orbit

Question 1

what are the bones of the orbit *

Answer 1

roof - orbital plate of the frontal bone

floor - orbital plate of the maxilla (thin) (cheek bone)

lateral wall - zygoma and greater wing of sphenoid (posterior to the zygoma)

medial wall - frontal process of maxilla, lacrimal bone (small), orbital plate of ethmoid (lamina papyracea), lesser wing of sphenoid

Question 2

what is a blowout injury

Answer 2

when there is driect trauma to the eye

blow put floor of orbit

eye drops into cheek cavity = double vision etc

Question 3

what are the orbital formina *

Answer 3

optic canal - optic nerve (CN2), opthalamic artery

inferior orbital fissure - maxillary division of trigeminal V2, infraorbital vessels

superior orbital fissure - CN involved in extrinxic muscle function (CN3 4 6), opthalmic division of trigeminal V1, opthalmic vessels, sympathetic fibres run with vessels

Question 4

what is the opthamlic artery *

Answer 4

the main blood supply to the eye

Question 5

where are the orbital foramina *

Answer 5

optic canal - in the lesser wing of the spenoid bone

superior orbital fissure - in lesser wing of sphenoid

inferior orbital fissure - lesser wing of the sphenoid (nerves run along maxilla and exit via the infraorbital fissure)

Question 6

what are the 2 categories of the extrinsic muscles of the orbit *

Answer 6

recti

obliques

Question 7

describe the recti muscles *

Answer 7

inferior, superior, medial and lateral

origin - at back of orbit in common tendinous ring

insertion - into the sclera, 5mm behind the corneal margin (anterior to the equator)

nerve supply - inferior superior and medial are innervated by oculomotor CN3, lateral abducens CN6

Question 8

describe the oblique muscles (extrinsic muscles of the orbit) *

Answer 8

inferior and superior

origin - inferior: in orbital surface of maxilla

Superior: from the body of the sphenoid

insertion - inferior: into the posterior/inferior quadrant of thee globe

superior: posterior/superior quadrant via the trochlea (bony spur in medial aspect of orbit)

nerve supply - inferior: CN3, superior: trochear nerve CN4

Question 9

what is the muscle of the upper eyelid *

Answer 9

levator palpebrae superioris

Question 10

describe the levator palpebrae superioris *

Answer 10

origen - lesser wing of sphenoid

insertion - into the superior tarsal plate and skin of the eyelid

nerve supply - CN3, and sympathetic supply to sm (important clincially)

Question 11

why is it important clinically that the levator palpebrae superioris has sympathetic innervation *

Answer 11

horner’s syndrome (loss os SNS to head and neck)

symptom is ptosis (drooping of upper eyelid)

Question 12

describe the path of the optic nerve and its insertion into the globe *

Answer 12

through the optic canal to the back of the globe

large nerve

retinal ganglion cells axons going back via optic chiasm to the occipital lobe

Question 13

what is the common tendinous ring, where is it *

Answer 13

origin for all the muscles in the orbit

back of the orbit

Question 14

describe the muscles and their location in the orbit *

Answer 14

levator palpebrae superioris - at the top of orbit, muscle to the upper eyelid

superior oblique - origin in c tendinous ring, up passes through pully system with trochlear, pass back to lateral superior quadrant of the globe, inserts into the posterior globe of the eye

superior rectus muscle - origin in common tendinous ring at back of orbit - insert into globe of eye anterior to equator

inferior oblique - originates in orbital plate of the maxilla (in the lower orbital nasal wall), inserts into the posterior globe of the eye

inferior rectus - origin in common tendinous ring at back of orbit - insert into globe of eye anterior to equator

lateral rectus - origin in common tendinous ring at back of orbit - insert into globe of eye anterior to equator

medial rectus - origin in common tendinous ring at back of orbit - insert into globe of eye anterior to equator

