Vision lectures

Question 1

what is refraction?

Answer 1

when light rays bend to form a sharp image on the retina

Question 2

what is accommodation?

Answer 2

the changes occurring in both eyes as it changes focus from a distant to a close object

Question 3

what causes refractive errors?

Answer 3

when there is a mismatch between how much we bend light rays in each eye

Question 4

what are the refractive media in the eyeball?

Answer 4

cornea
aqueous humor
lens
vitreous humor

Question 5

what does the eye need to do when an object is closer to you to maintain a clear image on the retina?

Answer 5

needs to bend light rays more

Question 6

what 3 processes occur simultaneously that comprise accommodation?

Answer 6

lens changes shape to become more spherical and thicker
pupil constricts
eyes converge

Question 7

how does the lens thicken during accommodation?

Answer 7

1/ ciliary muscle contracts making the ciliary body bulge
space in the middle decreases
suspensory ligaments become lax
lens is no longer under stretch
lens becomes thicker

Question 8

what muscle causes the pupil to constrict?

Answer 8

sphincter pupillae

Question 9

what branch of the autonomic nervous system innervates the sphincter pupillae?

Answer 9

parasympathetic

Question 10

where is the sphincter pupillae located?

Answer 10

around the border of the pupil

Question 11

what muscles are responsible for the eyes converging during accommodation?

Answer 11

medial rectus muscles

Question 12

what is myopia?

Answer 12

short sightedness

Question 13

what is hyperopia?

Answer 13

long sightedness

Question 14

what is astigmatism?

Answer 14

non spherical curvature of cornea (or lens)

Question 15

what is presbyopia?

Answer 15

long sightedness of old age

Question 16

what is the most common cause of myopia?

Answer 16

eyeball too long

Question 17

what are symptoms of myopia?

Answer 17

divergent squint in infants

headaches, complain of not being able to see blackboards/distant objects

Question 18

how is myopia corrected?

Answer 18

bending power is decreased using biconcave lenses:
spectacles
contact lenses
laser eye surgery

Question 19

what is the most common cause of hyperopia?

Answer 19

eyeball too short or cornea + lens too flat

Question 20

what objects appear hazy in astigmatism?

Answer 20

both close and distant objects

Question 21

why does the chance of developing long sightedness increase with old age?

Answer 21

lens gets less mobile/elastic so when the ciliary muscle contracts it is not as capable of changing shape as it was before

Question 22

what is phototransduction?

Answer 22

conversion of light energy to an electrochemical response by photoreceptors

Question 23

what do rods and cones have to do in order to illicit an electrochemical response?

Answer 23

activate optic nerve neurons (generate an action potential)

Question 24

what visual pigment is integrated in the lamellae of rods?

Answer 24

rhodopsin

Question 25

what visual pigments are integrated in the lamellae of cones?

Answer 25

opsins S, M and L

Question 26

what type of protein is rhodopsin?

Answer 26

integral transmembrane helical protein

Question 27

what is the chromophore of rhodopsin formed from?

Answer 27

vitamin A

Question 28

what happens when light forms on the 11-cis retinal?

Answer 28

it isomerises to all trans retinal

Question 29

what happens to photoreceptors in the dark?

Answer 29

the are kept depolarised by open sodium/calcium channels

Question 30

what happens in the phototransduction cascade when the Na+ channels close?

Answer 30

there is RELATIVE hyperpolarisation of photoreceptor cells

Question 31

how are the photoreceptor cells truly hyperpoolarised?

Answer 31

flux of Ca+ ions to the synapse with bipolar cell, which ultimately stimulates the retinal cell

Question 32

what will happen in any condition that affects vitamin A absorption?

Answer 32

vision will be affected, possibly leading to blindness. there will also be abnormal conjunctiva and corneal epithelium

Question 33

what can corneal melting lead to?

Answer 33

future opacification of the cornea

Question 34

what is the function of the intrinsic ocular muscles?

Answer 34

control pupil diameter and helps alter lens curvature to enable us to see near objects

Question 35

what is the function of the extrinsic muscles of the eye?

Answer 35

they move the eye

Question 36

what are the 4 straight muscles of the eye?

Answer 36

medial rectus lateral rectus inferior rectus superior rectus

Question 37

what are the 2 oblique muscles of the eye?

Answer 37

superior oblique | inferior oblique

Question 38

where do the recti muscles arise from?

Answer 38

the apex of the orbit from an annular fibrous ring

Question 39

where does the superior oblique muscle arise from?

Answer 39

the roof of the orbit posteriorly

Question 40

where does the inferior oblique muscle arise from?

