Vision 1

Question 1

define -

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

Answer 1

refraction

Question 2

define -

changing the shape of the len by the ciliary body to focus on far away/near objects by refraction?

Answer 2

accommodation

Question 3

what three mechanisms are involved in accommodation ?

Answer 3

• changing lens shape
• pupils constrict
• eyes converge

Question 4

how does the lens thicken?

Answer 4

1. ciliary body contracts making the ciliary body bulge
2. space in the middle decreases
3. suspensory ligaments become
4. lens is no longer under stretch so lens becomes thicker

Question 5

what shape does the lens become when it is relaxed?

Answer 5

more spherical

Question 6

when do the pupil constrict ?

Answer 6

when we are looking at an object up close and need to sharp focus

Question 7

what muscle is used to constrict the pupils ?

Answer 7

pupillary constrictor

Question 8

what autonomic response constricts pupils

Answer 8

parasympathetic response

Question 9

what cranial nerve constricts the pupil?

Answer 9

occulomotor nerve

Question 10

what extrinsic eye muscles are responsible for converging the eyes?

Answer 10

medial rectus

Question 11

what muscles tend to be thicker

• medial recti
• lateral recti

Answer 11

medial rectus

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

- increased curvature

Question 15

what is presbyopia ?

Answer 15

long sightedness of old age

Question 16

what is emmetropia?

Answer 16

perfect vision

Question 17

what is the most common cause of myopia?

Answer 17

eye ball is too long

Question 18

in myopia,

is the image focused infront or behind the retina?

Answer 18

in front

Question 19

myopia

- do close things look clear or hazy?

Answer 19

clear

Question 20

what are the common symptoms of myopia in toddlers?

Answer 20

loss of interest in sports/people. More interest in books, pictures.

Question 21

what are the common symptoms of myopia in infants ?

Answer 21

divergent squint

Question 22

what type of lens is used in glasses to correct myopia ?

Answer 22

biconcave to decrease the power of bending

Question 23

can laser eye surgery be used to treat myopia?

Answer 23

yes

Question 24

in hyperopia do close objects look hazy or clear?

Answer 24

hazy

Question 25

what are the anatomical differences in hyperopia?

Answer 25

eye ball is too short and lens is too flat

Question 26

in hyperopia, what kind of squint would a child have?

Answer 26

convergent

Question 27

why does children with hyperopia have to be treated immediately ?

Answer 27

to prevent a lazy eye

Question 28

where does the image focus during astigmatism?

Answer 28

the image is focused in two locations which causes double vision

Question 29

during astigmatism do close and distant objects appear clear or blurry?

Answer 29

distant and close objects appear hazy

Question 30

what type of glasses are used to correct astigmatism?

Answer 30

cylindrical glasses

Question 31

what is the cause of presbyopia?

Answer 31

the lens becomes less mobile with old age

Question 32

what type of glasses are used to correct presbyopia?

Answer 32

biconvex

Question 33

what is phototransduction ?

Answer 33

The energy in light waves need to stimulate photoreceptor cells on the retina conversion of light energy to electrical energy by rods and cones

Question 34

what is the shape of the outer segment of the - rod - cones

Answer 34

rod - rod shaped outer segment cones - cone shaped outer segment

Question 35

is a thin or thick lens more powerful?

Answer 35

thick

Question 36

name the two photoreceptors in the eye

Answer 36

rods | cones

Question 37

How does bleaching of the visual pigment result in phototransduction?

Answer 37

Phototransduction cascade.

Question 38

What role does Vitamin A play in the visual pigment?

Answer 38

visual pigment regeneration

Question 39

what channel closes as a result of the phototransduction casade ?

Answer 39

Na channels

Question 40

what are three symptoms which can be caused by vitamin A deficiency ?

Answer 40

- night blindness | - abnormal conjunctiva and corneal epithelium

Question 41

is Vit A water or fat soluble?

Answer 41

fat soluble

Question 42

what are two clinical signs of a Vitamin A deficiency ?

Answer 42

Bitots spots on conjunctiva | corneal ulceration

Question 43

describe the basic mechanism of a photon landing on a photoreceptor

Answer 43

1. photon lands on Rhodopsin 2. 11-cis isomer changes to all-trans isomer 3. this results in bleaching of a visual purple colour 4. Na channels close 5. results in hyper polarisation of the cell 6. Hyperpolarisation increases Ca ions which stimulates the retinal cells