Vitreous glutamate concentration and axon loss in monkeys with experimental glaucoma.

OBJECTIVE: To evaluate vitreous glutamate concentration and axon loss in monkeys with experimental glaucoma. METHODS: We induced unilateral chronic glaucoma by means of laser trabecular destruction in 14 rhesus and 6 cynomolgus monkeys. Intraocular pressure (IOP) was monitored weekly. We assessed optic nerve damage clinically and photographically. Vitreous, sampled immediately before enucleation, was analyzed for glutamate concentration by means of high-performance liquid chromatography. We quantified percentage of axon loss after histopathologic sectioning of the optic nerve, compared median glutamate concentration ratios, and assessed correlation of glutamate concentration, axon count, IOP, cup-disc ratio, duration of IOP elevation, and age. RESULTS: Median vitreous glutamate concentration in glaucomatous eyes was 7.0 micromol/L (range, 3.0-88.6 micromol/L) vs 6.7 micromol/L (range, 2.8-87.4 micromol/L) in control eyes. The ratio (glaucomatous to control eyes) was 1.08. We found no significant correlation between vitreous glutamate concentration ratio and any of the other variables. The IOP, disc cupping, and axon loss were correlated. CONCLUSIONS: We found no difference between vitreous glutamate concentration in glaucomatous and contralateral control monkey eyes when the entire data set was examined and no evidence of correlation between vitreous glutamate concentration and axon loss. CLINICAL RELEVANCE: Vitreous concentration of the excitotoxic amino acid glutamate, thought to be associated with retinal ganglion cell death in glaucoma, was not altered in this study.

Results of the use of the Ex-PRESS miniature glaucoma implant in technically challenging, advanced glaucoma cases: a clinical pilot study.

PURPOSE: To report results of implantation of the Ex-PRESS Miniature Glaucoma Implant (Optonol, Neve Ilan, Israel) shunt directly under the conjunctiva in advanced glaucoma. DESIGN: Noncomparative case series. METHODS: Chart review of eleven cases of Ex-PRESS implantation. Outcome measures included intraocular pressure (IOP), complications, visual acuity, and additional interventions. Failure was defined as unacceptably high IOP requiring revision or explantation. RESULTS: Four patients (36%) failed. Ten (91%) experienced hypotony during postoperative week one. In the seven nonfailures, mean pre and postoperative IOPs were 30.3 +/- 9.3 mm Hg and 13.6 +/- 4.4 mm Hg, respectively (P = .006). The logMAR visual acuity did not change significantly from baseline to follow up (logMAR 1.1 +/- 0.9 and 1.4 +/- 0.9, respectively, P = .13). There were no intraoperative complications. Postoperative complications in the 11 eyes included choroidal detachment in 3 (27%) and suprachoroidal hemorrhage in 2 (18%). Of the 7 successful cases, additional interventions were required in 4 (57%). CONCLUSIONS: Despite significant IOP reduction, the incidence of complications following Ex-PRESS implantation directly under the conjunctiva was unacceptably high in this group of patients.