Pach(apex)), and pachymetry thinnest (Pach(thin)) performed during pre-CXL clinical visit within one month of the procedure and were compared with the most remote follow up within three years post-CXL. A p-value of <0.05 was considered statistically significant. Results: A total of 223 eyes of 134 patients had undergone CXL of which 32 eyes of 18 patients were included in the study based on the inclusion criteria. The mean age was 26.8 (+/- 6.137) years; nine were males and 16 were right eyes. Mean BCVA was 0.383 logMAR (logarithm of the minimum angle of resolution) units which improved to 0.292 units post CXL (p=0.02) and K-max decreased from 57.4 to 56.60 diopters (p=0.048), both outcomes were statistically significant. Pach(apex) decreased slightly from 471 to 460 micrometers (p=0.099), K-mean was almost stable from 48.8 to 48.7 diopters (p=0.9), and Pach(thin) also decreased slightly from 455 to 445 micrometers (p=0.117), however, these outcomes were not statistically significant. Other studies reported similar improvements in K-max and visual acuity. Conclusion: Epi-on CXL is an effective treatment for halting the progression of keratoconus. Our results showed significant improvement in visual acuity and K-max readings indicating a halting of the progression of keratoconus in our patients. Long-term follow-up is required for all patients to assess detailed outcomes. Further studies comparing Epi-on CXL with other methods may be carried out.