Combined application of prophylactic corneal cross‐linking and laser in‐situ keratomileusis – a review of literature

Abstract

Laser in-situ keratomileusis (LASIK) is safe and effective laser refractive procedures in treating refractive errors. However, regression of treatment and iatrogenic keratectasia remain to be a major concern, especially in treating thin cornea with high ametropia. Collagen cross-linking (CXL) is an effective method in stopping keratoconus progression through increasing the biomechanical strength of the cornea. Adjuvant cross-linking to refractive procedures can theoretically help prevent regression and reduce the risk of keratectasia development by increasing the mechanical stability of cornea. During the procedure, riboflavin is directly applied to the corneal stroma, thereby reducing the need of de-epithelialization as in the conventional protocol for keratoconus. Currently, there is still no consensus regarding the indication of CXL during refractive procedure, nor any standardized treatment protocol. This article aims to summarize the current evidence regarding the use of adjuvant CXL in LASIK.

Comparative evaluation of progression rate in keratoconus before and after collagen crosslinking

“…It enables high-speed and high-resolution imaging of the Ant segment and identifies the Ant and post surfaces with high reliability and good repeatability 14. Chan et al showed that excellent reproducibility coefficient of SS-OCT for all corneal measurements in keratoconus eyes 15. In the same study, SS-OCT illustrated an intraclass coefficient of ≥0.952 for Ant and post BFS, Ks, Kf, Avg K and Cyl.…”

Refractive regression after laser in situ keratomileusis

“…With age, a natural form of cross‐linking occurs and stiffens the cornea. Given evidence that CXL strengthens the cornea and subsequently reduces the risk of regression, it would be expected that advancing age is linked with reduced regression. However, it has been reported that increasing age is associated with an elevated risk of retreatment for residual refractive error following LASIK .…”

“…CXL effectively ‘stiffens’ the cornea by activating a polymerization reaction of the corneal stromal collagen by generating reactive oxygen species with the use of ultraviolet light. Therefore, following the theory that regression occurs secondary to corneal thinning and forward protrusion, strengthening the cornea with CXL may be effective in the prevention of post‐LASIK regression and ectasia . Kanellopoulos et al .…”

“…CXL appears to be a safe and effective method of stabilizing the cornea after LASIK, and subsequently reducing the risk of refractive regression. However, the evidence is based on non‐randomized studies with variable study designs and follow‐up periods . CXL is certainly not without its limitations.…”

“…Therefore, following the theory that regression occurs secondary to corneal thinning and forward protrusion, strengthening the cornea with CXL may be effective in the prevention of post-LASIK regression and ectasia. [43][44][45][46] Kanellopoulos et al compared 65 eyes treated with CXL and LASIK and 75 eyes treated with LASIK only. 96 After 2 years, the authors found that prophylactic CXL improved refractive stability.…”