A New Parameter for Predicting the Postoperative Intraocular Lens Position: Angle-to-Angle Depth Assessed with Swept-Source Fourier-Domain Anterior Segment Optical Coherence Tomography

Abstract

Purpose: The crucial problem in intraocular lens (IOL) power calculation is imprecise prediction of the IOL position after cataract surgery. We evaluated the efficacy of a new algorithm to predict the postoperative anterior chamber depth (ACD) using the angle-to-angle depth (ATA-depth) measured by Fourier-domain anterior segment optical coherence tomography (FD-OCT).

Methods: Fifty-seven eyes (40 patients) that underwent phacoemulsification and IOL implantation of an AcrySof Toric IOL (Alcon, Fort Worth, TX) between November 2012 and April 2013 were examined to develop the new algorithm for predicting the postoperative ACD. The ATA depth was defined as the distance between the posterior corneal surface and the line connecting the anterior chamber angle of both sides measured preoperatively using FD-OCT (CASIA SS-1000, Tomey, Nagoya, Japan). The postoperative ACD was measured in each case 1 month postoperatively and analyzed by multiple linear regression for covariance with preoperatively defined variables including the ATA depth, the preoperative ACD (pre-ACD), and the radius of the anterior lens curvature (R) by FD-OCT, the axial length (AL), and the corneal radius by the IOLMaster (Carl Zeiss Meditec, Jena, Germany). The predicted postoperative ACD was determined from linear regression analysis of the pre-ACD and ATA depth and confirmed prospectively in the postoperative results of the 40 cataract procedures.

Results: The mean pre-ACD was 2.73±0.43 mm (range, 1.80-3.53), ATA depth 3.28±0.20 mm (range, 2.63-3.77), AL 23.97±1.37 mm (range, 21.89-27.63), and K 44.38±1.52 diopters (range, 39.27-46.73). Single regression analysis showed significant correlations between the postoperative ACD and the pre-ACD, R² = 0.71, P<0.001; ATA depth, R² = 0.65, P<0.001; AL, R² = 0.43, P<0.001; and R, R² = 0.13, P = 0.006. Using the two most significant variables (pre-ACD and ATA depth), the postoperative ACD was predictable according to a regression formula with an accuracy of 85.7% of the predictions within 0.1 mm. In the prospective study, the postoperative ACD was predicted with a correlation coefficient of 0.71.

Conclusions: Preoperative measurement of the ATA depth using anterior FD-OCT may be promising parameter to predict the postoperative lens position.

Keywords: 567 intraocular lens • 420 anterior chamber