Ophthalmology Flashcards
What are the 7 bones that make up the orbital wall
Orbital plate of frontal
Orbital plate of ethmoid
Orbital plate of maxilla
Palatine bone
Sphenoid bone
Zygomatic bone
Lacrimal bone
What are the orbital walls
Roof - orbital plate of frontal bone and lesser wing of sphenoid
Floor - orbital plate of maxilla and palatine
Medial - orbital plate of ethmoid, lacrimal and maxilla
Lateral - zygomatic and greater wing of sphenoid
What are the structures in the orbital walls that allow exit/entry of structures
Optic canal
Superior orbital fissure
Infraorbital foramen
Supraorbital notch
Name A-J
A- greater wing of sphenoid bone
B- superior orbital fissure
C- lesser wing of sphenoid bone
D- frontal bone
E- optic canal
F- ethmoid bone
G- Lacrimal bone
H- palatine bone
I- Maxilla
J- zygomatic bone
Name A-L
A- orbital plate of frontal bone
B- Optic canal
C- Superior orbital fissure
D- Infraorbital foramen
E- Orbital plate of ethmoid
F - Supraorbital notch
G- Frontal bone
H- Zygomatic bone
I- Maxilla bone
J- Sphenoid bone
K- Ethmoid bone
L- Lacrimal bone
Name A-D
A- supraorbital notch
B- Optic canal
C- Superior orbital fissure
D- Infraorbital foramen
What structure does optic canal transmit
Optic nerve
Ophthalmic artery
What structure does Superior orbital fissure transmit
Oculomotor nerve CN III
Trochlear nerve CN IV
Abducens nerve CN VI
Superior ophthalmic vein
Frontal nerve (branch of trigeminal)
Lacrimal nerve (branch of trigeminal)
Frontal nerve is a branch of
Ophthalmic division of trigeminal nerve CNV1
Lacrimal nerve is a branch of
Ophthalmic division of trigeminal nerve CNV1
Infraorbital foramen allows the passage of
Infraorbital nerve
infraorbital neurovascular bundle
Infraorbital nerve is a branch of
Maxillary division of trigeminal nerve CN V2
Supraorbital notch allows the passage of
Supraorbital nerve
Supraorbital neurovascular bundle
Supraorbital nerve is a branch of
ophthalmic division of trigeminal nerve
Which part of the orbital wall is the weakest
Inferior wall
Which orbital wall may also be damaged when the inferior orbital wall is damaged
Medial wall
Why do blowout fractures occur
Because the orbital rim is tough whereas the orbital wall is weaker hence pressure is transferred to the orbital walls and cause a fracture there instead
Which wall is most susceptible to blowout fractures
Inferior orbital wall
What can happen due to blowout fractures
Orbital fat herniates into maxillary sinus
Trap structures
- inferior rectus muscle -> unable to depress the eye
- infraorbital nerve -> parasthesia of face
Where does infraorbital nerve innervate
Sensory innervation to the skin of lower eyelid, side of nose, anterior cheek, upper lip
Hence blowout fractures affecting infraorbital nerve can cause parasthesia in those areas
What is the most superficial muscle of the eyelid
Orbicularis oculi muscle
What are the 2 parts of orbicularis oculi muscle
Orbital part
Palpebral part
Function of the parts of orbicularis oculi
Orbital - TIGHTLY closes the eyelid
Palpebral - GENTLY closes the eyelid
Innervation of orbicularis oculi
Facial nerve CN VII (it is a muscle of facial expression)
What are the structures deep to orbicularis oculi
Superior and Inferior tarsal plates
Medial and lateral palpebral ligaments
Levator palpebrae superioris
Orbital septum
Name A-F
A- lateral palpebral ligament
B- tendon of Levator palpebrae superioris
C- superior tarsal plate
D- medial palpebral ligament
E- inferior tarsal plate
F- orbital septum
What structures are in the tarsal plates
Meibomian glands
Function of meibomian glands
Secrete meibum to
- prevent evaporation of tear film
- prevent eyes sticking together when closed
Function of the orbital septum
Prevent spread of infection between superficial and deep parts of the orbit
Where does levator palpebrae superioris attach to
From sphenoid bone -> superior tarsal plate
What are the 2 components of levator palpebrae superioris
LPS and superior tarsal muscle (Smooth muscle)
Name A-D
A- levator palpebrae superioris
B- orbicularis oculi muscle
C- meibomian gland
D- superior tarsal muscle
Function of LPS
LPS- elevates upper eyelid
Superior tarsal muscle - widening eyes
Innervation of LPS
LPS - oculomotor nerve
Superior tarsal muscle - sympathetic nervous system
Where is the lacrimal gland located
Superolaterally at upper eyelid
Innervation of lacrimal gland
Secretomotor: Parasympathetic axons from CN VII
Sensory: lacrimal nerve from ophthalmic division of trigeminal nerve
