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The purpose of this study is to provide information as to which keratometry measurements and which intraocular (IOL) power calculation formulas are best predictive for optimal outcomes in patients with previous corneal refractive surgery undergoing cataract surgery.
Retrospective chart review of all consecutive post refractive surgery patients undergoing cataract removal and implantation of a monofocal or monofocal toric IOL from January 2018 to July 2019. Eyes with postoperative refraction at least 3 weeks after surgery were included. IOL power was calculated with the ASCRS Online Post-Refractive IOL Calculator using anterior keratometry and recalculated using total corneal power (TK) measured with IOL Master 700. Intraoperative aberrometry data was also collected. Emmetropic IOL power will be back-calculated and the accuracy of treatment will be determined and compared between the different formulas, keratometry methods and intraoperative aberrometry.
Data from 109 post myopic LASIK eyes, 46 of which had total corneal power available, were analyzed. Using TK, the Wang-Koch formula had the highest percentages of eyes with expected spherical equivalent refractive errors within 0.50D and 1.00D of plano (57% and 87% respectively). With anterior Ks the Barrett TrueK formula had the highest percentages within 0.50D and 1.00D of plano (64% and 92% respectively), but was not significantly better than Wang-Koch with TK within 0.50D and 1.00D (McNemar test, p > 0.2). Expected mean spherical equivalent results based on IA were not significantly different than for Barrett TrueK for within 0.50D or within 1.00D (McNemar test, p > 0.2).
Using measured total corneal power in existing post-LASIK formulas did not appear beneficial. The formulas themselves may have to be adjusted to account for TK. The best expected results were obtained with the Barrett TrueK formula and anterior keratometry. IA did not appear to materially improve sphere power determination.