Preoperative Factors Correlating With Intraocular Pressure Reduction after Phacoemulsification in Primary Angle Closure Glaucoma: A Cohort Study

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Abstract

PRECIS: Phacoemulsification achieved clinically significant 20% IOP reduction in PACG. Novel predictive model incorporating preoperative IOP and SS-OCT anterior segment parameters demonstrated good diagnostic accuracy (AUC 0.78). AIMS: To identify preoperative clinical and anatomical parameters that correlate with intraocular pressure (IOP) reduction after phacoemulsification in primary angle closure glaucoma (PACG) eyes. METHODS: This prospective cohort study recruited 149 PACG eyes from 149 Chinese patients who underwent phacoemulsification from 2015 to 2020 in a glaucoma clinic in Hong Kong. Anterior segment swept-source optical coherence tomography (SS-OCT) was performed in both darkness and room light before and at 6 months after surgery. Preoperative clinical and SS-OCT parameters were evaluated with generalized estimating equations (GEE) for their correlation with postoperative IOP changes. A linear discriminant function (LDF) was generated with a teaching set and tested in a validating set. The performance was evaluated with receiver operating characteristic curves. RESULTS: Cataract surgery alone effectively deepened the anterior chamber and widened the drainage angle, resulting in an average of 20% IOP reduction. Higher preoperative IOP predicted greater absolute IOP reduction after lens extraction at 6 months (β=-0.73, P<0.001) and 12 months (β=-0.76, P<0.001). Preoperative iridotrabecular contact (ITC) area, lens vault (LV), anterior chamber depth (ACD), iris rotation (IR), and ITC length correlated significantly with absolute postoperative IOP reduction. Age, sex, history of prior laser peripheral iridotomy (LPI), and baseline visual field (VF) did not show a significant correlation with IOP reduction after phacoemulsification. Based on these findings, we generated a mathematical formula (LDF) to predict IOP reduction after phacoemulsification in PACG eyes: -10.596 + 0.23 x preoperative IOP + 2.07 x ITC length + 1.16 x LV + 0.90 x ACD + 0.04 x IR. The Receiver operating characteristic curves (ROC) in a separate validating sample was 0.78 (95% CI: 0.67 - 0.88) at 6 months, and 0.70 (0.58 - 0.83) at 12 months. CONCLUSION: Preoperative SS-OCT-based anatomical parameters correlated significantly with IOP reduction after phacoemulsification in PACG. The derived LDF based on these parameters may help predict IOP reduction, and guide clinicians in deciding which PACG patients may need additional IOP-lowering procedures combined with phacoemulsification.

Abstract as published, via PubMed.