AIM: To assess the relation between central retinal artery (CRA) resistive index (RI) and retinal nerve fiber thickness measured by optical coherence tomography (OCT) in assessment of disease progress in cases of open angle glaucoma. METHODS: Twenty-three patients with diagnosed open angle glaucoma were included in this study. They were examined by colored duplex ultrasonography of CRA with estimation of RI of CRA and ophthalmic artery (OA) with estimation of CRA/OA RI ratio as well as OCT measurement of the average retinal nerve fiber layer (RNFL) thickness in order to assess the disease progress. RESULTS: There was strong inverse relation between the increased RI in CRA as well as the increased CRA/OA RI ratio and the decrease in average RNFL thickness in cases of open angle glaucoma. CONCLUSION: Assessment of CRA RI can indirectly assess the vascular changes associated with glaucoma and can assess the degree of retinal atrophy helping in evaluating prognosis thus guiding the choice of treatment.