Isolated-Check/dot Stimuli of about 10 Hz with luminance contrast of 10%, 15%, -10%, and -15% will be used to test each eye. Eight samples for each stimulus will be recorded. Each experimental run takes 2 seconds. The T-circ statistical method is performed to process the data, and the VEP signal to noise ratio (SNR) is calculated in order to obtain an optimized condition (stimulus and threshold) to separate glaucoma patients and normal group.