exam 1 Flashcards
what is the average horizontal visible iris diameter
11.8 mm
cornea is 11 high and 12 mm across
contacts sizes
soft
large scleral
RGP
soft - 13 -14
large scleral 17 mm
RGP 9 mm
what does prolate mean
what does hyperprolate mean
what causes it
steeper in the center and flatter in the periphery
hyperprolate= ketaconus
what does oblate mean
what causes it
flatter in the center and steeper in the periphery
caused by lasik prk coldera shape
what is coldera shape
caused by lasik
steeper on the peripher and flatter in the center
average thickness of cornea
center
near limbus
center - 530 microns or 0.530 mm
near limbus - 710 microns
cornea is steeper in the ________ and thicker in the _________
it is more curved anterior or posterior?
steeper in the center and thicker in the periphery
more curved posterior
what are the curvatures of the anterior and posterior
postiero 6.5 mm More curved
anterior 7.8 mm less curved
refracting power of eye
- cornea
- lens
-eye as a whole
- cornea - 45 D
- lens - 20
-eye as a whole - 65
chondroitin sulfate and dermatan sulfate are examples of what
where are they located
ground substance of stroma layer
what is fleischer ring
iron deposit at base of cone for keratoconus
name the layers of cornea
and thicknes
epithelium
-50 microns (10%)
bowmens layer
-10 microns
stroma
-500 microns (90%)
endothelial
-5 microns thick
-single cell layer (cell are 5 microns thick and 20 microns long)
what is macular dystrophy
results of too many GAGs (keratan sulfate- the most abundant gag usually)
autosomal recessive
name the three layers of cells of K epithelium
what is the percent of the cornea doe the epithelium make and thickness
1.superficial
2. wing
3. basal
what does basal cells secrete
Basement membrane
where are the fibroblasts of the cornea found and what is it called
where are they found
decrease in number as you move where
kerotinocytes
make collagen proteoglycan
inbetween lamallae of stroma
decrease in number as you move more posterior to the stroma
surface cells replaced by what cell
basal cells, wing cells, and peripheral and limbal cells
vitamin A deficiency causes what
keratinized epithelium of cornea
what has more microvilli the cornea or conjunctivi
cornea
where are microvili and microplicae located
epithelium Superficial
microvili is fingerlike microplicae is ridgelike
glycococalyx
what secretes it
what does it confer
what does it join
what secretes it
-superficial cells plasma membrain
what does it confer
-hydrophilic prop on anterior surface of euperficial epithelial cells
what does it join
-mucous layer of tears
nothing can go inbetween what cells
it instead goes where
which cell has responsibility of proper fluid exchange
superficial cells for both answers
it goes between them
tear film works with what to make a smooth optical surface
superficial surface layer
what cells of the epithelium are joined together with desmosomes gap junctions and adherens
what about tight junction
what cells are joined together with desmosomes gap junctions and adherens
-basal
what about tight junction
-superficial
describe the size and layers of the different cells of the k epithelium
Basement membrane
- layer of what cells
single layer basal cells
flat posteriorly
ground substance
where is it found?
what is it?
where is it found?
stroma
what is it?
amorphous gel
composed of GAGS, proteins, collagen
what cells of epithelium have the ability to divide
basal cells on the basement membrane
how does basal cells attatch to basement membrane or basal lamina
what cells secretes
basement membrane
glycocalyx
BM - basal cells
glycocalyx - plasma membrane of superficial cells
where are cornela stem cells
1 m around limbus
what is the corneal epithelium turn over
keratocytes turn over
cornea epithlium - 7 days
keratocytes turn over - 2 - 3 years
bowmans layer
- how thick
-describe what it consists of
-does it regenerate
10 microns thick
- how thick
10 microns
-describe what it consists of
random collagen fibrils and proteoglycans
-does it regenerate
no
what is kerotacan
where is it found
protein in stroma associated with kerton sulfate
what layer is not needed in the cornea
bowmans
the alger brush makes sure you do not penetrate what layer
bowmans
what does the stoma contain
what part of the sclera does it attach to
collagen keratocyes
and ground substance
attaches to anterior sclera
which layer has fibrils and which has bundles
bowmans and stroma
stoma has the bundles = lamellae
what is corneal plana
flat cornea caused by mutated keratocan protein (stroma)
stromal collagen
what percent constitutes DRY weight of cornea
size and arangement of fibrils
total lamellae
what percent constitutes DRY weight of cornea
- 70%
size and arangement of fibrils
-25-30 nanometeres
-parallel to corneal surface
amount of lamellae
-lamellae are bundles of fibrils
-200-300
keratocyte
what are they
% of the cell layer it resides in
turn over?
where are they found?
where are they found in highest frequency?
what are they
-fibroblasts that make collagen and proteoglycan in stroma
% of the cell layer it resides in
-2-3% of stoma
turn over?
