Ocular Blood Flow Autoregulation Mechanisms and Methods

Abstract

The main function of ocular blood flow is to supply sufficient oxygen and nutrients to the eye. Local blood vessels resistance regulates overall blood distribution to the eye and can vary rapidly over time depending on ocular need. Under normal conditions, the relation between blood flow and perfusion pressure in the eye is autoregulated. Basically, autoregulation is a capacity to maintain a relatively constant level of blood flow in the presence of changes in ocular perfusion pressure and varied metabolic demand. In addition, ocular blood flow dysregulation has been demonstrated as an independent risk factor to many ocular diseases. For instance, ocular perfusion pressure plays key role in the progression of retinopathy such as glaucoma and diabetic retinopathy. In this review, different direct and indirect techniques to measure ocular blood flow and the effect of myogenic and neurogenic mechanisms on ocular blood flow are discussed. Moreover, ocular blood flow regulation in ocular disease will be described.

Retinal Vascular Reactivity in Central Serous Chorioretinopathy

“…27,28 The consequent increase of the OPP triggers neural and hormonal regulatory systems responsible to keep, by vasoconstriction, blood flow constant within the eye. [27][28][29][30] In all the enrolled subjects we obtained a significant increase in BP and OPP during the exercise. However, the response we detected with OCT-A was different in CSCR patients compared to controls.…”

“…33,34 The maintenance of a constant blood flow in the retina seems to be ensured by local autoregulatory mechanisms of myogenic and metabolic nature, as well as by endothelialderived vasoactive substances and by the pericytes themselves. 29,30,35 The relative contributions of these mechanisms in the homeostasis of retinal circulation are ill defined, and the locus of the potential vascular dysregulation in CSCR remains to be elucidated. It could be a primary defect, or instead an end-organ alteration possibly due to systemic hypertension, a recognized risk factor for the disease.…”

Reduced Central Retinal Artery Blood Flow Is Related to Impaired Central Visual Function in Retinitis Pigmentosa Patients

“…It has been hypothesized that anatomical and functional changes in the retinal vessels of RP patients occur secondarily to loss of outer retinal function, possibly due to a hyperoxic state in the inner retina, extracellular matrix thickening, and/or reduced inner retinal metabolic demand due to a decline in trophic factors. 1,2 Longitudinal loss of visual field area over a 3-year period has been significantly correlated with a reduction in the diameter of the retinal arteries and veins adjacent to the optic nerve in RP patients. 1 Reduced choroidal 3,4 and retinal blood flow 5–7 have been documented in either early or advanced stage RP patients compared to normal controls.…”

Diurnal variation of pulse waveform parameters determined by laser speckle flowgraphy on the optic nerve head in healthy subjects

“…Ocular blood flow has an essential role of supplying adequate amount of oxygen and nutrients to the eye. [ 1 ] Blood flow in the optic nerve head (ONH) has been reported to be impaired in some ocular diseases such as glaucoma [ 2 ] and retinitis pigmentosa. [ 3 , 4 ] Thus, the assessment of ocular blood flow is very important for further comprehension of the underlying pathology of ocular diseases.…”