Ray-tracing Calculation Using Scheimpflug Tomography of Diffractive Extended Depth of Focus IOLs Following Myopic LASIK.

PURPOSE: To evaluate a ray-tracing formula for intraocular lens (IOL) calculation of diffractive extended depth of focus IOLs after myopic laser in situ keratomileusis (LASIK) compared to formulas from an established online calculator. METHODS: This retrospective, consecutive case series included patients after cataract surgery with implantation of an extended depth of focus (EDOF) IOL (AT LARA, Carl Zeiss Meditec; Symfony, Johnson & Johnson) and a history of myopic LASIK. Preoperative assessments included biometry (IOLMaster; Carl Zeiss Meditec) and corneal tomography, including true net power (TNP) (Pentacam; Oculus Optikgeräte GmbH). To evaluate the measurements, the simulated keratometry values (SimK) were compared to the TNP. Regarding IOL calculation, the mean prediction error, mean and median absolute prediction error (MAE and MedAE), and number of eyes within ±0.50, ±1.00, and ±2.00 diopters (D) from the Haigis-L, Shammas, and Barrett True K No History formulas to the Potvin-Hill and Haigis with TNP (Pentacam) formulas were compared. RESULTS: Thirty-six eyes matched the inclusion criteria with a mean spherical equivalent of -6.26 ± 3.25 diopters (D) preoperatively and -0.79 ± 0.75 D postoperatively. The mean difference from SimK and TNP was significantly different from zero (P < .001; -1.24 ± 0.81 D). The best performing formulas by MedAE were the Potvin-Hill and Barrett True K No History (0.39 ± 0.78 and 0.64 ± 1.00 D). The formula with the most eyes within ±0.50 D was the Potvin-Hill (64%), followed by the Barrett True K No History (44%). For MAE and percentage of eyes within ±0.50 D, the Potvin-Hill formula was significantly better than the Haigis-L, Shammas, and Haigis-TNP formulas (P < .05). CONCLUSIONS: Calculation of IOLs in patients who had LASIK remains less predicable than calculations for virgin eyes. Using ray-tracing to calculate diffractive EDOF IOLs after myopic LASIK, the Potvin-Hill formula outperformed established formulas in terms of the percentage within target refraction and the MAE. [J Refract Surg. 2021;37(4):231-239.].

Prediction accuracy of IOL calculation formulas using the ASCRS online calculator for a diffractive extended depth-of-focus IOL after myopic laser in situ keratomileusis.

BACKGROUND: To evaluate IOL calculation formulas provided by an online calculation tool from the ASCRS for an extended depth-of-focus (EDOF) IOL after previous myopic laser in situ keratomileusis (LASIK). SETTING: Department of Ophthalmology, Goethe University, Frankfurt, Germany. DESIGN: Retrospective consecutive case series. METHODS: Patients who underwent cataract surgery or refractive lens exchange with implantation of a diffractive EDOF IOL and who had a history of myopic LASIK were included. Biometry, refractive data regarding the LASIK procedure, target refraction, and postoperative refraction were collected. Mean prediction error, mean absolute error (MAE), and the number of eyes within ±0.5 diopters (D), ±1.0 D, ±1.5 D, and ±2.0 D were calculated with the following formulas from the ASCRS calculator: Shammas, Haigis-L, Barrett True-K, Barrett No History, Masket, modified Masket, and the average of all formulas (average). RESULTS: Twenty-five eyes matched the inclusion criteria. Mean spherical equivalent (SE) was -0.81 ± 0.69 D; the mean pre-LASIK SE was -6.4 ± 3.63 D. The formulas ranked by MAE were Shammas (0.7 ± 0.75 D), Haigis-L (0.72 ± 0.57 D), average (0.79 ± 0.8 D), Barrett True-K (1.14 ± 0.89 D), modified Masket (1.4 ± 1.15 D), Barrett No History (1.45 ± 0.7D ), and Masket (1.64 ± 1.27 D). The formulas with the most eyes within ±0.5 D were average (52%), Shammas (48%), and Haigis-L (44%) formulas. CONCLUSIONS: Calculation of IOLs in eyes with a history of refractive surgery remains a challenge. In this study, the Shammas and Haigis-L formulas performed best regarding MAE and percentage of eyes within ±0.5 D; however, the average of all formulas delivered reasonable results.