Opthalmology Anatomy Flashcards
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Orbital rim
Thin part of orbital rim?
What are they at risk of?
Complicatons of this?
Medial wall + orbital floor
* affected by orbital blowout fracture
* Comps: paraesthesia of skin of the face
How do eyelids protect the eyes? (4)
What do they contain? (4)
* Protect eyes: outer skin, inner conjunctiva, eyelashes, glands
* Contain: tarsal plate (maintains shape), meibomian glands (secrete lipids), obicularis oculi (CN7), levator palpabrie superioris (CN3, elevates upper eyelid)
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Lacrimal gland innervation?
Function?
CN7 (parasympathetic)
* produces tears
Lacrimal apparatus?
* Lacrimal gland produces tears
* Pushed towards medial triangle
* drains through lacrimal puncta
* eventually reaches inferior meatus of nasal cavity
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Layers of the eye? (3)
Fibrous - outer layer
* Sclera - white, fibrous
* Cornea - refraction
Uvea (vascular layer) - middle
* Iris
* Ciliary body - controls iris, shape of lens + aqueous humor secretion
* choroid - nutrition and gas exchange
Retina (photosensitive) - inner layer
Where is anterior segment of the eye?
Divided into? (2)
In front of lens
* anterior chamber = between cornea and iris, contains squeous humor
* Posterior chamber = between iris and suspensory ligaments, contaisn aqueous humor
Function of ciliary body of the eye? (3)
Where is it found?
Function
* controls iris
* shape of lens
* aqueous humor secretion
Found in uvea (middle layer)
Posterior segment of the eye?
Function?
Posterior segment is behind the lens, and makes up 2/3rds of the eye
* contrains vitreous body which secretes virteous humor (common place for “floaters”)
Describe circulation of aqueous fluid (4)
1) ciliary body
* secrete aqueous humor
2) aqueous circulates within posterior chamber and nourishes lens
3) squeous passes through pupil into anterior chamber, nourishes cornea
4) aqueous reabsorbed into scleral venous sinus (canal of Schlemm) at irodocorneal angle
Arterial supply to eye?
Opthalmic artery from internal carotid artery
What does the opthalmic artery divide into? (2)
Complication?
* Ciliary arteries + central artery of the retina
It is an end artery - cannot maintain tissue if occlusion occurs
Venous drainage of the eye? (2)
* Superior opthalmic vein drains into cavernous sinusvia superior orbital fissure
* Inferior opthalmic vein drains into superior opthalmic vein
Danger triangle of the face?
Infection in this area of the face can drain back into cavernous sinus and cause cavernous sinus thrombosis
Parts of the retina? (4)
Fundus
*posterior area where light is focused
Optic disc
* point of CN 2 formation
* only point of entry/exit of blood vessels + axons of CN2
* blind spot!!
Macula
* greatest density of cones
Fovea
* centre of macula
* area of most cute vision
Layers of the retina (from posterior to anterior)? (3)
Where do they retinal veins and arteries lie?
1) photoreceptors
2) ganglion cells
3) axons of ganglion cells
Retinal veins and arteries lie aterior to retina
Where is the blind spot of the eye?
Why?
Optic disc
* there are no photoreceptors in the optic disc
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What does interruption of flow in retinal artery branch/vein cause?
What about interruption of flow in central artery (end artery)?
* loss of an area of visual field corresponding to area of ischaemia
* monocular blindness
Where is light from objects in the right visual field processed?
Lower visual field?
* Left primary visual cortext
* upper part of visual cortext
Extrinsic muscles of the eye? (6)
What is different about the superior oblique muscle of the eye?
It passes through a pulley (the trochlear)
Functions of the external muscles of the eye? (6)
* Lateral rectus = laterally
* Medial rectus = medially
* Superior rectus = up and in
* Inferior rectus - down and in
* Superior oblique = down and out
* inferior oblique = up and out
Innervation of extrinsic muscles of the eye? (3)
* Lateral rectus = abducent nerve
* Superior oblique = troclear nerve
* All others = CN III (occulomotor)
Sensory innervation of the eye?
Trigeminal nerve
CN V1 (opthalmic) = upper eyelid, cornea, conjunctiva, tip + bridge of nose
CN V2 (maxillary) = lower eyelid, maxilla, ala of the nose, upper lip
CN V3 (mandibular) = mandible (except ridge of mandible, which is supplied by C2, 3)
Explain the blink (corneal) reflex? (4)
* AP’s conducted from cornea via CN V1 branches to trigeminal ganglion
* Then along CN V to pons
* CNS connections between CN V and CN VII
* AP’s conducted via CN VII to obicularis oculi
Route of sympathetic axons? (4)
* Originate from autonomic centres in brain
* Exit spinal cord with T1 - L2 spinal nerves (thoracolumbar outflow)
* Pass into sypathetic chains + all spinal nerves
* Pass into splanchnic nerves to supply organs
Function of splanchnic nerves?
