Lecture 11 - Anatomy + Eye Conditions Flashcards
What is the shape of the orbital cavity and how is it orientated?
Pyramidal
Apex pointing posteriorly
Base of pyramid superficial/anterior
Look at the last slide on image 8:
Label all the bones contributing to the bony orbit
1 = frontal
2 = sphenoid
3 = lacrimal
4 = ethmoid
5 = maxilla
6 = Zygomatic
What forms the medial wall of the orbital cavity?
Ethmoid
Lacrimal
What forms the lateral wall of the orbital cavity?
Zygomatic
Sphenoid
What forms the floor of the orbital cavity?
Maxillary bone
+
Zygomatic
What forms the roof of the orbital cavity?
Frontal bone
What are the 2 weakest parts of the orbital cavity?
Floor = maxillary + zygomatic
Medial wall = ETHMOID + lacrimal
Why can acute sinusitis involving the ethmoid sinus spread into the orbit?
The ethmoid is extremely thin
How can infection spread from the orbit out?
Tears drain via nasalacrimal duct from the orbit to the nasal cavity q
What sinus forms the floor of the orbit?
Maxillary air sinus
What is an orbital blow out fracture?
What causes it?
When there’s a sudden increase in Intra-orbital pressure from trauma to the eye/orbit
Fracture to the orbital floor (MAXILLA)
What is the most common part of the orbit to fracture in an orbital blowout fracture?
Maxilla (floor of orbit)
What is usually visible on a CT head of an orbital blow out fracture?
Orbital contents prolapse and bleed into maxillary sinus
Why do patients often have double vision worsened with upward gaze in orbital blowout fractures and periorbtal swelling?
Numbness over cheek, lower eye lid and upper lip on that side?
The muscles and soft tissues get stuck in fracture site preventing upward gaze
Numbness = infra orbital nerve can be damaged
What nerve does the infra-orbital nerve branch from?
Why can this be damaged in an orbital blow out fracture?
Maxillary division of the Trigeminal nerve (Vb)
Infraorbital nerve runs through the infraorbital Foramen of the maxillary bone
Look at the last slide and view the Head CT labelled 9:
What is this indicative of?
What can you see?
This is the anterior cranial fossa
This is a left sided orbital blowout fracture
Can be seen that the contents of the orbit have herniated into the maxillary sinus (since the black air isn’t visible)
What typically causes a orbital blowout fracture?
Punch/ball to face
How is orbital blowout fractures managed?
CT orbit
Avoid nose blowing, valsalva manoeuvres and driving till Diplopia gone
Surgical repair if symptoms persist after 2 weeks
What are the 3 main openings in the orbital cavity?
Optic canal
Superior orbital fissure
Inferior orbital fissure
What nerves run through the optic canal?
What blood vessels?
CN II (Optic nerve)
Artery = ophthalmic artery
What nerves run through the superior orbital fissure?
What blood vessels?
CN III, IV, Va and VI
(All the muscles moving the eye nerves and sensory of surface of eye Va)
Vein = superior ophthalmic vein which communicates with the cavernous sinus
What nerves run through the inferior orbital fissure?
Where does this nerve exit?
What blood vessels?
Infraorbital nerve which is a branch of the Maxillary division of Trigeminal (Vb)
Infraorbital then leaves orbit via Infraorbital Foramen
Vein = inferior opthalmic vein
What nerve is responsible for detecting pain from a wood chip hitting the eye?
Ophthalmic division of the Trigeminal nerve (Va)
What is the orbital septum?
Thin fibrous sheet of tissue that originates from the orbital rim that separates the Intra-orbital contents from muscle and subcutaneous tissue of eyelid
What is the important immune function of the orbital septum?
Acts as a barrier to stop infection spreading from the superficial eyelid area (pre-septal) into the orbital cavity proper
What is a pre-septal infection of the superfical eyelid region called?
