Fluorophotometric Study of the Effect of Cataract Surgery and Trabecular Micro-Bypass on Aqueous Humor Dynamics, Preliminary Results

Abstract

Purpose:: To evaluate the short term hipotensive efficacy and changes in aqueous humor dynamics of Glaukos iStent^® in combination with cataract surgery in primary open angle glaucoma (POAG) and ocular hypertensive (OHT) patients.

Methods:: Prospective, randomized, clinical evaluation study. 31 eyes of 31 patients diagnosed of POAG or OHT, IOP >17 mm Hg and <31 mm Hg if taking glaucoma medications and IOP >21 mm Hg and <35 mm Hg after washout with cataract were included. Subjects were randomized to group 1: two micro stents and cataract surgery (n=16) or group two: cataract surgery alone (n=15). Study visits included measurements of IOP (at one and three months after surgery), aqueous flow, outflow facility determined by fluorophotometry (at one month after surgery) (Fluorotron Master, COHERENT, Palo Alto, California), pachymetry and anterior chamber volume by Pentacam (Oculus Optikgeräte GMBH, Wetzlar, Germany).

Results:: Preoperatively no differences between both groups were found in demographic characteristics, mean IOP (24.1+/-1.75 mmHg versus 23.8+/-1.75 mmHg; p=0.51) and trabecular outflow facility determined by fluorophotometry (Ct) (0.128+/0.026 µl/min/mmHg versus 0.13+/-0.068 µl/min/mmHg; p=0.6). After surgery, statistical significant differences beetween both groups were found as follows: mean IOP at one month (16.7+/-2.9 mm Hg versus 19.13+/-1.6 mm Hg respectively, p=0.01, two patients in group 2 were receiving glaucoma medication) and at three months (15.13+/-2.4 mmHg versus 19.08+/-3.4 mmHg; p<0.001, three patients in group 2 were receiving glaucoma medication); mean percentage IOP reduction at one month (30.72 % versus 19.38 %; p=0.01) and at three months (37.4 % versus 19.53 %; p<0.001), Ct one month after surgery (0.64 (0.4-0.98) µl/min/mmHg versus 0.359+/-0.124; p=0.02) and increased Ct percentage (371 % versus 144.24 %; p=0.02). Aqueous humor flow rate: no differences were found between groups (p=0,43). Anterior chamber volume was significantly different after surgery in both groups (p<0,05).

Conclusions:: The available data suggest that Glaukos iStent^® in combination with the extraction of cataract and implantation of IOL significantly lowers IOP by increasing the trabecular outflow facility. Longer follow up is needed to assess the long-term hypotensive efficacy.

Clinical Trial:: www.clinicaltrials.gov NCT00326066

Keywords: intraocular pressure • outflow: trabecular meshwork • aqueous