Comparison of the Accuracy of Newer Intraocular Lens Power Calculation Methods in Eyes That Underwent Previous Phototherapeutic Keratectomy

PURPOSE: To evaluate the accuracy of intraocular tens (IOL) power calculations using ray tracing software in patients who had undergone phototherapeutic keratectomy (PTK). METHODS: In this retrospective case series, 37 eyes of 22 patients (mean age: 69.4 years; range: 56 to 85 years) who underwent cataract surgery after PTK were reviewed. The prediction error, defined as the difference between the estimated postoperative spherical equivalent and the postoperative manifest refraction at the spectacle plane, was calculated using the following formulas: OKULIX (Tedics, Dortmund, Germany), PhacoOptics (IOL Innovations ApS, Aarhus, Denmark), Barrett True K No History (NH), and Camettin-Catossi. The PhacoOptics formula was used in three different ways: historical method (H), no history method (NH), and C-constant method (CI. The median values of the arithmetic and absolute prediction errors among these six IOL calculation methods were compared. RESULTS: The median arithmetic errors (in diopters and percentages of eyes within +/- 0.50 D of the absolute errors were as follows: OKULIX (0.33, range: -2.20 to 2.50, 30.6%), PhacoOptics (H) (-0.12, range: -3.28 to 4.85, 22.2%), PhacoOptics (NH) (-0.25, range: -2.08 to 1.70, 48.4%), PhacoOptics (C) (0.04, range: -1.40 to 2.18, 48.5%), Barrett True K (NH) (-0.35, range: -1.90 to 1.89, 48.6%), and Camettin-Catossi (-0.19, range: -1.78 to 1.47, 59.5%). CONCLUSIONS: The PhacoOptics, especially the C-constant method (C), and Camellin-Calossi formulas were good options for calculating IOL powers in eyes that underwent PTK.