Periorbital/preseptal cellulitis
What is a post-septal infection of the orbital cavity proper called?
Post-septal cellulitis
What is an infection called that is anterior to the orbital septum?
Pre-septal/Periorbital cellulitis
What is an infection called that is poster to the orbital septum?
Post-septal/orbital cellulitis
What can cause peri-orbital cellulitis?
Secondary to superficial infections from bites or wounds
How does Periorbital cellulitis present?
Around eye can be swollen
Painful
BUT ocular function (eye movements and vision are FINE)
How does orbital (post-septal) cellulitis present?
Proptosis/exophthalmous (eye pushed towards in orbital cavity)
Reduced and painful eye movements
Reduced visual acuity
Why do patients with orbital cellulitis have painful eye movements and/or reduced visual acuity?
The exudate fluid/inflammation increases the Intra-orbital pressure compressing the optic nerve since the infection is postseptal/ in the orbit
Where can an orbital cellulitis spread to which is dangerous?
Can spread intracranially:
-cavernous sinus (then cause thrombosis)
-meningitis
What makes up the eye lids?
Skin
Subcutaneous tissue
Muscles
Tarsal plate
What are the 2 key muscles that run in the eyelid?
Orbicularis oculi (Palpebral part)
Levator Palpebrae superioris
What is the innervation and function of orbicularis oculi?
CN VII
Closes the eyelid
What is the innervation and function of Levator palpebrae superioris?
Retracts eyelid
CN III (occulomotor) and sympathetic fibres (smooth muscle part)
What does the levator palpebrae superioris insert into?
Tarsal plate and orbital septum
Go to the last slide and label image 1:
1 = Orbicularis oculi
2 = levator palpebrae superioris
3 = tarsal plate
What are the 2 types of glands located int he eye lids?
Meibomian glands
Glands associated with lash follicle
Where are meibomian glands located in the eyelids?
Go to last slide and label image 2:
In the tarsal plate
1 = meibomian glands in tarsal plate
2 = glands associated with hair follicle
What is the function of the Meibomian glands?
Modified sebaceous gland
Provide lipid layer of tear film
Preventing tear evaporation and spillage over lid
What is the function of the glands associated with lash follicles?
Sebaceous secreting oily substance
What are the 2 types of eyelid lumps?
Stye
Meibomian cyst
What structure of the eyelid is normally involved in a Stye?
Glands associated with the hair follicles
How does a Stye present?
Outer margin of eyelid
PAINFUL
Red with white punctum
What is usually the cause of a Stye ?
What is the treatment?
Infection of glands associated with hair follicles (staphylococcus)
Warm compress / oral abx
What is a Meibomian cyst?
Blockage of Meibomian gland (NON INFECTIVE CAUSE)
How does a Meibomian cyst present?
PAINLESS
Gradually enlarging firm lump
How is a Meibomian cyst treated?
1/3 solve spontaneously
Surgical incision if needed
What is a good differential between a Stye and meibomian cyst?
Stye = Painful lump on edge of eyelid
Meibomian cyst = PAINLESS lumb deeper in the eyelid
What is Blepharitis?
Inflammation of the whole eyelid margin
How does blepharitis present?
Dry, crusty, itch swollen and red eyelids
What can cause Blepharitis?
Staphylococcus infection of glands
Meibomian gland dysfunction
How is Blepharitis treated?
Warm compress
Lid hygiene
Go to the last slide and label image 3:
1 = lacrimal gland
2 = optic nerve
3 = ophthalmic nerve
4 = ophthalmic vein
What are the 3 layers of tear film?
Oily
Water
Mucus
What produces the oily component of the tear film?
Meibomian glands
What produces the watery component of the tear film?
Lacrimal Gland
What produces the mucus component of the tear film?
Conjunctiva (goblet cells)
What 3 apparatus form the tear film?
Meibomian glands
Lacrimal glands
Conjunctiva
Why is blinking useful?
