Retinal/Choroid Vascular Physiology (F) Flashcards
What is the vasculature that forms from the optic nerve head? 1. What do the vertical sprouts from the superficial plexus give rise to? 2
- primary vascular plexus
2. inner capillary plexus
Where do long and short posterior ciliary arteries first coalesce?
mesenchymal meshwork adjacent to the primitive RPE
When does substantial interarterial anasamosing occur during development?
4th month
What does the ophthalmic artery split into that supply the eye?
- central retinal artery (CRA, 2)
2. ciliary arteries (CA, 3)
What artery provide oxygen and nutrients to the inner retina?
central retinal artery
What arteries providesoxygen and nutrients to the RPE and outer retina (photoreceptors)?
ciliary arteries
Are retinal vessels innervated? 1. Is the choroid? 2
- no
2. yes
What is the percentage of O2 is delivered to the retina by the choroid? 1. Percentage of glucose? 2. Percentage of blood flow? 3
- 65%
- 75%
- 4%
What is the percentage of O2 is delivered to the retina by the choroid? 1. Percentage of glucose? 2. Percentage of blood flow? 3
- 65%
- 75%
- 4%
How is the foveola nourished?
through choroid only
What cells are tight junctions found in regards to the blood vessels of the retina?
endothelial cells
What is the superficial glia sheathed by? 1. What are the inner plexuses sheathed by? 2
- astrocytes
2. Muller cells
Are blood vessels of the choriocapillaris fenestrated?
yes
What are transported via transcellular mechanisms in the RPE?
nutrients and vitamin A
What mediates glucose transport (transcellularly) into retinal vasculature endothelial cells? 1. Where are these located? 2
- GLUT1
2. luminal and abluminal membranes
What are the major complications are associated with pathology of the inner retina and inner blood-retinal barrier?
- Loss of pericytes, and capillaries
- Increased tortuosity of retinal capillaries
- Microaneurysms
- Plasma protein leakage
- Neovascularization (advanced)
What is it called when the retina of premature infants are exposed to excess O2?
retinopathy of prematurity
What is it called when the retina of premature infants are exposed to excess O2?
retinopathy of prematurity (abnormal vascularization)
What is 90% of total glucose utilized by retina converted to?
lactate
Does the retina have higher metabolism in the light or dark?
dark
What is blood flow in the retina and choroid a function of?
muscular tonus of the arterioles and the state of contraction of the pericytes (because no sphincters)
What does an increase in lactate lead to?
Vasodilatory response
What does an increase in lactate lead to?
Vasodilatory response
What determines if light induces vasodilation or vasoconstriction?
presence of nitric oxide
What is a reduction in blood oxygen that preferentially affects the outer retina?
hypoxia
What does hypoxia cause in the retina? 1. How does it do this? 2
- Causes vasodilation in the retina and increases blood flow
- Due to release of retinal lactate and endothelium derived nitric oxide
What does hyperoxia cause in the retinal arterioles? 1. In the choroid? 2. What mediates these responses? 3
- Causes vasoconstriction of the retinal arterioles
- Choroidal blood flow does not change with increase in pO2
- ET-1 receptors (endothelin -1) in the retina
What does hypercapnia cause in the retina? 1. In the choroid? 2. What mediates these responses? 3
- Causes vasodilation in the retina and increases blood flow and decrease pH
- increases blood flow in the choroid
- endothelial release of prostaglandins and Nitric oxide
What does hypercapnia cause in the retina? 1. In the choroid? 2. What mediates these responses? 3
- Causes vasodilation in the retina and increases blood flow and decrease pH
- increases blood flow in the choroid
- endothelial release of prostaglandins and Nitric oxide
What is is the mean blood pressure in the ophthalmic artery minus the blood pressure in the central retinal vein called?
mean perfusion pressure driving blood through the retina
What does high IOP cause in the retina?
- Inner retina pO2 is unaffected due to autoregulation
2. Outer retina blood flow and pO2 decreases
What are the metabolic components that are tone relaxing? 1. Tone contracting? 2
- lactate, prostaglandins, and nitric oxide
2. Endothelin-1
What are the two mechanisms of production of nitric oxide (and where do each exist)?
- NOS1 (expressed in retinal neurons = ganglion, amacrine, horizontal, muller, photoreceptors, RPE)
- NOS3 (endothelial cells of the retina and choroidal vessels and pericytes of the retinal capillaries, and endothelium of optic nerve head)
Where is Endothelin-1 expressed in the eye?
endothelium, retinal neurons, astrocytes, and pericytes
What are prostaglandins mediated by?
adenyl cyclase and inhibition of calcium flux in smooth muscle cells
What are prostaglandins mediated by?
adenyl cyclase and inhibition of calcium flux in smooth muscle cells
What does sympathetic innervation do to the choroidal blood flow? 1. What is it mediated by? 2. What is it stimulated by? 3
- reduces choroidal blood flow
- vasoconstrictive alpha-receptors in smooth muscle cells
- neurotransmitter neuropeptide Y (NPY)
What does parasympathetic innervation do to the choroidal blood flow? 1. What is it mediated by? 2. What is it stimulated by? 3
- increases choroidal blood flow
- vasodilation
- acetyl choline, vasoactive intestinal peptide (VIP), PACAP, and NO
What acts as a modulator of synaptic transmission in vasodilation in the retina and choroid?
adenosine
