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Editors Selection IGR 11-2

Blood Flow: Diurnal fluctuation of blood flow parameters

Comment by Alon Harris on:

23802 Diurnal fluctuation of ocular blood flow parameters in patients with primary open-angle glaucoma and healthy subjects, Pemp B; Georgopoulos M; Vass C et al., British Journal of Ophthalmology, 2009; 93: 486-491

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Ever increasing evidence suggests that ocular blood flow deficits may be linked to glaucomatous optic neuropathy. Recent studies have also shown that diurnal fluctuations of intraocular pressure (IOP), blood pressure and ocular perfusion pressure (OPP) may occur in patients with primary openangle glaucoma (POAG). Considering the diurnal and nocturnal variability of these risk factor, this is therefore a topic of emerging importance. Pemp et al. (703) present a pilot investigation describing the diurnal fluctuations of two ocular blood flow parameters in 15 patients with POAG and 15 healthy controls. Measurements of ocular fundus pulsation amplitude (FPA) using laser interferometery and laser Doppler flowmetry (LDF) to measure choroidal and optic nerve head blood flow were included. Examinations were performed on the same eye at 08:00, 12:00, 17:00 and 21:00 in a darkened room in a seated position. The authors report that most of the outcome variables showed significantly larger fluctuations in patients with POAG compared to healthy controls. These changes were not associated with OPP or IOP. Changes over time correlated among the different ocular hemodynamic outcome measures in patients with POAG, but not in the control subjects.

There is a growing body of evidence that vascular dysregulation and fluctuation of ocular blood flow occur in glaucoma patients

One strong point of this investigation was the use of two imaging technologies to investigate the ocular circulation. Although FPA and LDF have limitations, the use of more than one imaging device sampling multiple ocular tissue beds is always recommended. Another strength is the attempt to stabilize hemodynamic conditions at each diurnal reading, utilizing repeated blood pressure measurements. A limitation of the current study is the small sample size (n = 15; each group) examined. Confirmation of these findings requires a much larger sample with appropriate statistical justification. Another limitation was the use of systemic hypertension treatments which were not excluded from the study populations. An additional confounding factor in the interpretation of the study results is that control subjects were not receiving IOP reducing therapies, while POAG patients were measured under a variety of hypotensive treatments.
These findings contribute to the growing body of evidence that vascular dysregulation and fluctuation of ocular blood flow occur in glaucoma patients.

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