Efficacy of Epi-on Versus Epi-off accelerated collagen cross-linking for the treatment of progressive keratoconus

Abstract

SUMMARY T ransepithelial CXL was designed to avoid the early postoperative pain and temporary worsening of vision associated with the standard (epi-off) CXL technique, by avoiding epithelial debridement. Our aim is to compare safety and efficacy of Transepithelial (epi-on) corneal collagen crosslinking as opposed to standard (epi-off) corneal collagen crosslinking, in the management of keratoconus, regarding changes in vision, corneal tomography and biomechanical properties of the cornea. Studies showed that Standard (epi-off) CXL is an effective method for management of keratoconus. Despite the initial decrease after 3 months, best spectacle-corrected visual acuity (BSCVA) showed improvement after 1 year. Which is also associated with significant flattening of the cornea (Kmax significant decrease after 1 year). Studies also showed decrease in central corneal thickness (CCT) after 1 year. Biomechanical properties of the cornea did not seem to improve after 1 year, with the decrease in corneal hysteresis (CH) and corneal resistance factor (CRF). There was temporary corneal haze noted postoperatively . Regarding transepithelial (epi-on) CXL, Although there was no postoperative haze or pain, evaluation did not show improvement in corneal condition. Despite the minimal flattening of the cornea after 1 year (Kmax insignificant decrease), the BSCVA showed a significant decrease after 1 year. CCT also showed a significant thinning after 1 year (even more than the thinning that occurred with Standard CXL). Also, biomechanical properties of the cornea did not seem to improve after 1 year, with the decrease in corneal hysteresis (CH) and corneal resistance factor (CRF). Transepithelial CXL does not effectively halt the progression of keratoconus in comparison with Standard CXL. However, this conclusion should be interpreted with caution due to the small number of studies and small number of patiants included in the studies. Further studies with larger number of patients are recommended.