Autoregulation of human optic nerve head blood flow in response to acute changes in ocular perfusion pressure

Abstract• Background: Studies in animals have demonstrated that optic nerve head (ONH) blood flow (Fonh) is autoregulated, but there is a lack of evidence for such a process in humans. Therefore, we investigated the relationship between Fonh and mean ocular perfusion pressure (PPm) in normal volunteers when PPm is decreased through elevation of the intraocular pressure (IOP). • Methods: Laser Doppler flowmetry (LDF) was used to measure relative mean velocity (Velohn), volume (Volonh) and Fonh of blood at sites of the ONH away from visible vessels, while PPm was decreased in two ways: (1) rapidly, by IOP increments of 15 s duration, and (2) slowly, by IOP increments of 2 min duration, both by scleral suction cup in one eye of each of nine subjects. • Results: A rapid and large decrease of PPm of more than 100% induced a decrease of more than 80% in Fonh. With the slower decrease in PPm Fonh remained constant down to a PPm of ≃22 mm Hg (IOP=40 mm Hg) and then decreased, predominatly due to a decrease in Velohn. Immediately after removal of the suction cup, Fonh increased transiently by 44% above baseline. • Conclusions: This study demonstrates efficient blood flow autoregulation in the OHN, which is probably brought about by an increase in vascular capacitance. The magnitude of the reactive hyperaemia agrees with the compensatory decrease in ONH vascular resistance during IOP elevation. The time scale of the autoregulatory process and the dependence of the hyperaemia upon duration of IOP elevation suggest a metabolic mechanism of autoregulation.

[1]  B L Petrig,et al.  Laser Doppler flowmetry in the optic nerve. , 1992, Experimental eye research.

[2]  C E Riva,et al.  Autoregulation of retinal circulation in response to decrease of perfusion pressure. , 1981, Investigative ophthalmology & visual science.

[3]  Douglas R. Anderson,et al.  Dynamic response of optic nerve head blood flow to increased intraocular pressure , 1996 .

[4]  D. R. Anderson,et al.  Blockage of axonal transport in optic nerve induced by elevation of intraocular pressure. Effect of arterial hypertension induced by angiotensin I. , 1983, Archives of ophthalmology.

[5]  M. Kaliner,et al.  Measurement of multiple microcirculatory parameters in human nasal mucosa using laser-Doppler velocimetry. , 1989, Microvascular research.

[6]  C E Riva,et al.  Laser Doppler measurement of relative blood velocity in the human optic nerve head. , 1982, Investigative ophthalmology & visual science.

[7]  Douglas R. Anderson,et al.  Distribution of axonal transport blockade by acute intraocular pressure elevation in the primate optic nerve head. , 1977, Investigative ophthalmology & visual science.

[8]  D. R. Anderson,et al.  Effect of elevated intraocular pressure on blood flow. Occurrence in cat optic nerve head studied with iodoantipyrine I 125. , 1983, Archives of ophthalmology.

[9]  R. Aaslid,et al.  Cerebral autoregulation dynamics in humans. , 1989, Stroke.

[10]  B. Petrig,et al.  Optic Nerve Head Laser Doppler Flowmetry: Principles and Computer Analysis , 1996 .

[11]  April Rasala Lehman,et al.  A Guide to Statistical and Data Analysis Using JMP and JMP IN Software , 1999 .

[12]  D. Newell,et al.  Assessment of cerebral autoregulation dynamics from simultaneous arterial and venous transcranial Doppler recordings in humans. , 1991, Stroke.

[13]  S. Hayreh The pathogenesis of optic nerve lesions in glaucoma. , 1976, Transactions. Section on Ophthalmology. American Academy of Ophthalmology and Otolaryngology.

[14]  A. Bill,et al.  Effects of raised intraocular pressure on retinal, prelaminar, laminar, and retrolaminar optic nerve blood flow in monkeys. , 1979, Investigative ophthalmology & visual science.

[15]  B. Petrig,et al.  Effect of decreased ocular perfusion pressure on blood flow and the flicker-induced flow response in the cat optic nerve head. , 1996, Microvascular research.

[16]  C E Riva,et al.  Blue field entoptic phenomenon and blood velocity in the retinal capillaries. , 1980, Journal of the Optical Society of America.

[17]  Paris Vii Rapid Autoregulation of Cerebral Blood Flow: A Laser-Doppler Flowmetry Study , 1992 .