LAUSR

Purpose Intra-ocular lens (IOL) power calculation in eyes with keratoconus typically results in hyperopic postoperative refractive error. We investigated the visual and refractive outcomes in keratoconus patients having cataract surgery with a toric IOL and compared IOL power calculation accuracy of conventional formulae and keratoconus specific formulae. Setting Ein-Tal Eye Center, Tel-Aviv, Israel. Design Retrospective case-series study. Methods Post-operative visual acuity and manifest refraction were examined. The error in predicted refraction and IOL power calculation accuracy within a range of 0.5 to 2.0 diopters were compared between different IOL calculating formulae. Results Thirty-two eyes with keratoconus were included. Visual acuity improved in all cases and subjective astigmatism decreased from -2.95+/-2.10 D to -0.95+/-0.80 D (p<0.001). Mean absolute errors were: Barrett True-K for keratoconus with measured or predicted posterior corneal power, 0.34 D; Barrett Universal II, 0.64 D; Kane Formula, 0.69 D; Kane Formula for keratoconus, 0.49 D; SRK/T, 0.56 D; Haigis, 0.72 D; Holladay 1, 0.71 D and Hoffer Q, 0.87 D. Barrett True-K formula with measured posterior corneal power, SRK/T and Kane Formula for keratoconus resulted in a prediction error within 0.5 D of 87.5%, 59.4% and 53.1%, respectively. Conclusions Cataract removal with a toric IOL significantly improves visual acuity and decreases astigmatism in keratoconic eyes with a topographic central relatively regular astigmatic component. Keratoconus specific formulae resulted in lower mean error in predicted refraction compared with conventional calculating formulae. Utilizing the posterior corneal power within the Barrett True K formula for keratoconus improved IOL power prediction accuracy.