Vision

Question 1

How close can an object and still be clear

Answer 1

20cm

Question 2

What happens during accommodation

Answer 2

Lens becomes thicker and more spherical
Pupil constricts
Eyes converge

Question 3

How does the lens thicken

Answer 3

Ciliary muscle contracts => Ciliary body bulges => suspensory ligaments become lax => lens no longer under stretch => lens becomes thicker

Question 4

What muscle constricts the pupil

Answer 4

Sphincter pupillae (Parasympathetic Occulomotor Cn III)

Question 5

What muscles causes eyes to converge

Answer 5

Medial Rectus (Occulomotor Cn III)

Question 6

What is the visual pigment in rods

Answer 6

Rhodopsin

Question 7

What is the visual pigment in cones

Answer 7

Cone opsins S, M and L

Question 8

How does bleeching of the visual pigment result in phototransdauction

Answer 8

Phototransduction cascade

Question 9

What is Vitamin A’s role in visual pigments

Answer 9

Visual pigment retention

Question 10

what is the state of photoreceptor cells in the dark

Answer 10

they’re at rest, kept depolarised by open Na+/Ca2+ channels

Question 11

Describe the phototransduction cascade

Answer 11

Photon activates Rhodopsin => Transducin-GTP => PDE => GMP => Na+ channel closes => Hyperpolarisation of cell => Stimulates the retinal cells

Question 12

Describe vitamin A deficiency

Answer 12

Can cause (night)blindness 
Conjunctiva becomes abnormal

Question 13

How can vitamin A deficiency occur

Answer 13

Malnutrition
Malabsorption syndromes e.g. coeliax dissease
Sprue

Question 14

Signs of Vitamin A deficiency

Answer 14

Corneal ulceration - use dye to show extent of ulcer
Bitot’s Spot in conjunctiva - Build up of keratin, found in conjunctiva, oval/triangular/ irregular in shape and white.
(sometimes first sign of deficiency)

Corneal melting which leads to future opacification of cornea.

Question 15

Function of Extrinsic/Extraocular muscles

Answer 15

move eye

Question 16

Function of Intrinsic muslces

Answer 16

Controls pupil diameter

Alter lens curvature to enable

Question 17

list the extraocular eye muscles

Answer 17

Superior Rectus
Inferior Rectus 
Medial Rectus
Lateral Rectus
Superior Oblique 
Inferior Oblique 
(Levator palpebrae superioris)

Question 18

Innervation of extraocular muscles

Answer 18

Lateral Rectus = Abudcens Cn VI
Superior Oblique = Trochlear Cn IV
Everything else = Occulomotor Cn III

Question 19

Where do the Recti muscles arise from

Answer 19

A annular fibrous ring at the apex of the orbit

Question 20

Where does the Superior Oblique arise from

Answer 20

Roof of the orbit Posteriorly

Question 21

Where does the Inferior Oblique arise from

Answer 21

Floor of orbit ANTERIORLY (only muscle to arise Anteriorly)

Question 22

Where does the Levator Palpebrae Superioris arise from

Answer 22

Roof of the orbit

Question 23

What effect does the Medical rectus have on the eye

Answer 23

Moves Medially

Question 24

What effect does the Lateral rectus have on the eye

Answer 24

Moves Laterally

Question 25

What effect does the Superior rectus have on the eye

Answer 25

Elevation (when LR has ABducted eye) | Intorsion (when when MR has ADDucted eye)

Question 26

What effect does the Inferior rectus have on the eye

Answer 26

Depression (when LR has ABducted eye) | Extorsion (when MR has ADDucted eye)

Question 27

What effect does the Superior Oblique have on the eye

Answer 27

Depression (when eye is ADDucted) | Intorsion (when eye is ABducted) clockwise

Question 28

What effect does the Inferior Oblique have on the eye

Answer 28

Elevation (when eye is ADDucted) | Extorsion (when eye is ABducted) anti-clockwise

Question 29

Which muslces Elevate/Depress the eye when it's ADDucted

Answer 29

Inferior and Superior Obliques

Question 30

Which muscles Elevate/Depress the eye when it's ABducted

Answer 30

Superior and Inferior Recti

Question 31

RADSIN?

Answer 31

Recti ADductors, Superiors INtortors recti secondary action = adduction SR secondary action = intorsion SO primary action = intorsion

Question 32

What fibres cross over in the optic chiasm

Answer 32

Nasal fibres (Medial)

Question 33

what fibres will the optic tract contain due to the crossing over

Answer 33

Temporal half of the ipsilateral eye and the crossed over nasal fibres from the contra lateral eye

Question 34

What happens to fibres from the optic tract

Answer 34

Synapse at the Lateral Geniculate Body of the THALAMUS

Question 35

Where does the optic radiation go after the LGB

Answer 35

Passes behind the internal capsule to reach the Primary Visual Cortex in the Occipital lobe

Question 36

What viual field does the Right visual cortex see

Answer 36

The left visual and vice versa

Question 37

What has been damaged in blindness of the right eye

Answer 37

Right optic nerve is damaged

Question 38

What has been damaged in Bitemporal Hemianopia

Answer 38

Optic Chiasm disrupted (nasal fibres affected) | Think Pituitary Adenoma

Question 39

What has been damaged in Contralateral homonymous Hemianopia {the left temporal field and right nasal field gone}

Answer 39

Right optic tract is damaged (Lesion after chiasm but before LGB) or Optic radiation is damaged (lesion after LGB but before primary visual cortex)

Question 40

Describe pathway of the Light reflex

Answer 40

Impulses travel accross optic nerve => optic chiasm => optic tract => MIDBRAIN (where the CN III nucleus is)

Question 41

What part of the brain do fibres involved in the light reflex go

Answer 41

NOT THE LGB Midbrain where the CN III nucleus is specifically the EDINGER-WESTPHAL NUCLEUS (part of CN III nucleus)

Question 42

Parasympathetic fibres, whose aim is to constrict the pupil, synapse in what structue in the orbit

Answer 42

Ciliary Ganglion (post-ganglionic fibres go through short ciliary nerves to constrictor pupillae)

Question 43

What is the term for unequal pupils

Answer 43

Anisocoria

Question 44

What condition can Anisocoria be found in

Answer 44

Horner's syndrome (disruption of nerve pathway from brain to face and eye on one side of body = decresed pupil size, ptosis (drooping eyelid, Anhidrosis (less sweating) on affected side of face

Question 45

In CN III palsy due to a medical cause,e.g. Diabetes, what happens to the pupillary reflex

Answer 45

Usually no damage to parasympathetic fibres => pupil still able to dilate

Question 46

Patient has CN III palsy + absent pupillary reflex what do you suspect

Answer 46

Cerebral artery aneurysm = Emergency