Vision 2

Question 1

What is your visual field?

Answer 1

Everything you see with one eye including the periphery

Question 2

How is visual field assessed?

Answer 2

By confrontation test or automated perimetry

Question 3

At the optic chiasma, which type of fibres cross to the opposite side?

Answer 3

Nasal fibres

Question 4

What kind of fibres does the optic tract contain?

Answer 4

Contains fibres from the (lateral) temporal half of the ipsilateral eye and the crossed-over nasal fibres from the contralateral eye.

In terms of visual field, the optic tract contains all the fibres from the opposite half of the visual field

Question 5

Where do the fibres from the optic tract synapse?

Answer 5

At the LGB of the thalamus

(Lateral geniculate body)

Question 6

Where do the fibres travel after reaching the LGB?

Answer 6

Optic radiation travels to reach the primary vidual cortex in the occipital lobe

Thus the Right visual cortex sees the left half of the visual field and vice versa.

Question 7

What damage do you expect when the right optic nerve is damaged?

Answer 7

Blindness in one eye

Question 8

What damage do you expect when the optic chiasma is damaged in the middle?

Answer 8

Bilateral hemianopia

Question 9

What damage would you expect with a right optic tract/right optic radiation that is damaged?

Answer 9

Contralateral homonymous hemianopia

Question 10

What sits below the optic chiasm?

Answer 10

Pituitary gland

Question 11

Look

Answer 11

Question 12

What are intrinsic muscles responsible for?

Answer 12

Control pupil diameter & helps alter lens curvature to enable us to see near objects

Question 13

What are extrinsic muscles responsible for?

Answer 13

They move the eye

Question 14

What is the origin and insertion of the eye muscles?

Answer 14

Question 15

What supplies the superior oblique muscle?

Answer 15

The trochlear nerve (CN 4)

Question 16

What supplies the lateral rectus?

Answer 16

The abducens nerve (CN6)

Question 17

Apart from the superior rectus and the lateral rectus, what are the other extrinsic muscles supplied by?

Answer 17

Occulomotor nerve (CN3)

Question 18

What are the following terms for binocular eye movement?

Answer 18

Dextroelevation, elevation, levoelevation

dextroversion, …………..levoversion

Dextrodepression, depression , levodepression

Question 19

When the lateral rectus is abducting the eye, what is the action of the superior rectus and the inferior rectus?

Answer 19

SR - Causes elevation

IR - causes depression

Question 20

When the medial rectus has the eye adducted what is the action of the superior rectus and the inferior rectus?

Answer 20

SR causes intorsion

IR causes extorsion

Question 21

What is the action of the superior oblique and the inferior oblique when the eyeball is abducted?

Answer 21

Superior oblique - intorsion

Inferior oblique - extorsion

Question 22

What are the actions of the msucles of the eye?

MR

LR

SR

IR

SO

IO

Answer 22

Question 23

Define strabisumus

Answer 23

Squint

Question 24

What are the names given to the two types of squint?

Answer 24

Esotropia - manifest convergent squint

Exotropia - divergeant squint

Question 25

What is amblyopia?

Answer 25

Lazy eye

Question 26

What is the cause of amblyopia?

Answer 26

Brain supresses the image of one eye leading to poor vision in that eye without any pathology (correctable in early years using eye patches to stimulate the “lazy” eye to work)

Question 27

What is diplopia?

Answer 27

Double vision

Question 28

What is often the cause of diplopia?

Answer 28

Usually occurs in squints as a result of nerve palsies

Question 29

What is the sympathetic and parasympathetic response to an increase / decrease illumination?

Answer 29

Incerase illumination - parasympathetic resoponse - both pupils contract

Decrease illumination - sympathetic - pupils dilate

Question 30

Where do fibres destined to activate the pupillary refles travel after the optic tract?

Answer 30

They don’t travel to the LGB, instead they travel to the midbrain where the third cranial nerve nucleus is situated

Question 31

What is the blue part of the diagram? What is its significance

Answer 31

It is the part of the nucleus of the third cranial nerve called the Edinger Westphal nucleus - It is for the parasympathetic fibres. The pupillary reflex goes down the the EWN on both sides

Question 32

What is the travel of the efferent impulses from the EWN?

Answer 32

Preganglionic fibres pass through the third cranial nerve into the orbit, they go to and synapse in the ciliary ganglion, postganglionic fibres go through short ciliary nerves to the constrictor papillae

Question 33

What is the name given to pupils being different sizes?

Answer 33

Aniscoria - happens in horner’s syndrome

Question 34

What is another pupil defect besides aniscoria?

Answer 34

Abnormal light reflex - pupils react abnormally to light

Question 35

What are some of the common causes of absent / abnormal pupillary reflex?

Answer 35

Any abnormality of the afferent limb centre / efferent limb centre of the reflex

Diseases of the retina - detatchment, degenerations of dystrophies

Diseases of the optic nerve - such as optic neuritis seen in MS

Diseases of the 3rd cranial nerve (efferent limb)

Question 36

If a patient with diabetes has 3rd cranial nerve palsy, and also has an absent pupillary reflex, what is a possilbe diagnosis?

Answer 36

Cerebral artery eneurysm - emergency

Question 37

Why does horners syndrome result in aniscoria?

Answer 37

Due to damage to the sympathetic inenrvation to the pupil

Question 38

What are other signs of horners syndrome besides the abnormal pupillary reflex?

Answer 38

Includes ptosis and anhidrosis

Question 39

Where do postaganglionic sympathetic fibres travel alongside?

Answer 39

Travel along with blood vessels in the head and neck

Horner’s syndrome can occur due to disruption at any point. An example would be Pancoast’s tumour of the lungs!