# IOL CALCULATION IN HIGHLY MYOPIC PATIENTS

## Description

Background: To determine the accuracy of the T2 formula as applied to highly myopic eyes, to compare the T2 formula to the SRK/T and Holladay 1 formulas, and to describe possible improvements for estimating corneal height and prediction error in two settings, the Hadassah Hospital, Ophthalmology Department, Jerusalem, Israel and Clínica Barraquer, Bogotá, Colombia. Methods: In this retrospective case series , optical biometer measurements were taken for 63 highly myopic patients (spherical power ≤ 5 D) undergoing uneventful crystalline lens phacoemulsification and insertion of an acrylic intraocular lens. Prediction errors were obtained, with estimations of ± 0.50 D, ± 1.00 D, and greater than ± 2.00 D. Methods to improve corneal height calculations are described. Results: The SRK/T (mean absolute error [MAE] = 0.418; median absolute error [MedAE] = 0.352) formula was the most accurate, followed by the T2 (MAE = 0.435; MedAE = 0.381) and Holladay 1 (MAE = 0.455; MedAE = 0.389) formulas. Both the SRK/T and T2 formulas overestimated corneal height, but values were higher with the T2 formula. Corneal height was more precisely estimated using an alternative method that, when combined with axial length optimization, resulted in lower MAE (0.425) and MedAE (0.365) values than when applying the T2 formula alone. Conclusions: The T2 formula seems to be less accurate than the SRK/T formula in highly myopic eyes. Improvements in corneal height estimations may result in better intraocular lens estimations. Key words: T2 formula, high myopia, corneal height estimation, cataract surgery, intraocular lens calculation .