Anatomy Flashcards
Position of optic canal in orbit
Medial
The eye is protected by the _____________ from a direct blow
Orbital margins
Which wall most often affeted in blowout fracture?
Medial wall
Fractured zygoma rotates:
Medially
What prevents spread of infection from periorbital to orbital cellulitis?
Orbital septum
Below eyelids
Tarsal plates (attachment for LPS)
Ligaments medial and lateral to eye
Medial and lateral palpebral ligaments
Limbus
Corneoscleral junction (external)
Conjunctival fornix
Where conjunctiva is reflected off sclera onto internal eyelid
Para supply to lacrimal gland
CN VII
Where do tears drain?
Superior and inferior puncta
Superior and inferior canaliculi
Lacrimal sac
Nasolacrimal duct
Outer fibrous layer
Sclera
Cornea
Vascular layer (uvea)
Iris
Ciliary body
Choroid
Where is aqueous produced?
Ciliary body
Anterior segment
Cornea Anterior chamber Iris Lens Ciliary body Posterior chamber
Anterior chamber
between cornea and iris
contains aqueous
Posterior chamber
Between iris and vitreous
Contains lens and aqueous
Posterior segment
Vitreous body
What are floaters?
Gel and clumping of collagen
Iridocorneal angle
In anterior chamber
Between cornea and iris (internal)
Angle in glaucoma
Raised IOP can cause:
Ischaemia of retina
Where is aqueous reabsorbed?
Canal of Schlemm at iridocorneal angle and trabecular meshwork
Area of greatest density of cones
Fovea (in centre of macula)
Cones are responsible for:
Day vision, colour vision, central vision
Rods are responsible for:
Night vision, peripheral vision
Blood to eye
Ophthalmic artery off ICA (through cavernous sinus)
Contents of cavernous sinus
III IV V1 V2 ICA VI
Carotid canal is in
temporal bone
Branches of ophthalmic artery
Central artery of retina
Nasal branches
Forehead branches
Ciliary arteries (choroid) = red eye
Venous drainage of eye
Superior ophthalmic vein to cavernous sinus (SOF)
Inferior ophthalmic vein to superior oph vein
Facial vein (valveless)
Layers of the retina
Photoreceptors
Bipolar cells
Ganglion cells
Axons of ganglion cells
Common tendinous ring of muscles attach round:
Optic canal
How to test superior and inferior rectus
Abduct eye
Then elevate or depress
How to test superior and inferior oblique
Adduct eye
Then elevate or depress
Pure elevation
SR and IO
Antagonists as rotators
Pure depression
IR and SO
Antagonists as add/abductors
Suspensory ligament of the eye
Fascial sling that holds the eye
Diplopia if drops down
CNV1 supplies
Upper eyelid
Cornea
Conjunctiva
Tip of nose
CNV2 supplies
Lower eyelid
Maxilla
Alae
Upper lip
CNV3 supplies
Mandible
TMJ
NOT the angle of the mandible (C2,3)
Blink (corneal) reflex
V1 of cornea to trigeminal ganglion to V in the pons to VII to palpebral part of orbicularis oculi
How do symp axons get to organs of head?
Descend SC Exit T1 Ascend symp trunk Synapse in sup cervical ganglion ICA plexus to opthalmic artery
Inferior cervical and 1st thoracic ganglia fuse to form
Stellate ganglion
How do para axons get to organs of head?
III (ciliary ganglion)
VII, IX (otic ganglion), X, sacral spinal nerves
Where does CN III join brainstem?
Between midbrain and pons
What nerves supply autonomic axons to iris and lens?
Ciliary nerves
Which nerve forms 1st part of blink reflex?
Long ciliary nerve
Which type of nerve synapses in ciliary ganglion?
