Anterior chamber depth, intraocular lens position, and refractive outcomes after cataract surgery

PURPOSE: To assess postoperative intraocular lens (IOL) position in relation to the cornea and iris, compare 2 devices for anterior chamber depth (ACD) measurement, and assess the impact of these factors on postoperative refraction in phacoemulsification. SETTING: Department of Clinical Sciences/Ophthalmology, Umea University Hospital, Umea Sweden. DESIGN: Evaluation of diagnostic test or technology. METHODS: Biometry and measurement of the anterior segment were performed preoperatively and postoperatively with the partial coherence interferometry (PCI)-based IOLMaster and the Pentacam HR Scheimpflug device. Predicted refraction was calculated with ACD estimations according to the Haigis formula and was compared with the actual postoperative refraction. Changes in ACD and the distance between the cornea-iris and the iris-lens/IOL were assessed from Scheimpflug images. The theoretical refractive impact of differences in ACD was calculated. RESULTS: The mean preoperative ACD and refractive prediction error, respectively, was 3.22 mm +/- 0.37 (SD) and 0.41 +/- 0.43 diopters (D) for the PCI device and 3.21 +/- 0.35 mm and 0.41 +/- 0.41 D for the Scheimpflug device; the difference was not statistically significant. The mean ACD, cornea-iris distance, and iris-lens/IOL distance changes were 1.62 +/- 0.38 mm, 0.78 +/- 0.29 mm, and 0.85 +/- 0.27 mm, respectively. The mean predicted refractive outcome from a 1.0 mm difference in ACD was 0.32 D. CONCLUSIONS: No difference was found between the measurement devices. Although the exact postoperative IOL position is difficult to predict, its impact on postoperative refraction was comparatively small compared with the impact of minor corneal curvature or axial length measurement errors.