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    CXL data dissected for further insights

    Minneapolis—Findings from comprehensive analyses of topographic outcomes after corneal collagen crosslinking (CXL) are consistent with previous information showing the procedure is effective for stabilizing keratometry in eyes with keratoconus or postLASIK ectasia. So far, however, the topographic outcomes do not appear to correlate with corrected or uncorrected distance visual acuity, according to Sumitra S. Khandelwal, MD.

    “Currently, there is good evidence showing CXL stabilizes topography and visual acuity in eyes with keratoconus, and while less data are available from large studies investigating CXL for ectasia after LASIK, it appears stabilization is also achieved in these postsurgical eyes,” said Dr. Khandelwal, Minnesota Eye Consultants, Minneapolis.

    “The findings are based on data from early follow-up to just 6 months, however, and from a relatively small number of eyes. In the future, we plan to conduct further analyses using data from a larger population, and because some argue that keratoconus and postLASIK ectasia are inherently different diseases, to see if there are differences between these two groups,” she added.

    The analyses included eyes enrolled through the Emory Eye Center, Atlanta, in two prospective clinical trials that randomly assigned eligible patients with keratoconus or postLASIK ectasia to CXL or sham treatment. One eye of each patient was selected as the study eye. R. Doyle Stulting, MD, PhD, and J. Bradley Randleman, MD, were also investigators in the study.

    “The data we are reporting are important because they are from a randomized, controlled single eye study, and we’ve reported previously that CXL improved visual acuity and steepest keratometry,” said Dr. Khandelwal, who completed her residency at Emory Eye Center. “The purpose of the present study was to analyze the topographic data in more depth.”

    Data were included from 27 treated and 25 control eyes in the postLASIK ectasia study and from 29 treated and 29 control eyes in the keratoconus study. All of the CXL procedures were performed with the standard Dresden technique, and topography was assessed with a Scheimpflug imaging device (Pentacam, Oculus) at baseline and after 1, 3, and 6 months.

    The endpoints analyzed included front and back keratometry parameters and seven keratoconus indices generated by the Scheimpflug unit (including index of surface variation, index of vertical asymmetry, keratoconus index, central keratoconus index, index of height asymmetry, index of height decentration, minimum radium of curvature radius of middle curvature, and central keratoconic index). Analyses for the control eyes and treated eyes were based on pooling of data from the two studies.

    Dr. Khandelwal reported that at 6 months, there were statistically significant differences between the control and treated eyes for front K flat, front K steep, front K average, front K max, and front K astigmatism.

    “Results from the serial measurements showed that the values tended to be similar in the control and treated eyes through 3 months,” noted Dr. Khandelwal. “Thereafter, however, the treated eyes were stable or even had a reduction in several keratometry measures, while the control eyes tended to worsen.”

    Dr. Khandelwal and her colleagues found no significant differences between the treated and control eyes at 6 months in mean back K flat or back K astigmatism values. Mean values for back K steep and back K average, however, were significantly lower in the treated eyes compared with the controls at 6 months. No statistically significant differences between groups in any of the keratoconus indices were seen.

    Dr. Khandelwal noted that after 6 months, all patients in the treatment group were offered CXL in the fellow eye and control patients were offered crossover to treatment.

    “We predict that we may see more differences in a larger population, and perhaps in a larger cohort with longer follow-up, we may find visual acuity correlates with keratometry. Unfortunately, we will not have many untreated eyes with follow-up beyond 6 months,” she concluded.

    Dr. Khandelwal has no financial interest in the material she presented.

    For more articles in this issue of Ophthalmology Times eReport, click here.

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