Para only
Symp and somatic sensory pass through but don’t synapse
Vestibulo-ocular reflex
Turns eyes in opposite direction of head movement
III, IV, VI, VIII
Oculocardiac reflex
Reflex bradycardia in response to tension on extraocular muscles or pressure on eye
V1 and X
Type of muscle in LPS
Skeletal and smooth
Mydriatic pupil
Non-physiologically enlarged pupil
Origin and insertion of Dilator pupillae
Fixed origin
Mobile insertion
Radial fibres
Miotic pupil
Non-physiologically contracted pupil, e.g. opiates
Blown pupil
Fixed dilated pupil
CN III pathology inhibiting para ciliary nerves
Sphincter pupillae
Circumferential, encricling
Pupillary light reflex
Retinal ganglion cells to optic nerve to chiasm to tract to pretectal nucleus in midbrain to EWN (now bilateral) to ciliary ganglion to sphincter pupillae of both eyes
Symp to lens
Ciliary muscle relaxes = suspensory ligament tightens = lens flattens for far vision
Para to lens
Ciliary muscle contracts = suspensory ligament relaxes = lens round for near vision
3 components of accommodation reflex
Bilateral pupillary constriction III
Bilateral convergence III
Bilateral relaxation of lens III
Types of lacrimation
Basal tears
Reflex tears (V1 and VII)
Emotional tears
How does VII get to lacrimal gland?
Greater petrosal nerve
presynaptic to pterygopalatine ganglion
postsynaptic to V2 to V1 to lacrimal gland
Monroe-Kellie hypothesis
To increase pressure in one place you have to decrease in another
Hydrocephalus
CSF overproduction
Enlarged ventricles, sunset sign
Symptoms of raised ICP in the eye
Diplopia LOV Blurred vision Papilloedema Dilated pupil
Sensory supply to dura
CN V
Layers of dura`
Endosteal and meningeal
Where is CSF produced and reabsorbed?
Produced in choroid plexus
Reabsorbed by arachnoid granulations
How do ventricles communicate?
IV foramen of monro (lateral to 3rd)
cerebral aqueduct (3rd to 4th)
2 medial and 1 lateral apertures (4th to central canal or subarachnoid space)
CN III palsy
Susceptible to compression in raised ICP (aneurysm, just posterior to post comm artery) Down and out Ptosis Loss of pupillary reflex Dilated pupil
Coning
Brain herniates through septa (folds of dura)
CN IV palsy
Long intracranial course = susceptible to damage, comes out posteriorly Contralateral palsy Eye can't move inferomedially Gaze to right = moves up Diplopia when looking down
CN VI palsy
Long intracranial course = raised ICP damages. Arises from pons
Medial deviation of eye
Types of conjunctiva
Palpebral
Bulbar
pH of tear film
7.6
What nerve needs to be intact for reflex tear production?
V
Layers of tear film
Lipid phase
Aqueous phase
Mucus phase
Layers of cornea
Epithelium Bowman's membrane Stroma Descements membrane Endothelium
Lens is attached to ciliary body by
Zonules
Pancoast tumour
Compresses symp chain = symp III LPS compromised = ptosis
Stimulus for accommodation reflex
Blurred image
Hutchison’s sign
Shingles vesicles on nose tip = V1 involvement = corneal involvement = acyclovir
Where does VI arise?
Pons
Through tendinous ring
Optic nerve and Ophthalmic artery (optic canal) Sup and Inf divisions III Nasociliary nerve VI (SOF)
Outside tendinous ring SOF
Lacrimal nerve
Frontal nerve
Superior ophthalmic vein
IV
Outside tendinous ring IOF
Inferior ophthalmic vein
Outside tendinous ring
LPS
SO
In tendinous ring
All 4 rectus muscles
Symptom of optic neuritis
Pain on eye movements (muscles attach to tendinos ring)
Progressive unilateral visual loss
Usually MS (young)
Shortest and thickest of rectus muscles
MR
Blowout fracture traps what muscle?
IR
Type of epithelial in retinal pigmented cells
Simple cuboidal
Where is blind spot?
15 degrees temporal
How many fibres decussate?
53%
Symptom of blowout fracture
Pain on upgaze
