Comparison of the Effectiveness of Different Formulas for Toric IOLs Optical Power Calculating at Lens Surgery in Patients after Penetrating Keratoplasty

Purpose . To compare the effectiveness of 9 calculating the IOL optical power formulas for toric monofocal IOL and wavefront formation mechanism IOL at cataract surgical treatment in patients after penetrating keratoplasty (PK). Patients and methods . The study included 68 patients (68 eyes) underwent cataract surgery after PK. 32 patients (32 eyes) were implanted with the EDOF IOL AcrySof IQ Vivity DFTx15 (group A), and 36 patients (36 eyes) were implanted with the monofocal IOL AcrySof IQ Toric SN6ATx (group B). The average period after the PK procedure in group A was 49.06 ± 18.48 months, in group B — 53.25 ± 17.19 months. The average age was 45.71 ± 13.65 years, 27 men, 41 women. The optical power of the IOL was calculated using the Holladay 1, Hoffer Q, SRK/T, Haigis, Kane, Barrett Toric Calculator, EVO formulas. The last two formulas were calculated with the predicted (PPC) and measured posterior corneal surface (MPC). Results . The lowest values of the median absolute error (MedAE) were noted for formulas that take into account the measured posterior surface of the cornea — Barrett Toric Calculator (in group A MedAE = 0.778; in group B MedAE = 0.805) and EVO (in group A MedAE = 0.799; in group B MedAE = 0.801). In group A, the highest percentage of hits within ±0.5 D and ±1.0 D were obtained for the Barrett (MPC) formulas (±0.5 D — 34.4%; ±1.0 D — 59.4%), Kane (±0.5 D — 31.3%; ±1.0 D — 56.3%) and EVO (MPC) (±0.5 D — 31.3%; ±1.0 D — 56.3%); in group B, within ±0.5 D for the Barrett (MPC) (16.7%) and EVO (MPC) (16.7%) formulas, within ±1.0 D for the Barrett (MPC) (41.7%), Kane (38.9%) and EVO (MPC) (38.9%) formulas. Conclusion . Using the posterior corneal surface parameters in the IOL optical power calculating allows more accurate target refraction in patients with PK. The Barrett Toric Calculator and EVO formulas with the introduction of posterior corneal surface parameters can be recommended for use in clinical practice of aphakia surgical correction in patients with previously performed PK.