Primary Angle-closure Eyes Closed The Purposes Of Laser Peripheral Iris After Resection Of The Anterior Chamber Angle Incidence And Pathogenesis Research

Purpose: To evaluate the prevalence of angle closure in eyes with primary angle closure (PAC) after laser peripheral iridotomy (LPI) and to determine the pathogenesis of this condition by comparing the anterior chamber and angle parameters among PAC eyes with severe angle closure after LPI, PAC eyes with mild angle closure after LPI and normal subjects.Participants and Methods: (1) Based on the principle of prospective intervention case series study, prophylactic LPI was performed in 39 patients with PAC in the Department of Ophthalmology at Peking Union Medical College Hospital. Ultrasound biomicroscopy (UBM) examination was carried out before and 2 weeks after LPI in these eyes. One randomly selected eye of each subject was measured. UBM parameters before LPI were compared with those after LPI, including iridotrabecular contact (ITC), iris-ciliary process contact (ICPC), angle opening distance (AOD), trabecular-ciliary process distance (TCPD), iris distance (ID), scleral spur-ciliary process distance (SSCPD) and trabecular-ciliary process angle (TCPA). (2) The PAC eyes mentioned above were classified into two groups according to the severity of angle closure after LPI, severe one ( angle closure range after LPI≥4 clock positions, 23 eyes)and mild one ( angle closure range after LPI≤3 clock positions, 16 eyes). Based on the principle of case control study, UBM parameters of the two PAC groups after LPI were compared with those of the group with normal anterior chamber depth (20 eyes), including ACD, ID, TCPD, TCPA, SSCPD.Results: (1) 79.49% (31/39) PAC eyes had wider angles after LPI. However, the proportion of eyes with UBM-identified ITC in≥1 clock position after LPI was 87.18% (34/39). (2) Among the three groups mentioned above, TCPD and TCPA were significantly smaller in eyes with severe angle closure after LPI compared to those with mild angle closure after LPI as well as the normal ones (P=0.0001). ACD was significantly smaller in eyes with PAC than eyes with normal anterior chamber (P<0.0001), however, there was no significant difference in ACD within PAC eyes. There were no significant differences among the three groups in ID and SSCPD. The correlation coefficient between angle closure range after LPI and TCPD was -0.4312 (P=0.0069) and between angle closure range after LPI and TCPA was -0.3958 (P=0.0126).Conclusions: Angle closure was common in PAC eyes after LPI. Anteriorly positioned ciliary process played a key role in the pathogenesis of angle closure after LPI in PAC eyes.