PREDICTION OF INTRAOCULAR-LENS POWER USING THE LENS HAPTIC PLANE CONCEPT

Purpose: To test algorithms for the preoperative estimation of the len s haptic plane (LHP) and to assess these in terms of predictability of postoperative refraction. Setting: St Erik's Eye Hospital, Stockholm, Sweden. Methods: Preoperative axial length, anterior chamber depth (A CD), and cataractous lens thickness were measured in consecutive cases scheduled for phacoemulsification and posterior chamber intraocular l ens (IOL) implantation. ?he algorithms tested used ACD and cataractous lens thickness to estimate LMP. The exact geometry of the IOL was use d to calculate postoperative ACD from LHP. Thick lens theory and parax ial ray tracing were used to calculate predicted postoperative refract ion. The calculated value was compared with actual refraction 3 to 6 m onths postoperatively. Results: Mean absolute average error in predict ed refraction was 0.38 diopters (D), with 78% of eyes within 0.50 D an d 97% within 1.00 D for the best algorithm. Conclusions: The predictab ility in postoperative refraction found by applying the LHP concept an d paraxial ray tracing was excellent. However, the small sample, with its unusually slight variation in axial lengths, did not allow statist ically significant differences between different postoperative refract ion prediction methods to be demonstrated.