Types? (2)
Relay sympathetic nerves to organs
* Cardiopulmonary splanchnic nerves - heart + lungs
* Abdominopelvic= abdominal and pelvic organs
How are sympathetics relayed to the eyes?
3 cervical ganglia = superior, middle and inferior
How are sympathetic nerves carried to the eyes?
* Travel from sympathetic trunk and synapse in superior cervical sympathetic ganglion
* Post-synaptic axons enter internal and external carotid nerves
* pass onto surface of internal and external carotid arteries
* carried to organs of the head
* opthalmic artery carries sympathetic axons to orbit
(no splanchnic nerves involved)
Parasympathetic outflow to eye?
Craniosacral outflow
* CN3 + 7
Route of CN III (occulomotor)?
What does it supply? (3)
Connects with CNS between midline and pons
* passes thru cavernous sinus
* exits via superior orbital fissure
Supplies
* somatic motor to superior, medial, inferior rectus + inferior oblique
* somatic motor to levator palpebrae superioris
* presynaptic parasympathetic axons to ciliary ganglion
Divisions of occulomotor nerve?
Suprior division = SR and LPS
Inferior division = MR, IR, IO and ciliary ganglion
Function of ciliary nerves?
Types? (2)
Function of long ciliary nerves?
Supply autonomic axons to control diameter of iris and shape of lens
* Long ciliary nerves = sympathetic, somatic sensory
* Short ciliary nerves = sympathetic, parasympathetic
Long ciliary nerves form first part of blink reflex
CN 3
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Autonomic reflexes of the eye? (6)
* Wide eye opening of fight or flight
* Pupil dilation/constriction (light reflex)
* focusing lens far + near vision (accommodation reflex)
* Lacrimation (tera production)
* vestibulo-ocular reflex (stabilises gaze on object during head movement)
* Oculocardiac reflex - reflex bradycardia in respode to pressure on eye or extraocular muscle tension
Sympathetic vs parasympathetic functions of the eye? (4)
Sympathetic
* open eyes wider
* pupil dilation
* focus on far objects
* emotional lacrimation
Parasympathetic
* pupil constriction
* focus on near objects
* reflex lacrimation (wash foreign body)
How can we blink consciously but also as a reflex?
levator palpabrae superioris contaisn skeletal and smooth muscle
Explain the reflex of opening eyes wider
Postsynaptic sympathetic fibres reach levator palpebrae superioris via:
* superior cervical sympathetic ganglion
* internal carotid nerve
* internal carotid plexus
* carried on opthalmic artery
* to orbit
What is a non-physiologically nlarged pupil called?
Ax?
Mydriatic pupil
* mydriatic drugs
How are dilator pupillae fibres arranged?
* originate around external circumference of iris - fixed
* insert around internal cicrumference of iris - mobile
What is responsible for dilating the pupil?
Constricting the pupil?
* dilate = sympathetics
* constrict = parasympathetics
what is a non-physiologically constricted pupil?
Ax?
miotic pupil
* horner’s syndrome
what is a ficed “pin point” pupil indicative of?
Fixed dilated pupil?
* Serious pathological sign - e.g. opiate drugs
* serious pathological sign e.g. CN III pathology
Which muscle contricts the pupil?
Sphincter pupillae fibrs - around internal circumference of iris
Pupillary light reflex? (3)
* 1st neurones = retinal ganglion cells pass via optic nerve to optic chiasm then midbrain
* 2nd neurones (bilateral) = synapse in midbrain
* 3rd neurones (bilateral) = CN III to ciliary ganglion
* 4th neurones = short ciliary nerve to sphincter pupillae muscles
What connects ciliary body to lens?
What is the autonomic supply to ciliary muscles that control the lens?
Suspensory ligaments of lens
* parasympathetics (no sympathetics)
Explain control of lens?
Ciliary muscle relaxes in “far vision”
* no parasympathetic signal
* ligament tightens and lens flattens to focus on object in the distance
Ciliary muscle contracts in “near vision”
* parasympathetic
* ligament relaxes and lens becomes spherical to focus on near objects
3 components of the accommodation reflex? (3)
1) bilteral pupillary constriction (CN III)
2) bilateral convergence (medial rotation of both eyes) - CN III
3) bilateral relaxation of the lens (CN III)
What are basal tears? (3)
* important in corneal health
* clean, nourish and hydrate the avascular cornea
* contain lysozyme
What are reflex tears?
* In response to mechanical or chemical stimulation
* Sensory = CN VI (cornea)
* motor = CN VII
What is horner’s syndrome?
Ax? (5)
S/s? (4)
Impaired sympathetic innervation to head and neck
Ax
* neck trauma
* carotid dissection
* internal jugular vein engorgement
* cervical node metastasis
* pancoast tumour
S/s
* miosis
* ptosis
* reduced sweating (anhydrosis)
* increased warmth and redness
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