Question 15

describe the function of the superior oblique muscle *

Answer 15

contraction = move pupil down and out

Question 16

function of the superior rectus *

Answer 16

straight forward contraction pulls pupil up

Question 17

describe the function of the inferior oblique muscle *

Answer 17

moves the pupil up and ou t

Question 18

describe the function of the inferior rectus *

Answer 18

depresser muscle - move pupil down

Question 19

describe the function of the lateral rectus *

Answer 19

abduct the eye - pull the pupil away from the midline

Question 20

describe the function of the medial rectus *

Answer 20

adduct the eye - move pupil to the middle

Question 21

describe ISOLATED muscle actions - ie not what would happen in real life *

Answer 21

LR - abduction

MR - adduction

SO - depressor and abductor

IO - elevator and abductor

SR - adduction and elevation

IR - adduction and depression

Question 22

describe how you test the muscle action of the orbit clinically *

Answer 22

you need to get eye so that it is line with the muscle that you are testing

LR and MR - see whether eye follows finger - adduction/abduction (remember 1 eye will adduct and one will abduct in persuit so different muscles are being used in each eye)

to check depression - adduct/abduct first so you can isolate the muscle that is causing the depression. when adducted - SO, abducter - IR

elevation - also need to adduct/abduct first - adduct - IO, abducted - SR

Question 23

what are the nerves of the orbit superficially

Answer 23

optic - made of axons of ganglion cells in retina

oculomotor - has 2 rami, motor fibres to MR, SR, IF, IO, LPS (eyelid), PNS fibres

trochear - motor to SO

abducens - motor fibres to LR

Question 24

what are the branches of the opthalmic division of the trigeminal nerve

Answer 24

lacrimal

frontal branches into supratrochlear and supraorbital,

nasocilary branches to ciliary ganglion PNS, ethmoidal and infratrochlear

Question 25

describe the location of the nerves of the orbit and how they reach the orbit

Answer 25

oculomotor goes through superorbital fissure trigeminal ganglion sits in Meckel's cave, opthalmic division enters orbit through superorbital fisure branches of the opthalmic division of the trigeminal nerve - frontal nerve, lacrimal nerve (going to lacrimal gland on lateral orbit)

Question 26

describe the location of the CN in the cavernous sinus and relevance of this

Answer 26

in the lateral wall except abducens CN6, runs with the internal carotid infection/thhrombosis here can affect all these nerves

Question 27

describe the ciliary ganglion

Answer 27

PNS innervation sits behind globe of eye preganglionic fibres are in the inferior ramus of oculomotor nerve postganglionic fibres are in the short ciliary nerves they innervate the sphincter pupillae and ciliary muscle

Question 28

describe the blood vessels of the orbit

Answer 28

opthalmic artery supplies blood to central artery of retina, muscular branches, ciliary, lacrimal, supratrochlear and supraorbital branches opthalmic veins - superior (drain into cavernous sinus - potential route of infection back into cranial cavity) inferior (drain into the pterycoid plexus - no passage into the cranial cavity)

Question 29

why is it important to look at arteries in eye clinically

Answer 29

check that they are ok also check systemic disease in diabetics - can see diabetic retinopathies in people with trauma see papilloedema indicate raised intracranial pressure

Question 30

summarise the lacrimal system

Answer 30

lacrimal gland in the anterolateral superior orbit PNS secretomotor fibres are from facial nerve CN 7 - they come from the pterygopalatine ganglion, pass through zygomaticotemporal branch and then join lacrimal nerves. (ganglion is behind the cheek) lacrimal nerves are sensory branches of trigeminal lacrimal sac in medial canthus of eye - drains into inferior meatus of the nose via the nasolacrimal duct

Question 31

describe tears

Answer 31

they wash across the cornea have a protective function keep eye moist collect in lacrimal sac and drain through nasolacrimal duct into nose

Question 32

what could be the problem if someone presents with a dry eye

Answer 32

a PNS problem - no production of tears

Question 33

what are the afferent and efferent arms of the corneal reflex \*

Answer 33

afferent - CN5 efferent - CN7

Question 34

what are the afferent and efferent arms of the pupillary light reflex \*

Answer 34

afferent - CN2 efferent - CN 3

Question 35

What are the afferenet and efferent nerves of the accommodation reflex \*

Answer 35

Afferent CN2 efferent CN 3

Question 36

Describe the optic nerve \*

Answer 36

Extension of brain from retina to visual centers of the brain leaves the orbit through the optic canal

Question 37

Describe the oculomotor nerve \*

Answer 37

Leaves the brain stem between meidbrain and pons passes through the cavernous sinus branches into superior and inferior divisions just before orbit they enter the orbit through superior orbital fissure lying in the common tendinous ring superior branches passes up over CN2 innervatibg the superior recurs an elevator palpebrae superioris inferior branch has 3 branches innervatibg medial, inferior rectud and inferior oblique 3rd branch of inferior gives rise to the ciliary ganglion - this is the pns root to ganglion

