Eye Flashcards
Which bone makes up the roof of the orbit?
Orbital plate of the frontal bone
Which bone makes up the floor of the orbit?
The maxilla
Which structure is being indicated here?
Supraorbital notch/foramen
Which structures are being indicated here?
- Optic canal
- Superior orbital fissure
(Both part of sphenoid bone)
Which structures of which bone are indicated here?
Infraorbital canal and foramen of maxilla
Which bone of the orbit is indicated in blue?
Lacrimal
Which bone of the orbit is indicated in yellow?
Orbital plate of ethmoid bone
Which structure protects the eye from a direct blow?
The orbital margins
Which bones tend to fracture in an orbital blowout fracture and why?
Orbital plate of ethmoid bone (medial wall)
Maxilla (floor)
They are extremely thin - 0.5-1mm thick
How does a fractured zygoma tend to displace?
Tends to rotate medially to the floor of the orbit
Which structure is held within the infraorbital canal?
Infraorbital NVB
Which muscle makes up the ‘sphincter’ of the eye and what movement does it allow?
Obicularis oculi
Allows us to screw up the eyes
Which two ligaments attach the eyelid to the orbital rim?
Medial and lateral palpebral ligaments
Which structure is being indicated here and what is its function?
Tendon of levator palpebrae superioris
Contains skeletal and smooth muscle to elevate the superior eyelid
Which structures are being indicated here?
Superior and inferior tarsal plates
What is the orbital septum?
A sheet of fascia attaching to the peripery of the orbital rim
What does the orbital septum do?
Assists with preventing the spread of infection from superficial (periorbital cellulitis) to deep (orbital cellulitis)
What is the conjunctival fornix?
Where the conjunctiva is reflected off the sclera and onto the internal aspect of the eyelid
What is the name given to the orbital opening into the nasolacrimal duct?
Puncta
What is the name of the junction between the cornea and the sclera?
The limbus
What is the parasympathetic supply of the lacrimal gland?
CN VII
What is the name of the superior end of the nasolacrimal duct?
Lacrimal sac
Where should corneal reflections be seen normally?
Slightly medial i.e. nasal side of the pupil (as opposed to temporal side)
What are the two parts of the outer fibrous layer of the eye?
Sclera
Cornea
What is the function of the sclera?
Protects the eye
Provides attachment for the extraocular muscles
What is the function of the cornea?
Provides 2/3 of the eye’s refractive power
What are the three parts of the uvea?
The iris
The ciliary body
The choroid
What is the vascular layer of the eye?
The uvea
What is the function of the ciliary body of the eye?
Control of the iris and the shape of the lens
Secretion of aqueous humour
What is the photosensitive layer of the eye?
The inner retina
What is the function of the choroid?
Nutrition and gaseous exchange for the other layers
Which is the ‘vascular’ layer of the eye?
Choroid
What is the vitreous body?
A structure in the posterior segment which holds a clear gel consisting of ~98% water that provides pressure to hold the retina in place
What is the anterior chamber?
The space containing aqueous humour between the cornea and the iris
What is the posterior chamber?
Contains the lens and aqueous (humour) and is located between the iris and the vitreous body
What is the function of the ciliary body?
Controls the refractive shape of the lens and the secretion of aqueous humour
What is the area of most acute vision in the eye?
The fovea centralis in the macula - contains the largest density of cones
What is the only vein that drains the retina?
Central vein of the retina
Which structures are being indicated here?
How do the opthalmic veins drain the orbit?
Anteriorly: orbit drains into the facial vein
Posteriorly: inferior opthalmic vein drains mainly into superior opthalmic vein, and drains into the cavernous sinus
Through which structure does the superior opthalmic vein drain into the cavernous sinus?
Superior orbital fissure
What is the retinal blood supply provided by?
The central retinal artery
The central retinal vein
Which artery do the ciliary arteries branch from?
Opthalmic artery
What is the result of an occlusion of a retinal artery branch/branch retinal vein?
An area of visual loss corresponding to the area of ischaemia
What is the result of a complete interruption of flow to the central retinal artery or vein?
Monocular blindness
Which structure does the ‘blind spot’ of the visual field correspond to?
The optic disc
What are the three layers of the retina posterior - anterior?
- Photoreceptors
- Ganglion cells
- Axons of ganglion cells
Where in the brain are the visual cortices?
In the occipital lobes
Where in the visual pathway does synapse occur?
Right and left sides of the thalamus
Does light picked up in the temporal retina cross over in the optic chiasm as the action potentials travel in the visual pathway?
