Ultrasound biomicroscopic features associated with angle closure in fellow eyes of acute primary angle closure after laser iridotomy.

Objective: To investigate the frequency of appositional angle closure and related anatomic characteristics in fellow eyes of Chinese subjects with acute primary angle closure (APAC) after laser peripheral iridotomy (LPI).

Methods: Cross-sectional study. Methods: Consecutive subjects with APAC presenting from April 2006 to September 2006 at the Glaucoma Service of Peking University Eye Center, Peking University Third Hospital. Methods: Under dark conditions, fellow eyes were divided into 2 groups based on the detection of appositional angle closure by ultrasound biomicroscopy (UBM). For all subjects, UBM parameters were measured to evaluate the different anatomic features between the 2 groups. Darkroom provocative tests (DRPTs) and gonioscopy were performed to investigate the relationship between angle closure and intraocular pressure. Methods: Central anterior chamber depth (ACD); angle opening distance(500) (AOD(500)); angle recess area(750) (ARA(750)); trabecular-iris angle (T-I angle); trabecular-ciliary process distance (TCPD); peripheral iris thickness (IT(1)); iris-zonule distance (IZD); and the position of the iris insertion.

Results: Thirty-four post-LPI fellow eyes of 34 patients with APAC (8 men, 26 women; mean +/- standard deviation age 66.3+/-7.2 years, range 54-83) were included. Peripheral anterior synechiae (PAS) were not observed in any subject. Appositional angle closure was observed in at least 1 quadrant in 13 (38.2%) of the 34 patients. Compared with eyes without appositional closure, eyes with appositional closure showed significantly lower AOD(500), ARA(750), and T-I angle in 4 quadrants; shorter TCPD in the inferior and temporal quadrants; and thicker IT(1) in the superior and nasal quadrants (P<0.05). The DRPT results were positive in 3 (11.1%) of 27 eyes with appositional closure in 0 to 2 quadrants and in 3 (75.0%) of 4 eyes with appositional closure in 3 to 4 quadrants (P = 0.0164).

Conclusions: Under dark conditions, more than one third of fellow eyes of APAC showed appositional angle closure after LPI. The anatomic findings indicate a narrower angle, a more anterior position of the ciliary body, and a thicker peripheral iris in fellow eyes of APAC after LPI may be associated with an increased risk for progressive angle closure.