Shorter Duration, Higher Ultraviolet A Irradiation (UVA) Fluence Collagen Cross-linking (CCL) for Keratoconus (KCN) Frank A. Killian, MD and A. John Kanellopoulos, MD New York University School of Medicine/Manhattan Eye, Ear Nose and Throat Hospital, New York, NY, USA and Laservision.gr, Athens, Greece *The authors of the study have no financial interests to disclose

Shorter Duration, Higher UVA Fluence CCL for KCN Purpose To evaluate the safety and efficacy of shorter duration, higher UVA fluence for collagen cross- linking in KCN We designed a prospective, randomized comparative case series to evaluate CCL at a higher UVA light intensity (from 3mW/cm2 to 7 mW/cm2) while using the same adjunct 0.1% topical riboflavin sodium phosphate solution

Shorter Duration, Higher UVA Fluence CCL for KCN Methods 15 patients with bilateral keratoconus were studied All cases were evaluated for changes in UCVA, BCVA, refraction, keratometry (K), topography, endothelium cell count and cornea clarity All eyes received CCL with topical 0.1% riboflavin solution and were randomized with regard to UVA duration 15 eyes received CCL with 7mW/cm2 for 15 minutes while the15 contra-lateral eyes received CCL with 3mW/cm2 for 30 minutes Mean follow up was 1.5 years

Shorter Duration, Higher UVA Fluence CCL for KCN Results The mean improvement of UCVA was 0.2 to 0.4 BCVA improved from 0.4 to 0.7 The mean change in spherical equivalent was 1.5 D reduction in myopia, the mean change in cylinder was 2.1 D reduction The mean highest keratometry was 51.2 D pre-op and 48.5 D post-op There was no statistical difference in the means for the two groups

Shorter Duration, Higher UVA Fluence CCL for KCN Table 1: Comparison of shorter duration, higher UVA Fluence CCL vs standard CCL

Shorter Duration, Higher UVA Fluence CCL for KCN Figures 1 and 2: Patient with slit lamp photograph of CCL changes in the cornea 3 months post-op (above) and pre-op and post-op Pentacam changes (right)

Shorter Duration, Higher UVA Fluence CCL for KCN Conclusions Shorter duration, higher UVA fluence CCL appears to be a safe and effective method for ectatic stabilization in KCN Shorter duration may cause less cell toxicity due to less corneal dehydration and shorter exposure of keratocytes and endothelial cells to UVA light and riboflavin Further studies are needed to validate this data