Changes in Intraocular Pressure and Angle Structure after Dilation in Primary Angle-Closure Suspects with Visually Significant Cataract

Abstract

To evaluate the safety of pupillary dilation in primary angle-closure suspects (PACS) with concurrent visually significant cataract (VSC), to identify risk factors associated with elevated intraocular pressure (IOP), and to describe changes in anterior segment anatomy after pupillary dilation. Prospective study. Patients with PACS and VSC and no prior laser or intraocular surgery were recruited. Visually significant cataract was defined as best-corrected visual acuity ≤ 20/40 due to cataract. Subjects' eyes were dilated with 0.5% tropicamide and 0.5% phenylephrine hydrochloride. A standardized eye examination, biometry, and swept-source OCT (SS-OCT) were performed before dilation. Intraocular pressure and SS-OCT were repeated 1, 4, and 6 hours postdilation (PDH1, PDH4, and PDH6, respectively). All parameters were compared between time points before and after dilation using paired t test. Linear regression models were used to determine the risk factors associated with postdilation IOP changes. Change in IOP and SS-OCT parameters from baseline. Seventy-eight eyes from 78 patients were included, with 78, 66, and 12 patients completing the study at PDH1, PDH4, and PDH6, respectively. Mean IOP increased from 14.8 ± 2.6 mmHg at baseline to 15.5 ± 3.5 mmHg at PDH1 (P= 0.03) and decreased to 14.9 ± 3.1 mmHg at PDH4 (P= 0.09). Four patients (5.13%) and 3 patients (3.85%) had an increase in IOP ≥ 5 mmHg at PDH1 and PDH4, respectively. Two patients (2.56%) and 1 patient (1.28%) had an increase in IOP ≥ 8 mmHg at PDH1 and PDH4, respectively. None developed acute primary angle-closure during the observation period. Almost all anterior chamber parameters showed a significant increase after dilation at PDH1 and PDH4, except lens vault and iris volume, which decreased at PDH1 and PDH4 from baseline. Increase in anterior chamber depth was negatively associated with the level of IOP elevation after dilation (P < 0.01). Dilation of patients' eyes with PACS and VSC in this cohort appears to have a low risk for IOP spike. This may be associated with relaxation of the ciliary muscle leading to posterior displacement of the lens-iris diaphragm and deepening of the anterior chamber.