Anatomic predictors of intraocular pressure change after phacoemulsification: an AS-OCT study

Abstract

Introduction: Phacoemulsification surgery is known to alter anterior segment structure parameters and also intraocular pressure (IOP). We set out in this study to investigate the relationship between the two parameters by using anterior segment optical coherence tomography (AS-OCT). Purpose: To evaluate anterior segment and lens parameters associated with IOP lowering after phacoemulsification. Study design: Prospective longitudinal single centre study. Materials and methods: All consented study participants underwent uneventful phacoemulsification with foldable intraocular lens implantation. IOP measurement, gonioscopy, and AS-OCT measurements were performed pre- and postoperatively at one month. Customised software (Zhongshan Angle Assesment Programme, ZAAP) was used to measure various anterior chamber parameters. A-scan biometry was used to measure axial length (AL), lens thickness (LT), and to calculate lens position (LP) and relative lens position (RLP). Results: Eighty-six eyes from 86 patients were included in this study. The mean IOP reduced significantly after phacoemulsification (from 16.2 ± 2.4 mmHg to 14.1 ± 2.6 mmHg at one week and 14.4 ± 2.3 mmHg at one month, P < 0.001). In the multivariate regression model, preoperative IOP and AL were the only significant parameters associated with percentage change in IOP (p < 0.001). Conclusion: Change in IOP post-phacoemulsification is dependent on preoperative IOP and AL. Greater percentage change in IOP is seen in eyes with shorter axial length.