Correlation between pupil diameter and angle configuration in the dark room provocative test

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

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.

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).

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.