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Sonja Wamsley, MD, MPH; B’Ann T. Gabelt, MS; David B. Dahl, MS; Gary L. Case, PhD; Robert W. Sherwood, BS; Christian A. May, MD; M. Rosario Hernandez, DDS; Paul L. Kaufman, MD

Arch Ophthalmol. 2005;123:64-70.

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 µmol/L (range, 3.0-88.6 µmol/L) vs 6.7 µmol/L (range, 2.8-87.4 µmol/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.

Author Affiliations: Departments of Ophthalmology and Visual Sciences (Drs Wamsley and Kaufman and Ms Gabelt) and Biostatistics and Medical Informatics (Mr Dahl), University of Wisconsin Medical School, Madison; Peptide Synthesis Facility, University of Wisconsin Biotechnology Center, Madison (Dr Case); Biotechnology Resource Center, Cornell University, Ithaca, NY (Mr Sherwood); Department of Anatomy, Friedrich Alexander University, Erlangen, Germany (Dr May); and Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, Mo (Dr Hernandez).

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