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Editors Selection IGR 15-2

Clinical Examination Methods: Blood Flow: Factors affecting Ocular Blood Flow

Comment by James Tan on:

74076 The effects of antioxidants on ocular blood flow in patients with glaucoma, Harris A; Gross J; Moore N et al., Acta Ophthalmologica, 2018; 96: e237-e241

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This paper reports ocular blood flow findings in open angle glaucoma (OAG) patients receiving a fixed dietary supplement containing vitamins (C, E, B6, B12, folate), minerals (magnesium), and agents considered to be heart-healthy (omega-3 fatty acid, flaxseed oil) and to have antioxidant properties (gingko bilobaextract, bilberry fruit extract, taurine, alpha lipoic acid, N-acetylcysteine, grape seed extract). The hypothesis was that dietary supplementation with this 'optic nerve formula' would have a beneficial effect on ocular hemodynamic parameters of retinal and retrobulbar blood flow. The study design was a randomized, double blind, placebo-controlled, cross-over study of 45 subjects with OAG.

After treatment with the dietary supplement for a month, peak systolic and end diastolic velocity of blood flow in retrobulbar vessels were significantly higher compared with placebo controls based on non-invasive measurements (e.g., ultrasound and laser Doppler flowmetry). An accompanying reduction in vascular resistance was seen in central retinal and short posterior ciliary arteries in the treated group. Mean blood flow in superior and inferior temporal retinal arteries and recruitment of retinal capillaries was also higher in the treated group (p<0.05 for all significant differences). Daytime IOP and ocular perfusion pressure readings were found to be similar between the groups. The hemodynamic findings were captured following a relatively long period (1 month) of using the supplements.

Whether the hemodynamic observations are accompanied by functional and structural differences are further important questions to answer, especially in the context of progressive glaucoma

These observations are in line with previous reports of lower blood volume, flow and velocity in regions of the neuroretinal rim, temporal peripapillary retina and retrobulbar vessels in OAG (and normal tension glaucoma) patients compared with normal controls. The present study did not define OAG by IOP level. Concurrent use of glaucoma and other systemic medications in both groups may have confounded hemodynamic observations, although randomization is expected to have minimized this effect. In future studies it would be interesting to know if non-glaucomatous eyes show similar responses to those reported for OAG eyes. Whether the hemodynamic observations are accompanied by functional and structural differences are further important questions to answer, especially in the context of progressive glaucoma.

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