Objective: To study the associations between changes in pupil diameter and in the 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 participants (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) than 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 2 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 participants at 3 minutes than at 1.5 hours of dark adaptation [44 (63%) eyes vs. 31 (44%) eyes; P<0.05]. Final interocular pressure 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 adaptation (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 carried out after a long-term dark adaptation and may be used to identify suspects of primary angle closure.