Abstract
Objective: To evaluate the long-term safety and efficacy of corneal cross-linking in keratoconus patients with thin corneas.

Methods: Forty eyes of 25 subjects having progressive keratoconus with thinnest corneal thickness (TCT) less than 400 µm were evaluated. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal topography, and endothelial cell loss were assessed at baseline and followed at six-month interval till the end of 1st year of follow up and then yearly till the fifth year, de-epithelization of cornea was performed, followed by ultrasound pachymetry to measure TCT. Hypoosmolar riboflavin (0.1%) solution was applied after every 2 minutes for 25 minutes. Ultraviolet A (UVA) irradiation was performed for 30 minutes along with riboflavin for every 2 minutes.

Results: Mean TCT was 381.5 ± 13.2 µm (range: 344–396 µm) without corneal epithelium. Following hypotonic riboflavin instillation, mean TCT increased by 97.8 ± 12.1 µm (range: 83–112 µm) for a mean thickness of 478.1 ± 14.9 µm (range: 409–506 µm). The average follow-up period was 61.79 ± 6.19 months (range: 42–68 months). Corrected distance visual acuity, pachymetry values and posterior elevation showed no significant difference before and after CXL at 5 years follow-up. Corneal astigmatism and maximum keratometry reading (Kmax) were significantly reduced. Mean reduction of endothelial cell count was 1.5% at the last follow-up visit.

Conclusions: CXL with UVA and hypoosmolar riboflavin was effective in stabilizing keratoconus progression in patients with thin corneas however further studies are required to confirm our results.

Key words: corneal cross-linking, keratoconus, riboflavin, thin cornea