Comparison of Refractive Outcomes of Different Intraocular Lens Power Calculation Formulas in Keratoconic Patients Undergoing Phacoemulsification

Purpose: In the present study we have tried to find the most reliable intraocular lens (IOL) power calculation formula in patients with keratoconus (KCN) and cataract. Methods: In a prospective case series between October 2010 and March 2012, eligible patients with cataract and KCN underwent phacoemulsification with IOL implantation. Preoperatively, based on IOL master keratometric data IOL power calculation was subsequently performed by means of six well-known formulas: Haigis, Holladay 1 and 2, Hoffer Q, SRKII, and SRKT. Postoperatively the “desired IOL power” was back-calculated in order to determine the most accurate formula for IOL power calculation. Results: Fourteen patients (20 eyes) with nuclear sclerosis and KCN were cumulatively enrolled. The mean age was 56.7 years±13.8 (SD) (range, 23 to 70 years). Nine patients (64%) were males. In mild KCN subgroup, SRK II and SRK-T represent as the “matched formulas” within defocus range of less than 1 D in 66.6% of cases. In moderate KCN subgroup, Hoffer Q, Holladay 1, Holladay 2, SRK II and SRK-T II represent as the “matched formulas” within defocus range of less than 1 D in 75% of cases. Finally in severe KCN subgroup, SRK II represents as the “matched formula” in 50% of cases. Conclusion: Findings of the present study suggest that irrespective of axial length classification, the SRK II formula can be considered as “the ideal formula”; the one with the most reliable outcome in all stages of KCN.