[Studies of mechanism of primary angle closure glaucoma using ultrasound biomicroscope]

Abstract

Objective: To investigate the mechanism of primary angle closure glaucoma (PACG) especially the role of the changes of ciliary body using ultrasound biomicroscope (UBM) combined with general A scan.

Method: 99 eyes with PACG, including 50 eyes with acute and 49 eyes with chronic PACG, were evaluated and 58 normal eyes were in the control group.

Results: Compared with the normal eyes the PACG eyes had their anatomic features. They had a smaller corneal diameter, shorter axial length, shallower anterior chamber, thicker lens, more relative anterior location of lens, swelling of ciliary process and anterior rotation of ciliary body. All these differences were significant statistically (P < 0.05). Compared with the chronic PACG eyes the acute PACG eyes had a shallower anterior chamber and a more anteriorly situated lens position. The differences were significant statistically (P < 0.01). Compared with the normal eyes the acute PACG eyes had a shorter ciliary body - lens distance and the difference was significant (P < 0.05); the chronic PACG eyes also had a shorter ciliary body-lens distance, but the difference was not significant (P > 0.05).

Conclusions: The PACG eyes have their anatomic features. Among these factors the pupillary block caused by the anterior displacement of lens and the narrow angle induced consequently are the common mechanism. The swelling ciliary process, the positional changes of the ciliary body and age-related thicker lens are possibly the initial causes causing the forward movement of lens, and the pupillary block plays a more important role in the pathogenesis of acute PACG.