Describe how does lacrimal fluid move
- Produced in lacrimal gland and washes over the eye
- Pushed over to the medial angle every time we blink
- Drains through the lacrimal puncta
- Than to the canaliculi -> lacrimal sac -> nasolacrimal duct
- Nasolacrimal duct drain into the inferior meatus in nasal cavity
Where does the nasolacrimal duct drain into
Inferior meatus of nasal cavity
Name A-E
A- Lacrimal gland
B- Canaliculi
C- Lacrimal sac
D- Lacrimal puncta
E- Nasolacrimal duct
What does the conjunctiva cover
The sclera and the inside of eyelids
It does not cover the cornea
The conjunctiva is avascular/vascular
Vascular
Name A-F
A- iris covered by cornea
B- conjunctival vessel
C- lower eyelid lined by conjunctiva
D and E- white sclera covered by conjunctiva
F- corneoscleral junction
Name A-C
A- Iris
B- Pupil
C- Cornea
What is the outermost layer of the eye
Fibrous layer consisting
- sclera (posterior 5/6)
- cornea (anterior 1/6)
What are the features of the cornea
It is densely innervated
It provides 2/3 of refractive power
It is completely avascular
Since the cornea is completely avascular, what structures supplies its nutrition
Aqueous humour in anterior chamber
Which nerve innervates the cornea
Ophthalmic division of Trigeminal CNV1
Function of sclera
Provides attachment for extra ocular muscles
The sclera is avascular/vascular
Vascular but less vascularised than conjunctiva
What is the 2nd layer of the eye
Uvea - consisting of iris, ciliary body and choroid
What are the 3 parts of uvea
Iris
Ciliary body
Choroid
The uvea is avascular/vascular
Vascular
Function of the iris
Pigmented membrane with a central opening (pupil) which can be adjusted in size in response to light
What muscles control the size of the iris
Dilator pupillae muscle
Sphincter pupillae muscle
Theses are within the iris
How does the pupil dilate (mydriasis)
When the dilator pupilllae muscle contract
Innervation of the dilator/sphincter pupillae muscle
Dilator - sympathetic
Sphincter - parasympathetic
Function of the ciliary muscle
Control shape of lens for accomodation
Produce aqueous humour
What are the 2 parts of ciliary body
Ciliary muscle - consist of smooth muscles
Ciliary processes
Function of the choroid
Highly vascularised to provide nutrition and gas exchange to outer layers of the retina
What are the 2 segments of the eye
Anterior
Posterior
Where is the anterior segment located at
In front of the lens
What are the 2 parts of anterior segment
Anterior chamber
Posterior chamber
Describe the location of anterior and posterior chambers of the anterior segment
Anterior chamber - between cornea and iris
Posterior chamber- between iris and suspensory ligaments
What is contained in the anterior segment of the eye
Aqueous humour produced by ciliary muscles
What is contained in the posterior segment of the eye
Vitreous body containing vitreous humour
Describe the circulation of aqueous humour
- Ciliary body and process secretes the aqueous humour
- The aqueous humour circulates within the posterior chamber and nourishes the lens
- The aqueous then passes through pupil into anterior chamber to nourish the cornea from the posterior aspect
- Aqueous reabsorbed into scleral venous sinus at iridocorneal angle -> drained into systemic venous system
Where is the scleral venous sinus located at
Iridocorneal angle
What holds the canal of schlemm (scleral venous sinus) open
Trabecular meshwork
What happens when the trabecular meshwork is blocked
Acute angle closure glaucoma
What is the interior (posterior) surface of the eye called
fundus
What structures does the fundus consist of
Retina
Optic disc
Macula
Fovea
What are the 4 layers of the retina, from deepest to most superficial
Retinal pigment epithelium
Photoreceptors
Bipolar neurons
Ganglion neurons
Since the photoreceptors of the retina is at the deep layer of retina, it means that
Light needs to pass through the layers of neurons and capillaries before it reaches the photoreceptors
The axons of the ganglion neurons come together to form the
Optic disc
Why is the optic disc called the blind spot
Because there are no photoreceptors there
Optic disc is the only point of
entry/exit for blood vessels and axons
the axons exit the optic disc to form the optic nerve
What is the macula
Center of the retina which has the greatest density of cones
Rods vs cones
Cones
- can provide coloured vision,
- activated at high levels of light (due to less pigments) ,
