Binocular Vision: Lecture 5: Visual Direction (2)

Question 1

1. All object on a Particular Visual Line in Object Space form images on the SAME RETINAL POINT and thus have the Same Visual Direction
2. An Object on the Primary Visual Line of Either eye will appear to be on the Primary Visual Line of the Cyclopean Eye
3. Every visual line in the visual field on 1 eye has a corresponding visual line in the other eye, and the corresponding visual lines have identical perceived visual directions.

Answer 1

1. Laws of Oculocentric Visual Direction
2. Laws of Egocentric Visual Direction
3. Laws of Identical Visual Direction

Question 2

Egocenter and Heterophoria

1. If you occlude one eye, what will you see happen to the target?
2. What will exert an influence on the Perceived Egocentric Direction?

Answer 2

1. It will look like it gets displaced in the same direction as the eye rotation
2. the Position of the Covered eye.

Question 3

Corresponding Retinal Points

1. They’re pairs of points (1 in each eye). When stimulated quickly or at the same time, what is perceived?
2. Corresponding points have corresponding what?

Answer 3

1. they’re perceived to lie in a Single Common Visual Direction
2. have corresponding lines of sight. An object lying anywhere on either of these lines of sight will be seen as lying in a single visual direction

Question 4

1. When eyes fixate binocularly, an image formed on both foveas is seen as what?
   a. What is this CALLED?
2. For every point in a VF, there is a point in what?

Answer 4

1. As a Single Straight-ahead visual direction
   a. COMMON SUBJECTIVE PRINCIPAL VISUAL DIRECTION
2. in the other eye’s retina whose visual direction is identical (CRP)

Question 5

1. A Retinal Locus at Eccentricity (aL) from the fovea in the left eye will have a corresponding point where?
2. Corresponding points would have what type of displacement?
3. If this is repeated for Several Equal Values of aL and aR, we obtain a plot of points in visual space, each imaged on what?
4. Vieth-Muller Circle: Define

Answer 5

1. at an Identical Angle aR from the fovea in the right eye
2. the same Horizontal displacement from the fovea in each eye as well as the same vertical displacement
3. on corresponding retinal points in the two eyes
4. It’s a Circle that INTERSECTS the Fixation point and the Entrance Pupils of each eye

Question 6

Binocular Disparity (1)

1. Images on corresponding points are perceived as what?
2. The Perception of depth arises from the stimulation of what?

Answer 6

1. as Arising from targets at the same distance

2. of Non Corresponding Retinal Points

Question 7

Binocular Disparity (2)

1. Images of a single object that DO NOT stimulate corresponding retinal points, if Viewed MONOCULARLY, would be perceived as Lying how?
2. The difference in position in relation to corresponding points b/w images in the two eyes is called what?

Answer 7

1. in different visual directions.

2. a BINOCULAR DISPARITY (can be horizontal and Vertical)

Question 8

Binocular Disparity (3)

1. Does horizontal binocular disparity allow the perception of stereoscopic Depth?
2. How can Horizontal binocular disparity be classified?

Answer 8

1. YES

2. As Crossed or Uncrossed in relationship to the fixation point (the point at which the 2 eyes are converged)

Question 9

1. Crossed Disparity: Define

2. Uncrossed Disparity: Define

Answer 9

1. points seen as NEARER than the fixation point, w/in the Vieth-Muller Circle (lines of sight cross in front of the fixation point)
2. Points farther than the fixation point have lines of sight that meet behind the fixation point.

Question 10

1. Upper Limit of Disparities that can still produce Single vision is determined by what?
2. Vertical Disparities do not directly give rise to a perception of depth as do what disparities?

Answer 10

1. PANUM’s AREA

2. Horizontal Disparities

Question 11

1. What does Crossed disparity involve? (what kind of shift)

2. Uncrossed disparity involves what kind of shift?

Answer 11

1. Temporal Shift of the images in 1 or Both Eyes
2. Nasal ward shift

**Read in the book about Crossed disparity (Lecture 5: Visual Direction: Slide 16)

Question 12

Diplopia and Confusion

1. Points beyond what area will not be seen as fused or single?
2. Objects whose images are formed on corresponding retinal points are perceived as lying in the same what?
3. What about images formed on widely separated non-corresponding retinal points?

Answer 12

1. Panum’s Area
2. in the same binocular visual direction
3. they’re perceived as arising from different visual directions

Question 13

1. What happens if a distant object is fixated BIFOVEALLY, how will a Nearer Object in front of it be imaged?
   a. What if these points are far enough apart?

Answer 13

1. It’ll be imaged on the TEMPORAL RETINA of each eye on noncorresponding points
   a. We see the object as Double (CROSSED DIPLOPIA)

Question 14

1. What is diplopia a Direct consequence of?

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Answer 14

1. of the R and L neural images arriving at different locations in V1, and thus neural fusion CANT HAPPEN

Question 15

1. What is UNCROSSED DIPLOPIA?

Answer 15

1. Fixating a near object, and the DISTANT OBJECT is seen as DOUBLE (Left eye sees left image and right eye sees right image)

Question 16

1. Define BINOCULAR CONFUSION

a. When does this occur?

Answer 16

2 DIFFERENT OBJECTS seen in 1 direction or location

a. when an image is formed on one locus in one eye, but a non identical image is formed on its corresponding point in the other eye. The result: 2 Different objects are seen superimposed in the same location

Question 17

Diplopia and confusion can be eliminated in the strabismic visual system by doing 1 of 2 things

Answer 17

1. Suppressing the DIPLOPIC image in the Strabismic Eye

or

2. Shifting the 0 Reference Point for Directionality in the Strabismic Eye

Question 18

Beads

1. Eyes converged at the Bead…How will it look?
2. Over convergence?
3. Under Convergence?

Answer 18

1. Locus at which the 2 Foveas point (the BEAD) is seen as SINGLE, while all other loci along the string are seen as DOUBLE
2. 2 images of the string will be seen as CROSSING in FRONT of the BEAD (bead now looks DIPLOPIC)
3. the Perceived crossing is BEHIND the BEAD)

Question 19

Anomalous Retinal Correspondence

1. In strabismus, how does the patient learn to REMOVE the diplopic image?
   a. How?

Answer 19

1. by REMAPPING the Corresponding POINTS!
   a. The Fovea of the Strabismic Eye is NOT the ZERO REFERENCE, but the retinal Locus pointing at the same Object as the fovea of the other eye is now recalibrated to be the ZERO REFERENCE

Question 20

Anomalous Retinal Correspondence

1. What is Anomalous Correspondence?
2. So why is there no diplopia or confusion when the eye is strabismic?

Answer 20

1. It’s an adaptation to strabismus where an Eccentric Locus pointing straight ahead in the Strabismic Eye is REMAPPED to correspond to the fovea of the NONstrabismic Eye under Binocular Conditions
2. Because ALL points in the Field are again Corresponding (ARC)