10-18-05 Clinical Anatomy of the Eye
Terms
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Orbicularis oculi muscle
innervation
how arranged
function
what happens in paralysis -
- orbicularis oculi muscle (VII innervation)
o circumferentially arranged
o closes eye
o paralysis – eye stays open -
Meibomian glands
how are they arranged
where are they located
what do they secrete - vertically oriented, large, secrete an oily substance that’s important component of the tear film – all within the tarsal plate
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5 importatnt aspects of orbit
limits and contents
lymphatics? -
- orbital septum limits anteriorly
- seven bones limit it elsewhere
- orbital fat suspends the globe
- no orbital lymphatic system
- nerves, arteries, veins - Which bones make up the wall, floor, enterance of optic foramen or orbit.
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floor= maxillary
medial wall=ethmoid
lesser wing of phenoid contains optic canal - b/w what bones is the superior orbital fissure, what passes thru sup. orb. fis.,
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- between G. and L. sphenoid wings
- cranial nerves III, IV, and VI
- ophthalmic division of CN V (V1)
- superior ophthalmic vein
- sympathetic fibers variably come through -
optic foramen
what passed thru
what bone does it enter thru
what muscle can compress it and where? -
Optic Foramen
- sphenoid bone is at the orbital apex
- optic nerve (CN II)
- see cut edges of recti muscle surrounding optic nerve at the optic foramen – if swell could compress optic nerve
- ophthalmic artery -
extraocular muscles
how many are there
name them and what are they innervated by? -
Extraocular muscles
- 7 are under voluntary control
- levator palpebrae superioris muscle (CN III)
o opens eye
- Muller’s muscle (sympathetic)
o Under surface of LPS; helps hold open eye (still be able to open/close, but would see a droop with a sympathetic deficit)
o Not functional in Horner’s syndrome
- 4 rectus muscles
o named for their locations where they insert onto the globe
- 2 oblique muscles
o insert obliquely on the globe
o control torsion of the eye
o superior oblique contracts and rotates eye counterclockwise/intorsion
 runs through a cartilaginous loop (= trochlea)
 origin is at orbital apex
o inferior oblique contraction creates extorsion
 has its origin in anteromedial part of orbit -
origins of eye muscles
where do the rectus muscles insert?
if they swell what happens and where dz does this resemble -
- slide showed all rectus muscles insert at apex around the optic foramen, through which optic nerve leaves the orbit
o think swelling muscles = nerve compression, like Graves disease “thyroid ophthalmopathy -
Conjunctiva
where located
type of epithelium
what are diff portions of conjuctiva
what is name of where cornes meets sclera? -
- lines undersurface of eyelids and ant surface of globe
- stratified, non-keratinized epithelium
- palpebral portion
o lines the eyelids
o self-reflects in the fornix
- bulbar portion
o overlying the sclera
o lining anterior globe
o inserts onto cornea (not visible because it’s clear)
- deep to that, can see where cornea meets sclera = “limbusâ€
o good descriptive term for where objects, problems in eye are located (as reference point) -
Lacrimal system components
what is function (2 functions)
What are the layers, where do they come from and why are they important.
