Neuro: eye

Question 1

what produces the watery aqueous humour and where is it absorbed

Answer 1

ciliary body (produced)

reabsorbed = sinus venous (canal of schlemm)

Question 2

how do you increase refractive power of the lens

Answer 2

Relaxation of suspensory ligaments

Lens becomes thicker

Increase in refractive power

Lens bends light more effectively - reducing focal length of the lens

Question 3

normal intraocular pressure

Answer 3

12-22mmHg

Question 4

What feature, seen on fundoscopy, would suggest raised intraocular pressure?

Answer 4

Papilledema - optic disc swelling

Question 5

what is the limbus

Answer 5

Sclerocorneal junction

Question 6

Why might a loss of sympathetic innervation cause mild drooping (ptosis) of the eyelid?

Answer 6

Inactivates superior tarsal muscle (muller’s muscle) which normally lifts the eyelids
(under the Levator palpebral superioris)

Question 7

Why might more of the sclera be visible in anxiety states / hyperthryoidism?

Answer 7

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

Question 8

What is an orbital “blowout” fracture?

Answer 8

Blunt trauma to eye eg. Punch to eye

Inferior medial walls giveway

this can raise intraorbital pressure

Question 9

3 layers/tunics of eye

Answer 9

Fibrous - sclera/cornea

Vascular

neural - retina/fovea

Question 10

components of the vascular tunic

and what are they known as

Answer 10

Choroid
Ciliary body
Iris

these are known as the “uveal tract”

Question 11

what corresponds to the physiological blind spot (On the retina)

Answer 11

optic disc

Question 12

what branch is the central retinal artery and where does the vein drain into

Answer 12

CRA branch of ophthalmic artery

CRV drains into superior opthalmic vein

Question 13

clinical term for inflammation within the vascular tunic of the eye

Answer 13

uveitis

uvea = iris/choroid/ciliary body of vascular tunic

Question 14

what fibres make up the suspensory ligament

Answer 14

zonule

the tension in the fibres flattens the anterior surface of the lens

Question 15

what structures provides the refractive power of the eye

Answer 15

curvature of transparent cornea = 2/3rds of the refractive power (~40diopters)

lens curvature = 1/3rd (20 diopters)

Question 16

what fossa is the lens found in

Answer 16

hyaloid fossa

Question 17

posterior/anterior chambers and segments

Answer 17

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

Question 18

myopia

Answer 18

short sightedness

eye grows too long (front to back) >24mm

long distance objects are blurred because light is focused in front of the retina

Question 19

cranial nerves supplying the eye

+ what muscles do they supply + where do they emerge from

Answer 19

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

Question 20

What is transtentorial herniation?

and what might be a warning sign

Answer 20

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

Question 21

origin of the 6 extra ocular muscles

Answer 21

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

Question 22

2 muscles that intort the eye

Answer 22

superior oblique and medial rectus

Question 23

Weakness of which extraocular muscle might affect reading or walking downstairs?

Answer 23

superior oblique

Question 24

clinical features of complete 3rd nerve palsy

Answer 24

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)

Question 25

part between tonsils in cerebellum

Answer 25

uvula

Question 26

What is the vesibulo-ocular reflex and which part of the cerebllum contributes to it?

Answer 26

Moving head to side/body is moving, eyes remain straight looking vestibularcerebellum (Follicular nodular lobe)

Question 27

Which features of being drunk are due to impairment of cerebellar function?

Answer 27

Slurred speech Gait Dysmetria - lack of coordination of movement  (type of ataxia)

Question 28

cerebellar peduncles medial inferior and superior

Answer 28

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

Question 29

palpebral fissue

Answer 29

vertical space between medial and lateral canthi

Question 30

tough sclera of eye

Answer 30

fibrous layer of globe and continuous with dura mater surrounding optic nerve

Question 31

difference between the visual and anatomical axis

Answer 31

around 22.5

Question 32

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?

Answer 32

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.

Question 33

what does outer/fibrous layer consist of (eye)

Answer 33

sclera cornea limbus

Question 34

what is the area called where the optic nerve arises from the sclera

Answer 34

lamina cribrosa

Question 35

what does the neural layer of eye consist of

Answer 35

macula lutea retina fovea centralis

Question 36

where does the neural retina end

Answer 36

at ora serata

Question 37

hyaloid canal

Answer 37

transparent canal running through vitreous body from optic nerve disc to lens

Question 38

equivalent of gyri and sulci in cerebellum

Answer 38

folia = gyri fissures = sulci

Question 39

In advanced raised intracranial pressure the tonsils may herniate through the foramen magnum and cause death by compressing which part of the brain stem?

Answer 39

The medulla, which contains vital (cardiorespiratory) centres.

Question 40

dysmetria

Answer 40

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

Question 41

3 functional divisions of cerebellum

Answer 41

vestibulocerebellum - flocculonodular lobe = balance/equilbrium Spinocerebellum - vermis + anterior lobe = gait/posture/tone neocerebellum/cerebrocerebellum - posterior lobe + tonsils = coordination/smooth accurate movements / speech articulation

Question 42

Q Which might Goliath not have seen David and his slingshot? (Clue: growth hormone)

Answer 42

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)

Question 43

Why is the superior oblique sometimes called the tramp’s muscle?

Answer 43

because of the way it deflects the pupil: down and out.

Question 44

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]?

Answer 44

intortion As it no longer rotates the eye, and is straightened out – allowing it to simply depress the eye

Question 45

Diplopia (double vision) on far lateral gaze is most likely to be caused by weakness of which muscle?

Answer 45

Lateral rectus (supplied by CN VI).

Question 46

what nerve is the constrictor papillae innervated by

Answer 46

PARASYMPATHETIC innervation by oculomotor | that arise from edinger-westphal nucleus