Purpose: To describe the changes of anterior chamber and angle configuration in the dark room provocative test (DRPT) using AS-OCT and to evaluate the correlation between these changes and the DRPT result. Method and Subject: subjects aged 35 years and whose peripheral anterior chamber were S 1/4 corneal thickness were recruited. The anterior segment of the eye was imaged under both light and dark conditions using AS-OCT. The analyzed parameters were: (1) central anterior chamber depth (ACD)
(2) pupil diameter (PD)
(3) iris curvature (IC)
(4) number of meridians with closed angles (NCA)
(5) Anterior chamber angle (ACA). Statistical analyses include: the difference in parameters between light and dark. Result: A total of 64 eyes of 41 subjects were recruited. ACD (p = 0.083), PD (p=0.000), IC (p=0.003) ,NCA (p=0.000), ACA (p=0.000) were different significantly between light and dark. The NCA and ACA in the dark was significantly correlated with the amount of IOP elevation induced by Dark-room prone position provocative test (with r=0.731 and r= -0.691). Conclusion: The test may be useful in the early diagnosis of primary angle closure.