Corneal Cross-linking and Refractive Surface Ablation in Patients With Asymmetric Corneas

Corneal cross-linking (CXL) by the photosensitizer, riboflavin (vitamin B2), and ultraviolet A (UVA) light increases corneal rigidity and has been described as an effective method for stabilizing the cornea in patients with progressive keratoconus. The photochemical reaction in this procedure causes the collagen to form additional covalent connections between its fibers, which stabilizes the stromal collagen fibers, improving the collagen's structure and the cornea rigidity. It is a relatively safe procedure with low rates of complications Photorefractive keratectomy (PRK) it is a traditional technique for refractive surgery. In cases of irregular corneas or re-operation normally the favorite ablation profile chosen is the guided surgery, topography guided or wavefront guided, showing better results. This technique is also relatively safe procedure with low rates of complications. One of the most unwanted complications of this surgery and also rare is corneal ectasia.

Combining PRK and CXL is already done in patients with keratoconus and suspected keratoconus.

This combined procedure uses the principle that CXL stiffen the cornea making it possible to reduce corneal thickness with PRK without weakening corneal strength. Literature show better results, in keratoconus, with simultaneous procedures. Guedj et al performed PRK in keratoconus suspects and within 5 years he did not found any corneal ectasia.

Inclusion criteria

• bilateral asymmetric topography with inferior steepening
• corneal thickness of 440 micra at the thinnest point
• inferior-to-superior index (I-S) between 1.0D and 1.4D
• maximum keratometric steepness < 47.00D
• stable refraction more than 1 year.

Exclusion criteria

• forme fruste keratoconus and keratoconus
• previous eye surgery
• previous eye trauma
• confirmed pregnancy