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A comparison of results between 15 and 30 minute riboflavin saturation times during collagen cross-linking for keratoconus

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Session Details

Session Title: Cross-linking I

Session Date/Time: Monday 15/09/2014 | 14:30-16:30

Paper Time: 15:18

Venue: Capital Hall A

First Author: : C.Samarawickrama AUSTRALIA

Co Author(s): :    E. Chan   A. Poon   M. Loughnan   G. Snibson     

Abstract Details


To compare changes in corneal curvature 2 years following corneal collagen cross-linking (CXL) using 15 or 30 minute riboflavin saturation times for progressive keratoconus.


This is a retrospective chart review of patients treated with CXL from 3 private practices in Melbourne, Australia.


Thirty cases per group were included in the analysis. The CXL treatment protocol was identical in both groups with a variation only in duration of riboflavin saturation prior to ultraviolet A (UVA) irradiation. CXL was performed following removal of corneal epithelium to a diameter of 9mm. Isotonic solution of riboflavin 0.1% was instilled on the cornea at regular intervals. Corneal thickness was measured using ultrasound regularly prior to and during UVA exposure (3mW/cm2 for 30 minutes) to ensure the thickness remained above 400µm. At completion of the treatment, a bandage contact lens was applied and treatment was initiated with chloramphenicol and fluorometholone drops QID. Computerised videokeratography was performed prior to CXL and every year thereafter. Pentacam (Oculus, Wetzlar, Germany) and Orbscan II (Bausch & Lomb, Utah, USA) images were used for monitoring the 15 minute group while only the Pentacam was used in the 30 minute group. Measurements obtained included steepest simulated keratometry value (Ksteep) and maximum corneal power (Kmax). Results are reported as mean ± standard deviation. Student’s t-test was used to determine the significance of the difference between groups. A chi-square test was used to determine the significance in the numbers of eyes progressing ≥1.0D in each group.


There was no statistically significant difference in either age or mean duration of follow-up between the two groups (p=0.5 for both). At baseline, mean Kmax and Ksteep were no different (p>0.05). After 12 months, the change in Ksteep from baseline was +0.18±1.78D (p=0.9) and -0.31± 0.70D (p=0.8) in the 15 minute and 30 minute groups respectively. The change in Kmax was +0.07±1.94D (p=0.6) and +1.97±9.22 (p=0.3) respectively. After 2 years, Ksteep in the 15 minute group increased by a mean of +0.54±1.78D and eyes in the 30 minute group flattened by -0.21±0.74D, the difference of which approached significance (p=0.06). After 1 year follow-up, 4 eyes in the 15 minute group had progressed by more than +1.0D (Ksteep), increasing to 6 eyes by 2 years. In the 30 minute group no eyes progressed by more than +1.0D after 1 year and 1 one eye progressed by more than +1.0D after 2 years (p=0.06). Possible confounding factors will be discussed.


No difference was detected in the effect of CXL using either 15 minute or 30 minute riboflavin saturation on corneal curvature measured using videokeratography after 1 year. At 2 years, a trend towards a greater effect in the 30 minute group was identified.

Financial Interest:


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