Evaluation of plasma glutamate levels in normal tension glaucoma

Abnormal metabolism of the neurotransmitter glutamate is implicated in a number of neurodegenerative conditions. Patients with migraine have been shown to have elevated plasma glutamate levels. Migraine is a risk factor both in terms of prevalence and progression in normal-tension glaucoma (NTG). The aim of this study was to determine whether or not plasma glutamate levels are also elevated in NTG.

Patients were recruited into 2 groups, NTG and control, according to inclusion and exclusion criteria. Patients with migraine were excluded from both groups. Fasting blood samples were collected in lithium heparin tubes, transported on ice, and centrifuged for storage at -21 degrees C. Plasma glutamate levels were measured by an amino acid analyser. Data for each group were compared by applying the Mann-Whitney test. Ethical approval and independent statistical advice for the study was obtained.

A total of 27 subjects were recruited: 14 to the NTG group and 13 to the control group. No significant difference was found between the plasma glutamate levels in the 2 groups (p = 0.67).

Although an association between normal tension and migraine is recognized, unlike studies in migraine sufferers, this study finds no evidence that patients with NTG have elevated plasma glutamate.