What makes up the roof border of the orbit
The frontal plate of the frontal bone and the lesser wing of the sphenoid
Role of the roof border
separates the orbit from the anterior cranial fossa
What makes up the lateral border of the orbit
The zygomatic bone and the greater wing of the sphenoid
role of the lateral border of the orbit
separates the temporal fossa from the orbit
What makes up the floor of the orbit
maxillary bone and the zygoma
role of the roof of the orbit
separates the orbit from the maxillary air sinuses
role of the medial border of the orbit
separates the orbit from the ethmoidal air sinuses
what makes up the medial border of the orbit
the maxilla, the orbit plate of the ethmoid, the body of the sphenoid and the lacrimal bone
what is the apex of the orbit and what does it contain
the orbit canal and it contains the optic nerve and ophthalmic artery
orbital blow out #
medial and inferior walls are thin so a direct blow may cause a #
risks of a medial orbit wall #
ethmoidal and sphenoidal sinuses may be involved
risks of a inferior wall #
the maxillary air sinuses may be involved and the infraorbital nerve which can cause altered sensation of cheek. May also have diplopia.
What does an eye lowered to the inferior orbital floor and diplopia suggest?
zygoma # which has rotated medially
- remember the suspensory ligaments are attached laterally to the zygoma
The layers of the eyelid from superficial to deep
skin and superficial fascia orbicularis occuli tarsal plates levator apparatus conjunctiva
Parts of the orbicularis occuli muscle
orbital part and the palpebral part
innervation of the orbicularis occuli
facial nerve CNVII
role of the orbicularis occuli muscle?
orbital part - tightly close the eye
palpebral part- gently close eyelid
What is the orbital septum and where is it found?
sheet of fascia between the orbicularis occuli and the tarsal plates that helps prevent the spread of infection from superficial to deep
What are tarsal plates?
2 plates deep to the palpebral region of the orbicularis muscle. 2 plates: superior tarus (upper eyelid) and the inferior tarus (lower eyelid)
role of the tarsal plates
contain tarsal glands(Meibomian gland) that secrete an oily substance to keep the eyes moist and prevent them sticking when eyes are closed
also give structure
what is the levator apparatus
2 muscles that act to open the eyelid: levator palpebrae superialis (LPS)and the superior tarsal muscles
only present in the upper eyelid
role of the LPS and innervation
opens the eyelid and is innervated by the oculomotor nerve CNIII
Location of the superior tarsal muscle, innervation and role
Underneath the LPS
assists the LPS in opening the eye
sympathetically innervated
what is conjunctiva
thin mucous membrane folded onto the sclera
What is the pupil?
gap in the iris which allows light to be passed through before being focused on the retina
What is the limbus?
where the cornea and sclera meet- the corneascleral junction
what secretes lacrimal fluid and where is it secreted?
lacrimal gland
secretes fluid onto the conjunctiva and cornea of the eye
where is the lacrimal gland located?
anterior in the superiolateral aspect of the orbit in the lacrimal fossa (depression in the frontal bone)
what innervates the lacrimal gland
parasympathetic CNVII
direction of travel of lacrimal fluid
fluid is produced in the lacrimal gland and is washed over into the medial angle of the eye where in travels through the lacrimal punctuae into the canaliculi into the lacrimal sac then into the nasolacrimal duct where it eventually meets the inferior meatus.
location of the nasolacrimal duct
in a groove formed by the lacrimal and maxilla
How many layers of the eye are there? What are there names?
3:
fibrous (outer)
Uvea (middle)
Retina (inner)
What is contained in the fibrous layer and what is their role?
Sclera and cornea
sclera: muscle attachment
cornea: major refractive power
What is in the uvea (and their function) and what is characteristic about the uvea?
VVVV vascular
Iris: controls pupil diameter and consequently how much light in
choroid: gas and nutrient exchange
ciliary body: contains ciliary muscles for accommodation and secretes aquaeous humour
What is included in the retina and what is the function
fovea
Optic disc: where the optic nerve enters
macula
What is the difference between the anterior segment and posterior segment?
Anterior segment is infront of the lens, the posterior segment is behind the lend
What is the posterior segment filled with
virteous humour
how is the anterior segment divided and what is it filled with?
Anterior chamber: between iris and cornea
Posterior chamber: iris and suspensory ligaments
both filled with aqueous humour
Differences in production between aquaeous humour and virteous humour?
