The Comparative Study of Refractive Index Variations between Haigis, Srk/T and Hoffer-Q Formulas Used for Preoperative Biometry Calculation in Patients with the Axial Length >25 mm.

Background: To compare refractive index variation between Hoffer-Q, Haigis and SRK/T formulas used for preoperative biometry calculation in patients with axial length >25 mm, undergoing cataract surgery.

Materials And Methods: This is a randomized clinical trial study was performed on 54 eyes of 54 patients with ages of 40-70 years old and axial length >25 mm classified into three groups that their IOL POWER were calculated by Haigis, SRK/T and Hoffer-Q formulas before undergoing cataract surgery. Their refractive index variations were calculated from the difference between predicted refractive error formula and actual post-operative refractive error formula.