Objective: To investigate anterior and posterior chamber diameters in primary angle-closure (PAC) and to correlate them to
the angle opening parameters.

Material and Method: Fifty eyes of PAC and 45 age-matched controls underwent ultrasound biomicroscopy (UBM; model
P60, Paradigm Medical Industries Inc., Salt Lake City, UT) scanning. Superior, inferior, temporal and nasal angle opening
parameters were obtained. Anterior chamber diameter, indicated by angle-to-angle diameter (AAD) and posterior chamber
diameter, indicated by sulcus-to-sulcus diameter (SSD), were analyzed.

Results: Mean age was not different between PAC and controls, 59.80 + 9.11 versus 56.33 + 13.39, respectively (p = 0.140).
PAC demonstrated a relatively smaller eye than the controls; e.g., corneal diameter, anterior chamber depth (ACD) and axial
length, (all p < 0.05). AAD was shorter in PAC than the controls, 10.16 + 0.58 versus 10.88 + 0.55 mm, (p < 0.001). AAD
was correlated to PAS extent (r = -0.358), ACD (r = 0.659), SSD (r = 0.636) and scleral spur to iris root insertion (r = 0.505),
(all p < 0.001). SSD was also smaller in PAC than controls, 10.16 + 0.45 versus 10.52 + 0.52 mm, (p = 0.001).

Conclusion: Crowded anterior segment of PAC can be demonstrated by a novel parameter of AAD and SSD, obtained with
a newer model of UBM. The shorter AAD indicates the greater PAS extent and smaller angle. Both parameters are independent
to scleral spur, and are simple to evaluate PAC.

Keywords: Angle-closure glaucoma, Ultrasound biomicroscopy, Anterior chamber diameter, Posterior chamber diameter,
Peripheral anterior synechia, Asian