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ESA 4 - Head and Neck > The Eye > Flashcards

Flashcards in The Eye Deck (29)
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Contents of the superior orbital fissure

Lacrimal nerve
Frontal nerve
Trochlear nerve
Superior oculomotor
Inferior oculomotor


Contents of inferior orbital fissure

Zygomatic branch of facial nerve


Contents of optic canal

Optic nerve, optic artery and vein


Describe the structure and function of the lacrimal apparatus

Lacrimal gland lies in fossa on superolateral part of orbit and secretes lacrimal fluid,
Drains through lacrimal ducts to lacrimal sac at medial angle of eye,
When the cornea gets dry, the eye blinks and the eyelids carry a film of fluid over the eye and sweeps dust and foreign material back to the medial angle.


Describe the gross structure and function of the eyeball

Spherical to permit a variety of movements within the orbit
Light sensitive cells transduce light energy into electrical impulses, and have a direct connection to the brain via the optic nerve
Electrical impulses are processed by the brain, resulting in sight and reflex functions


What is a blowout fracture?

Fracture of the orbital floor (maxillary bone) leading to herniation of the orbital contents into the maxillary sinus

Caused by trauma or injury leading to a sudden increase in intraorbital pressure

Causes vertical diplopia (as the inferior rectus muscle is trapped), enopthalmos, infra orbital anaesthesia


Symptoms of an orbital fracture

Lid swelling
Impaired vision
Restricted eye movements
Reduced visual field
Enopthalmos (or exopthalmos due to increased pressure)


Describe the nerve supply to the eye

Special sensory = optic nerve
Sensory supply to cornea = ophthalmic nerve
Motor innervation = oculomotor, trochlear, abducens (SO4 LR6 R3)
Parasympathetic = fibres from ciliary ganglion travel with inferior oculomotor nerve to sphincter papillae and ciliary muscles
Sympathetic = fibres from superior cervical ganglion travel with superior oculomotor to dilator papillae and tarsal muscles


Describe the structure of the optic nerve

It is an extension of the brain, so is surrounded by cranial meninges: Pia mata, arachnoid mata, dura mata

Has central artery and vein


What are the three layers of tissue around the eyeball

Sclera = protective outer fibrous layer, forms white of the eye, provides attachment for extraocular muscles, has transparent part at front to let light through (cornea).

Choroid = middle vascular layer, gives red light reflex, terminates anteriorly as the ciliary bodies.

Retina = inner layer with photoreceptors


What are the macula lutea, fovea centralis and optic disc?

All parts of the retina

Macula lutea is a specialised area for visual acuity, containing the most photoreceptors

Fovea centralis is the centre of the macula lutea

Optic disc is the circular depressed area where the optic nerve enters, has no photoreceptors (blind spot)


Describe the structure and function of the lens and iris

Lens = a transparent biconcave disc enclosed in a capsule, attached to the ciliary bodies by suspensory ligaments. Contraction of ciliary bodies changes the shape of the lens to focus light to the back of the retina

Iris = thin contractile diaphragm with a central aperture (pupil) for the transmission of light. Sphincter and dilator papillae muscles control the pupil size


Describe the different segments and chambers within the eye

Anterior segment = anterior to the lens, contains aqueous humor.
Split into anterior chamber (between the cornea and iris) and the posterior chamber (between the iris and the lens)

Posterior segment = posterior to the lens, contains vitreous humor


What is the function of aqueous humor and where is it made/found?

Provides 02 and nutrients to the lens

Produced by the ciliary bodies and flows out via the trabecular meshwork

Found in the anterior segment


What is the function of vitreous humor and where is it found?

Jelly like substance, supports lens and holds retina in place

Found in the posterior segment


Describe the structure and attachments of the eyelids

Palpebral conjunctiva over inner surface of eyelid
Bulbar conjunctiva covers the cornea (not over the iris)

Tarsal plates (connective tissue bands) strengthen the eyelids, contain the tarsal glands to lubricate the edge of the eyelids and prevent them sticking together


Difference between a style and a meibomian cyst

Meibomian cyst is inflammation of the tarsal glands

A style is inflammation of the ciliary glands

Both lead to obstruction of the ducts and a painful swelling in the eyelid


Describe the muscles and neural innervation involved in opening the eyelids

Levator Palpebrae Superioris - attached to the lesser wing of the sphenoid bone above the optic foramen, raises the superior eyelid, innervated by the Oculomotor nerve

Superior Tarsal Muscle - smooth muscle within the LPS, assists the LPS, sympathetic innervation


Explain the difference between partial and complete ptosis

Partial ptosis- occurs in damage to the sympathetic trunk in the neck (Horners syndrome) leading to denervation of the superior tarsal muscle

Complete ptosis- occurs in damage to the oculomotor nerve due to aneurysm, raised intracranial pressure or cavernous sinus thrombosis


What is glaucoma and what are the different types?

Glaucoma is raised intraocular pressure due to increased aqueous humor leading to compression of the retinal arteries and subsequent retinal damage and loss of vision.

Open angle: reduced outflow of aqueous humor through the trabecular meshwork, increases angle between cornea and iris.
Causes painless, gradual loss of vision

Closed angle: iris is forced against the trabecular meshwork, preventing drainage.
Emergency, can rapidly cause blindness


Describe cataracts and their clinical presentation

Flattening and hardening of the lens leading to gradual loss of vision and inability to focus light (glares)
Causes = diabetes, steroids, idiopathic


Describe orbital cellulitis and its clinical presentation

Inflammation of the eyelids due to infection
leading to pain, sticky discharge, fever, restricted eye movements, loss of vision, loss of colour vision


Describe thyroid eye disease and its clinical presentation

Ocular irritation leading to redness, diplopia, exopthalmos, lid retraction, lid lag, proptosis

Can lead to restrictive myopathy (due to enlarged extraocular muscles), optic neuropathy (muscles compress optic nerve), corneal ulceration


Describe the presentation of possible nerve palsies affecting the extraocular muscles

Oculomotor nerve palsy: down and out eye, pupil dilation, ptosis

Trochlear nerve palsy: paralysis of SO, patient can't depress abducted eye, diplopia walking down stairs, head tilt away from side of lesion

Abducens nerve palsy: paralysis of LR, patient can't abduct eye


What is papilloedema?

Swelling of the optic disc due to increased intracranial pressure (eg. Haemorrhage, tumour)
Pressure reduces venous return from the eye so fluid collects in retina and is visible in ophthalmoscopy


What is retinal detachment and how does it present?

Neural layer of retina separates from pigmented layer of retina, following a blow to the eye

Leads to flashes of light, 'floaters', darkening of peripheral vision


Describe occlusion of the retinal artery/vein and how they present

Central retinal artery occlusion: occurs in elderly due to embolism, leads to immediate and total blindness

Central retinal vein occlusion: occurs due to thrombosis, dehydration, leads to slow, painless loss of vision.
Gives stormy sunset appearance of retina due to numerous haemorrhages


Describe the blood supply to the eye

Opthalmic artery (branch of ICA)

Central artery of retina = specific branch to the retina


What bones make up the orbit and its walls

Apex = optic canal
Superior wall = frontal and sphenoid
Inferior wall = maxillary and zygomatic
Lateral wall = zygomatic and sphenoid
Medial wall = ethmoid, maxillary, lacrimal and sphenoid