Ocular: Sclera And Episclera 2 Flashcards
How are Corneal lamellae stacked?
Perpendicularly on top of each other
How are collagen arranged in sclera?
Random interweaving to help with strength and flexibility
What does sclera look opaque?
Because light is scattered
Are there more or less collagen fibroblasts in the sclera when compared to the cornea?
Less
What are the gags in the sclera? And are there more of less in he sclera compared to cornea?
-dermatan sulfate and chondroitin sulfate
-less gags bc less hydrated
What makes up the elastin in the sclera?
Fibrillin
What does a mutation in fibrillin cause?
Marfan’s syndrome which is thinning/stretching of the sclera
What can thinning/stretching of the sclera lead to in the eye?
High myopia and potentially posterior staphyloma
An OCT of a very myopic person would be ___ shaped
U shaped
Collagen synthesis in myopes __________
Decreases
An eye is myopic typically due to…
Longer axial length
In myopia scleral ________ are lost
Proteoglycans
OVERALL in myopia the sclera _____ and ________
Thins and weakens
Sclera is thin and distensible until age ___
3
If you have a thin sclera, and increase in IOP can cause…
Stretching of the sclera and enlarged eye (bupthalmos)
Why does sclera become more rigid as you age?
Corneal cross-linking occurs
Color of sclera in newborns:
Blue/grey
Color of sclera as you increase in age
Mild yellowish hue due to lipid degeneration
Color of conj/sclera due to liver disease
Yellow
Color of sclera in osteogenesis imperfecta
Blue
Osteogenesis imperfecta is a deficiency in what? What does it cause?
-Type I collagen
-causes the sclera to not be opaque and uveal structures become visible
Ehlers-danlos syndrome
-Hereditary connective tissue disorder that manifests clinically with skin hyper-elasticity, hyper-mobility
-casues blue sclera
Melanocytosis
Excessive melanocytes in skin and parts of the sclera
Oculodermal melanocytosis causes an increased risk for _________
Melanoma
Scleral hyaline plaques are caused by:
-UV exposure along with wear and tear from nearby rectus insertions
-causes scleral thinning (blue/grey color)
Innervation of anterior sclera
LPCN
Innervation of posterior sclera:
SPCN
Vascular supply of sclera:
Post., Middle, and ant aperatures
Where does sclera receive nutrients?
Episcleral and choroidal capillary beds
Functions of the sclera:
-provide globe with internal support and resistance
-provide attachment for EOM insertions into globe
ROC of the sclera
12mm
ROC of the cornea
8mm
The LARGER the radius of sclera =
The flatter
The SMALLER the radius of sclera =
The STEEPER
External scleral sulcus:
-transition between flatter sclera den steeper cornea
**essentially the limbus
Aqueous drainage structures within the internal scleral sulcus:
-trabecular mesh work
-canal of schlemm
Interna scleral sulcus is bounded anteriorly by _____
Cornea
Internal scleral sulcus bounded posteriorly by ___________
Scleral spur
Scleral spur:
inner sclera that contributes and continues to anterior chamber angle
What is scleral spur continuous with anteriorly?
Trabecular meshwork
Posteior scleral spur is the origin of the…
Longitudinal ciliary muscle fibers
Lamina fusca is an inner scleral layer that contains: (cell types)
-many Melanocytes
-MORE elastin fibers
Lamina fusca is the transition zone between…
Sclera and ciliary body/choroid
Lamina fusca contains what?
Suprachoroidal and supracilairy space
Suprachoroidal injection movement:
drug moves within space posteriorly then inward to the retina
Lamina cribrosa:
-meshwork of connective tissue that optic nerve axons and central retinal vessels pass though
Lamina cribrosa is the _________ part of the sclera
Thickest
Lamina cribrosa is ________ interwoven into a combination of different _____________
Elastin, collagen types
Where are the retinal ganglion cells damaged in glaucoma?
Lamina cribrosa
Glaucoma:
increased IOP that causes posterior bowing or thinning as well as pore enlargement and focal defects in lamina cribrosa
If glaucoma is not treated, what happens?
collapse of lamina cribrosa
