Sclera Flashcards
Fibroblasts , collagen, proteoglycans are all found in what ?
Cornea/sclera/iris
sclera
Scleara has __% of water __% dry weight
A) 70-30
B) 80-20
C)50-80
D)70-10
70-30
75% of they dry weight is
(Fibroblasts/collagen/proteoglycans) fiber
collagen
Type __ collagen is able to resists tension and is also found in bone and tendon
A) 3
B) 4
C)1
D)5
type 1
T/F type 4 collagen is found is the most abundant and is found in bone and tendon
F type 1
Like the cornea the sclera is also _______ except for the superficial vessesl fo the episclera and the intracleral vascular plexus
avascular
Which two places are exceptions of where there is vascularization in the sclera
episclera,
intrascleral vascular plexus
intrascleral vascular plexus is located (posterior/anterior) to the limbus
posterior
Overlying the sclera is the _____
episclera
The posterior sclera contains the scleral _____ and the _________ for passage of the optic nerve.
canal
lamina cribrosa
Passage for the long and short posterior ciliary arteriers , short ciliary veins, ciliary nerves, vortex veins are all perforated sites on the (anterior/posterior) sclera
posterior
Tendonsof the recti muslces insert into the (deep/superficial) sclera collagen
superficial
T/F 5% of the total surface are of the globe comes from the sclera
F. 95%
sclera thickness (increase/decreases) towards the equator and (increases/decreases) near the optic nerve
decreases
increases
The mean scleral thickness is ___ at the corneascleral limbus and ____ at the equator
A) 0.40 - 0.39
B) 0.53-0.29
C)0.53-0.39
D)0.40-0.29
- 53mm
0. 39mm
Average scleral fiber ranges from ___to ___ nm
A) 25-400
B) 35-230
C)25-230
D)35-400
25-230
Corneal fiber diameter is ___(abnormal/uniform)__ at 25 mm
uniform
T/F collagen fibers of the sclera are arranged in bundles , and are parallel
F. corneal fibers are parallel not scleral
scleral fibers only arranged in bundles
What are the three distinct fiber types in the sclera fiber system
elastic, elaunin, oxytalan
Vision deprivation in a patient can cause axial (elongation/shortness) of teh ocular globe cuasing (myopia/hyperopia)
elongation
myopia
Changed in rate of proteoglycan synthesis and accumulation within the sclera can cause (hyperopia/myopia)
myopia
With increase in age the sclera undergoes a progressive (regeneration/degeneration) of collagen and elastic fibers -and a (gain/loss) of GAG -and scleral (hydration/dehydration) -and accumulation of which two (calcium/potassium/lipids/ions)
all of these cause:
(increase/decrease) in tissue density
sclera (thickness/thinning) and yellowing
(decrease/increase) sclera elasticity
degeneration
loss
dehydration
calcium/lipids
increase
thinning
decrease
Stroma of the sclera is devoid of ______ however it does allow the passage of ____
innervation
nerves
The _(parasympathetic/sympathetic)\_\_ scleral spur cell innervation is present only in cynomolgus monkesy but seems to be absent in humans but (parasympathetic/sympathetic) are .
sympathetic
parasympathetic
Which type of innervation is absent or rare in both monkeys and humans?
cholinergic innervation
Why has there been a resent interest in transcleral delivery of molecules and drugs to potentially treat posterior segment disease??
due to the difficulty reaching therapeutic conecntration of a drug transcorneally
T/F intravitreal or intravenous delivery may achieve therapeutic concentration and has no side effects
F. it may have unwanted side effects
Transcleral delivery of drugs primary mechansim is diffusion through (lipid/aqueous) pathway?
aqueous
Tissue hydration
tissue thickness
size and volume fraction of proteoglycans present
all are controlling ______ rates
diffusion
the sclera swells least near a pH of __
A) 3
B) 4
C)1
D)5
4
What two functions have been studied that affect the swelling or hydration of the sclera ?
pH and ionic strength
Surgical thinning (increases/decreases) sclera permeability
increases
Age, cryotherapy, diode laser treatment do NOt alter sclera (rigidity/permeability)
permeability
Change of IOP 15 to 60 mm Hg can (increase/decrease) sclera permeability to small molecules by half
decrease
scleral permeability is a (weak/strong) funciton of transsceral pressure
weak
scleral permeabiliyt is a (weak/strong) funciton of molecular weight
strong
with increased molecular weight and radius, scleral permeability (increases/decreases)
decreases
When the sclera is exposed to various prostaglandins in organ culture there is (increased/decreased) permeability
This causes an (increase/decrease) expression of matrix metalloproteinases
increased
increased
The (increase/decrease) in sclera permeability may be one mechanism by which prostaglandins (increase/decrease) IOP when used topically.
increase
decrease
Taking advantage of thinner regions of tisuee
Increasing sclera hydration
Transient modificatoin of sclera ECM
–are all ways for (small/large) molecules to be deliver ______
large
transclerally
Changd in the ________ parameters of the sclera had rather small effects on teh permability of small compounds , such as conventional drugs
physiochemical
