Laser iridectomy influence on anatomical and functional characteristics in primary angle-closure glaucoma and relative papillary block
PURPOSE: To research the effect of laser peripheral iridectomy (LPI) on anatomical, topographical and functional indicators in primary angle-closure glaucoma with relative pupillary block. METHODS: We examined 20 patients (34 eyes) with primary angle-closure glaucoma (PACG) and relative pupillary block. Stages of glaucoma: I - 28 eyes, II - 3 eyes and III - 3 eyes. Ophthalmologic examination included viso- metry, biomicroscopy, gonioscopy, tonometry, perimetry, ophthalmoscopy, ultrasound biometry. All patients underwent a single-stage LPI with the use of laser Nd:YAG SYL-9000 Premio (“LightMed”, Taiwan). To investigate the depth and volume of the anterior chamber we used Pentacam HR (“Oculus”, Germany). To investigate anatomic and topographic relationships of anterior chamber angle and iridocilliary zone structures we used ultrasound biomicroscopy (UBM) on UBM Hi-scan (“Optikon”, Italy). Obtained measurements included the anterior chamber depth (ACD), trabecular-iris angle (TIA), trabecular-iris distance at 500 micrometers (TID), trabecular-ciliary process distance (TCPD), iris-ciliary processes distance (ICPD), cross-sectional area posterior chamber. We measured viscoelastic properties of the corneoscleral capsule of the eye and intraocular pressure with Ocular Response Analyzer (“Reichert”, США). RESULTS: LPI in patients with relative pupillary block in PACG leads to an increase in anterior chamber volume by 19.57 mm <sup>3</sup> on average and practically doesn't change its depth. According to UBM an increase in the TIA was noted in all cases after LPI, on average by 17.49° temporally, and 16.52° nasally; TID increased on average by 0.21 microns from the temporal and 0.18 microns from the nasal side; TCPD increased on average by 0.09 microns from the temporal and 0.07 microns from the nasal side; ICPD decreased on average by 0.08 microns from the temporal and 0.12 microns from the nasal side. After LPI posterior chamber cross-sectional area decreased by 0.25 mm <sup>2</sup> temporally and 0.27 mm <sup>2</sup> nasally. LPI lead to intraocular pressure lowering of 3.29 mm Hg on average. CONCLUSION: UBM revealed specific anatomic and topographic features of the iridocilliary zone structures, inherent relative pupillary block in PACG, and their change after LPI. Increase of TIA and TID values, decrease of ICPD and the posterior chamber cross-sectional area values explain the increase in anterior chamber volume and the invariance of its depth reference value. LPI carried out in at patients with PACG and relative pupillary block, leads to an improvement of the functional space of the iridocilliary zone structures and a decrease in perfusion pressure.