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Calculating optimal intraocular lens (IOL) power is challenging in eyes that have previously undergone keratorefractive surgery. This study retrospectively assessed the use of OptiwaveTM Refractive Analysis (ORA) based upon the type of post-refractive surgery (post-hyperopic or post-myopic PRK/LASIK).
This was a retrospective analysis of data collected by the ORA system from multiple centers in the US, limited to post-refractive surgery eyes implanted with monofocal lenses manufactured by Alcon. Primary endpoints included mean and median difference between absolute ORA prediction error and preoperative formula. These differences were also calculated for cases where implanted IOL power differed from that of the planned preoperative lens, and the difference in the percentage of cases where the ORA or the preoperative prediction error was ≤ 0.5 D. The results were stratified based upon type of post-refractive surgery (post-hyperopic or post-myopic PRK/LASIK).
Stratification of results by post-refractive type shows that the difference between ORA and preoperative planned power was greater in post-myopic eyes than in post-hyperopic eyes (-0.15 D vs -0.02 D, respectively). In cases where the implanted lens power was different from the planned power, the post-myopic group had a larger mean difference in error than the post-hyperopic group (-0.18 D vs -0.03 D, respectively). The post-myopic group had a greater percentage of cases where the ORA or preoperative prediction errors were ≤ 0.5 D than the post-hyperopic group (difference: 14.0% vs 3.0%, respectively).
Post-myopic eyes had larger differences in prediction error in favor of ORA than post-hyperopic eyes. Both the ORA and the preoperative calculations were similar for eyes post-hyperopic PRK/LASIK. Hence, the data suggest that the ORA calculation performs better for eyes post-myopic PRK/LASIK than it performs for eyes post-hyperopic PRK/LASIK.