Lecture 1

Question 1

what are 3 advantages of having 2 eyes?

Answer 1

having a spare eye, larger FOV, and better visual function due to binocular summation

Question 2

how large is our monocular field?

Answer 2

145 degrees

Question 3

how large is our total visual field?

Answer 3

180+ degrees

Question 4

how large is our binocular visual field?

Answer 4

130+ degrees

Question 5

what is stereopsis?

Answer 5

it arises from the subtle difference between images in each eye

Question 6

what is the real advantage of binocularity?

Answer 6

highly accurate depth perception

Question 7

what happens if you fail to align the two eyes?

Answer 7

strabismus, amblyopia, diplopia, suppression, etc.

Question 8

what can occur if the two eyes are aligned but the system is stressed?

Answer 8

incorrect refractive balance, dissimilar images between eyes due to anisometropia or retinal disease, over/under convergence, and conflicts between accommodation and convergence

Question 9

what are 3 misconceptions about binocular vision?

Answer 9

some assume that the only advantage to binocular vision is stereopsis, without binocular vision you have no depth perception, and some think that stereoscopic depth perception helps them judge depth for distant objects

Question 10

what is physical space?

Answer 10

the “real world” or 3D space around us and all the objects located in it (also known as object space)

Question 11

what is visual space?

Answer 11

your perception of the physical space in relation to you - it is a construct of the brain

Question 12

what is the goal of vision?

Answer 12

to construct a visual space that looks like a physical space

Question 13

what happens when the visual space doesn’t match the physical space?

Answer 13

normal = optical illusion 
abnormal = metamorphopsia

Question 14

what is visual direction under monocular conditions called?

Answer 14

oculocentric = eye centered

Question 15

what is the Principal Visual Direction (PVD)?

Answer 15

the direction signaled by the fovea, the oculocentric sense of “straight ahead” and has zero direction

Question 16

under monocular conditions how is the oculocentric (visual direction) measured?

Answer 16

the angle between PVD (principal visual direction) and the secondary visual direction

Question 17

what is the oculocentric direction if the angle < 0?

Answer 17

negative angle (to the left side)

Question 18

what is the oculocentric direction if the angle > 0?

Answer 18

positive angle (to the right side)

Question 19

what happens to the oculocentric direction as the eye moves to fixate on a new target?

Answer 19

as you shift the direction of the fovea - the PVD also shifts with it

Question 20

what is a local sign?

Answer 20

a unique oculocentric direction associated with a specific retinal point and is determined by retinotopic mapping of the retinal locus in LGN and cortex

Question 21

what shows the neural basis of local signs?

Answer 21

mechanical visual phosphenes

Question 22

what determines the local sign size?

Answer 22

the brain (not retina)

Question 23

what relates to local sign size and what is it the basis for?

Answer 23

relates to retinal eccentricity and is the basis for directional discrimination

Question 24

how large are foveal local signs?

Answer 24

1/7 the size of foveal cones

Question 25

what is the basis for hyperacuity (Vernier acuity)?

Answer 25

local sign size

Question 26

are peripheral local signs larger or smaller than peripheral cones?

Answer 26

much larger

Question 27

what is a local sign disorder?

Answer 27

metamorphopsia - a perception of object shape that differs from its true shape

Question 28

what are 2 causes of metamorphopsia?

Answer 28

neuroanatomical (retinal diseases or strabismus, amblyopia) and optical (keratoconus)

Question 29

what is eccentric fixation (EF)?

Answer 29

PVD becomes associated with the local sign of peripheral retina other than the fovea, the patient perceives straight ahead and is not aware they are off center

Question 30

what two conditions can eccentric fixation be found in?

Answer 30

strabismic amblyopia and long term (years) macular disease

Question 31

what is eccentric viewing (EV)?

Answer 31

PVD is still associated with the fovea and the patient is aware of using peripheral vision to see

Question 32

what conditions can eccentric viewing be found in?

Answer 32

short term macular disease and in low vision rehab

Question 33

what is the visual direction under binocular conditions called?

Answer 33

egocentric = head centered

Question 34

what is the cyclopean eye?

Answer 34

represents a single hypothetical eye located approximately midway between the two eyes

Question 35

if you are gazing at an object located directly in front of the head, what is the oculocentric and egocentric directions?

Answer 35

oculocentric direction of each eye = 0

egocentric direction = 0

Question 36

if you are gazing at an object located directly in front of the right eye, what is the oculocentric and egocentric directions?

Answer 36

oculocentric direction of each eye = 0

egocentric = positive angle (to the right of the head direction)

Question 37

the brain receives input from both eyes and computes the egocentric direction based on what 2 sets of data?

Answer 37

the retinal location of the objects image in each eye (oculocentric) and each eye’s orientation or direction of gaze

Question 38

if you are looking at a target to the left side of the head without turning the head, what are the oculocentric and egocentric directions?

Answer 38

oculocentric OD = 0
oculocentric OS = 0
Egocentric = negative

Question 39

if you are looking at a target to the right side of the head with turning the head at the object, what are the oculocentric and egocentric directions?

Answer 39

oculocentric OD = 0
oculocentric OS = 0
egocentric = 0

Question 40

while fixating on a target located straight ahead and you notice a second target at your right side, what is the oculocentric direction for the second target?

Answer 40

oculocentric OD = positive
oculocentric OS = positive
egocentric = positive