-2 - 3 years
where are they found?
-inbetween lamellae
where are they found in highest frequency?
anterior stroma
what is the difference between Stromal Lamellae for ….
anterior
posterior
anterior (1/3)
-lamellae are thin
-branch interweave (crosslink - more rigid)
posterior (2/3)
-lamellae are thicker moving more posteriorly
-form thin layer that binds to decements
what is sclerocornea
scleralization of cornea caused by mutated keretocan protein in stroma
what is the basement membrane of the corneal endothelium
how often does it get produced
does it regenerate
descemet membrane
it is always being produced and increases in thickness as you get older
it regenerates
what is the main purpose of proteins in the stroma
bind with water to space fibrils exactly
what is Lumican and where is it found
what happens if your deficient
protein in stroma
important for collagen spacing, and collagen sizing
no lumican = cloudy, 3 X increase in light scatter maximal increase to posterior stroma , thick fibrils in posterior stroma
does it regenerate?……..
descemet membrane
bowmans
endothelial
DEScemet membrane
-DOES regenerate
bowmans
-no regeneration
endothelial
-no regenation
what is bullous keratopathy
decrease in cell density of endothelial
whose job is to pump
endothelium
what happens as endothelial cells die
neighboring cells change shape and increase in size
what are guttae and what are the different classifications for it
protusions of the descemets membrane
- fuchs
- surrounding epithelial cells are abn
-central
causes swelling - hassall henle bodies
-surrounding epithelial cells are norm
-periphery
-normal to have
-identical to fuchs histopathologically
cornea strives to be what % water
if it changes by ____ % edema will occur or light scatter
78
5% or more will cause edema or light scatter
what is deturgescence
process the stroma does to dehydrate to kept it transparent
turgid vs turbid
turgid = swollen
turbid = opaque
turgid leads to turbid
what two layers function as diffusion barriers to tears and aqueous
how do they do this
endo and epithelium
sites of active ion transport inducing osmotic water movement out of stroma
what produces swelling pressure that pulls water in stroma
proteoglycan
what layers have role in hydration?
what do they do and how does it do it
which has the primary role of maintaining transparency?
_____Epithelium________
- ion pumps
pumps ions through cells
- aquaporins
2 way osmotic water transport
nothing goes inbetween them only through
_____endothelium _______
-ion transport systems
counteract imbibition of water
**primary role of maintaining transparency ** loss will = increased imbibition
what happens when there is loss or damage of endothelial cells
increased imbibition of water
what forms vascular arcade of limbus
what does it branch from
anterior cilliary artery
ophthalmic artery
neovascular stages
what are ghost vessels
emptying of blood vessels when you remove CL that has caused neovascularization
how is oxygen supplied to cornea
diffusion from tear fluid which gets it from the air
also from
-aqueous
-limbal capillaries
what happens when cornea is hypoxic
lactate produced
increase in H ions so decrease in pH (acid)
loss of K
cells shrink
it causes corneal edema
compare swelling when using CL at night…..
conventional hydrogel CL
silicone hydrogel CL
conventional hydrogel CL
-8% -15%
silicone hydrogel CL
- 4 % (same as non CL wears)
NERVES of cornea
what nerve provides perilimbal nerve ring
compare the amount of nerve endings to skin
what are the sensory nerve derived from
where do nerves terminate
what layers do not have nerves
where do they enter
NERVES of cornea
- what nerve provides perilimbal nerve ring
- long ciliary nerves - compare the amount of nerve endings to skin
-400 - 500 X more in K - what are the sensory nerve derived from
-ciliary nerve which branches from V1 (ophthalmic branch) - where do nerves terminate
- wing cells - epithelium - what layers do not have nerves
-basement membrand and endothelium - where do they enter
-stroma where they are demylinated and then begin to branch
Nerves of cornea….
