Objective:To investigate the role the lens dimensions played on the pathogenesis of primary angle-closure glaucoma. Methods:38 eyes of 20 patients with primary angle-closure glaucoma(PACG) and 35 eyes of 22 normal individuals without ocular abnormalities were examined. The anatomical parameters of the lens and other structures of the anterior segment were calculated using B ultrasound, computer image processing and ultrasound biomicroscopy(UBM). The parameters were compared between the patients and normal subjects. Correlation analysis was used to determine the relationship between the radii of curvature of the anterior lens surface(RCALS) and the other parameters of the anterior segment. Results:Compared with the normal eyes, the eyes of PACG had thicker lens, steeper curvature of anterior lens surface, decreased depth of the anterior chamber, narrower chamber angle, and more anterior position of the ciliary bodies and lens. All these differences were significant(P < 0.05 or P < 0.01). In the PACG group, the RCALS had significantly negative correlation with the central and peripheral lens thickness(P < 0.01 and P < 0.05 respectively), and had positive correlation with relative lens position, anterior chamber depth(ACD), angle-open distance at 500 um(AOD500), trabecular iris angle(TIA) and trabecular ciliary processes distance(TCPD, P < 0.05 or P < 0.01). Conclusion:The occurrence of PACG is relevant to the abnormal anatomical structures of the anterior segment. Among all factors, the lens parameters play an important role in the pathogenesis. Increased lens thickness, relative more anterior position of lens,especially steepened curvature of anterior lens surface are predisposing factors of the pathologic phenomenon in PACG including pupillary blockage, shallow anterior chamber, secondary closure of chamber angle and elevation of intraocular pressure.