which layer makes up most of the tear film and what percentage -
- tear film is anterior most functional part of eye
- keeps eye from drying out (therefore important for cornea health)
- also provides a smooth refractory surface for maximizing vision
- Layers of the tear film
o Directly contacting cornea is MUCIN layer
 Allows watery layer to distribute evenly on cornea surface
 Contributed to by goblet cells in fornix, and caruncle (funny pinkish structure in corner of eye)
 Cornea surface is hydrophobic
o Aqueous (90% of composition)
 Contributed by lacrimal gland in superotemporal portion of orbit
o Oily layer
 Prevents evaporation
 Produced by Meibomian glands
***Tear film is one of the most important surfaces of the eye!!** -
Cornea
What are the 2 main functions and what is it made of -
- Structural
o coat of eye, continuous with sclera at limbus
- optic
o collagen lamellae are precisely arranged
o disrupted arrangement causes unclear cornea (therefore unclear vision) -
cornea
what are the 5 layers and describe each, especially endothelium -
- from front to back – 5 layers
o epithelium, similar to that of conjunctiva – stratified, non-keratinized
o Bowman’s layer – very compact, if damaged, may not heal as strongly so therefore subsequently injured more easily
o Stroma – bulk of corneal thickness
o Dessime’s membrane (?) basement membrane for the endothelium
o I know that’s only 4 layers, but that’s all he said
- Most important part of this is the endothelium
o Monolayer, post-mitotic, so we lose throughout life
o One important function is to pump fluid out of the cornea
 All that fluid around the cornea wants to make the cornea swell – cornea is a relatively dry tissue when functional
 If swells, becomes opaque, surface no longer smooth -
Lens
suspended by what...which are connected to what
what ahppens when ciliary body contracts -
- suspended in the eye by zonules, little collagen filaments that connect ciliary body (CB) to lens of eye
- CB controls lens shape by controlling contraction inputs on zonules (=accommodation, to see far and near)
o Relaxed state, lens relatively flat – allows for distant focal point
o Ciliary body contracts – lens thickens, moves focal point closer
o With time this function lost, need reading glasses (presbyopia)
 presbyopia theories
• ciliary muscle becomes fibrotic and can’t react vigorously
• lens hardens and harder to change shape
• Zonules become stretched over time, so for same amount of muscular energy, not getting as much “oomph†with your muscles
 Probably some combination of all 3 -
Uveal tract
consists of? -
- middle “coat†of the eye, vascular
o innermost “coat†is the neural coat, or retina
- consists of iris (anterior), ciliary body, choroids -
iris
how are muscles arranged, how many, named, innervated by -
- Primary function is to control the pupil size
- Paired muscles
o radially oriented dilator muscle (causes pupil to get larger)
o sphincter muscle around edge of pupil (parasympathetic control)
o ciliary body controls accommodation (parasympathetic control) - How do we get the sympathetic and parasympathetic innervation up to the iris? go neuron1 to neuron 2 etc.
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Sympathetics
- start in ipsilateral hypothalamus
- 1st order neuron projects down spinal cord
o synapses C8/T2
- 2nd order neuron leaves cord, ascends
o synapses in superior cervical ganglion
- 3rd order neuron travels with carotid artery through cavernous sinus, through Optic foramen, sup orbital fissure, or both
o Gets to iris, lacrimal glands, Mueller’s muscle
- So lesion anywhere in those areas will cause loss of sympathetic input – miosis, ptosis, anhydrosis on that side of face. (Classic Triad of Horner’s Syndrome)
Parasympathetic – more direct route
- start at EW nucleus, CN III
- jump off in inferior orbit and synapse in ciliary ganglion, carried to iris -
choriod
where is it and what does it do? -
- Posteriormost component of uveal tract
- Primary job is to supply the retina with the nutrients of blood (not blood directly)
o Job of phototransduction is a metabolically active one – requires lots of oxygen and substrate
o Highest flow of blood to any tissue in body is choroid
- Middle vascular coat between retina and sclera -
RPE
what satnd for
whaere located
functions -
RPE: the gatekeeper between choroid and retina
- RPE diseases result in significant loss of vision
- RPE is the pigmented monolayer external to the neurosensory retina (NSE)
o RPE + NSE = RETINA
- Nurtures and supports photoreceptors
- Vitamin A processing
- Minimizes light scattering because heavily pigmented
o Otherwise, you would have decreased visual contrast
- It is the outer blood-retinal barrier (BRB), has tight junctions
o The inner BRB (supplied by the retinal arteries) has even more tight junctions - axons leave the eye via _______.
- lamina cribrosa
- constriction due to pituitary galnd resutls in what?
- betemporal hemoanopsia