The effect of lens parameters on the development of the primary angle-closure glaucoma

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.

Effect of primary iris and ciliary body cyst on anterior chamber angle in patients with shallow anterior chamber

Objective:To evaluate the prevalence of primary iris and/or ciliary body cysts in eyes with shallow anterior chamber and their effect on the narrowing of the anterior chamber angle.Methods:Among the general physical check-up population,subjects with shallow anterior chambers,as judged by van Herick technique,were recruited for further investigation.Ultrasound biomicroscope(UBM) was used to detect and measure the cysts located in the iris and/or ciliary body,the anterior chamber depth(ACD),the angle opening distance at 500 μm(AOD500),and the trabecular-iris angle(TIA).A-scan ultrasonography was used to measure the ocular biometry,including lens thickness,axial length,lens/axial length factor(LAF),and relative lens position(RLP).The effect of the cyst on narrowing the corresponding anterior chamber angle and the entire angle was evaluated by the UBM images,ocular biometry,and gonioscopic grading.The eye with unilateral cyst was compared with the eye without the cyst for further analysis.Results:Among the 727 subjects with shallow anterior chamber,primary iris and ciliary body cysts were detected in 250(34.4%) patients;among them 96(38.4%) patients showed unilateral single cyst,21(8.4%) patients had unilateral double cysts,and 42(16.8%) patients manifested unilateral multiple and multi-quadrants cysts.Plateau iris configuration was found in 140 of 361(38.8%) eyes with cysts.The mean size of total cysts was(0.6547±0.2319) mm.In evaluation of the effect of the cyst size and location on narrowing the corresponding angle to their position,the proportion of the cysts causing corresponding angle narrowing or closure among the cysts larger than 0.8 mm(113/121,93.4%) was found to be significantly higher than that of the cysts smaller than 0.8 mm(373/801,46.6%),and a significant higher proportion was also found in the cysts located at iridociliary sulcus(354/437,81.0%) than in that at the pars plicata(131/484,27.1%).In evaluating the effect of the cyst on the entire anterior chamber angle,the eyes with multiple and multi-quadrants cysts manifested significant narrowing of the entire anterior chamber angle as compared with the eyes without cysts,based on the data analysis in comparison of TIA,AOD500,and gonioscopic grading evaluation.The unilateral single or double cysts in the eyes had no significant effect on narrowing of anterior chamber angle as compared with eyes without cysts.The iris and/or ciliary body cysts did not seem to affect the axial length,ACD,lens thickness,RLP,LAF.Conclusions:The prevalence of primary iris and ciliary body cyst was 34.4% in the subjects with shallow anterior chamber.The cysts larger than 0.8 mm,locating at iridociliary sulcus,or multiple and extensive cysts were inclined to cause the angle narrowing or closure.