A Colour Doppler Study of Retrobulbar Blood Flow Parameters in Patients of Primary Open Angle Glaucoma: A Case Series from India

Abstract

Objectives: This study compared the blood flow velocities in Ophthalmic Artery, Central Retinal Artery and Short Posterior Ciliary Arteries using Colour Doppler Imaging in patients of POAG and healthy subjects and assessed the effect of reducing the intraocular pressure in POAG patients on retrobulbar blood flow. Background: Present definition of ‘Primary Open Angle Glaucoma’ considers raised intraocular pressure (IOP) as one of the risk factors for this disease. Association of alterations in ocular blood flow has been considered another risk factor, Moreover the eye being treated for glaucoma could be a part of wider systemic dysfunction of auto-regulation of ocular blood flow. This hypothesis is further backed up with the recognition of normal tension glaucoma as a clinical entity and observation of progressive glaucomatous damage despite IOP control. This study was, thus, undertaken to study retrobulbar blood flow using colour Doppler imaging (CDI) in patients of glaucoma and to see how the control of IOP affected these parameters. Methods: This is a prospective cohort study involving 43 freshly diagnosed patients of POAG and 30 controls. Peak systolic velocity (PSV) and mean end diastolic velocity (EDV) and resistivity index (RI) were studied in ophthalmic artery (OA), in central retinal artery (CRA) and short posterior ciliary arteries (SPCA). Values were compared with those of normal controls and also pre and post treatment among patients of POAG. Results: Mean PSV and EDV were found to be significantly low in OA and CRA only in patients of POAG compared to controls. Once target pressure was achieved, blood flow parameters were similar to non glaucomatous eyes. Conclusions: Blood flow in retrobulbar vessels is reduced among glaucomatous eyes as compared to the normal population. Once target pressure is achieved, blood flow parameters become similar to non glaucomatous eyes suggestive of improved blood flow as a function of reduced IOP. Colour Doppler imaging is not found to be reliable for measuring blood flow in SPCA. Role of RI as a true measure of resistance to blood flow is unclear.