influence what of the cornea
Loss of corneal anesthesia & nerve endings lead to
influence what of the cornea
-metabolism
-tissue maintence
Loss of corneal anesthesia & nerve endings lead to
-loss of integrity
-cell adhesion
-decreased mitosis
-epitheliam permeability
-decreased wound healing
neurotrophic keratitis
causes what
caused by what
causes what
- stromal melting
-perforation
caused by what
-HSV HZV
proparacaine
how long does it take to work
how long does it last
how long does it take to work
-30 seconds
how long does it last
-15 min
what is A and B disease
scattering of an incident ray of light by each _____________ collagen fibril irs canceled by interference from other scattered ray
collagen fibril
compare mono dispersed media vs polydisperse media
monodispersed media (cornea like) has increased light transmission and less spatial dispersion compared to poly disperse (sclera like)
what is destructive interference
a good thing
spacing of fibers + index of refraction
Lumican deficient stromas displayed ___________ X backscatter light with maximal increase confined to ____________
Lumican deficient stromas displayed _____3______ X backscatter light with maximal increase confined to _____posterior stroma_______
dry eye is when tear film is hypo or hyper osmolarity
hyper
refracting power of cornea in air vs water
how can we improve vision under water
air is about 47
water is about 6.3
loses its refractive power
improve it by accomodation or make pupil smaller by increasing depth field
what is the refractive index of cornea
1.376
visible wavelenths are betweenwhat
ultra violet and infrared
lesser/greater amounts of UV are absorbed by cornea as wavelength decreases
greater
uvc is how many nm
200-290
describe how the eye transmits/absorbs ate different wave lengths
200-300 nm
- cornea absorbs (cellular elements)
300-400 nm
-cornea transmits and lens absorbs
corneal action spectrum peaks at what wavelength
what wavelength is the cornea most sensitive
what is produced when the cornea absorbs this wavelength
270 nm
260 - 270nm (UVR - ultraviolet radiation)
when absorbed it creates ROS = dangerous
UVR radiation number
what part of cornea absorbs
what can be a line of defense
260-270 ultraviolet
epithelium and bowmans layer
ascorbate (vitamin C)
what is photokeratitis
UVR injury snow blindness welders keratitis sunlamps
usually delayed for about 8 to 12 hrs from exposure
welders have _____ times the maximum permissible exposure of UV even with helmets
4-5
what prevents leaking of tears to cornea
what prevents leaking of aqueous humor to cornea
what prevents leaking of tears to cornea
- tight junctions (zonula occludens) in the epithelium
what prevents leaking of aqueous humor to cornea
-tight junctions (macula occuldens) of endothelium
what is more leaky epi or endothelium
why is this beneficial
how does it happen
endothelium
because aquous humor supplies nutrients
10 nm wide intercellular space created by macular occludens
where is the site of epithelial stem cells
palisades vogt
(transition of cornea to sclera - highly vascularized papillae)
what doe ion transporters do
where are they located
what ions are major driving forces
transport water osmotic gradients down its concentrationfrom stroma to
-tear film
-anterior chamber
in epi and endothelium
Cl- and Na +
how do ions move across epithelium vs endo
where does cornea get its glucose
aqueous humor thorugh leaky endothelial cells
what happens to pH with lactate
increase in H + ions so decrease in pH(acid)
loss of K
cells decrease in size
what stimulates production of matrix and enhances adhesion when the epithelium is is healing
growth factors
(EGF epithelium growth factor)
(TGFB transforming growth factor)
what is one of the most important metabolic pumps
how many are there and where are they
what inhibits it
what increases it
Na/K ATPase
basolateral side of epithelial
3 million on single cell
inhibited by Ouabain (cardiac glycoside) = corneal swelling & cytokines
increased by steriod
compensatory pumps
when do they start being made
where are they
when does the mechanism fail
compensatory pumps
when do they start being made
-2000 - 270 cells/mm2
where are they
-endothelial cells
when does the mechanism fail
-500 cells/mm2 or less
-cells to flat to add sprinkles
-stromal edema (such as with fuchs)
name factors that can alter endothelial pumps
-Na/K inhibitorys
-carbonic anhydrase inhibitors
-low cell density
-low temp
what regulates differentiation and prolifferation of epithelium cells
growth factors
what are bullae
how to tread
bullae is formed when epithelial cells have edema and lift from basement membrane it causes this.
looks like cyst
treat with muro128 or 5% sodium chloride
describe epithelaial edema & stromal edema
describe corneal sx
dsaek and dmek only replaces endothelium, can also just remove descemets membrane and be fine just takes long
what are khodadoust lines
white blood cells on endothelium rejection line fro cornea graft rejection
What cell has a turn over of 2-3 years
Keratinocytes
what cells have centripetal movement
what layer does this involve
limbal and peripheral cells
what is plalisades of vogt
vascularized papillae at transition of cornea and conjunctiva
site of epithelial stem cells
how long does differention of basal cells to surface cells take
7-14 days
what is desquamation
slough of epithelial cells
what are the effects of wound in epithelium and what is the purpose of it
- edema
(increase flow of fluid due to disrupted junction and pumps) - loss of protective barrier
both caused by epithelium junction damage
describe basic wound healing steps in epithelium
- injury
- cells slide
- mitosis
- cells attach to basement membrane
describe what happens right after injury to epithelium
- mitosis stops
- Growth factors from stroma and epi come
- desmosome dissociate
- wound edges develope filopodia (migration of cells)
importance of adhesion molecules in wound healing
no hemidesmosomes present so this is used for leadign edge of epi sheets to adhere to BM
what provides provisional matrix when epi wound healing
when does it occur
fibronectin
right after injury (first stage)
where doe epithelial cells attatch to when healing
fibronectin matrix
when does proliferation start again
when does it stop
what regulates it
after migration of cells
stops after normal density is established
regulated by growth factors
epithelium is healed quickly ( 60 -80 microns/ hr) unlesssss what
the basment membrane is involved which can take months to heal
corneal erosion is caused by what
treatment?
