Ocular: Uvea - Choiroid Flashcards
What percentage of blood flow to the eye goes to the choroid?
85%
What is the suprachoroid?
A thin connective tissue layer that merges with the sclera and is a point of rapid branching of vessels that have pierced the sclera
Where is the choroid firmly attached to the sclera?
Where the SPCA enter and where the vortex veins exit
Where are the ciliary nerves located?
In the suprachoroidal space
What is the suprachoroidal space?
A potential space between choroid and sclera that continues anteriorly with the supraciliary space
What is the lamina fusca?
Innermost layer of the sclera that is separated from the uvea by the suprchoroidal/supraciliary space
What is the choroidal stroma?
A vascularized connective tissue where collagen fibrils surround vessels in a circular pattern
What cells are located in the choroidal stroma?
-melanocytes
-fibroblasts
-immune cells
What is the choriocapillaris?
-An anastomosing capillary bed with wide lumen diameter (20-50microns)
-single layer of endothelial cells with fenestrations (mostly on retinal side)
-directly nourishes RPE
Where is the choriocapilaris the most dense?
Under the macula
What helps you control the flow in the choriocapillaris?
Contractile Pericytes
What is the lobular arrangement of the choriocapillaris?
-arteriole branch enters center of each lobule
-venules form periphery of lobules
How is the choroid innervated?
Short ciliary nerves and branches
Where does sympathetic innervation to the choroid come from? What does it cause?
Superior cervical ganglion, vasoconstriction
Where does parasympathetic innervation to the choroid come from? What does it cause?
Pterygopalatine ganglion, vasodilation
What are intrinsic choroidal neurons? What do they do for the choroid?
-local autonomic regulation of thermal and mechanical stimuli
-release vasodilators (nitric oxide and VIP)
Choroidal vessel tiers from outer to inner choroid (larger to smaller in size):
-Hallers layer (larger arteries where veins converge on ampullae)
-sattlers layer(feeding arterioles)
-choriocapillaris (single layer capillary bed)
Blonde fundus:
less pigmented choroid where vessels are more exposed
What is the bruch’s membrane?
A compound basement membrane composed of elastin and collagen between RPE and choriocapillaris BMs
How many layers and in the bruch’s membrane?
5 layers total
What is seen in the collagenous layers of the bruch’s membrane?
Proteoglycans and GAGs surrounding various collagen sub-types
Order from the sclera stroma inward:
-sclera stroma
-lamina fusca/suprachoroid
-hallers layer
-sattlers layer
-choriocapillaris
-bruch’s membrane
-RPE
How thick is the bruch’s memnbrane?
3 microns
What happens to transport across bruch’s membrane as you age?
Decreased membrane transport of water and waste —> accumulates in RPE and cause lipofuscin accumulation
What are the five layers of bruch’s membrane? Inner to outer
-BM of RPE
-inner collagenous layers
-elastic layer
-outer collagenous layer
-choriocapillaris BM
What is a drusen? And where are they located?
Accumulation of cellular fragments and basal laminar material within inner collagenous layer of bruch’s membrane
What is choroidal neavascularization?
- a break in bruch’s membrane
-creates an abnormal growth of blood vessels from choroid to retina
-wet vs dry AMD
Normal transport across the choroid -> retina:
-nutrients from choroid to RPE/neural retina
-water and waste metabolites go from neural retina to choroid (get rid of wastes)
What happens when transport is decreased between choroid and retina?
-Lipofuscin accumulates within the RPE
-lipids build up in bruch’s
-lipid stops nutrient input to retina and passage of water impeded
What are the functions of the choroid?
-deliver oxygen/nutrients to photoreceptors/RPE while removing waste metabolites
-prevent backscatter of light towards retina
What is the function of the suprachoroidal space?
Passageway for vessels and nerves (LPCN) heading anteriorly
What is Nevus?
-focal concentrations of melanocytes that occur in 4-8% of Caucasian’s
-benign but need monitored for malignant transformation
-USE RED FREE FILTER to determine if choroidal or a chirpy (spelling idk)
What governs the flow in the choroid?
Starling forces
What pressure is the IOP in the eye?
Hydrostatic pressure
What does a severe drop in IOP during surgery cause?
-decrease in tissue hydrostatic pressure
-leads to bulk flow of fluid from choroidal capillaries into tissues
-causes massive choroidal edema
Other casues of effusions that aren’t surgery:
-inflammatory conditions ->increase vessel permeability -> edema
-ruptured vessel = hemorrhagic effusion
Where do most vessels enter the choroid?
From the sclera posteriorly
Choroidal effusion causes the choroid to be _____________ to the sclera anteriorly
Less adherent
What happens in regard to the choroid during hypotony?
Choroid more likely to detach from the sclera anteriorly due to effusion
What happens to vortex veins during choroidal effusion?
There is a lack of anastomoses between the vortex veins during—> edema cannot drain to other vortex veins —> localized appearance
Is choroidal effusion a retinal detachment issue?
NOOOOO
