Prediction of postoperative effective lens position using iris root depth in primary angle-closure diseases

Purpose: To evaluate the role of a new parameter, iris root depth (IRD), in intraocular lens power calculation using ultrasound biomicroscopy (UBM) in primary angle-closure diseases (PACDs), and to compare the accuracy of 6 formulas in PACDs: Barrett Universal II (BUII), Haigis, Hill-Radial Basis Function (RBF) v. 3.0, Hoffer Q, Kane and Sanders Retzlaff Kraff/Theoretical (SRK)/T. Setting: Zhongshan Ophthalmic Center, Guangzhou, China. Design: Retrospective consecutive case series. Methods: Patients diagnosed with PACDs who had undergone cataract surgery were reviewed to first evaluate the performance of 6 formulas. Then preoperative UBM examinations of 58 eyes were used to measure IRD and predict effective lens position (ELP) to generate the Haigis IRD formula. The accuracy of Haigis IRD was compared with BUII, Haigis and Kane formulas. The SD of predicted error was the main indicator evaluating formula performance, according to heteroscedastic analysis. Results: 103 eyes (103 patients) were included. The SDs of Kane (0.59, P = .01), RBF 3.0 (0.61, P = .02) and SRK/T formula (0.62, P = .04) were significantly lower than Hoffer Q. Modified with IRD, Haigis IRD generated the lowest SD (0.41), which was significantly lower than Haigis formula (0.54, P = .03) and was equal to Kane formula (0.45, P = .37). Conclusions: Kane, RBF 3.0 and SRK/T were more accurate in PACD eyes. Optimized with IRD, Haigis IRD formula achieved the lowest SD and had comparable accuracy with Kane formula. IRD could be a promising parameter to improve accuracy of IOL power calculation for PACDs.