Combined surface ablation+CXL for keratoconus

Keratoconus treatment should be aimed to improve the optical inefficiency of the irregular cornea and halt the disease progression that may lead to the need for corneal transplantation. Corneal collagen cross‐linking (CXL) using Riboflavin and ultraviolet A has been used to stabilize the cornea with progressive keratoconus or ectatic corneal disorders after corneal refractive procedures. Studies demonstrated that the simultaneous wavefront optimized (WG PRK) or topography guided (TG PRK) approach of photore‐fractive keratectomy (PRK) plus CXL offers improvements in uncorrected distance acuity (UDA), best distance acuity(BDA), and topographic irregularity, even if the surgical goal is not a refractive end point. Combining photorefractive keratectomy (PRK) with CXL or accelerated CXL offers keratoconus patients both stability and improvement in functional vision. However, different excimer laser platforms have different ablation patterns and different algorithms for topography‐guided ablation. Additionally, mechanical and laser debridement of the corneal epithelium (PRK versus transepithelial PRK) may result in different patterns of ablation and different clinical results. Though the conventional refractive components of sphere and cylinder may be simultaneously incorporated into the treatment profile, in the treatment of keratoconus, tissue sparing is the prime consideration, and therefore, PRK typically limits the maximum depth of tissue ablation to less than 50mm. Several CXL protocols result in more cross‐linking and a greater increase in Young's modulus, less corneal cross‐linking (a smaller increase in Young's modulus) may still have the same clinical effect (in terms of disease stabilization). In other words, the optimum CXL parameters to produce the clinically desired effect (in terms of stabilization or prophylaxis) are not known. A reduction in HOA after TG‐PRK in keratoconus eyes (with or without the addition of CXL) is not surprising and is a consistent finding in published studies. Diffuse corneal haze, which emerges in a few days after CXL in virtually all eyes, generally resolves over time. It is identified as a dust‐like change in the stroma. In addition, some patients suffer from scarring that persists and can decrease visual acuity. However, these two words— “haze” and “scar”—are sometimes used interchangeably in the literature.