Author(s) agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Research Paper RELATIONSHIP BETWEEN OCULAR PERFUSION PRESSURE AND RESISTIVITY INDEX IN THE OPHTHALMIC ARTERY IN BOTH PRIMARY OPEN ANGLE GLAUCOMA AND NORMAL-TENSION GLAUCOMA PATIENTS AND CONTROLS IN A TERTIARY HOSPITAL IN NIGERIA Uwah, Akaninyene Innocent 1 , Elizabeth Akon Awoyesuku 2 and Emmanuel, O. Megbelayin 1 1 Department of Ophthalmology, University of Uyo Teaching Hospital, 2 Department of Ophthalmology, University of Port Harcourt Teaching Hospital, Rivers State, Nigeria. Abstract AIM: To establish the relationship between ocular perfusion pressure and resistivity index in the ophthalmic artery in both primary open angle glaucoma and normal-tension glaucoma patients and controls in a tertiary hospital in Nigeria. METHODS: The study was an observational case-control study conducted between January 2019 and June 2019. One hundred and eight patients (54 glaucoma patients and 54 controls) were consecutively selected into the study. All participants underwent blood pressure measurement by using a standard mercury sphygmomanometer which was validated with a similar sphygmomanometer. Subjects were made to have at least 5 minutes of rest before the systolic and diastolic blood pressures were measured. The also had a Colour Doppler Imaging to measure resistivity index and blood flow velocity in the ophthalmic and central retinal arteries. For comparison between the two groups, all data were subjected to Student T-test. Pearson linear correlation test was performed to study the relationship between resistivity index and ocular perfusion pressure in the glaucoma and control groups. Statistical significance was set at p<0.05. RESULTS: There was a negative relationship between Resistivity Index in Ophthalmic artery and Diastolic Ocular Perfusion Pressure in glaucoma patients and this relationship was statistically significant. (r= -0.319, p=0.019). In controls, there was no significant relationship between Resistivity Index in Ophthalmic artery and Diastolic Ocular Perfusion Pressure (r= -0.015, p=0.914). There was however no statistically significant relationship between Resistivity Index in Ophthalmic Artery and Systolic Ocular Perfusion Pressure in glaucoma Journal of Global Biosciences Peer Reviewed, Refereed, Open-Access Journal ISSN 2320-1355 Volume 10, Number 4, 2021, pp. 8497-8511 Website: www.mutagens.co.in URL: www.mutagens.co.in/jgb/vol.10/04/100401.pdf