To introduce a rapid and objective electrophysiological technique that can assess visual function in the magnocellular pathway, which is thought to be affected in early-stage glaucoma.

The clinical study will evaluate a novel instrument designed to record visual evoked potentials elicited by stimuli determined in prior research (Greenstein et al., 1998; Badr et al., 2003) to drive select visual pathways that exhibit glaucomatous damage in an efficient and automated manner. The results obtained with this novel device will be compared with results obtained using an existing commercial device. Statistical results, sensitivity and specificity, will be generated for the assessment of the accuracy of the test to discriminate glaucoma patients from controls. Repeatability of the test will also be analyzed based on the test-retest results.

Visual evoked potential (VEP) is a measure of neural function in the eye and brain. Three skin electrodes are placed on the surface of the scalp to record the electrical activity from the brain while the subject is observing a flickering stimulus with isolated-check/dot pattern. The whole procedure is non-invasive and the risks are negligible.

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.

Inclusion Criteria:

• Age: 40 - 75 years old
• Visual acuity: 20/30 or better

Exclusion Criteria:

• Eye disease other than glaucoma