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Brain Activations in fMRI induced by Color Stimulation in Patients with Normotensive Glaucoma

Jan Lešták, Jaroslav Tintera, Lukáš Ettler, Zuzana Svatá and Pavel Rozsíval

Objective: The aim was to find, whether the activations in fMRI induced by black-white and yellow-blue stimulation in patients with normotensive glaucoma will be similar to those in patients with hypertensive glaucoma.
Methods and subjects: The authors examined eight patients with various stages of normotensive glaucoma using functional magnetic resonance imaging (fMRI). The group was compared to a group of eight healthy persons. Measurements were performed on the Philips Achieva 3T TX MR system using the BOLD method. Optical stimulation was provided by black-white and yellow-blue checkered patterns alternated with their negatives with a frequency of 2 Hz. Each measurement consisted of a sequence with five 30-second periods of active phase and five resting periods of the same length. The obtained data were processed by SPM 8 software and general linear model (GLM). The difference in the number of activated voxels when using the black-white (BW) or yellow-blue (YB) stimulations was tested by a t-test. Statistical maps of BW>YB and BWYB differences of patients and controls were thresholded at the uncorrected threshold of p=0.001 and the number of voxels statistically compared by a t-test.
Results: The mean value of the difference in the number of activated voxels when using the BW vs. YB stimulation was only 6% for the patients and 2% for the controls. Both the BW>YB and the BWConclusion: The authors demonstrated that in the patients with normotensive glaucoma there are no corresponding functional changes in the cerebral cortex. Similarly to healthy individuals, the authors did not find differences in activation using BW and YB stimulation. Normotensive glaucoma pathogenetically behaves in a different way compared to hypertensive glaucoma.