Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease

Abstract

We review the cellular and physiological mechanisms responsible for the regulation of blood flow in the retina and choroid in health and disease. Due to the intrinsic light sensitivity of the retina and the direct visual accessibility of fundus blood vessels, the eye offers unique opportunities for the non-invasive investigation of mechanisms of blood flow regulation. The ability of the retinal vasculature to regulate its blood flow is contrasted with the far more restricted ability of the choroidal circulation to regulate its blood flow by virtue of the absence of glial cells, the markedly reduced pericyte ensheathment of the choroidal vasculature, and the lack of intermediate filaments in choroidal pericytes. We review the cellular and molecular components of the neurovascular unit in the retina and choroid, techniques for monitoring retinal and choroidal blood flow, responses of the retinal and choroidal circulation to light stimulation, the role of capillaries, astrocytes and pericytes in regulating blood flow, putative signaling mechanisms mediating neurovascular coupling in the retina, and changes that occur in the retinal and choroidal circulation during diabetic retinopathy, age-related macular degeneration, glaucoma, and Alzheimer's disease. We close by discussing issues that remain to be explored.

Clinical science effects of different mydriatics on retinal and choroidal parameters in healthy adults observed by widefield swept-source optical coherence tomography

“…Choroidal circulation is primarily governed by signals from the sympathetic and parasympathetic nervous systems. 11 Contrary to theoretical expectations, our research revealed that tropicamide alone and in combination with phenylephrine had a minimal impact on the thickness and vessels of the central and mid-peripheral choroid. These findings are consistent with those reported by lovino et al , 13 Öner et al , 20 Özdemir and Şekeroğlu.…”

“…Phenylephrine, an adrenergic receptor agonist, acts as an alpha-1 adrenergic receptor agonist and mimics sympathetic properties to regulate vascular constriction. Choroidal circulation is primarily governed by signals from the sympathetic and parasympathetic nervous systems 11. Contrary to theoretical expectations, our research revealed that tropicamide alone and in combination with phenylephrine had a minimal impact on the thickness and vessels of the central and mid-peripheral choroid.…”

Clinical science effects of different mydriatics on retinal and choroidal parameters in healthy adults observed by widefield swept-source optical coherence tomography

“…Choroidal circulation is primarily governed by signals from the sympathetic and parasympathetic nervous systems. 11 Contrary to theoretical expectations, our research revealed that tropicamide alone and in combination with phenylephrine had a minimal impact on the thickness and vessels of the central and mid-peripheral choroid. These findings are consistent with those reported by lovino et al , 13 Öner et al , 20 Özdemir and Şekeroğlu.…”

“…Phenylephrine, an adrenergic receptor agonist, acts as an alpha-1 adrenergic receptor agonist and mimics sympathetic properties to regulate vascular constriction. Choroidal circulation is primarily governed by signals from the sympathetic and parasympathetic nervous systems 11. Contrary to theoretical expectations, our research revealed that tropicamide alone and in combination with phenylephrine had a minimal impact on the thickness and vessels of the central and mid-peripheral choroid.…”

Evaluation of retinal vascular density and related factors in youth myopia without maculopathy using OCTA

“…Most of the fovea is an avascular zone characterized by active local metabolism 13 , maintaining the blood flow in a relatively stable state. Previous studies showed no significant difference in the foveal avascular zone (FAZ) area between myopic and control groups, consistent with our results 14 , 15 . Min et al, in contrast, concluded that the FAZ area was significantly larger in the myopic eyes 16 .…”

Relationship between Retinal Vessels and OCT-Derived Retinal Neural Parameters

“…In addition, we found INL was associated with Vessel Area Density. This is consistent with the findings in a previous study 34 , which proposed the retinal vascular network had a more important role for the inner retina, while the oxygen and nutrition supply of the outer retina could rely on the choroid 27 .…”

Clinical science effects of different mydriatics on retinal and choroidal parameters in healthy adults observed by widefield swept-source optical coherence tomography

“…Choroidal circulation is primarily governed by signals from the sympathetic and parasympathetic nervous systems. 11 Contrary to theoretical expectations, our research revealed that tropicamide alone and in combination with phenylephrine had a minimal impact on the thickness and vessels of the central and mid-peripheral choroid. These findings are consistent with those reported by lovino et al , 13 Öner et al , 20 Özdemir and Şekeroğlu.…”

“…Phenylephrine, an adrenergic receptor agonist, acts as an alpha-1 adrenergic receptor agonist and mimics sympathetic properties to regulate vascular constriction. Choroidal circulation is primarily governed by signals from the sympathetic and parasympathetic nervous systems 11. Contrary to theoretical expectations, our research revealed that tropicamide alone and in combination with phenylephrine had a minimal impact on the thickness and vessels of the central and mid-peripheral choroid.…”

Evaluation of retinal vascular density and related factors in youth myopia without maculopathy using OCTA

“…Most of the fovea is an avascular zone characterized by active local metabolism 13 , maintaining the blood flow in a relatively stable state. Previous studies showed no significant difference in the foveal avascular zone (FAZ) area between myopic and control groups, consistent with our results 14 , 15 . Min et al, in contrast, concluded that the FAZ area was significantly larger in the myopic eyes 16 .…”

Relationship between Retinal Vessels and OCT-Derived Retinal Neural Parameters

“…In addition, we found INL was associated with Vessel Area Density. This is consistent with the findings in a previous study 34 , which proposed the retinal vascular network had a more important role for the inner retina, while the oxygen and nutrition supply of the outer retina could rely on the choroid 27 .…”

Clinical science effects of different mydriatics on retinal and choroidal parameters in healthy adults observed by widefield swept-source optical coherence tomography

“…Choroidal circulation is primarily governed by signals from the sympathetic and parasympathetic nervous systems. 11 Contrary to theoretical expectations, our research revealed that tropicamide alone and in combination with phenylephrine had a minimal impact on the thickness and vessels of the central and mid-peripheral choroid. These findings are consistent with those reported by lovino et al , 13 Öner et al , 20 Özdemir and Şekeroğlu.…”

“…Phenylephrine, an adrenergic receptor agonist, acts as an alpha-1 adrenergic receptor agonist and mimics sympathetic properties to regulate vascular constriction. Choroidal circulation is primarily governed by signals from the sympathetic and parasympathetic nervous systems 11. Contrary to theoretical expectations, our research revealed that tropicamide alone and in combination with phenylephrine had a minimal impact on the thickness and vessels of the central and mid-peripheral choroid.…”

Evaluation of retinal vascular density and related factors in youth myopia without maculopathy using OCTA

“…Most of the fovea is an avascular zone characterized by active local metabolism 13 , maintaining the blood flow in a relatively stable state. Previous studies showed no significant difference in the foveal avascular zone (FAZ) area between myopic and control groups, consistent with our results 14 , 15 . Min et al, in contrast, concluded that the FAZ area was significantly larger in the myopic eyes 16 .…”

Relationship between Retinal Vessels and OCT-Derived Retinal Neural Parameters

“…In addition, we found INL was associated with Vessel Area Density. This is consistent with the findings in a previous study 34 , which proposed the retinal vascular network had a more important role for the inner retina, while the oxygen and nutrition supply of the outer retina could rely on the choroid 27 .…”