Intraocular Lens Power Calculations For Cataract Surgery In Post-Laser Refractive Surgery Eyes

To evaluate the refractive prediction accuracy of Haigis –L (standard K), Barrett True K (Standard K) and Barrett True K (Total Keratometry) formulas in post- refractive eyes undergoing cataract surgery

Department of Ophthalmology, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom

Medical records of patients with previous laser refractive surgery who underwent cataract surgery between July 2021 and January 2022 were retrospectively identified and analysed. Exclusion criteria included intra & post-op complications, co-pathology that affected visual outcome, and eyes without post-op refraction. Data collected included predicted post-op refraction (PPOR), actual post-op refraction, standard keratometry and total keratometry. Barrett True K PPOR were calculated using the Barrett True K online calculator on the ASCRS website. Refractive prediction error was calculated as the difference between the PPOR and the actual post-op refraction.

31 eyes were included for analysis. Using Barrett True K (Standard K) formula, 77.4% of eyes were within 0.5D; 77.4% eyes within 0.75D; 90.3% within 1D of refractive prediction error respectively. On the other hand, Haigis -L formula only had 50% eyes within 0.5D; 69.2% eyes within 0.75D and 84.6% eyes within 1D of refractive prediction error respectively. As this was a retrospective analysis, only 8 eyes were identified to have had biometry performed using the IOL Master 700. Using the Barrett True K (Total Keratometry) formula, all 8 eyes were within 0.5D of refractive prediction error.

Barrett True K (Standard K) formula is better than Haigis-L formula in predicting the post-op refraction in cataract surgery patients with previous laser refractive surgery. We will need to evaluate more eyes using the Barrett True K (Total Keratometry) formula by performing IOL Master 700 biometry in more patients to be able to conclude on the accuracy of Barrett True K (Total Keratometry) formula in our department.