Long term results of a prospective randomized bilateral eye comparison trial of higher fluence, shorter duration ultraviolet A radiation, and riboflavin collagen cross linking for progressive keratoconus

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Abstract
Purpose: To evaluate the safety and efficacy of higher fluence cornea collagen cross linking (CXL). Methods: Twenty-one patients with bilateral keratoconus had randomized CXL in one eye (group A) with 7 mw/cm2 for 15 minutes; the other eye (group B) had the standard 3 mw/cm2 for 30 minutes; 50 um PTK with the Eye-Q 400 Hz Excimer laser (Wavelight, Erlagen, Germany) was used for epithelial removal. The patients were evaluated postoperatively at the following intervals: day 1, day 4, month 1, month 3, and then every 6 months. Results: For groups A and B respectively, in mean values: uncorrected distance visual acuity (UDVA) improved from 20/60 to 20/38, and 20/62 to 20/40; best corrected visual acuity (BCVA) from 20/30 to 20/25 in both groups; mean sphere was reduced by 2.5 and 2.1 diopters; mean cylinder was reduced by 2.9 and 2.5 diopters on average; Steepest K was reduced from 49.5 to 46.1, and from 48.7 to 45.8 diopters. There was no ectasia progression in any of the cases during the follow-up time studied. There was no change in the endothelial cell count. All patients returned to full activities postoperatively within a month. Four cases from group A and five cases from group B had delayed epithelial healing (completed by postoperative day 9). No other adverse effects were noted in any of the cases studied. Mean follow-up was 46 months (18–56). Corneal optical coherence tomography (OCT) revealed diffused light scattered in anterior two-thirds of the cornea stroma, which was more intense and much broader in diameter in group A than in group B. Conclusion: This novel technique offers similar clinical results in ectasia stabilization without any adverse effects noted.