Pilocarpine induces an increase in the anterior chamber angular width in eyes with narrow angles

Aim-To determine the mechanical effects of pilocarpine on the trabecular-ir is angle opening in eyes with narrow angles, compared with its effects on h ealthy control subjects with wide angles. Methods-A narrow angle was defined as 25 degrees or less of trabecular-iris angle on ultrasound biomicroscopic examination. The change in anterior cha mber depth (ACD), trabecular-iris angle (TIA), angle opening distance (AOD, distance between trabecular meshwork and iris) measured at 250 mu m and 50 0 mu m from the scleral spur (AOD250 and AOD500), and iris thickness was de termined in 30 eyes of 30 patients (13 men and 17 women, between 63 and 82 years (mean 70.4 years)) with narrow angles and in 30 sex and age matched c ontrol subjects with wide angles before and 1 hour after the instillation o f 2% pilocarpine hydrochloride by ultrasound biomicroscopy. Results-In all eyes with narrow angles, pilocarpine increased the TIA, AOD2 50, and AOD500; these changes increased significantly and linearly as the c orresponding pretreatment values decreased (r = 0.807, p = 0.0001; r = 0.78 7, p = 0.0001; r = 0.852, p = 0.0001). Of 30 eyes with wide angles, 23 eyes whose ACD was 2670 mu m and more showed a decrease in the TIA, AOD250, and AOD500; the changes in TIA, AOD250, and AOD500 also significantly correlat ed with the corresponding pretreatment values (r = 0.913, p = 0.0001; r = 0 .882, p = 0.0001; r = 0.895, p = 0.0001). Pilocarpine induced a smaller dec rease in ACD in eyes with narrow angles than in those with wide angles (p = 0.0001). There was a linear correlation between the increase in ACD change and the decrease in pretreatment ACD in eyes with narrow angles and those with wide angles (r = 0.781, p = 0.0003; r = 0.798, p = 0.0001). Conclusions-The finding that pilocarpine increases angular width in patient s with narrow angles indicates that this agent is useful for treating patie nts with narrow angles and angle closure glaucoma. The prediction of the pi locarpine induced change in the angle may assist ophthalmologists in treati ng such patients.