No
Does light picked up in the nasal retina cross over at the optic chiasm as the action potential travels along the visual pathway?
Yes
Where do the rectus muscles of the eye all originate and insert?
They have a common origin - common tendinous ring attached to the bones surrounding the optic canal
All insert into the sclera just posterior to the cornea
What are the 7 extraocular muscles?
4 rectus - superior, inferior, lateral and medial
2 obliques - superior and inferior
Levator palpebrae superioris
What is the trochlea of the eye?
A fibrous structure used as a pulley by the superior oblique muscle of the eye
It attaches superomedially to the rim of the eye
What is the motor innervation to the extraocular muscles?
LR6 SO4 AO3
Lateral rectus - abducens
Superior oblique - trochlear
All others - oculomotor
Which muscle abducts the eye?
Lateral rectus
If a patient is asked to look to the left, which muscles in each eye are working?
Left eye - lateral rectus
Right eye - medial rectus
What movement of the eye does the inferior oblique provide?
Elevates from the aDDucted position
What movement of the eye does the superior oblique provide?
Depresses the eye from the aDDucted positon
Which muscles are working in each eye if the patient is asked to look left and upwards?
Left eye - lateral rectus and superior rectus
Right eye - medial rectus and inferior oblique
Which muscles are working if the patient is asked to look up?
Both eyes - superior rectus and inferior oblique
Which muscles are working if the patient is asked to look down?
Both eyes - inferior rectus and superior oblique
What is the general sensory nerve supply to the upper eyelid, the cornea, all the conjunctiva and the the skin of the root/bridge/tip of the nose?
Opthalmic nerve CN V1
What nerves are involved in the blink reflex?
Afferent: Cornea - V1 - V - pons
Efferent: VII - obicularis oculi
How does sympathetic innervation reach the orbit?
Sympathetic fibres exit the spinal cord at T1, and travel upwards to synapse in the superior cervical chain
Post synaptic fibres enter the external carotid nerve and internal carotid nerve, attached to the arteries
They are carried along the arteries to the orbit
What structures are being indicated here?
What is the base of skull course of the oculomotor nerve?
Superior orbital fissure
Where does the oculomotor nerve connect with the CNS?
Junction between midbrain and pons
What is the function of the ciliary nerves?
Supply autonomic axons to the iris to alter diameter of pupil and to change refractive shape of lens
What structures are there in the ciliary ganglion?
Presynaptic fibes of CN III
Postsynaptic sympathetic fibres from the superior cervical ganglion
Postsynaptic fibres from the ciliary ganglion
General sensory fibres from the cornea and conjunctiva
What are the four autonomic relfexes of the eye?
Pupil dilation/constriction
Lacrimation
Maximal eyelid elevation
Focussing the lens
What is the vestibulo-ocular reflex?
Turns the eyes in the opposite direction to a head movement
What nerves are involved in the vestibulo-ocular reflex?
Vestibulocochlear VIII
Oculomotor III
Trochlear IV
Abducens VI
What is the oculocardiac reflex?
Reflex bradycardia in response to pressure on the eye or tension on extra ocular muscles
Which nerves are involved in the oculocardiac reflex?
Opthalmic nerve V1
Vagus X
What changes to the eye does sympathetic innervation cause?
Open eyes wider
Pupil dilation
Focus on far objects
? emotional lacrimation
What changes to the eye does parasympathetic innervation cause?
Allow obicularis oculi to work
Allow less light into eye
Focus on near objects
Reflex lacrimation
What is a non-physiologically dilated pupil called?
A mydriatic pupil
Which muscle allows pupil dilation and what is its origin and insertion?
Dilator pupillae
Origin around the external circumference of the iris
Insertion around the internal circumference of the iris
Which muscle allows constriction of the pupil and where is it located?
Sphincter pupillae
Internal circumference of the iris
What is a non-physiologically constricted pupil known as?
A miotic pupil
What is the special sensory afferent limb of the light reflex?
Optic nerve CN II
What is the light reflex called in the stimulated eye and the other eye?
Stimulated - direct light reflex
Other - consensual light reflex
What is the motor limb of the light relfex?
Oculomotor CN VIII
Which structure connects the surface of the lens and the ciliary body?
Suspensory ligament of the lens
How does the ciliary body change the shape of the lens to allow the eye to focus on object in the distance?
Ciliary muscle relaxes
The suspensory ligament tightens, flattening the lens
No parasympathetic inneravation involved
How does the ciliary body change the refractory shape of the lens to allow focus on near objects?
Ciliary muscle contracts - parasympathetic innervation
Suspensory ligament relaxes and makes the lens spherical
