Background: Primary open-angle glaucoma (POAG) is one of the leading causes of blindness worldwide. The death of retinal ganglion cells in POAG is reflected by increased cupping of the optic disc, loss of nerve fiber layer and functional visual field defect. Objective: The aim of the work was to assess the role of Pattern Visual Evoked Potential (VEP) in diagnosis of primary open angel glaucoma. Patients and methods: We studied 40 eyes of 21 subjects, the eyes were classified into 2 groups: Group I included 20 eyes of 11 patients with primary open angel glaucoma and Group II included 20 eyes of 10 normal control (age and sex) matched group. All eyes underwent a full field ophthalmic, OCT and pattern VEP. Results: OCT results showed significant reduction of retinal nerve fiber layer (RNFL) thickness in glaucoma and glaucoma suspect eyes in the majority of quadrants as well as in the average RNFL thickness p < 0.001. The pattern VEP of glaucomatous patient when compared to normal control group reported affection of the VEP by causing both reductions in amplitude and increases in latency. And by statistically analysis of the results that there were highly statistically significant differences between both groups of the VEP measurements (p < 0.001). Conclusion: The pattern visual evoked potential (VEP) has been shown to be sensitive to optic nerve lesions caused by ischemia and glaucoma has also been reported to affect the VEP by causing both reductions in amplitude and increases in latency.