Vision

Question 1

How much of the eye’s optical power comes from the cornea?

Answer 1

2/3

Question 2

what muscles control the lens’ thickness?

Answer 2

ciliary muscles

Question 3

what’s accommodation in a vision context?

Answer 3

adjusting the lens (thicker/thinner)

Question 4

What happens to the lens to view close objects?

Answer 4

thickens (more refractive)

Question 5

What happens to the lens to view far objects?

Answer 5

is thinner

Question 6

What’s myopia?

Answer 6

nearsightedness

Question 7

What’s hyperopia?

Answer 7

farsightedness

Question 8

What’s presbyopia?

Answer 8

farsightedness due to age (loss of elasticity)

Question 9

What’s astigmatism?

Answer 9

blurry vision due to spherical aberrations of the eye

Question 10

Why is the fovea more visually developed?

Answer 10

1 - skinnier, denser cones
2 - not pushed away (unlike most retina)
3 - avascular (few blood vessels)

Question 11

What part of photoreceptors is light sensitive?

Answer 11

outer segment

Question 12

How long do outer segments of photoreceptors last? What happens to them?

Answer 12

12days

Shed, phagocytosed and replaced

Question 13

Where are photoreceptor outer segments created?

Answer 13

in the retinal pigment epithelium

Question 14

Key difference between Rods and Cones

Answer 14

Rods = scotopic (dim light)

Cones = photopic (bright light)

Question 15

How come photoreceptors signal via graded potentials?

Answer 15

Information travels distances short enough for graded potentials to suffice

Question 16

How many cone types are there? What’s the difference?

Answer 16

3 - spectral sensitivity

S (blue), M (green), L (red)

Question 17

How do photoreceptors signal to bipolar cells?

Answer 17

Through glutamate

Question 18

True or False? ON and OFF bipolar cells send axons to the same retina layer.

Answer 18

False

Question 19

How is light intensity represented in the visual system?

Answer 19

Through action potential frequency

Question 20

How does the retina account for all light intensities if limited to a 1000 range?

Answer 20

Through adaptation

same luminance fires at different rates based on background intensity

Question 21

True or False? Each cone is the center of either an ON or OFF pathway

Answer 21

False. Not outside the fovea (multiple receptors feed into one GC)

Question 22

True or False? All ganglion cells are for seeing color

Answer 22

False. Some are for edges, motion, …

Question 23

What’s the difference between luminance and brightness?

Answer 23

Luminance: physical measurement of intensity

Brightness: the sensation of intensity

Question 24

What causes direction selectivity in retinal ganglion cells?

Answer 24

Asymmetric lateral inhibition:

1 side has inhibitory signal, not the other

From that side, inhibition occurs before excitation which nullifies the signal

Question 25

What's the purpose of parasol (magnocellular) ganglion cells?

Answer 25

Luminance and motion

Question 26

What's the purpose of midget (parvocellular) ganglion cells?

Answer 26

Red/Green

Question 27

What's involved in the optokinetic reflex?

Answer 27

Directionally selective GC Nucleus of Optic Tract Cranial nerves + eye muscles

Question 28

True or False? The retina perceives the world the same as the brain

Answer 28

False. Images arrive flipped and must be processed

Question 29

Describe the organization of the LGN

Answer 29

6 layers bottom 2 --> parasol GC, motion, transient, project to 4Ca top 4 --> midget GC, color, sustain, project to 4Cb Koniocellular GC in between, project to 2/3

Question 30

How's is V1 structured?

Answer 30

Retinotopically, fovea over-represented orientation pinwheels (all orientation in RF) occular dominance bands

Question 31

What is stereopsis? How does it work for humans?

Answer 31

It's depth sensation two nearby objects are seen with both eyes at slightly different locations some binocular cells respond maximally to different disparities

Question 32

What's strabismus?

Answer 32

eyes don't align Two forms: exotropia (cross), esotropia (outwards) can lead to amblyopia (one eye ignored)

Question 33

What are blobs?

Answer 33

possible conduit of color vision

Question 34

Other than the where pathway, what else does the middle temporal (MT) detect?

Answer 34

motion: integrate smaller RF to see bigger picture (avoids the aperture problem)

Question 35

What is cataract and how to solve it?

Answer 35

Clouding of the lens remove and replace artificially

Question 36

What is glaucoma?

Answer 36

Often high intraocular pressure leading to optic nerve damage

Question 37

What is macular degeneration?

Answer 37

AMD, affects HiRes vision Wet (leaky blood vessels) or Dry

Question 38

What is retinitis pigmentosa

Answer 38

Degeneration of photoreceptors in the peripheral retina (tunnel vision)

Question 39

What is diabetic retinopathy?

Answer 39

Blood vessels leak their contents or neovascularization

Question 40

What is blindsight?

Answer 40

V1 damage leading to loss of conscious vision (can't see object, but knows it moves)

Question 41

What is hemispatial neglect?

Answer 41

Eyes work but half the visual field isn't processed (unawareness) due to stroke or brain injury

Question 42

What is cerebral akinetopsia?

Answer 42

Damage to the MT makes dynamic scenes appear as refreshing static images

Question 43

What is prosopagnosia?

Answer 43

Face blindness

Question 44

What is split brain?

Answer 44

severed callosum no exchange between brain hemispheres

Question 45

What is cell therapy?

Answer 45

Attempts to use stem cells to grow and implant new cells

Question 46

What is gene therapy?

Answer 46

Correct damaging or null mutations by delivering the correct copy

Question 47

What is a retinal prosthetic implant?

Answer 47

implant of electric chip that stimulates GC involves goggle based head-worn camera system

Question 48

What is optogenetic therapy?

Answer 48

make remaining cells in retina light sensitive