Evaluation of Wang-Koch optimisation of axial length for intraocular lens power calculation in myopic eyes

Abstract

Background: Refractive outcome has become more relevant in myopic patients. Refractive surprises are mainly caused by errors in axial length (AL) measurement.

Aim: This study aimed to evaluate the accuracy of intraocular lens (IOL) power calculation in myopic eyes using the AL measured by optical biometry versus an optimised AL calculated by the Wang-Koch method.

Setting: Ophthalmology Department, Cairo University and Ophthalmic Diagnostic and Laser Unit, Cairo University Hospitals, both in Cairo, Egypt.

Methods: A prospective study of 30 eyes of 23 patients with ALs greater than 25.0 mm that underwent phacoemulsification with IOL implantation in the capsular bag. The LENSTAR was used for preoperative IOL power calculation using the Holladay 1 formula and the LENSTAR AL (group 1), and for back-calculation of the prediction error (PE) for the same 30 eyes using the Holladay 1 formula and the optimised AL (group 2). Postoperative PEs and mean absolute errors (MAEs) were calculated six weeks after surgery.

Results: The postoperative spherical equivalent was within ± 1.00 dioptre (D) of predicted in 86.7% and 90.0% of eyes, respectively, (p = 0.69). However, 66.7% of eyes had a hyperopic outcome in group 1, in comparison to 20.0% that would be left hyperopic using the optimised AL in group 2 (p < 0.05).

Conclusion: The Wang-Koch method of optimising the AL would have significantly reduced the percentage of eyes rendered hyperopic using the LENSTAR AL from 66.7% to 20.0%. This difference represents a clinically significant improvement in IOL power prediction in these eyes.