Ultrasound biomicroscopy and intraocular-pressure-lowering mechanisms of deep sclerectomy with reticulated hyaluronic acid implant

Purpose: To evaluate the anatomic characteristics and intraocular pressure (IOP) lowering mechanisms of deep sclerectomy with reticulated hyaluronic acid implant (DS with RHAI) using ultrasound biomicroscopy (UBM). Setting: Eye Clinic, Department of Neurological and Vision Sciences, University of Verona, Verona, Italy. Methods: Thirty patients with primary open-angle glaucoma not controlled by medical therapy had DS with RHAI in 1 eye. A complete ocular examination and UBM study were performed 1, 3, 6, and 12 months postoperatively and thereafter at 6 month intervals. Eleven parameters were evaluated, the most important of which were IOP, surgical success in lowering IOP to 21 mm Hg or less with or without additional medical therapy, UBM appearance of the site of DS with RHAI, size of the decompression space, presence of a filtering bleb and supraciliary hypoechoic area, and scleral reflectivity around the decompression space. Results: After a mean follow-up of 11.4 months +/- 4.7 (SD), the mean percentage reduction in IOP compared to preoperatively was 38% (from 26 +/- 4.5 mm Hg to 16.2 +/- 3.8 mm Hg; P =.0001), Twenty-four patients (80%) had an]OP less than 21 mm Hg; however, 7 of these eyes (23%) required additional IOP-lowering medical therapy. The operation failed in 6 patients (20%) despite additional therapy. Ultrasound biomicroscopy revealed a reduction in the size of the decompression space from 6 months postoperatively and its disappearance in 2 cases, The difference in size at the last follow-up and at 1 month postoperatively (maximum length 2.41 +/- 1.02 mm versus 3.53 +/- 0.51 mm) was significant(P =.0001).At the last examination, a filtering bleb was present in 18 patients (60%), a supraciliary hypoechoic area in 18(60%), and hyporeflectivity of the scleral tissue around the decompression space in 14 (47%). These 3 UBM characteristics were detected singly and in various combinations. The simultaneous presence of all 3 characteristics in the same eye correlated significantly with a higher surgical success rate (P =.004). Conclusions: Ultrasound biomicroscopy showed that filtering bleb formation was frequent in eyes having DS with RHAI but that it was not the only surgically induced IOP-lowering mechanism, increased uveoscleral and transscleral filtration may be equally important.