Question 38

What is the edinger Westphalia nucleus \*

Answer 38

The pns pregnaglionic nucleus - pns outflow to the ciliary ganglion

Question 39

Describe the pretectum \*

Answer 39

Group of 7 nuclei most known function is the pupillary light reflex controlled by the olivary pretectal nucleus

Question 40

What is horners syndrome \*

Answer 40

Loss of sons function in head because of a lesion

Question 41

What are the 3 typical features of horners syndrome \*

Answer 41

Pupillary constriction because of paralysis of the dilator pupillary muscle partial ptosis- dropping of upper eyelid due to paralysis of superior tarsal muscle absence of sweating on the ipsilateral side of face and neck due to absence of innervatibg of the sweat glands,

Question 42

Describe the tarsal muscle \*

Answer 42

Superior tarsus in upper eyelid - part of the levator palpebrae superioris inferior in lower eyelid they are plates of dense connective tissue

Question 43

Describe the path of the sympathetic fibers of the orbit \*

Answer 43

Arise from t1 enter sympathetic chain through the white rami communicants - ascend to superior cervical ganglion - synapse with post ganglion fibers post gang fibres travel with internal carotid artery and branches (ophthalmic artery) then either go through the ciliary ganglion and join with short ciliary nerves, or pass through long ciliary nerves - both reach eye innervate the dilator pupillary muscle

Question 44

Describe the superior cervical ganglion \*

Answer 44

Area of c1-2

Question 45

What is the effect of loss of CN3

Answer 45

Complete ptosis - loss of supply to legatos palpebrae superiosis

Question 46

describe the action of the ciliary muscle \*

Answer 46

it is controlled by parasympathetics from the oculomotor nerve contraction of the ciliary muscle decreases the size of the ring formed from the ciliary body - reducing tension on the suspensory ligament of the lens therefore the lens is more relaxed so rounded causing accomodation for near vision that is why eyes get tired looking at near objects becasue of contraction of the ciliary muscle

Question 47

describe the action of the sphincter pupillae \*

Answer 47

muscle fibres in the iris innervated by parasympathetics from oculomotor nerve when contract they constrict pupil

Question 48

describe the action of the dilator pupillae \*

Answer 48

fibres in the iris innervated by sympathetics from the superior cervical ganglion T1 contraction dilates the pupil

Question 49

how do you test if someone has a squint\*

Answer 49

shine light 40cm away from eye straight on the light should be reflected symaettrically from the cornea on both eyes - if unsymetrical - show have a squint which is ocular misalignment - used to test the muscle function of the eye when pt looks at light, reflection should be nasal to the centre of both pupils

Question 50

describe opthalamoscopy

Answer 50

you vcan see the vitreous chamber of the eye using an opthalmoscope - small battery operated light with tiny lens so yoiu can see the vitreous chamber and the posterior wall of the eye you can see the optic nerve, the typical 4 branches of the central retinal artery and the fovea shine the light in the eye and look for the red reflex - then get closer until you can see the arteries of the eye

Question 51

describe 6th nerve palsy \*

Answer 51

affect to lateral rectus muscle unable to abduct so eye deviates in souble vision bad when looking to side of effected eye because eye cant move in that direction

Question 52

describe 4th nerve palsy \*

Answer 52

superior oblique muscle is affected eye looks medial and is raised

Question 53

describe the conjunctiva \*

Answer 53

it is a thin membrane covering the posterior surface of the eyelid it covers the full extent of teh posterior surface of the eyelid and reflects onto the sclera it attaches to the membrane at the junction between the sclera and conjunctiva a conjuctival sac is formed when eyes are closed and upper and lower extensions of these sacs are the superior and inferior conjunctival fornices

Question 54

importance of the conjunctiva \*

Answer 54

keep the eye and inside surface of eyelid lubricated and moist so eye can open without friction which would cause eye irritation

Question 55

describe the eyelid anatomy \*

Answer 55

space between eyelids when open is the palpebral fissure the layers of the eyelids are; skin, subcutaneous tissue, vol muscle, orbital septum, tarsus, conjunctiva the superior eyelid has 2 more muscles than the lower eyelid

Question 56

describe the innervation of eyelid \*

Answer 56

sensory is from trigeminal branches - opthalmic and maxillary nerve motor is from - facial, oculomotor and sympathetic fibres

Question 57

function of the eyelid \*

Answer 57

spread tears across the eye protect the eye from foreign bodies