Distributes tear film across surface of eye rinsing and lubrication the conjunctivae and cornea
Where are the lacrimal glands located?
Top lateral side of each eye
Describe the movement of tear film :
Made by lacrimal gland
Moves across eye, drained into a hole called the Lacrimal Punctum
Hole leads to Lacrmial canaliculi which drain into the lacrimal sac and down the NASOLACRIMAL DUCT
What structures hold the eyeball in place?
Suspensory ligament
6 extra ocular muscles
Orbital fat
What is a common sign that a retrobulbar/retro orbital pathology has occured?
What is the medical term for this?
Globe/eyeball displaces anteriorly
Proptosis/exophthalmos
What is the difference between Proptosis and exophthalmos?
Proptosis = anterior displacement of an organ
Exophthalmos = anterior displacement of eye ball
What part of the eye is affect by autoantibodies in Graves’ disease causing Proptosis of the eye (exophthalmos)?
Retroorbital tissues
What is the transparent membrane called that covers the entire surface of the eye except for over the cornea?
Conjunctiva
What is the conjunctiva?
Mucus membrane that has blood vessels within it
How are the conjunctiva structured?
Reflects onto inner surface of the eyelids stopping you losing contact lenses behind your eye
What is the junction between the sclera and the cornea called?
Limbus
What are the 2 types of painless causes of a red eye?
Conjunctivitis
Subconjunctival haemorrhage
What is conjunctivitis?
Uncomfortable gritty PAINLESS feeling of the eye making it RED
Usually accompanied by a watery discharge
What is the main cause of conjunctivitis?
What are some other causes?
Virus infection
Bacterial infection
Allergic
How does conjunctivitis caused by a virus present differently to a bacterial infective conjunctivitis?
Virus = water discharge
Bacteria = thick purulent discharge
How is conjunctivitis managed?
Self limiting
Don’t share towels and wash hands since Very contagious
What is a subconjunctival haemorrhage and how does it present?
Small bleed between conjunctiva and sclera
Bloody eye
Painless
Go to the last slide and fill out the condition seen in image 4:
Sub conjunctival haemorrhage
How many layers does the eyeball have?
3 layers
What makes up the 3 main layers of the eye?
Outermost to innermost
Sclera
Choroid
Retina
What is the sclera?
The white of the eye that is continuous with the dura (meningeal layer) of the optic nerve
What structure does the sclera become as it moves anteriorly of the eyeball?
Transparent CORNEA
What is the choroid of the eye?
The vascular layer of the eye
What structures are continous with the choroid?
Ciliary body
Iris
What is the term given to the collective of the choroid + ciliary body + iris?
Uveal tract
What suspends the lens?
Suspensory ligaments
How do the central retinal artery and vein reach the eye?
The run through the middle of the optic nerve to supply the Retina
What is the optic disc?
Area where there are no photoreceptors
What is the retina?
Region with photoreceptors
Is continuos with the optic nerve
Go to the last slide and label image 5:
1 = sclera
2 = choroid
3 = retina
4 = ciliary body
5 = iris
6 = pupil
7 = suspensory ligaments
8 = macula
9 = optic disc
10 = central retinal artery and vein
11 = optic nerve
What are some condition causing PAINFUL acute red eye?
Acute closed angle glaucoma
Scleritis
Keratitis
Corneal injury (abrasion, ulcer)
Uveitis
How can a corneal ulcer be seen?
Add Fluor in dye then view under blue light
Defect appears in green
What is Keratitis?
Inflammation (infective or non infective cause) of cornea
What is Scleritis?
Inflammation of sclera
INTENSE PAIN
What is Uveitis?
Inflammation of the iris
How is uveitis normally treated?
Anti inflammatories
Steroids
When is pain with uveitis worse?
Reading or bright light
When a patients looks up with scleritis why can you see a blue patch in the sclera?
