Vision 2

Question 1

What are the two types of ocular muscle?

Answer 1

Intrinsic and extrinsic

Question 2

What are the functions of intrinsic ocular muscles?

Answer 2

Controlling pupil diameter, altering lens curvature to enable short range focus

Question 3

What is the function of extrinsic ocular muscles?

Answer 3

Moving the eye

Question 4

What are the four straight extrinsic ocular muscles?

Answer 4

Medial, lateral, superior and inferior rectus

Question 5

What are the two oblique extrinsic muscles?

Answer 5

Superior and inferior oblique

Question 6

Where do the recti muscles arise from?

Answer 6

The apex of the orbit from an annular fibrous ring called the trochlea

Question 7

Where does the superior oblique muscle arise from?

Answer 7

The roof of the orbit posteriorly

Question 8

Where does the inferior oblique arise from?

Answer 8

The floor of the orbit anteriorly

Question 9

What muscle runs above the SR elevating the eyelid?

Answer 9

Levator palpebrae superioris

Question 10

What nerve innervates the superior oblique?

Answer 10

Tochlear

Question 11

What nerve supply the lateral rectus?

Answer 11

Abducent

Question 12

What nerve supples the majority of the muscles of the eye?

Answer 12

Oculomotor

Question 13

What is the action of the superior rectus?

Answer 13

when the eye is abducted the SR causes elevation

When the eye is adducted the SR causes intorsion

Question 14

What is the action of the inferior rectus?

Answer 14

When the eye is abducted the IR causes depression

When the eye is adducted the IR causes extortion

Question 15

What is the action of the superior oblique?

Answer 15

When the eye is adducted the SO causes depression

Overall it causes intorsion, depression, abduction

Question 16

What is the action of the inferior oblique?

Answer 16

When the eye is adducted the IO causes elevation

Overall, the IO causes extorsion, elevation, abduction

Question 17

What should looked for in suspected right third nerve palsy?

Answer 17

Drooping eyelid, eye only has full movement laterally

Question 18

What should be looked for in suspected left fourth nerve palsy?

Answer 18

Eye moving up when adducted

Question 19

What should be looked for in suspected abucent nerve palsy?

Answer 19

Eye being adducted, eye not able to adduct

Question 20

What is strabismus?

Answer 20

Squint

Question 21

What are the two kinds of strabismus?

Answer 21

Esotropia - convergent

Exotropia - divergent

Question 22

What is amblyopia?

Answer 22

Lazy eye - where the brain suppress the image of one eye leading to poor vision in that eye without any pathology

Question 23

What is diplopia?

Answer 23

Double vision - usually occurs in squints occurring as a result of nerve palsies

Question 24

Describe the visual field

Answer 24

Everything that can be seen with one eye, including the periphery

Question 25

In what orientation do images form on the retina?

Answer 25

Upside down, they are inverted in the retina

Question 26

Describe the optic pathway

Answer 26

All fibres from the eye pass through the optic nerve tot he optic chiasm
At the chasm the medial nasal fibres cross to the opposite side
So the optic tract contents fibres from the lateral/temporal half of the ipsilateral eye and the crossed-over fibres from the contralateral side
This corresponds to all fibres from the opposite side of the visual field
Fibres from the optic tract synapse at the LGB (lateral geniculate body) of the thalamus
From here the optic radiation passes behind the internal capsule (retro-lentiform) to reach the Primary Visual Cortex area in the Occipital lobe

i.e. the right visual cortex sees the let half of the visual field and vice versa

Question 27

What would be the effect of a lesion to the right optic nerve?

Answer 27

Blindness in the right eye

Question 28

What would be the effect of the optic chasm being disrupted in the middle?

Answer 28

Bitemporal hemianopia

Question 29

What would the effect be of a right optic tract lesion?

Answer 29

Contralateral homonymous hemianopia

Question 30

What would the effect of damage to the optic radiation?

Answer 30

Contralateral homonymous hemianopia

Question 31

What are the intrinsic muscles of the eye?

Answer 31

Ciliaris
Constrictor pupillae - circular
Dilator pupillae - radial

Question 32

Does increased illumination lead to a parasympathetic or sympathetic response?

Answer 32

Parasympathetic - pupils contract

Question 33

Does decreased illumination lead to a parasympathetic or sympathetic response?

Answer 33

Sympathetic - pupils dilate

Question 34

Do the fibres relating to pupillary reflex activation use the same pathway as the normal fibres?

Answer 34

No, they do not go to the LGB but instead leave the optic tract to go to the midbrain where the IIIn nucleus is situated. Part of it is the EWN for parasympathetic fibres. The fibres go to both sides of the EWN

Question 35

What is anisocoria?

Answer 35

Pupils of differing size

Question 36

Describe the efferent pathway of the light reflex

Answer 36

From the EWN nucleus, preganglionic fibres pass through IIIn into the orbit. Parasympathetic fibres go to synapse at the ciliary ganglion. Postganglionic fibres go through short ciliary nerves to constrictor pupilae = pupillary constriction on both sides

Question 37

What is Horner’s syndrome?

Answer 37

Anisocoria due to damage to the sympathetic innervation to the pupil - therefore affected pupil constricted