Refractive Accuracy of Barrett True-K vs Intraoperative Aberrometry for IOL Power Calculation in Post-Corneal Refractive Surgery Eyes

My name is Dr. Karolinne Maia Rocha. I am an ophthalmic surgeon at the Medical University of South Carolina’s Storm Eye Institute in Charleston, where I specialize in advanced cataract, cornea, and refractive procedures. My colleagues and I conducted an investigator-initiated trial to compare the refractive predictability of intraoperative aberrometry using the ORA® System and the Barrett True-K or Barrett Universal II formulas for intraocular lens power calculation. This was done in normal eyes and eyes with a history of corneal refractive surgery. To examine the relative performance of ORA® in this context, we compared our results to those obtained with pre-operative biometry. Our retrospective analysis covered 170 consecutive post-corneal refractive surgery eyes of 110 patients and 103 consecutive normal eyes of 81 patients who underwent cataract surgery or refractive lens exchange at a single surgical center. Pre-operative biometric data were collected using the IOLMaster^ 500 or IOLMaster^ 700, with IOL calculations performed using the Barrett Universal II formula for normal eyes and Barrett True-K for post-refractive surgery eyes. Intraoperative aberrometry with ORA® was carried out in the aphakic state, before IOL implantation. Key outcomes included mean absolute refractive prediction error and the percentages of eyes with a prediction error within plus or minus 0.50, 0.75, and 1.00 D. In total, we analyzed data from 64 post-hyperopic LASIK or PRK eyes, 81 post-myopic LASIK or PRK eyes, 25 post-RK eyes, and 103 normal eyes. Across these groups, mean patient age ranged from 63 to 68 years. Post-operatively, we observed no significant difference in mean absolute refractive prediction error between intraoperative aberrometry and the preoperative formulas for any refractive category. Similarly, we found no significant differences in the percentages of eyes with absolute prediction error within 0.50 D, 0.75 D, or 1.00 D in any category. When we analyzed prediction error within ±0.50 D, we found that intraoperative aberrometry and pre-operative biometry agreed in 28 to 49% of post-refractive surgery eyes, with the highest frequency of agreement in post-myopic LASIK or PRK eyes and the lowest frequency in post-RK eyes. Intraoperative aberrometry and the Barrett formulas agreed in 62% of normal eyes. In cases where intraoperative and pre-operative calculations did not agree, intraoperative aberrometry had better prediction accuracy in post-hyperopic LASIK or PRK eyes, while pre-operative calculations performed better in all other categories. Even with ongoing refinements in IOL power formulas and intraoperative diagnostics, ensuring that target refraction is met after cataract surgery can still pose challenges, including in post-refractive surgery eyes. As patients with a history of refractive surgery increasingly become candidates for cataract surgery, ensuring that visual outcomes can be maximized for these patients is extremely important. Intraoperative aberrometry using the ORA® System with VerifEye+ gives cataract surgeons the ability to use aphakic spherical equivalent, preoperative axial length, and corneal power measurements to calculate IOL power. In this study, we found that ORA® provided comparable IOL power calculation accuracy to the Barrett True-K and Universal II formulas based on pre-operative measurements in post-corneal refractive surgery and normal eyes. In parallel, we observed potential advantages in accuracy with intraoperative aberrometry in post-hyperopic LASIK or PRK eyes. Taken together, these results provide important insights for cataract surgeons and support the use of intraoperative aberrometry in post-refractive surgery eyes. © 2022 Alcon Inc. US-ORA-2200016