VISION PT 2

Question 1

whats far point vision

Answer 1

distance beyond which no change in lens shape

Question 2

what happens to lens as distance grows farther

Answer 2

gets thinner + flattened through ciliary muscle relaxation

Question 3

what happens to sympathic and parasympathetic activity as distance of object grows farther

Answer 3

Increased sympathetic activity
Decreased parasympathetic activity

Question 4

whats emmetropia

Answer 4

state in which eye is relaxed and focused on object (~20ft/6m away)

Question 5

describe refraction in far point vision

Answer 5

Least amount of refraction here because rays come in nearly parallel and lens is relaxed

Question 6

describe focusing with close vision

Answer 6

For objects closer than 20ft, vision is initially unfocused, so adjustments must be made

Question 7

what are three major aspects of focusing with close vision

Answer 7

accomodation of lens, constriction of pupils, convergence of the eyeballs

Question 8

what does accommodation of lens do to ciliary muscles and what happens to the lens as a result

Answer 8

Contract ciliary muscles (parasympathetic)
Lens bulges increased refractory power

Question 9

what does construction of the pupils enhance and prevent

Answer 9

Enhances accommodation effect by reducing pupil size; Prevents divergent light rays from entering

Question 10

describe how convergence of the eyeballs keeps vision keeps objects being viewed

Answer 10

Medial rotation of the eyeballs keeps object being
viewed, focused on retinal foveae

Question 11

describe near point vision

Answer 11

distance where max bulge of lens occurs (4 in), increases w/ age

Question 12

whats myopia and why does it happen

Answer 12

near sighted; distant objects are blurred; usually because eyeball is too long

Question 13

what are objects focused on in myopia

Answer 13

Objects are focused in front of the retina rather than on it

Question 14

how is myopia corrected

Answer 14

concave lens which diverge light right before they enter the eyes

Question 15

whats hyperopia

Answer 15

far sighted; near object blurred because eye is shorter than usual

Question 16

what are distant objects focused on in hyperopia

Answer 16

Distant objects are focused behind the retina

Question 17

how do you correct far vision/hyperopia

Answer 17

Use convex lenses to correct
Converges light more and focus on retina

Question 18

is hyperopia usually present at birth

Answer 18

yes

Question 19

what presbyopia

Answer 19

as you age, eye lens loses it’s ability to focus on nearby objects which causes them to appear blurry

Question 20

what are photoreceptors

Answer 20

Modified neurons with “tips”

Question 21

what do photoreceptors convert light to

Answer 21

light from the visible electromagnetic radiation into signals that stimulate biological processes

Question 22

what activates photoreceptors

Answer 22

when light hits the retina

Question 23

what are the two types of photoreceptors

Answer 23

rods and cones

Question 24

what are cones for

Answer 24

for bright light (and colors)
 Not sensitive to dim light

Question 25

wha are rods for

Answer 25

for dim light
 Not sensitive to colors (reason for poor night vision)

Question 26

what is the outer segmented for a photoreceptor

Answer 26

the receptor that contains visual pigments (different between rods and cones)

Question 27

when are photoreceptors renewed and why

Answer 27

Renewed nightly to offset damage of bright light

Question 28

what does the inner segment of photoreceptors contain

Answer 28

contains nuclei and cell organelles (connected to outer by cilia)

Question 29

what are rods responsible for

Answer 29

scoptoic (night) vision; very sensitive to light and can respond to a single photon

Question 30

what will produce a visible flash

Answer 30

Six closely spaced rods, each stimulated by single photon

Question 31

do we have more rods or cones

Answer 31

rods (over 100 milion)

Question 32

what happens to rods when light intensity increases

Answer 32

saturate quickly

Question 33

does the foveal area have rods

Answer 33

no; Density of rods peaks at about 20 degrees from fovea → Better peripheral vision

Question 34

describe sensitivity/adaption/responsibiltiy of cones

Answer 34

Low sensitivity
 Not sensitive to dim light
 Adapted to bright light (daylight)
 Responsible for photopic vision

Question 35

do cones saturate

Answer 35

Never saturate at steady light level at any intensity

Question 36

describe how cones pathways result in high resolution vision

Answer 36

Non-converging (direct) pathways in foveal area result in detailed high-resolution vision
→ But in small areas of visual field

Question 37

what are the three types of cones/visual pigments

Answer 37

1) L-sensitive to long wavelengths (red)
2) M-middle wavelength (green)
3) S- short wavelength (blue)

Question 38

describe photoreceptor regeneration and how easy they’re damaged

Answer 38

damaged easily and regenerate easily - outer segment renewed every 24 hours
(destroyed by intense light)

Question 39

how does photoreceptor regeneration compare to gustatory and olfactory regeneration

Answer 39

› Gustatory and basal epithelial cells replaced every 7-10 days
› Olfactory sensory neurons are replaced every 30-60 days

Question 40

differntiatite what happens to eyes when looking at something close vs far away

Answer 40

when looking at something far away, rays coming at us straight on so we dont need to bend our lens (flatten it out/relax instead)

when things are really close, rays are moving outwards as
they’re coming toward our eye, so we need to bend/buldge/round them (so
need to contract ciliary body)