- EBMD epithelial basement membrane dystrophy
- preve trauma or abrasion
weakly adhered epi cells
treatment is debriding or removing epithelium
what happens when bowman membrane is injured
it is replaced not regenerated
replaced by
1. epithelim
2. stroma like fibrous tissue (fibroblast and connective tissue form scar)
what are the wound healing steps in stroma
include important cells
- destruction
- remove bad tissue with polymorphonuclear leukocytes (PMN) but also macrophages proteoglycanases collagenases - synthetic
- fibroblast make new collagen and proteoglycans, closure of wound - remodel
-initial scar turns more clear change in organization of collagen
what cell maintains balance of destruction and synthesis of ECM
keratocytes
what happens to keratocytes when there is an injury
1.they increase in number
2. they change into myofibroblasts (can change back after heal
-these produce EXCM degrade
collagen and have cytokines
-bed contraction
- cause scar
whats stronger scar in stroma or normal uninjured stroma
normal stroma
polymorphonuclear leukocytes (PMN) improtant for
destruction phase of stroma repair
what steps occur when descemets membrane is injured
regenerated via stromal keratocyes or endothelium
how does the endothelium repair
do the endothelium cells divide
it usually compensated with hypertrophy or limited migration
it doesnt usually divide but can with injury
what is the purpose of fuchs crypts
it allows deeper access to deeper stroma (IRIS)
pupillary margin rests where
anterior to lens
and anterior to iris termination
what is the thinnest part of the iris and how thin is it
where is it in regards to the ciliary body
iris root
0.5 mm thick
it sits anterior to ciliary body
what is iridodialysis
what is rubeosis iridis
_______Iridodialysis __________
iris root breaks and iris dissociates
caused by trauma
causes bv damage and nerve damage
______rubeosisi iridis _________
(neovascularization of iris)
what layer of iris
is absent at crypts
is continuous with ciliary body
has Blood vessels
forms iris processes near ciliary body
has sphincter muscles
has fibroblasts and lymphocytes mas and macrophages
is absent at crypts
-anterior border
is continuous with ciliary body stroma
has Blood vessels
stroma
forms iris processes near ciliary body
anterior border
has sphincter muscles
stroma
has fibroblasts and lymphocytes mas and macrophages
-stroma
what encircles iris bloodvessels
where is the minor circle of iris
are iris capillaries finestrated
what is part of the blood aquous barrier
where is the major circle of iris found
what encircles iris blood vessels
-collagen to help it stay put and to prtect against kink
where is the minor circle of iris
-in stroma
are iris capillaries finestrated
-no
what is part of the blood aquous barrier
-iris capillaries
where is the major circle of iris found
-cilliary body near iris root
where is the sphincter muscle
how many motor segments and how is it innvervated
stroma in pupillary zone
20 motor seg each individually innervated innervated by parasympathetic
name the three grooves found on the back side of iris
- radial contraction furrow
- structure fold of schwabe
- ciliary contraction folds
the arcades originate from what
what does it go through
originates from minor arterial circle
goes towards pupil through sphincter
name the layers of iris
anterior border layer
stroma
iris sphincter, vasculature
stroma
iris dilator
anterior epithelium
posterior epithelium
sensory innervation of iris
sympathetic
para sympathatic
_____Sensory_______
nasociliary - uvea
_____sympathic _____
fibers from superior cervical ganglion to iris dilator
_____parasympathetic____
fibers from ciliary gangion to sphincter
what is iris bombe
synechia posterior causes increase in pressure and pushes iris forward
what has the most pigment anterior or posterior epi
which has columnar cells
which has cuboidal cells
which has basment membrane coverage. what else does it cover
whch has myoepithelil cells
what has the most pigment anterior or posterior epi
-posterior
which has columnar cells
-posterior
which has cuboidal cells
-anterior on apical side
which has basement membrane coverage. what else does it cover
-posterior, also covers posterior chamber
whch has myoepithelil cells
-anterior
equation for finding the degree of variation in size
standard deviation/ mean
normal numbers for
polymegathism
pleomorphism
density
polymegathism
- coefficient variaion (CV)
<40 and 25%
pleomorphism
-hex
>50% 70-80%
density
25000
epithelium innervated by
endo innvervated by
epi short and long ciliary nerve
endo not inervated
Most abundant GaG
Keratan SULFATE too
