Standard and hypoosmolar corneal cross-linking in various pachymetry groups

PURPOSE: To investigate the influence of corneal thickness on the outcome of corneal cross-linking (CXL) for progressive keratoconus.

METHODS: In this cohort study, 72 unilateral eyes were treated by CXL and divided into three groups according to central corneal thickness (CCT) measured by ultrasound pachymetry after 30-minute riboflavin. Group 1 (CCT <400 μm) underwent hypoosmolar CXL; group 2 (CCT 400 to 460 μm) and group 3 (CCT >460 μm) underwent standard CXL. Visual acuity, refraction, topography, ultrasound and optical pachymetry, intraocular pressure, endothelial cell count, and complications were evaluated 1 year post-CXL.

RESULTS: Ultrasound CCT after riboflavin instillation decreased significantly in groups 1 and 2 (-57 ± 44 μm and -39 ± 23 μm, respectively) and increased in group 3 (+15 ± 37 μm). One year post-CXL, maximal keratometry decreased significantly in group 2. Keratoconus progression was halted in 92% (group 1), 97% (group 2), and 86% (group 3). Optical pachymetry decreased significantly in all groups. Corrected distance visual acuity improved significantly in groups 1 and 3. No significant difference was found in visual acuity, keratometry, optical pachymetry, or endothelial cell density change between groups. Complication rates were comparable between the groups; there was no significant difference in CXL failure (p = 0.687) or corrected distance visual acuity loss (p = 0.617).

CONCLUSIONS: During CXL, corneas with CCT less than or equal to 460 μm seem to dehydrate faster than corneas with CCT greater than 460 μm. Both standard and hypoosmolar CXL are safe and effective treatments, with comparable amounts of stabilization after 1 year.