Verification of a formula developed to predict the postoperative intraocular pressure after cataract surgery in primary angle-closure glaucoma

Background: The aim of this study was to verify the accuracy of a formula predicting postoperative intraocular pressure (TOP) after phacoemulsification and intraocular lens implantation (PHCE-IOL) in primary angle-closure glaucoma (PACG). In a retrospective chart review of patients with PACG who underwent PHCE-IOL between 2011 and 2014, we collected preoperative TOP, axial length, anterior chamber depth (ACD), number of pre-PHCE glaucoma medications, and TOP and glaucoma medications at 1 month and 3 months post-PHCE. Methods: Post-PI-ICE IOP values at 1 month and 3 months were compared with those predicted using the formula: postoperative TOP = 6.354 + 0.186 pre-PHCE TOP x pre-PHCE ACD. Agreements between measured and predicted TOP values were analyzed using correlation coefficients and Bland Altman plots. Results: Of the 62 eyes included, the average pre-PHCE TOP was 19.47 +/- 5.84 mm Hg. Post-PHCE TOP values were 14.94 +/- 4.03 mm Hg at 1 month and 14.21 +/- 3.51 mm Hg at 3 months. Patients using more preoperative medications tended to show greater postoperative declines in medication usage. Predicted TOP significantly correlated with post-PHCE TOP measured at 1 month (R = 0.314, p = 0.013) and 3 months (R = 0.325, p = 0.01). Bland-Altman plots of difference against average of measured and estimated TOP revealed two cases falling outside +/- 1.96 standard deviation at 1 month, and five cases at 3 months, indicating good consistency between measurement and prediction. Conclusion: This formula was useful for predicting TOP at 1 month and 3 months after PHCE-IOL in PACG. It aids clinicians in preoperative assessment of whether PHCE-IOL alone is likely to achieve acceptable postoperative TOP control. Copyright (C) 2016, the Chinese Medical Association. Published by Elsevier Taiwan LLC.