[Corneal cross-linking with hypo-osmolar riboflavin solution for keratoconus with thin corneas]

The aim of this study was to evaluate the 1-year results of 32 keratoconic eyes with thin corneas which were treated by hypo-osmolar riboflavin solution and ultraviolet A (UVA) collagen cross-linking (CXL).

Patients with progressive keratoconus and a corneal thickness (CT) less than 400 µm (without epithelium) were included in this study. The CT was measured with an ultrasound device (Tomey SP-3000, Nishi-ku, Nagoya, Japan). An increase in the maximum topographic K-value at the apex of keratoconus and a reduction in corneal thickness with or without changes in visual acuity (VA) within the last year were considered to be progression. A total of 32 eyes with an additional follow-up within 1 year were evaluated before and after the procedure. Examinations consisted of an evaluation of VA, corneal topography, slit-lamp microscopy and corneal thickness measurements.

Preoperatively the mean corneal thickness (with epithelium) was 382.3±41.9 μm and after removal of the epithelium the thickness of the cornea was reduced to 337.0±51.9 μm. After the application of hypo-osmolar riboflavin solution the mean value increased to 451.8±46.7 μm. Preoperatively the mean K-value of the apex of the keratoconus was 65.6±11.2 dopters, and 1 year after treatment this value remained relatively unchanged at 64.9±11.0 diopters (P=0.839). Mean VA at the time of the treatment was 0.63±0.37 logMAR and 1 year after the treatment this value was not statistically different (0.59±0.42 logMAR; P=0.662). In the last follow-up examination 1 year after the procedure all corneas were transparent without any scarring lesions in the stroma.

The results of this study using hypo-osmolar riboflavin solution in a cross-linking procedure for thin corneas showed a stability of keratoconus 1 year after CXL. Application of the hypo-osmolar riboflavin solution prevented cross-linked corneas from developing stromal scars.