Aquaeous is continuously produced whereas virteous is not
Circulation of aquaeous humour
Secreted by ciliary body into the posterior chamber and nourishes the lens.
it then travels through the pupil into the anterior chamber and nourishes the cornea and is then reabsorbed at the canal of schelmn @ iridocorneal angle.
blood supply to the eye and main branches
ophthalmic artery (branch of int carotid)
2 main branches:
central artery of the retina (end)
Ciliary arteries
why is the central artery of the retina so important?
its an end artery so occlusion leads to blindness vvv quickly
venous supply to orbit
superior and inferior ophthalmic veins
the inferior mainly drains into superior vein and they both then drain into the cavernous sinus
the facial vein also does a tiny amount
what is the danger triangle
between eyes over nose and down to upper lip… abscess here would be drained back into the cavernous sinus and couls cause a cavernous sinus thrombosis which is life threatening
What is the optic disc and where is it located?
located medially on the posterior wall of the retina. it is where the optic nerve CNII leaves the eyeball and where arteries/ veins enter/leave. (no photoreceptors)
Where is your blind spot?
optic disc
Where is the macula and what is the function?
Just lateral to the optic disc and has the greatest density of cone cells so v important for light vision.
Where is the fovea and what is its function?
just lateral to the optic disc in the centre of the macula. it is must important for vision acuity (sharp images not blurred)
How many extraocular muscles are there and what are they called?
7 superior rectus inferior rectus medial rectus lateral rectus superior oblique inferior oblique 1 levator palpebrae superioris
Attachments of extraocular muscles
all originate from the common tendinous ring and attach onto the sclera
what is the somatic motor innervation of the extraocular muscles
LR6
SO4
AO3
Innervation and clinical test of lateral rectus
abduction into the same plane and the sup and inf rectus
CNVI
Innervation and clinical test of superior rectus
Elevates eye when it is abducted
CNIII
innervation and function of inferior rectus
CNIII
when the eye is abducted it depresses the eye
innervation and clinical test of medial rectus
innervated by CNIII
adducts the eye
innervation and clinical test of inferior oblique
elevates the eye when it is adducted
CNIII
innervation and clinical test of superior oblique
depresses the eye when it is adducted
CNIV
muscles involved in pure elevation
inferior oblique and superior rectus
muscles involved in pure depression
inferior rectus and superior oblique
What is the sensory innervation of the face and the divisions
Trigeminal nerve CNV it has 3 divisions: CNV1: opthalmic CNV2: maxillary CNV3: Mandibular
What is the name of nerve V1 and what it innervates
Opthalmic:
- upper eyelid
- cornea
- conjunctiva
- skin down centre of nose
Name of nerve V2 and what it innervates
Maxillary:
- side of nose
- lower eyelid
- skin of lower lip
- maxilla
Name of nerve V3 and what it innervates
Mandible:
- bottom lip
skin over mandible and temporomandibular joint
What innervates the temporomandibular joint
Supplied by spinal nerves C2 and C3
Explain the corneal Reflex:
Sensory/Afferent:
AP conducted from cornea via CNV1 to terminal ganglion then along CNV to pons
There is a CNS connection between CNV and CNVII
Motor/Efferent:
AP conducted along CNVII to the palpebral part of the occularis occuli to cause blinking
where do sympathetic axons exit the spinal cord
T1-L2 spinal nerves
How is sympathetic outflow describes
Thoracolumbar
What are splanchnic nerves
supply blood vessels and visceral organs (symp axons)
How do sympathetic axons from the spinal cord reach the orbit
pre synaptic sympathetic axons leave the spinal cord at T1 spinal nerve and ascend upwards with the sympathetic trunk and synapse in the superior cervical sympathetic ganglion.
post synaptic sympathetic axons enter the internal and external carotid nerves and pass onto the surface of internal and external carotid arteries. they are carried to the organs of head and neck on the surface of the branches of the internal and external carotid arteries. the ophthalmic artery carries sympathetic axons in the orbit.
What artery carries sympathetic axons to the orbit
ophthalmic artery
What cranial nerves are parasympathetic
X, IX, VII, III
how is the parasympathetic supply described
Craniosacral
Where does CN III synapse
ciliary ganglion
where does CN VII synapse
synapses in pteygopalatine ganglion and the post synaptic fibres travel to the lacrimal gland
where does the parasympathetic sacral spinal nerves innervate
hindgut
pelvis
peroneoum
What is the name of CN III
Oculomotor
Is CN III motor or sensory?
Motor
Is CN III sympathetic or parasympathetic?
Parasympathetic
Route of CN III
passes through the cavernous sinus, exits via superior orbital fissue and enters orbit
Where does the oculomotor supply somatic motor supply to?
SR IR MR IO LPS
Where does CN III synapse and what occurs after synapse?
