Ophthamology Flashcards
What 6 bones is the orbit made up of?
Frontal Zygomatic Maxillary Sphenoid Ethmoid Lacrimal
What bones have orbital plates? Why is this relevant?
The frontal bone, maxillary and ethmoid have orbital plates which are flatter they are thin walled and therefore fracture easily
The optic canal is located _____1_____ for passage of ________2__________
1) posteromedially
2) optic nerve and ophthalamic artery
Superior orbital fissure is formed by? What nerves are found going through this?
the gap between the greater and lesser wings of the sphenoid bone
cranial nerves responsible for the movement of the eye are found coming through here (3,4 and 6)
and CNV1
The shape of the orbit is described as being a _______
What is the apex and the base?
pyramid
Apex is at the optic canal and base is anterolaterally
Base is a combination of medial, lateral, superior and inferior margins
Why is the eye well protected?
Eye is very well protected due to superior margin overhanging inferior and the bones that surround are quite tough
Describe a blow-out fracture of the orbit? What is a complication?
There is a fracture of one of the walls of orbit but the orbital rim remains intact. This is typically caused by a direct blow to the central orbit from a fist or ball. If impact around the bony orbit is strong enough pressure can be transferred to the thinner bones and will get fracture of the thinner bones.
Trap door fracture, fracture of the orbital floor where the inferiorly displaced blowout fracture recoils back to its original position and potentially entraps contents of the orbit.
What is the most external part of the eyelid? What is the function?
Orbicularis oculi muscle which is responsible for closing the eyelids
Describe what is in the deeper layer of the eyelid?
Superior and inferior tarsus
Orbital septum
Palpebral ligaments
Describe the orbital septum and its function?
The orbital septum is a thin, fibrous membrane that serves as a barrier between the superficial lids and the orbit.
Describe the tarsus of the eyelids and their function?
There are two plates; the superior tarsus (upper eyelid) and inferior tarsus (lower eyelid). They act to form the scaffolding of the eyelid, and are composed of dense connective tissue. The superior tarsus also acts as the attachment site of the levator palpebrae superioris.
The lacrimal gland produces lacrimal fluid and has parasympathetic innervation originating from branches of?
Facial nerve- CN7
Greater petrosal nerve
Lacrimal gland is located _____1____ in the orbit. Fluid washes over eye and is pushed in a ___2__ angle and drains through ____3______ into ___4____ and then into ____5_____ duct eventually into _____6________
1) superolaterally (just below eyebrow)
2) medial
3) lacrimal punta (small opening- dot on eyelid)
4) lacrimal sac
5) nasolacrimal
6) inferior nasal meatus
How many extra ocular muscles are there? What are they?
Seven
4 rectus muscles: superior, inferior medial and lateral rectus muscles
2 oblique muscles: superior oblique and inferior oblique
1 levator palpebrae superioris
All extra ocular muscles apart from _____ insert onto the sclera
Levator Palpebrae Superioris which inserts onto the skin and tarsus of superior eyelid
All rectus muscles originate from _______ and insert onto ______
common tendinous ring
Sclera
The superior oblique muscle originates from ___1__ and inserts onto ____2_____
1) sphenoid bone
2) sclera
The inferior oblique muscle originates from ___1__ and inserts onto ____2_____
1) orbital plate of maxilla
2) sclera
The levator palpebrae superioris muscle originates from ___1__ and inserts onto ____2_____
1) lesser wing of sphenoid
2) skin and tarsus of superior eyelid
Describe the trochlea in the orbit?
The trochlea of superior oblique is a pulley-like structure in the eye. The tendon of the superior oblique muscle passes through it. Situated on the superior nasal aspect of the frontal bone, it is the only cartilage found in the normal orbit.
NOTE THAT THE TROCHLEAR NERVE ONLY INNERVATES SUPERIOR OBLIQUE WHICH HAS A TROCHLEA!
Describe the innervation of the extraocular muscles?
Lateral Rectus= CN6 - the abducent nerve because it ABDUCTS the eye
Superior Oblique= CN4- the trochlea nerve because it HAS A TROCHLEA
All others= CN3- oculomotor - CLUE IN THE NAME
LR6 SO4 AO3 (apparently it’s catchy?)
What is the lacrimal lake?
pool of tears in the lower conjunctival cul-de-sac, which drains into the opening of the tear drainage system
What is the lacrimal papilla and punctum?
In medical terms, the lacrimal papilla is a small conical elevation on the margin of each eyelid at the basal angles of the lacrimal lake. Its apex is pierced by a small orifice, the lacrimal punctum where fluid drains into the lacrimal sac.
What is the iris?
coloured part of the eye that controls the size of the pupil in the middle
What is the pupil?
a hole located in the center of the iris of the eye that allows light to strike the retina.
What is the sclera?
white of the eye, opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some elastic fibre. The sclera is completely covered in conjunctiva.
