Ocular: Sclera And Episclera Flashcards
What is apart of the fibrous tunic:
Sclera and cornea
What is the tenon’s capsule?
-transparent layer of fascia on top of the episclera in the bulbar region
-“a potential space” between the conj and episclera (dr naja said this)
What does the tenon’s capsule form?
A socket that allows the globe to move
What is the episclera?
Thin but IMPORTANT vascular layer on top of the sclera
What is the sclera?
dense connective tissue layer that provides the globe with structure and support
What does the sclera provide attachment for?
EOM insertions into the globe
What is the limbus?
Transitional band of tissue running 360 degrees around the cornea
What does the limbus contain?
Corneal stem cells
conjunctival does not course _________ AT ALL meaning that it does not cover the entire _____
Posteriorly, globe
Is the sclera vascular?
NOOOO
Is episclera vascular?
YESSSS
Order of layers from anterior to posterior on the scleral side of the limbus:
-conj epithelium
-conj stroma
-tenons capsule
-episclera
-superficial episcleral plexus
-deep episcleral plexus
-sclera
Another name for the tenon’s capsule:
Fascia bulbi
What perforates the tenon’s capsule?
EOM tendons as well as vessels and nerves
Where is the tenon’s capsule the thickest?
Equator
How is equator situated?
Anterior to posterior NOT nasal to temporal
Orbital fat prolapse:
Benign protrusion of intraconal and extraconal orbital fat
(“I would know this”)
What is responsible for keeping the intraconal fat from migrating?
Tenon’s capsule
If intraconal fat migrates anterior, what is likely responsible?
Weak tenon’s capsule
Sub-tenon’s injection
An injection into the space between the episclera and sclera delivered when there is severe inflammation to the entire eye
-(we don’t do this in practice)
Episclera is a _____, ______, _________ tissue layer
Slim, loose, connective tissue layer
The episclera becomes _______ posterior to the rectus muscle insertions
Thinner
What can make episcleral veins more prominent?
Elevated episcleral venous pressure
When episcleral network becomes congested what happens?
-Limbus has a rose coloration
-corneal inflammation
-iris dysfunction
Anterior episcleral vessels:
Anterior ciliary arterial branches
Posterior episcleral vessels:
SPCA branches
What do episcleral veins drain aside from blood? Where does it drain into?
Aqueous humor from schlemm’s canal, superior ophthalmic vein
Episcleral arterial circle is ________ to MACI
Superficial
What vessels are responsible for ciliary flush?
-anterior ciliary arteries connected to the episcleral arterial circle
What is seen in ciliary flush?
Dilated, deep conjunctival and episcleral vessels around the cornea
What is inflamed in conjunctivitis?
Conjunctival plexus
What is inflamed in episcleritis?
Superficial episcleral plexus
What is inflamed in scleritis?
Deep episcleral plexus
How does sclera get the few nutrients that it needs?
Diffusion!
-inner surface from uveal vessels
-outer surface from deep episcleral vessels
Are there capillary beds in the sclera?
NO, but many vessels pass through
What are Anteiror scleral aperatures for and where are they?
Anterior ciliary vessels, at the limbus
Anterior scleral foramen is a space for what?
Cornea
Which muscle does not have two anterior ciliary arteries (ACAs)
Lateral rectus
Intrascleral nerve loops
LPCN in the suprachoroidal space that flips on itself and forms a dark spot in the sclera
Middle scleral aperatures are ______ _____ passageways
Vortex vein
Posterior scleral aperatures allow what to pass through:
-SPCA
-SCN
Posterior scleral foramen is a passage for the ____ _____
Optic nerve
Rectus muscles furthest to closest in relation to the limbus:
-SR
-LR
-IR
-MR
**SLIM
Spiral of tillaux
Imaginary ring connecting the recti muscle insertion points
SR insertion distance
7.7
LR insertion distance
6.9
IR insertion distance
6.5
MR insertion distance
5.5
Where is the thickest par tif the sclera and how thick is it?
Surrounding the optic nerve, 1mm
Where is the thinnest part of the sclera and how thick is it?
Just posterior to rectus muscles, 0.3mm
Thickness of sclera at the limbus:
0.75mm
What is the path of the rectus tendons?
Penetrate the tenon’s capsule and episclera and merge with the sclera (EOM collagen and sclera collagen intertwine)
Lamellae
Bundles of collagen fibrils
Fibrils
Aggregates of parallel collagen
What is the predominant collagen type in sclera stroma?
Type I
Fibroblasts:
-Produce and degrade proeoglycans and collagen
-pull fibrils into parallel bundle (lamellae)
