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 a cid implant (DS with RHAI) using ultrasound biomicroscopy (UBM). Setting: Eye Clinic, Department of Neurological and Vision Sciences, Univer sity 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 a nd UBM study were performed 1, 3, 6, and 12 months postoperatively and ther eafter at 6 month intervals. Eleven parameters were evaluated, the most imp ortant of which were IOP, surgical success in lowering IOP to 21 mm Hg or l ess with or without additional medical therapy, UBM appearance of the site of DS with RHAI, size of the decompression space, presence of a filtering b leb and supraciliary hypoechoic area, and scleral reflectivity around the d ecompression space. Results: After a mean follow-up of 11.4 months +/- 4.7 (SD), the mean perce ntage 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]O P less than 21 mm Hg; however, 7 of these eyes (23%) required additional IO P-lowering medical therapy. The operation failed in 6 patients (20%) despit e additional therapy. Ultrasound biomicroscopy revealed a reduction in the size of the decompression space from 6 months postoperatively and its disap pearance 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 wa s present in 18 patients (60%), a supraciliary hypoechoic area in 18(60%), and hyporeflectivity of the scleral tissue around the decompression space i n 14 (47%). These 3 UBM characteristics were detected singly and in various combinations. The simultaneous presence of all 3 characteristics in the sa me eye correlated significantly with a higher surgical success rate (P =.00 4). Conclusions: Ultrasound biomicroscopy showed that filtering bleb formation was frequent in eyes having DS with RHAI but that it was not the only surgi cally induced IOP-lowering mechanism, increased uveoscleral and transsclera l filtration may be equally important.