What is the conjunctiva?
The conjunctiva is a tissue that lines the inside of the eyelids and covers the sclera (the white of the eye)
What is the cornea?
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber.
What is the conjunctival fornix?
Where the eyelid meets the conjunctiva
What is the limbus?
border of the cornea and the sclera
What are the three main layers of the eye?
Fibrous outer layer
Uvea- vascular, middle layer (iris, ciliary body and choroid)
Retina- photosensitive inner layer
The Anterior Segment of the eye is the area _______ and it is divided into ___________
in front of lens divided into: anterior chamber (between cornea and iris) posterior chamber (between iris and suspensory ligaments)
The Posterior Segment is the area _______ and contains _______
behind lens
contains vitreous body and vitreous humour
The anterior chamber is filled with _____1_____ which is produced by ___2______ and provides nutrients to ____3____ The outflow of this is through the trabecular meshwork and canal of _____4____ Any factor that impedes this outflow will increase ____5___
1) aqueous humor
2) ciliary body
3) avascular cornea
4) Schlemn
5) Intraocular pressure
The vitreous humour/ body fills the cavity between the ________ It has a role in _________
retina and the lens
protecting eye and helping it hold it’s shape
The blood supply of the eye is via the _____ which is a branch of _______
ophthalmic artery
internal carotid artery
The central artery of the retina and vein (branches of ophthalmic artery) travel in the ___1____ and are the only ______2________
1) optic nerve
2) artery and vein to the retina
The optic disc is the point of formation of _______
the optic nerve- CN2
What is the macula?
Sensitive spot in the centre of retina that has the greatest density of cone cells
What is the fovea?
centre of the macula
depression, 1.5mm diameter
area of most acute vision
Describe the blind spot in the human eye?
Small portion of the visual field of each eye that corresponds to the position of the optic disc within the retina. There are no photoreceptors in the optic disc and, therefore, there is no image detection in this area.
Explain the visual pathway?
Light from objects in the left visual field strike the nasal retina of the left eye and the temporal retina of the right eye. Whilst light from the right visual field strikes the nasal retina of the right eye and the temporal retina of the left eye.
At the optic chiasm the nerve fibres arising from the nasal retina cross to opposite sides of the brain, nerve fibres from temporal retina do not. This mean that light from the left visual field is process in the right primary visual cortex and light from the right visual field is processed in the left primary visual cortex. Lower and upper fields also cross.
Basically if seeing something from left side left eye goes to nasal so it can cross to right but right eye goes to temporal so it stays on right.
What are the three axes of the eye?
Vertical - abduction / adduction
Transverse - elevation/ depression
Anteroposterior - extorsion / intorsion
What occurs around the vertical axis?
abduction/adduction
direction of gaze
What occurs around the transverse axis?
elevation/depression
direction of gaze
What occurs around the anteroposterior axis?
intorsion/extorsion
superior pole of eyeball
What is the action of levator palpebrae superioris?
Elevates the superior eyelid
What is the action of the superior oblique muscle?
Abducts, depresses and medially rotates eyeball
What is the action of the inferior oblique muscle?
Abducts elevates and laterally rotates eyeball
What is the action of the superior rectus muscle?
Elevates adducts and and rotates eyeball medially
think overall it adducts to pull back into proper plane
What is the action of the inferior rectus muscle?
Depresses, adducts and rotates eyeball laterally
think overall it adducts to pull back into proper plane
What is the action of the medial rectus muscle?
Adducts the eyeball
What is the action of the lateral rectus muscle?
Abducts the eyeball
How can you clinically test the lateral rectus muscle?
Abduction of the eye
Explain how you can clinically test the superior rectus muscle?
Elevate eye in abduction
this is because it cannot do adduction or rotate medially when eye fully abducted so definitely testing this muscle
Explain how you can clinically test the inferior rectus muscle?
Depress the eye in abduction
this is because cannot adduct or rotate laterally so know testing this muscle
Explain how you can clinically test the medial rectus muscle?
Adduction of the eye
Explain how you can clinically test the inferior oblique muscle?
Elevate eye in adduction
Explain how you can clinically test the superior oblique muscle?
Depress eye in adduction
Which muscles can depress the eye?
Superior oblique and inferior rectus
These antagonise each other as rotators
Which muscles can elevate the eye?
Superior rectus and inferior oblique
These antagonise each other as rotators
What nerve gives sensory innervation to the face?
Trigeminal nerve
Name a somatic reflex of the eye?
Corneal reflex/ blink reflex
What is the corneal reflex/ blink reflex?
Blinking of eyes elicited by stimulation of the cornea
Describe the sensory afferent and motor efferent limbs of the corneal reflex?
