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Keith H. Edwards, Warren E. Hill, Harvey S. Uy, Simone Schneider; Improvement In The Achievement Of Targeted Post-Operative MRSE With Laser Anterior Capsulotomy Matches The Theoretical Model. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6715.
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To determine the impact of laser anterior capsulotomy on the achievement of targeted post-operative spherical equivalent and comparison to a theoretical model.
Patients presenting for cataract surgery were recruited on to this study after signing the IRB approved informed consent document. Laser treated eyes underwent laser anterior capsulotomy with or without laser phacofragmentation. Control eyes underwent manual capsulorrhexis and conventional phacoemulsification and all surgeries were conducted by a single surgeon using the same surgical technique and IOL. Post-operative manifest refractive spherical equivalent was assessed at six-months after surgery and compared to that targeted at time of surgery. Deviation from the intended result was compared between laser and manually treated eyes and compared to a theoretical model that assesses the contribution of various factors that influence the refractive outcome.
At six months data for 249 laser treated eyes and 123 manually treated eyes were available for analysis. Mean (SD) deviation from target MRSE was -0.21 (0.39)D for the laser eyes and +0.55 (0.41)D for manually treated eyes (p<0.001). Mean (SD) absolute deviation from intended MRSE was 0.42 (0.39)D and 0.59 (0.35)D respectively (p<0.001). Laser treated eyes were within 0.12D of target in 11.6% of cases compared with 4.1% of manually treated eyes and 78.7% were within 0.50D for laser eyes and 52.8% for manually treated eyes (p=0.003). An estimation of the absolute error in IOL calculation can be made from the various components of that calculation. This predicts that eliminating the configuration of the rhexis from the absolute error of the refractive outcome would reduce that error by 0.18D.
Laser anterior capsulorrhexis produces an incremental but significant reduction in the deviation from the intended post-operative refractive outcome. The reduction in absolute deviation from target MRSE in this large series of patients was 0.17D which closely correlates with the theoretical improvement of 0.18D. Significantly more cases were within 0.50D of the target in the laser group. Remaining factors influencing the refractive outcome include biometry, keratometry, the IOL formula used, retinal thickness around the fovea and the manufacturing tolerance of the IOL.
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