Neuro: eye Flashcards
what produces the watery aqueous humour and where is it absorbed
ciliary body (produced)
reabsorbed = sinus venous (canal of schlemm)
how do you increase refractive power of the lens
Relaxation of suspensory ligaments
Lens becomes thicker
Increase in refractive power
Lens bends light more effectively - reducing focal length of the lens
normal intraocular pressure
12-22mmHg
What feature, seen on fundoscopy, would suggest raised intraocular pressure?
Papilledema - optic disc swelling
what is the limbus
Sclerocorneal junction
Why might a loss of sympathetic innervation cause mild drooping (ptosis) of the eyelid?
Inactivates superior tarsal muscle (muller’s muscle) which normally lifts the eyelids
(under the Levator palpebral superioris)
Why might more of the sclera be visible in anxiety states / hyperthryoidism?
usually only Small portion of sclera is often visible below the iris but not above
but then More of the upper sclera. during anxiety/hyperthyroidism
excaberation of sympathetic nervous system–> increased contraction of muller’s muscle(superior tarsal muscle) via sympathetic fibres = widen eyes
What is an orbital “blowout” fracture?
Blunt trauma to eye eg. Punch to eye
Inferior medial walls giveway
this can raise intraorbital pressure
3 layers/tunics of eye
Fibrous - sclera/cornea
Vascular
neural - retina/fovea
components of the vascular tunic
and what are they known as
Choroid
Ciliary body
Iris
these are known as the “uveal tract”
what corresponds to the physiological blind spot (On the retina)
optic disc
what branch is the central retinal artery and where does the vein drain into
CRA branch of ophthalmic artery
CRV drains into superior opthalmic vein
clinical term for inflammation within the vascular tunic of the eye
uveitis
uvea = iris/choroid/ciliary body of vascular tunic
what fibres make up the suspensory ligament
zonule
the tension in the fibres flattens the anterior surface of the lens
what structures provides the refractive power of the eye
curvature of transparent cornea = 2/3rds of the refractive power (~40diopters)
lens curvature = 1/3rd (20 diopters)
what fossa is the lens found in
hyaloid fossa
posterior/anterior chambers and segments
the chambers are within the anterior segment of the eye
So within anterior segment:
AC is the aqueous humor-filled space inside the eye between the iris and the cornea’s innermost surface, the endothelium
PC space behind the peripheral part of the iris, and in front of the suspensory ligament of the lens
myopia
short sightedness
eye grows too long (front to back) >24mm
long distance objects are blurred because light is focused in front of the retina
cranial nerves supplying the eye
+ what muscles do they supply + where do they emerge from
III: oculomotor between cerebral peduncles
- Medial, inferior and superior rectus
- Inferior oblique
- Levator palpebrae superioris
- Sphincter pupillae (parasympathetic)
- Ciliaris muscle (parasympathetic)
IV: trochlear below inferior colliculi (exits brainstem posteriorly)
-superior oblique
VI: abducens from pontomedullary junction
- lateral rectus
What is transtentorial herniation?
and what might be a warning sign
Medial temporal lobe (uncus/parahippocampal gyrus) –> tectorial hiatus (—>foramen magnum) —> compression of oculomotor
may occur due to hemispheric space occupying lesion eg. tumor/haematoma (swelling/oedema)
sudden dilation of one pupil = oculomotor on one side is damaged
origin of the 6 extra ocular muscles
4 rectuses = common tendinous ring
inferior oblique = ring orbital surface of maxilla
superior oblique = from common tendinous–> trochlea(attached to sphenoid)–> posterior superior of eye
2 muscles that intort the eye
superior oblique and medial rectus
Weakness of which extraocular muscle might affect reading or walking downstairs?
superior oblique
clinical features of complete 3rd nerve palsy
extropia - eyes outward
(because LR still working)
hypotonia - downward
(because SO still working)
ptosis - drooping eyelids
(no levator palpebrae superioris muscle)
mydriasis - pupil dilation (no ciliaris)
part between tonsils in cerebellum
uvula
What is the vesibulo-ocular reflex and which part of the cerebllum contributes to it?
Moving head to side/body is moving, eyes remain straight looking
vestibularcerebellum (Follicular nodular lobe)
Which features of being drunk are due to impairment of cerebellar function?
Slurred speech
Gait
Dysmetria - lack of coordination of movement (type of ataxia)
cerebellar peduncles
medial
inferior and superior
medial (largest)
-afferent neurones
inferior
- afferent from medulla oblongata
- gives spinal proprioceptive information for gait and balance
superior
- projects upwards to mibrain
- main efferent pathway from cerebellum(dentate nucleus)—> thalamus
palpebral fissue
vertical space between medial and lateral canthi
tough sclera of eye
fibrous layer of globe and continuous with dura mater surrounding optic nerve
difference between the visual and anatomical axis
around 22.5
During clinical testing of the superior and inferior rectus muscles, the eye would ideally be abducted by how many degrees, so that the visual and anatomical axes coincide?
Due to the direction of the medial and lateral walls there is a difference between the visual and anatomical axis. When the eyes are abducted by 22.5o, then the superior and inferior rectus muscles act as pure elevators and depressors of the eye. Contraction of the superior and inferior rectus muscles from the primary position would also cause rotation of the eye globe which is not suitable for differentiating between muscles in a clinical setting.
what does outer/fibrous layer consist of (eye)
sclera
cornea
limbus
what is the area called where the optic nerve arises from the sclera
lamina cribrosa
what does the neural layer of eye consist of
macula lutea
retina
fovea centralis
where does the neural retina end
at ora serata
hyaloid canal
transparent canal running through vitreous body from optic nerve disc to lens
equivalent of gyri and sulci in cerebellum
folia = gyri
fissures = sulci
In advanced raised intracranial pressure the tonsils may herniate through the foramen magnum and cause death by compressing which part of the brain stem?
The medulla, which contains vital (cardiorespiratory) centres.
dysmetria
problem in the ability in estimating distances during movements and placing limbs accurately when reaching for targets
hyper metria = overshooting/can’t reach
hypo metria = attempting to reach for something and end up knocking it over
3 functional divisions of cerebellum
vestibulocerebellum
- flocculonodular lobe = balance/equilbrium
Spinocerebellum
- vermis + anterior lobe = gait/posture/tone
neocerebellum/cerebrocerebellum
- posterior lobe + tonsils = coordination/smooth accurate movements / speech articulation
Q Which might Goliath not have seen David and his slingshot? (Clue: growth hormone)
As goliath may have had a growth-hormone-secreting (somatotroph) pituitary adenoma (acromegaly) which would explain his gigantism and may have lead to bitemporal hemianopia (tunnel vision)
Why is the superior oblique sometimes called the tramp’s muscle?
because of the way it deflects the pupil: down and out.
Use the method shown in the lecture to explain the action of superior oblique when the eye is in the primary (anatomical) position?
then use the same method to explain why the superior oblique acts as a pure depressor of the adducted eye [as in clinical testing]?
intortion
As it no longer rotates the eye, and is straightened out – allowing it to simply depress the eye
Diplopia (double vision) on far lateral gaze is most likely to be caused by weakness of which muscle?
Lateral rectus (supplied by CN VI).
what nerve is the constrictor papillae innervated by
PARASYMPATHETIC innervation by oculomotor
that arise from edinger-westphal nucleus
