Prevalence and mechanism of appositional angle closure in acute primary angle closure after iridotomy.
OBJECTIVE
A prospective observational case series to assess the prevalence of appositional angle closure in darkness among iridotomized Chinese eyes after acute primary angle closure (APAC) with the use of both clinical methods and ultrasound biomicroscopy.


METHODS
Sixteen Chinese patients who had history of APAC and subsequent successful treatment with laser peripheral iridotomy were examined. Fourteen additional control subjects were studied. Gonioscopy and ultrasound biomicroscopic examination were performed in the dark. Gonioscopic appearance of the angle was assessed, and quantitative measurements of the angle from the ultrasound biomicroscopic images were taken.


RESULTS
Of the APAC eyes 55.6% had appositionally closed angle clinically and in 38.9% only Schwalbe's line was visible on gonioscopy. Ultrasound biomicroscopy confirmed structurally different anterior segments between eyes with APAC and the control eyes. In particular, the trabecular-ciliary-process distances were markedly different between the two groups.


CONCLUSIONS
This study documented a high prevalence of appositional closure in iridotomized eyes after APAC in Chinese patients. The anteriorly positioned ciliary body, as documented in these cases by ultrasound biomicroscopy, is the likely mechanism of the angle crowding in this patient population.
Yeung
Barry Y M
BY
Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China. ymyeung@ha.org.hk
Ng
Philip W C
PW
Chiu
Thomas Y H
TY
Tsang
Chi Wai
CW
Li
Felix C H
FC
Chi
Chung Chai
CC
Lai
Jimmy S M
JS
Tham
Clement C Y
CC
Lam
Dennis S C
DS
D000208:Acute Disease; D000368:Aged; D002924:Ciliary Body / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000601:surgery*; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure; D032801:Iridectomy; D007498:Iris / Q000000981:diagnostic imaging / Q000473:pathology*; D053685:Laser Therapy; D008297:Male; D033401:Microscopy, Acoustic; D011183:Postoperative Complications; D015995:Prevalence; D011446:Prospective Studies; D014129:Trabecular Meshwork / Q000000981:diagnostic imaging / Q000473:pathology*