Synapses at ciliary ganglion
gives off 2 division superior and inferior
superior innervates: SR, LPS
inferior innervates: IR, IO, MR and ciliary ganglion
What does the autonomic (sympathetic) axons in the ciliary nerve control
Diametre of iris
refractive shape of lens
(sympathetic innervates the sphincter papillae muscles)
Difference in short and long ciliary nerves
long: sympathetic and somatic sensory
short: sympathetic and parasympathetic
what are the autonomic reflexes of the eye
wide eye opening pupillary dilation/constriction accommodative reflex lacrimation production vestibulooccular reflex occulocardiac reflex
What the sympathetic reflexes in the eye
OPens eye wider
get more light into eyes
focus on far objects
emotional lacrimation
what reflexes are the parasympathetic reflexes in the eye
Get less light into eye focus on near objects reflex lacrimation (foreign body)
What muscle is responsible for the opening eyes wider response
LPS
What muscle does the LPS contain and what is the innervation
Smooth and skeletal muscle
the skeletal muscle is innervated by the oculomotor nerve
the smooth muscle is sympathetically innervated to allow allow fight or flight
how do the sympathetic fibres reach the LPS muscle
leave the spinal cord and travel to the superior cervical sympathetic ganglion then axons travel via the internal carotid artery via a plexus then the artery divides and the axons are carried on the ophthalmic artery
What nervous system causes pupillary dilation and in what scenario does it happen
SYMPATHETICS
in dim light, flight or fight or if PT is sick
what is a mydriatic pupil and what causes it
Non physiologically enlarged pupil
mydriatic drug
what fibres causes pupil dilation and how
dilator pupillae fibres (originate around the external circumference of the iris and insert around the internal circumference of iris)
supplied by the symp nervous system- contraction of the pupillae causes pupil dilation
What nervous system causes pupil constriction and in what scenario does it happen?
Parasympathetic
occurs in bright light and rest and digest
what is a miotic pupil and what is it a component off
non-physiologically enlarged pupil
component of horners syndrome
What can a fixed dilated or fixed pin point pupil suggest
fixed dilated: CN III pathology
fixed pin point: opiates
what muscles cause pupil constriction
sphincter pupillae fibres encircle the pupil and there contraction causes constriction
what is the pupillary light reflex and the mechanism
when a light is shone in one eye it causes bilateral constriction
Sensory: signal sent by the optic nerve (CN II: IPSILATEAL)
CNS connections occur in midbrain
Motor: signal is bilateral along CNIII (oculomotor)
what is the direct light reflex
constriction in the eye stimulated with light
what is the consensual light reflex
constriction in the non stimulated eye
what is the 4 neurone chain of the pupillary light reflex
1) retinal ganglion cells send an AP via the ipsilateral optic nerve which crosses at the optic chiasm and synapses in the pretectal nucleus
2) located in midbrain and connects the pretectal nucleus to the next synapse the Edinger Westphal nucleus (bilateral )
3) pass from the EW nucles to the CNIII then to its inferior division to synapse in the ciliary ganglion
4) course in the short ciliary nerves to the sphincter papillae muscles
what is the refractive power of the lens vs the cornea?
cornea: 2/3 of refractive power
lens: 1/3 of refractive power
what connects the lens and ciliary body
suspensory ligament of lens
what controls the shape of the lens
parasympathetic
describes what happens in relaxation of the ciliary muscles
relaxation of the ciliary muscles puts tension on the suspensory ligaments causing the lens to flatten out
happens in long vision
happens when the parasympathetic supply is switched off
describe what happens in contraction of ciliary muscles
contraction of the ciliary muscles causes the suspensory ligament to relax and the lens to become spherical
occurs in short vision
happens under parasympathetic stimulation
what shape of lens has a greater refractive e power
spherical has a greater refractive power than flat
what is the natural position of your lens
spherical
why do people need reading glasses as they get older
lens becomes less flexible and more fibrous so cannot spring into sphere as easily
what is the accommodative light reflex and why is it needed
changing focus distance
if looking at something in the distance the cornea does enough light bending to focus an image on the retina whereas close up the cornea is not enough to bend an image and the lens in needed
how do you clinically asses the accommodative reflex
ask the patient to look at something in the distance and then to quickly look at something very close in the midline
what 3 components are assessed in the accommodative reflex:
1) bilateral pupillary constriction
2) bilateral convergence
3) bilateral relaxation of lens
what are the 3 types of lacrimation
1) basal
2) reflex
3) emotional
what are basal tears
constant tears that clean and nourish cornea. also contain lysosome the enzyme that degrades bacterial cell walls.
what are reflex tears
tears in response to mechanical or chemical stimulation. afferent in CN V1 and efferent is CN VII (autonomic parasympathetic)
what is horners syndrome and what are the symptoms
horners is impaired sympathetic innervation to the head and neck
symptoms are ipsilateral: miosis, ptosis, reduced sweating and inc warmth and redness