The changes in intraocular pressure and angle structure after pupillary dilation in patients with primary angle closure suspect and visually significant cataract

Abstract

Purpose : Pupil dilation is a concern for patients with narrow angles. Previous study showed it was safe for patients with primary angle closure suspect (PACS) without visually significant cataract (VSC). However, with cataract development, the angle has become narrower. There is no study to examine whether it is safe to dilate pupil for patients with PACS and VSC, which is one of the most important preoperative examinations. Moreover, there is no study to quantitatively examine the change in angle structure with pupil dilation in these patients. This study is to answer the two questions.

Methods : This is a prospective study for subjects with PACS and VSC who do not have prior any laser or surgery history. Subjects underwent a pupil dilation with 0.5% Tropicamide eye drops before cataract extraction surgery. Detailed ophthalmic evaluation including biometry, anterior segment optical coherence tomography (AS-OCT) and intraocular pressure (IOP) were performed before the dilation as baseline. IOP and AS-OCT measurements were repeated at 1 hour (PDH1) and 6 hours after pupil dilation (PDH6). IOP, angle opening distance at 500um (AOD500), trabecular iris area at 500um (TISA500), angle recess area at 500um (ARA500) and anterior chamber depth (ACD) were measured and compared between baseline and PDH1, also between baseline and PDH6 by paired t-test.

Results : A total of 16 eyes from 16 patients with an average age of 71.4±8.5 years were included in the study with 63% of females. As expected, pupil size was largest at PDH1 and smallest at baseline. There were no significant changes in IOP over time. All angle structure measurements showed a significant increase at PDH1, and then back to baseline at PDH6. The ACDs were significantly deepened at both PDH1 and PDH6 than baseline. There was 1 patient whose IOP was elevated by more than 5mmHg, but there was no patient developing acute angle closure during the 6 hours after dilation.

Conclusions : It is safe to dilate the pupil in patients with PACS and VSC. Dilation with 0.5% Tropicamide relaxes ciliary muscle, leading to posteriorly displacement of lens-iris diaphragm and deepening of anterior chamber. On average, angle structures were surprisingly slightly enlarged at 1 hour after dilation but back to baseline at 6 hours after dilation.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.