Correlation between Pupil Diameter and Angle Configuration in the Dark Room Provocative Test

Dejiao Li, MD, Ningli Wang, MD, PhD, Bingsong Wang, MD, Tao Wang PhD, Shuning Li, PhD, Lijia Chen, MD, and Dapeng Mu PhD

Purpose: To study associations between changes in pupil diameter and in anterior chamber angle configuration during the dark room provocative test.

Methods: The study included 70 suspects of primary angle closure (study group) and 40 normal subjects (control group). Using anterior segment optical coherence tomography (AS-OCT), we measured the anterior chamber angle configuration and pupil diameter at 3 minutes and at 1.5 hours of dark adaptation.

Results: In the study group, the mean number of closed angle segments was significantly (P<0.001) higher at 3 minutes of dark adaptation (3.9±2.3) that at room light conditions (2.6±2.2) or at 1.5 hours of dark adaptation (3.1±2.1), with no statistically significant (P>0.05) difference between the two latter values. In the study group, the pupil diameter was significantly associated with the number of closed angle segments at 3 minutes of dark adaptation (P<0.01), but not at 1.5 hours of dark adaptation (P=0.13). Defined as an increased number of closed angle segments, the dark room test was positive in a significantly higher number of subjects at 3 minutes than at 1.5 hours of dark adaptation (44 (63%) eyes versus 31 (44%) eyes; P<0.05). Final IOP was statistically better correlated with the angle configuration segments assessed at 3 minutes (correlation coefficient r2= 0.33) than at 1.5 hours of dark adaption (r2= 0.21).

Conclusions: After short term dark adaptation of 3 minutes, the assessment of the anterior chamber angle configuration by AS-OCT is more reliable than as if performed after a long term dark adaptation and may be used to identify suspects of primary angle closure.

Key words: Pupil diameter; Darkroom provocative test; Primary angle closure glaucoma; Anterior segment optical coherence tomography