Fluorophotometric study of the effect of the glaukos trabecular microbypass stent on aqueous humor dynamics

PURPOSE. To evaluate the changes in aqueous humor dynamics and the efficacy and safety of the iStent (Glaukos Corp., Laguna Hills, CA), in combination with cataract surgery. METHODS. This investigation was a prospective, randomized, clinical study in patients with open-angle glaucoma or ocular hypertension who were undergoing cataract surgery. Aqueous flow (F) and trabecular outflow facility (C(T)) were measured by fluorophotometry before surgery and at months 1, 6, and 12 in both groups. RESULTS. Thirty-three eyes of 33 patients were randomized to either two stents and cataract surgery (n = 17, group 1) or cataract surgery alone (n = 16, group 2). Before surgery, F and C(T) were similar in groups 1 and 2 (1.78 +/- 0.44 and 1.74 +/- 0.82 microL/min, P = 0.18; 0.12 +/- 0.03 and 0.13 +/- 0.06 microL/min/mm Hg, P = 0.71, respectively). After surgery, there were no changes of note in F, however, C(T) increased in both groups. At 1 year, C(T) was 0.45 +/- 0.27 microL/min/mm Hg in group 1 and 0.19 +/- 0.05 microL/min/mm Hg in group 2 (P = 0.02), which represented increases of 275% and 46%, respectively. Mean IOP reduction was also greater in group 1 than in group 2 (6.6 +/- 3.0 mm Hg vs. 3.9 +/- 2.7 mm Hg; P = 0.002). The mean number of medications was significantly lower in group 1 than in group 2 (0.0 vs. 0.7 +/- 1.0, respectively; P = 0.007). CONCLUSIONS. Compared with cataract surgery alone, implantation of the iStent concomitant with cataract extraction significantly increased trabecular outflow facility, reduced IOP, and reduced the number of medications at 1 year. Longer follow-up is needed to assess the long-term effect on outflow facility. (ClinicalTrials.gov number, NCT00326066.).