- for high visual acuity
Function of the macula
Central high acuity coloured vision
What is the fovea
Depression at the center of macula for high acuity vision
Name A-L
A- Anterior chamber
B- Cornea
C- corneoscleral junction
D- ciliary body and muscle
E- Ciliary process
F- Optic nerve
G- Central retinal vein and artery
H- Fovea
I- sclera
J- Choroid
K- Retina
L- posterior chamber
What is the main blood supply to the eye
Ophthalmic artery
Ophthalmic artery is a branch of
Internal carotid artery
What are the main branches of the ophthalmic artery
Central retinal artery
Posterior ciliary arteries
Anterior and posterior ethmoidal arteries
What structure is supplied by the central retinal artery
Retina
What structure is supplied by the posterior ciliary arteries
Optic nerve head
What is the clinical significance of anterior and posterior ethmoidal arteries
They form the Kiesselbach’s plexus
If anterior nosebleed, it is likely to be due to anterior and posterior ethmoidal arteries
What veins are responsible for most venous drainage of the eye
Superior and inferior ophthalmic vein
The inferior ophthalmic vein drains into
Superior ophthalmic vein
The superior ophthalmic vein drains into
Cavernous sinus
How does cavernous sinus exit the skull
through superior orbital fissure
What’s the vein that drains the retina
central retinal vein
Name A-F
A- anterior and posterior ethmoidal arteryes
B- ciliary arteries
C- Ophthalmic artery
D- internal carotid artery
E- central retinal artery
F- central retinal vein
Name A-E
A- Maxillary sinus
B- Inferior ophthalmic vein
C- Cavernous sinus
D- Superior ophthalmic vein
E- facial vein
Describe the course of sympathetic innervation of the body
- passes down the spinal cord
- exits the spinal cord with T1-L2 spinal nerves and enter the sympathetic chains
- travel along the sympathetic chain to reach the desired level
- pass into anterior and posterior rami
- then pass into splanchnic nerves to reach the organs
How do sympathetic innervations reach the head and neck
- the nerve fibres exit in T1 and ascend within the sympathetic chain
- Synapses at superior cervical ganglion
- post synaptic axons pass onto the surface of internal and external carotid arteries
- so that these axons follow the arteries up to the organs of the head
Where do the sympathetic axons for head and neck synapse
Superior cervical ganglion
Which artery does sympathetic axons follow in order to supply the eye
ophthalmic artery
How do parasympathetic axons leave the CNS
via
- CN III oculomotor
- CN VII facial
- CN IX glossopharyngeal
- CN X vagus
- spinal nerves
Parasympathetic fibres to the orbit synapses at
Ciliary ganglion
What other axon fibres travel through the ciliary ganglion. Do they synapse there
General sensory
Sympathetic
No, they do not synapse there
Which nerve supplies the parasympathetic fibres to the orbit
CN III
Where is the ciliary ganglion located at
Between the optic nerve and lateral rectus muscle
Describe the sensory innervation of the face
By CN V trigeminal nerve
CN V1
- upper eyelid and above
- cornea
- conjunctiva
CN V2
- lower eyelid to upper lips
CN V3
- lower lips to chin
Describe the nerves involved in the blink reflex
- sensory action potentials produced by the cornea sent to CN V1
- CN V1 travels to the trigeminal ganglion then along the trigeminal nerve to CNS
- CNS connects CN V1 with CN VII (which innervates the orbicularis oculi muscle)
- Impulse sent to CN VII to stimulate contraction of orbicularis oculi muscle
Describe the pupillary light reflex
- light is shine on one eye
- this generates action potential that is sent to both pretectal nuclei in the brain
- which stimulates another 2 nuclei (oculomotor nuclei)
- those 2 nuclei then send action potentials along the CN III (parasympathetic) to the sphincter papillae muscle to constrict both pupils = consensual light reflex
Describe the lacrimation reflex
- sensory stimuli triggers action potentials to be sent along CN V1 lacrimal nerve
- action potentials travel to the CNS then sent to parasympathetic fibres originating from CN VII to trigger lacrimation
Describe the lens accommodation reflex
To focus on far objects
- suspensory ligaments tighten to flatten the lens
To focus on near objects
- parasympathetic
- suspensory ligaments relax to curve the lens
What is the vestibule-ocular reflex
Reflex that turns the eyes in the opposite direction to a head movement to stabilise gaze on an object during head movement
