Biometry & IOL power calculation Watch on YouTube! Permanent link! Calculation of IOL power 1. Refractive: IOL power = 18+ 1.25 X Preoperative refraction (SE) 2. Theoretical formulae. 3. Second generation formulae. 4. Third generation formulae: Holladay II, SRK-T & Hoffer Q. 5. AI hybrid. Holladay’s Data Screening Criteria to identify unusual measurement and require further validation. Repeat measurement if: 1. Axial length < 22.0 mm or > 25.0 mm. 2. Average corneal power < 40.0 Diopters or > 47.0 Diopters. 3. Calculated emmetropic IOL power > 3.0 Diopters of average power for the specific lens type....