Diurnal Intraocular Pressure and the Relationship With Swept-Source OCT-Derived Anterior Chamber Dimensions in Angle Closure: The IMPACT Study.

Abstract

To evaluate diurnal intraocular pressure (DIOP) among individuals with primary angle closure (PAC) or primary angle-closure suspect (PACS). Additionally, the hypothesis that greater DIOP fluctuation is related to smaller angle parameters was investigated. Forty Caucasian newly referred untreated patients with bilateral PAC or PACS were recruited. Intraocular pressure (IOP) was measured hourly between 9 AM and 4 PM with Goldmann applanation tonometry. Diurnal IOP fluctuation was defined as difference between maximum and minimum IOP. Angle opening distance (AOD), trabecular-iris angle (TIA), angle recess area (ARA), and trabecular-iris space area (TISA) were measured with anterior segment optical coherence tomography (AS-OCT) in dark (0.3-0.5 lux) and light (170-200 lux) on the same day as DIOP measurements in eight angle sections. Intraocular pressure declined as the day progressed (P < 0.001), unrelated to presence of peripheral anterior synechiae (PAS). At each time point, eyes with PAS (n = 31) had significantly higher IOPs than eyes without PAS (n = 49; P = 0.043). Diurnal IOP fluctuation varied from 1.50 to 14.50 mm Hg (mean 5.99 mm Hg, SD 2.70 mm Hg). Diurnal IOP fluctuation was unrelated to PAS. Multiple-predictor models investigating association of angle dimensions and greater DIOP fluctuation were statistically significant for AOD 750 (light), ARA 750 (light and dark), TISA 500 (light), TISA 750 (light), TIA 500 (light), and TIA 750 (light and dark). Diurnal IOP variation has clinical implications given that IOP level is used to distinguish between diagnostic categories of PACS and PAC. Optical coherence tomography angle parameter measurements may predict for magnitude of IOP diurnal fluctuations in at-risk patients, which may be clinically useful when a clinical intervention is being considered.