Ultrasound biomicroscopy in diagnosis of intraocular blocks in patients with primary closed-angle glaucoma

Purpose
To study anatomo-topographic relations of structures in the iridociliar zone in Uzbekistan patients with different pathogenesis of the block of the anterior chamber angle (ACA) in primary closed-angle glaucoma (CAG).

Material and methods
We examined 92 patients of Uzbek nation (161 eyes) with hyperopic type of eyeball (axial length is less than 23 mm). The main group comprised 72 patients (125 eyes) with primary CAG. Control group included 20 healthy people (36 eyes) without glaucoma with transparent lens).
In addition to routine tests, we used gonioscopy and ultrasound biomicroscopy which were performed by ultrasound biomicroscope Humphrey 840. We measured 8 parameters using C.Pavlin’s method and calculated section area of the posterior chamber.

Results
Significant (p<0.001) anterior position of the ciliary body, shallow anterior chamber (1,60±0,04 mm) and closure of ACA with joining of the root iris zone to the cornea were typical of all patients with CAG. We found specific feature of spatial relations of structures in the iridociliar zone typical of either, one or another mechanism of ACA block. Main differences were pronounced in parameters and configuration of the posterior chamber. Patients with relative pupil block had preserved triangle shape of the posterior chamber with significant (р<0,001) increase in depth (0,65±0,01 mm) and section area (by 1.3 times) as compared to the norm. Patients with flat iris syndrome preserved triangle shape of the posterior chamber but the latter was partially filled with ciliary processes displaced forward, thus its parameters in height (0,46±0,01 mm) and length (2,46±0,03 mm) significantly (р<0,001) differed from those in the norm and the group with pupil block. Calculated area of the posterior chamber free of ciliary processes was significantly decreased being two times less than in healthy people and 2.7 times less than in patients with pupil block. UBM revealed symptoms of the block induced by the lens. In these cases, the posterior chamber lost correct triangle configuration with significant р<0,001) decrease in section area by 1.3 times as compared to the norm and by 1.8 times as compared to relative pupil block. The distance «iris– lens» also (p<0.001) decreased to 0,21±0,01 mm and was less than the norm (0,33±0,01 mm) and cases with relative pupil block (0,37±0,01 mm).

Conclusions
UBM revealed qualitative and quantitative signs of intraocular blocks depending on pathogenetic mechanisms of ACA block that allowed grounded treatment of primary CAG.