Calculation of lens power using new biometry formulas

Purpose: Using the biometric and refractive data of the patients before the phacoemulsification surgery; calculation of the intraocular lens (IOL) power with 6 different biometric formulas and comparison of the accuracy of the formulas according to the postoperative refractive results. Material and Method: The data of 65 eyes of 43 patients who were diagnosed with cataract and underwent phacoemulsification surgery in the Ophthalmology Clinic of Istanbul University Istanbul Faculty of Medicine between January 2016 and July 2019 were retrospectively analyzed. Results: The mean age of 43 patients included in the study was 64,65 ± 8,23 (47-86) years. The mean axial length was found to be 23,5±0,7 mm (22,01-24,5). The IOL power corresponding to the target refraction value in the patients was calculated according to the SRK/T formula. Result refraction values of the patients were determined by the examinations performed at and after the postoperative 3rd month. While the preoperative best corrected visual acuity (BCVA) of the patients was 0,44±0,4 logMAR, the postoperative BCVA was 0,08±0,04 and there was a significant increase (p<0,001). Using the optical biometry measurements of the patients, the target refraction values that would emerge with the Hoffer Q, T2, Ladas Super Formula, Barrett Universal II and Hill-RBF formulas when implanted with the same refractive power were noted. The difference between the target refraction values determined by the formulas used and the spherical equivalents of the patients' result refractions was noted and the refractive deviation values between the formulas were compared. The refractive deviation was found 0,29±0,29 D with SRK/T formula, 0,27±0,27 D with T2 formula, 0,3±0,24 D with Hoffer Q, 0,3±0,26 D with Ladas Super Formula, 0,33±0,28 D with Barrett Universal II formula and 0,27±0,29 D with Hill-RBF formula. The percentages of cases with refractive deviation degrees of the formulas from -0,50 to +0,50 D were as follows: T2 formula with 87,7%, Hill-RBF with 86,2%, Hoffer Q and SRK/T formulas with 84,6%, Barrett Universal II with 83,1%, Ladas Super Formula with 81,5%. Refractive deviation percentages of the formulas between -1,00 D and +1,00 D were determined as follows: Hoffer Q and Hill-RBF with 98,5%, T2 formula, Ladas Super Formula, Barrett Universal II and SRK / T formula with 96,9%. There was no statistically significant difference between the formulas in terms of refractive deviation values (p>0,05). Conclusion: The chance of reaching the target refractive value with a refractive deviation within ±1 D of the 6 biometry formulas included in the study is 96,9% and above. Each of these formulas can be safely used to calculate preoperative IOL power in normal-length eyes.