NS 20 vision

Question 1

what is the basic structure of the eye?

Answer 1

3 layes

• sclera +cornea
• choroid/ ciliary body/ iris
• retina

Question 2

describe the features of sclera/ cornea

Answer 2

• tough connective tissue
• sclera white
• cornea transplant

Question 3

describe the features of the choroid/ ciliary body/ iris

Answer 3

• highly vascular
• choroid ; absorbs aquous humour
• iris - regulates light entering eye

Question 4

what does the retina contain?

Answer 4

contains photoreceptors such as rods and cones

Question 5

what are the 2 fluid filled cavities called?

Answer 5

aqueous humor

vitreous humor

Question 6

how does glaucoma arise?

Answer 6

flow of aqueous humor from posterior to anterior chamber- disruption of balance of flow

Question 7

what do the ganglion cells respond to?

Answer 7

contrast movement, colour and detail

Question 8

what is the fovea?

Answer 8

the central portion of the eye that only contains cones

sharpest vision and greatest colour discrimination

Question 9

what does the optic disk not contain?

Answer 9

no receptors

Question 10

what are the reasons for the fovea’s high visual acuity?

Answer 10

• thinning if retinal layers
• lack of rods, high concentration of cones
• low convergence

Question 11

what produces a blind spot?

Answer 11

lack of rods and cones at blind spot

Question 12

what are the elements of the pathway?

Answer 12

optic nerve 
optic chiasma 
optic tract 
lateral geniculate body of thalamus 
optic radiations 
striate cortex (primary visual cortex)

Question 13

trace the pathway from the right visual feild

Answer 13

• right visual field
• imaged on left retina
• temporal fibres dont cross
• nasal fibres cross at optic chiasma
• right field represented in left - optic tract
• relay/processing in LGN
• projects to left primary visual cortex

Question 14

where is the left half field represented?

Answer 14

in right optic tract

Question 15

projection from upper retinal quadrant arise from where?

Answer 15

lower visual field

Question 16

which sulcus have the projections from upper righ retinal field on top of it and the lower projections below it?

Answer 16

calcarine sulcus

Question 17

what is the blood supply to the primary visual cortex?

Answer 17

largely posterior cerebral

Question 18

list the 4 types of blindness occuring due to lesions in the pathway (look at diagram )

Answer 18

• monocular blindness
• bitemporal hemianopia
• homonymous hemianopia
• upper quandrantanopia

Question 19

what is the pupillary light reflex?

Answer 19

adjust the site of pupil in response to light

Question 20

decribe the route of the afferents

Answer 20

retinal ganglion cell
pretectal region
oculomotor nuclei
ciliary ganglion

Question 21

which muscle constricts the pupil?

Answer 21

cell bodies in the ciliary ganglion project to muscles which constrict to the sphincter pupil

Question 22

do the afferents in a light reflex pass directly to pretectal regions?

Answer 22

yes

Question 23

what is the accommodation reflex?

Answer 23

an automatic response from when you switch focus from an object thats far away to one that is closer
this response enables you to switch between objects and maintain focus

Question 24

when looking far away are muscles relaxed or constricted?

Answer 24

relaxed

Question 25

define normal vision

Answer 25

able to focus both distant and near objects

Question 26

define myopia and give treatment

Answer 26

• short sighted
• able to focus on near objects
• unable to focus on distant
• eye ball relatively too long
• treatment concave lens to diverge light

Question 27

define hyperopia

Answer 27

• long sighted
• unable to focus on near objects
• eye ball relatively too short
• treatment convex lens to converge light

Question 28

define presbyopia

Answer 28

• normal age change
• gradual loss of accommodation
• lens are less elastic
• ciliary muscles are weaker
• near point; 100mm in young adults
• 800 mm in old age

treatment convex lens to converge light

Question 29

define saccade gaze shifts

Answer 29

rapid gaze shift to fix peripheral object on fovea

Question 30

what does saccade involve?

Answer 30

OPPOSITE frontal eye field (forntal lobe)

Question 31

define pursuit movements in gaze shift

Answer 31

smooth movements to keep objects fixed on fovea

Question 32

where is it intitated? (pursuit)

Answer 32

in visual cortex of SAME SIDE

Question 33

what are the effects of acommodation reflex?

Answer 33

• lens thickening
• pupillary constriction
• convergence of the eye