Answer 40

floor of the orbit anteriorly

Question 41

what muscle elevates the eyelid?

Answer 41

levator palpebrae superioris

Question 42

where does the LPS lie?

Answer 42

above the superior rectus

Question 43

what nerve supplies everything except the superior orbit and the lateral rectus muscle?

Answer 43

oculomotor nerve

Question 44

what does the trochlear nerve supply?

Answer 44

superior orbit

Question 45

what does the abductent nerve supply?

Answer 45

lateral rectus

Question 46

where does the LPS muscle originate?

Answer 46

roof of orbit

Question 47

where do all recti muscles originate from?

Answer 47

tendinous ring

Question 48

where does the superior oblique originate from?

Answer 48

lesser wing of sphenoid

Question 49

where does the inferior oblique originate from?

Answer 49

medial part of orbit floor

Question 50

where do both oblique muscles of the eye insert?

Answer 50

sclera posteriorly

Question 51

where do all rectus muscles insert?

Answer 51

sclera anteriorly

Question 52

what is the action of the superior rectus?

Answer 52

elevation when abducted | intorsion when adducted

Question 53

what is the action of the inferior rectus?

Answer 53

depression when abducted | extorsion when adducted

Question 54

what is the action of the superior oblique?

Answer 54

depression when adducted intorsion abduction

Question 55

what is the action of the inferior oblique?

Answer 55

elevation when adducted extorsion abduction

Question 56

what are some signs of right third nerve palsy?

Answer 56

drooping eyelid | eye only able to move laterally and slightly downwards

Question 57

what are some signs of left fourth nerve palsy?

Answer 57

eye moves up when adducted

Question 58

what are some signs of abducent nerve palsy?

Answer 58

eye being adducted | eye not able to abduct

Question 59

what is the medical term for a squint?

Answer 59

strabismus

Question 60

what is esotropia?

Answer 60

manifest convergent squint

Question 61

what is exotropia?

Answer 61

manifest divergent squint

Question 62

what is ambylopia?

Answer 62

"lazy eye" where brain supresses the image of one eye leading to poor vision in that eye without any pathology

Question 63

what is diplopia?

Answer 63

double vision which usually occurs in squints occuring as a result of nerve palsies

Question 64

what is your visual field?

Answer 64

everything you see with one eye including the periphery

Question 65

where do all nerve fibres from the eye pass through?

Answer 65

the optic nerve and then to the optic chiasma

Question 66

where do fibres from the optic tract synapse?

Answer 66

lateral geniculate body of the thalamus

Question 67

what kind of nerve fibres does the optic tract contain?

Answer 67

fibres from the temporal half of the ipslateral eye and nasal fibres from the contralateral eye

Question 68

where is the primary visual cortex?

Answer 68

occipital lobe

Question 69

what does the right visual cortex see?

Answer 69

left half of the visual field and vice versa

Question 70

what would you expect to happen if the right optic nerve is damaged?

Answer 70

blindness in one eye

Question 71

what would you expect to happen if the optic chiasma was disrupted in the middle?

Answer 71

bitemporal hemianopia (blindness)

Question 72

what would you expect to happen if the right optic tract was damaged

Answer 72

left sides of both eyes will be blind

Question 73

what would you expect to happen if the right optic radiation was damaged?

Answer 73

contralateral homonymous hemianopia

Question 74

what are the 3 intrinsic eye muscles?

Answer 74

ciliaris muscle constrictor pupillae dilator pupillae

Question 75

what are the ciliaris and constrictor pupillae muscles innervated by?

Answer 75

cranial nerve 3 (parasympathetic)

Question 76

what is the dilator pupillae innervated by?

Answer 76

plexus around blood vessels (sympathetic)

Question 77

where do fibres destined to activate the pupillary reflex travel to?

Answer 77

midbrain - to the edinger westphal nucleus of both sides

Question 78

what is the clinical term for when both pupils are different sizes?

Answer 78

anisocoria

Question 79

what are the steps in pupillary constriction?

Answer 79

EWN > preganglionic parasympathetic fibres pass through 3rd CN into orbit > parasympathetic fibres go to and synapse in the ciliary ganglion > postganglionic fibres go through short ciliary nerves to constrictor pupillae all of this leads to pupillary constriction of both sides

Question 80

what can cause an abnormal/absent pupillary reflex?

Answer 80

diseases of the retina - detachment/degenerations or dystrophies any abnormality of the afferent limb centre/efferent limb of the reflex diseases of the optic nerve - optic neuritis diseases of the 3rd cranial nerve

Question 81

what is horners syndrome?

Answer 81

anisocoria due to damage to the sympathetic innervation to the pupil