The Eye Flashcards
Basal corneal epithelial cells are anchored to Bowman layer by?
Hemidesmosomes
Limbus houses _____ ____ ___ and _______ which link schlemm canal to aqueous veins
corneal stem cells
collector channels
The sclera is vascualr or avascular?
Avascular
What overlies the sclera
Episclera - 2 vascular layesr deep and superficial
The retina has dual circulation - what is it
Inner retina by reintal vessles
Outer retina by choroid
Radius of cornea
8mm
Radium of sclera
12mm
Which is greater in the globe? the equatorial or polar radius
equatorial
What is the anteroposterior diameter of the adult eye
23-25mm
Transverse diameter of adult eye
24mm
Average ACD
3.11mm
Average volume of anterior chamber
220 uL
Posterior chamber colume
60uL
Total volume of adult eye
6.5-7ml
Volume of vitreous gel
5-6ml
Grossly what are the 3 layers ofthe globe
outer protective layer middle vascular inner neural layer
Uvea is made up of
Choroid, Ciliary body, iris
What are the 3 layers of the precorneal tear film
Lipid
Aqoud
Mucin
Lipid layer of pre corneal tear film produced by?
Meibomian gland
Aqueous layer of pre corneal tear film produced by?
Lacrimal gland
Mucin layer of pre corneal tear film produced by?
goblet cells
What mediates the interaction of the mucoaqueous layer with the surface epithelial cells of the corena
Glycocalyx
Is the cornea vascular or avascualr
Avascualr
What are the 5 layers of the cornea
Epithelium
Bowman Layer
Stroma
Descemet
Endothelium
Cornea radius of curvature
7.8mm
Cornea refractive index
1/376
Dioptre power of cornea
43.25
Total refractive power of eye
58.60
Cornea derives nutrients from?
Aqueous humour
Horiszontal diameter of cornea
12mm
Vertical diameter of cornea
11mm
Which is more curved - posterior or anterior surface of the cornea
Posterior
Where is the cornea thinnest
centrally
Where is cornea flatter
in the periphery
Anterior surface of corena is covered by _________ ____ ______ epithelium
Non keratinized
stratified
squamous
How many cells layers is the nonkeratinized stratified squamous epitherlium
4-6layers
How thick is the non keratnized stratifies squamous epithelium
40-50 micormeter
Corneal surface epithelial cells are attached by?
Tight junctions
After injury is Bowman’s layer restored
No forms scar tissues
After injury is Descemet layer restored
Yes
Corneal stroma is _% of total corneal thickness
90%
THe stroma is composed of ______-_____ _____, ground substance and ______ ______
collagen producing keratocytes
collaged lamellae
Ground substance is made up of ?
Proteoglycans
What is the basal lamina of the corneal endothelium
Descemet membrane
What is Descement membrane thickness at birth and adulthood
birth 3-4um
10-12um
Descemet membrane is rich in Type _ collagen
Type IV
Peropheral excresecences of Descemets membrane is known as
Hassal Henle Warts
Central excresxcences of Descemets membrane is known as
corneal guttae
Corneal endothelium os composed of ______ layer of _____ cells
single layer of hexagonal cells
HExagonal cells of the corneal endothelium are derived from
neural crest
Adult density of corneal endothelial cells is
3000mm2
Specular microscopy is used to visualise
Endothelial cells - size shape distribution
The transition zone between the peripheral cornea and anterior sclera is known as the
limbus
Limbal palisades of Vogt house the ?
corneal stem cells
Schwalbe line is the termination of
Descemet membrane
Where is the sclera thinnest?
Behind insertions of the rectus muscles
Where is the sclera thickest?
Posterior pole around optic nerve head
Most common site of scleral rupture following blunt trauma
Supernasal quad near limbus
circumferential arc parallel to corneal limbus opposte site of impact
behind the insertion of rectus muscles
Endothelial cells in schlemm canal are joined by?
tight junctions
Lens contributes __D of 60D to eyes focusing power
20S
equatorial diameter of lens at birth
6.5mm
Equatorial diameter of lens in adult
9-10mm
AP width of lens at birth
3mm
AP width of lens in adulthood
6mm
accomadation is acheived by ______ contraction
ciliary muscle
Lens capsule rich in Type _ collagen
Type IV
Pedicle
Cone
Spherule
Rod
How many rods in the retina
100-125 millin
How many cones in the retina
6-7 million
Which layer of retinal are muller cells nuclei locates
inner nuclear layer
What type od cells are Muller cells
Glial cells
What is the role of glial cells in the retina
Structural support and nutrition
main type of collagen in vitreous
type 2
What is the venous drainage of the conj
super and inf ophthalmic veins
refractive index of cornea
1.376
what is the total refractive power of the cornea
43
50% of stroma is _____ collagen
type 1
Descemet’s is mainly type __ collagen
type IV
where is glucose supply to corneal epithelium from?
tear film
where is glucose supply to corneal endothelium from?
aqueous
Main way glucose is metabolised in the cornea
anaerobic glycolysis
what is the most common corneal proteoglycan
keratan sulphate
does pupillary dilatation increase or reduce diffraction
reduce
does pupillary dilatation increase or reduce chromatic abberation
increase
light entering at the edge of the pupil is less effective at stimulating photreceptors than light entering centrally because it meets the receptors obliquely rather than head on is called
Stiles-Crawford effect
Pupil dilatation increases or reduces the Stiles Crawford effect
increases
Mydrisasis is caused by contraction of
dilator pupillae
Mydriasis is stimulated by __________ _____ nerves passing through ciliary ganglion
Noradrenergic sympathetic
Miosis is stimulated by contraction of
sphincter pupillae
Miosis is stimulated by ________ postganglionic ______ fibres from the ciliary ganglion
chloinergic parasympatheitc
In Horner’s pupil, will cocaine dilate the pupil
No, increased adrenergic activity by preventing reuptake has no effect on interrupted neural pathway
Hydroxyamphetamine will dilate a _____ and ____ neruone Horner but not a _____ order neurone lesion
Hydroxyamphetamine will dilate a 1st and 2nd neruone Horner but not a 3rdorder neurone lesion
The lens has greater curvature ______
anteriorly
lens diameter
10mm
Lens placode develops from surface ectoderm at what day
27 days
Lens placode invaginates into optic cup to from lens vesicle at day
33
anterior lens suture is ___ shaped
Y
posterior lens suture is _____ shaped
inverted Y
Aquaporin-0 functions as a ?
water channel
in the lens sodium is low/high and potassium is low/high
sodium low and potassium high
most important antioxidant in the lens
glutathione
choroid has high/low flow and high/low oxygen excahnge
high flow low exchange
choroidal vessels are embedde in type __ collagen matrix
III
what are the 3 vessel layers in the choroid called
choriocappilaris and Hallers and Sattlers
which layer in the choroid has larger vessel forms
Hallers layer
Lamina vitrea also called____ _______
Bruchs membrane
what are the 5 layers of lamina vitrea
RPE, collagen, elastic, collagen, choriocappilaris
choriocapillaris is most dense and widest where in the retina
macula
choriocapillaris receives blood from which layer
sattler’s layer
less/more laserp power required for photocoagulation of darkly pigemented fundu
less
main type of collagen in the vitreous
type II
