The purpose of this prospective study was to test the hypothesis that blood flow autoregulation in the optic nerve head has less reserve to maintain normal blood flow where there is a blood pressure induced decrease in ocular perfusion pressure compared to an intraocular pressure induced decrease. They measured the optic nerve head blood flow in two groups of anaesthetised primates, one group had their blood pressure reduced by administration of pentobarbital, the second group had their intraocular pressure increased via an anterior chamber reservoir. Their results showed that optic nerve head blood flow was significantly different between the two groups, showing a greater decline in the blood pressure group. This vulnerability of the optic nerve head to low blood pressure adds to the evidence related to the haemodynamic pathophysiology in glaucoma and ophthalmologists should take this into account in the clinical setting.

Optic nerve head blood flow response to reduced ocular perfusion pressure by alteration of either the blood pressure or intraocular pressure.
Wang L, Cull GA, Fortune B.
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Khadijah Basheer

Moorfields Eye Hospital, London, UK.

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