Sensory: APs conducted by CNV1 when feel something touch the cornea
Motor: Action potentials conducted via CN VII
To eyelid part of orbicularis oculi
Name 4 autonomic reflexes of the eye?
wide eye opening of fight or flight
pupillary light reflex
accommodation reflex
lacrimation reflex
Sympathetic innervation will do what 4 things to the eye?
Open eyes wider
Get more light into eyes
Focus on objects further away
Potentially involved in emotional tears
Parasympathetic innervation will do what 3 things to the eye?
Get less light into eye
Focus on near objects
Reflex lacrimation
Parasympathetic innervation ___1___ the pupil and sympathetic innervation ___2____ the pupil
1) constricts
2) dilates
What muscle is responsible for pupil constriction?
Sphincter pupillae
What muscle is responsible for pupil dilation?
Dilator pupillae
Special sensory (afferent) limb of the pupillary light reflex is ____1____ and conducted by __2__. CNS connections occur in the __3____ The motor limb of the reflex is __4___ via ___5___.
1) ipsilateral
2) CN II
3) midbrain
4) bilateral (consensual vs direct eye)
5) CNs III
Describe the lens accommodation reflex in far vision?
the ciliary muscle relaxes in “far vision”
ligament tightens & lens flattens to focus on an object in the distance
Describe the lens accommodation reflex in near vision?
the ciliary muscle contracts in “near vision”
ligament relaxes & lens becomes spherical to focus on near objects
What are the three types of tears? Purpose?
Basal > for health of avascular cornea
Reflex > extra tears in response to mechanical or chemical stimulation
Emotional
What is the sensory and motor limb in reflex tears?
afferent limb is CN V1 from cornea/conjunctiva
efferent limb is parasympathetic axons originating from CN VII (via the pterygopalatine ganglion)
Sympathetic innervation exits spinal cord from levels?
T1-L2
Describe sympathetic innervation to the orbit?
Exits at T1
Passes all the way up the chain into the cervical region and synapses in the superior cervical ganglion
What ganglia is involved in parasympathetic innervation to the orbit? What nerve is it related to?
Ciliary ganglion
Oculomotor nerve
What are the meninges?
protective coverings surrounding brain and spinal cord
3 layers of the meninges?
Dura mater
Arachnoid mater
Pia mater
Describe dura mater?
Outer layer
hard, tough covering, contains dural venous sinuses
Describe arachnoid mater?
Middle layer
has arachnoid granulations
Describe pia mater?
Inner layer
mater that adheres to the brain
What contains the CSF?
The subarachnoid space (space between arachnoid mater and pia mater)
Ventricles of the brain
You can obtain sample of CSF from lumbar puncture at what levels?
L3/L4 or L4/5 IV disc
CSF is produced in?
The choroid plexus
Why is ICP important to know about in ophthalmology?
65-75% of patients with ICP will report visual problems
transient blurred vision
double vision
loss of vision
papilloedema (swelling of optic disc due to increased ICP)
pupillary changes
Why is the optic nerve particularly effected by raised ICP?
The optic nerves are technically just continuations of the CNS tract so are covered in meninges so any raised ICP will be transmitted along the subarachnoid space in the nerve sheath.
Why is the oculomotor nerve susceptible to damage in increased ICP?
Due to its position
If problems with oculomotor nerve due to increased ICP what will not work?
Paralysis of somatic motor innervation: 4 extra-ocular muscles and eyelid (inferior oblique, LPS, medial and inferior rectus, superior rectus). Paralysis of parasympathetic innervation sphincter of pupil
What will an eye with paralysed oculomotor nerve look like? Explain
lose/slowness of pupillary light reflex (loss of parasympathetics), dilated pupil, ptosis (can’t use LPS), eye turned inferolaterally (can only use the superior oblique and the lateral rectus muscle when try to look straight on)
When you ask a patient with a paralysed oculomotor nerve to look straight ahead what will happen?
They will look down and out
Inferolaterally
Can only use superior oblique and lateral rectus
Why is the trochlea nerve susceptible to damage from increased ICP?
Due to its long length and long intracranial route
Which cranial nerve has the longest intracranial course?
Trochlea nerve
What is paralysed if trochlea nerve is damaged?
The superior oblique muscle
What will happen in a patient’s eye if lose the function of the trochlea nerve?
When ask patient to look to the right the eye moves superomedially as inferior oblique is unopposed so it can’t stay in proper plane.
What is paralysed if the abducent nerve is damaged?
Lateral rectus
What will happen in a patient’s eye if they lose the function of the abducent nerve?
Eye cannot move laterally in horizontal plane
Medial deviation of the eye
What nerve is paralysed… when patient is asked to look straight on their eye moves inferolaterally?
Oculomotor nerve
What nerve is paralysed… when patient is asked to look to the right the eye move superomedially?
Trochlea nerve
What nerve is paralysed… there is medial deviation of the eye?
Abducent nerve
