Outcomes of corneal collagen cross linking prior to photorefractive keratectomy in prekeratoconus

The combination of corneal collagen cross linking (CXL) and refractive surgery, such as photorefractive keratectomy (PRK) has been studied extensively that it is important for visual function improvement. This combination might improve corneal stabilization and reshape the corneal tissue. The debating issue is regarding the appropriate timing between CXL and PRK combination surgery, whether it should be performed before or after surgery, as well as on the safety and efficacy of this combined surgery. The mechanism of CXL is believed when riboflavin as a photosensitizer is saturated on the cornea while exposed to ultraviolet irradiation, thus it is excited into an activate state that generating some reactive oxygen species. This processes lead to the formation of covalent bond between collagen molecules that increase the cornea biomechanics. Previous studies CXL followed by PRK removed the cross-linked stiffer anterior cornea. We assumed that our finding is important for the basis of further study.