Thin sclera exposes choroid
What are the 2 substances that fill the eye?
Aqueous humor = watery
Vitreous Humor = firm jelly like
Where is aqueous humor (watery) located?
Between lens and cornea
Where is vitreous (jelly like) humor located??
Posterior to lens in contact with the retina
There are 2 chambers where aqueous humor is located, where are these 2 chambers?
Anterior chamber = between cornea and iris
Posterior chamber = between iris and lens
Where is aqueous humor produced?
In the posterior chamber by the ciliary bodies
Where does the aqueous humor drain?
At a canal at the iridocorneal angle
Angle between the iris and the cornea
Describe the movement of aqueous humor from production to drainage:
Made by ciliary body
Moves from posterior chamber to anterior chamber
Goes to iridocorneal angle
Drains into trabecular mesh work in the canal of schlemm
What is Glaucoma?
Damage to the optic nerve (CN II) due to raised Intra-ocular pressure
What causes Acute Glaucoma?
Acute closed angle Glaucoma
When there’s an acute narrowing of the iridocorneal angle
Leads to intraoccular rapidly rising
How does Acute closed angle glaucoma present?
Older patients
Acutely PAINFUL RED eye with BLURRED vision
Irregular oval shaped fixed pupil (iris pushed forward)
Nausea and vomiting (happens with IOP)
Why is acute angle closure glaucoma an ophthalmological emergency?
Its sight threatening
If not treated with either drugs or surgery rapidly will have irreversible sight loss
What causes chronic glaucoma?
Where the trabecular mesh work leading into the canal of schlemm gets slowly degraded with age
This leads to aqueous humor building up in eye very slowly so IOPP raises very slowly
How does chronic glaucoma present?
Gradual loss of peripheral vision since the IOP slowly rises since the iridocorneal angle is still open but the trabecular meshwork is slowly degenerating
What is the optic cup?
The bright light seen in the eye within the optic disc
What is an indicator w.r.t the optic cup of GLaucoma?
Increased optic cup:disc ratio on fundoscopy
What is the point on the retina with the point of highest visual acuity/central vision?
Macula (+fovea)
What is the fovea?
Area within the macula that is the thinnest layer of the retina where there are lots of cones present
What are the 2 types of photoreceptors in the retina?
Rods
Cones
How are cones and rods and retinal ganglion cells structured in the retina?
Retinal ganglion cells nearest to vitreous humor which are the axons of the optic nerve
Rods and cones deepens layer
Go the last slide and label the fundoscopic image labelled 6:
1 = macula densa
2 = optic disc
3 = retinal artery
4 = retinal vein
What is the most common cause of blindness in the UK?
Macula degeneration
What is macula degeneration?
Bilateral degeneration of the macula (thins and atrophy’s)
Leads to gradual but noticeable loss of central vision
What is the main artery supplying the orbit and eye?
What branch of this sublimes the retina?
Ophthalmic artery
Central retinal artery
What structure does the central retinal artery run through?
Optic nerve
Had to penetrate through meningeal layers
What 2 blood supplies does the retina need in order to function?
Central retinal artery
Underlying vascular choroid layer (fed by ciliary arteries)
How does Central Retinal Artery Occlusion present?
What causes it?
Sudden painless loss of visions in one eye
Caused by embolus blocking central retinal artery
How can Central Retinal Artery Occlusion be detected on Fundoscopy?
The retina is pale due to ischaemia
Causes RED CHERRY SPOT MACULA (very obvious due to paler ischaemic retina)
What is the main venous drainage of the orbit and the eye?
Ophthalmic veins (superior and inferior)
Where do t he superior and inferior ophthalmic veins drain too and why is this a concern with orbital infections?
Cavernous sinus
Means orbital infections can spread intracranially
Go the last slide and label the image labelled 7:
1 = superior ophthalmic vein
2 = inferior ophthalmic vein
3 = to cavernous sinus)
4 = facial vein
