Surgical site characteristics after CLASS followed by ultrasound biomicroscopy and clinical grading scale: a 2-year follow-up.

Objective: This study describes the imaging of the filtering area in CO laser-assisted sclerectomy surgery (CLASS) using ultrasound biomicroscopy (UBM) combined with the Indiana Bleb Appearance Grading Scale (IBAGS) and evaluates the mechanism by which CLASS lowers the intraocular pressure (IOP).

Methods: Twenty-eight cases (28 eyes) of primary open-angle glaucoma that could not be controlled by drugs underwent CLASS. At 1, 3, 6, 12, 18, and 24 months after surgery, IBAGS was used to evaluate the external morphology of the filtering blebs, and UBM was used to describe and measure their internal structure.

Results: During the early period after CLASS, most cases showed diffuse filtering blebs with a serious degree of congestion. At the end of follow-up, most cases did not present filtering blebs. All patients showed an intact and thin trabeculodescemetic membrane (TDM) with an average thickness of 0.094 ± 0.017 mm. The scleral reservoir size gradually decreased over time and tended to stabilize after 18 months. At 3 and 6 months after surgery, 53.57% of the patients had abnormalities in the TDM area, and after laser goniopuncture treatment, the scleral reservoir became slightly larger and the IOP decreased. The TDM thickness was not correlated with postoperative IOP, and the scleral reservoir size was negatively correlated with IOP.

Conclusion: During the early phase after CLASS, the subconjunctival and suprachoroidal pathways may be the main mechanisms lowering IOP; over time, internal drainage pathways such as the intrascleral, trabecular-meshwork, and suprachoroidal pathways play greater roles in lowering IOP.