Flashcards in Binocular Vision and Disparity (M2) Deck (50):
If the patient is a right esotrope and they are attempting to fixate on an object straight ahead (and can with the left eye), what type of diplopia are they experiencing?
Is stereothreshold usually larger (poorer) or smaller (better) than vernier acuity threshold?
What is the circle that includes the fixation point and the two entrance pupils where objects have equal oculocentric angles? 1. What is the retinal disparity of these points? 2
1. Vieth-Muller Circle
What is the relative depth (Δd) corresponding to a particular disparity (η)?
the stereoscopic depth interval
What is the equation used to calculate the relative disparity for a Wheatstone stereoscope?
η(rad) = - (X(L) - X(R))/(dist from eyes)
What is the first stereoscope that used mirrors?
Wheatstone mirror stereoscope
What is the optical device to effectively increase the PD in the measurement of disparity? 1. What does this do and what is it used for? 2
2. decreases stereoscopic depth interval to help tell if hitting targets far away (in war)
What is the image presentation of separate targets presented one to each eye called (not real world objects)? 1. What are examples of this in clinic? 2
1. dichoptic stimulation
2. Stereoscope, anaglyph, polaroid, alternating shutters
When looking at cards with a black background and red lettering, what color lens would be able to see the lettering? 1. What color lens wouldn't be able to see it? 2
1. red lens
2. green lens
How does fixating in front or behind an object impact the stereothreshold? 1. What can this help to find clinically? 2
1. raises threshold
2. reveal micro-strabismus
How close does an object have to be to determine stereoscopically that it is closer than a star?
d = 825m = 2,707 ft
What area on the retina has the lowest stereothreshold?
What is the equation to calculate the relative disparity for dichoptic stimulation?
η(rad) = (X(L) - X(R))/d
What is the critical retinal disparity for double vision called?
What is an area in the retina of one eye, which when stimulated simultaneously with a point in the retina of the other eye provides single binocular vision? 1. What does this allow for? 2
1. Panum's area
2. fusion of small disparities so single vision on Randot even with disparity present
What does the sign indicate for relative disparity?
What is the cortical mechanism in which images from two eyes are integrated into single perceptual whole?
During the Hess Lancaster Screen with a white screen and a red light shone on the screen, what color glasses (R or G) is able to see the light? 1. Not able? 2
1. red lens
2. green lens
Is an object outside the Vieth-Muller circle positive or negative in value?
What is the equation used to calculate the relative disparity for a Brewster stereoscope?
η(rad) = (X(L) - X(R))/(dist from lens)
What is the difference in the angles of binocular parallax called? 1. What is the equation? 2
1. relative disparity
2. γ(1) - γ(2) = φ(L) - φ(R)
What is the stimulus to stereopsis? 1. When does it mature? 2
1. LATERAL disparity
2. 4 months
What is the difference in absolute (retinal) disparity between two objects called (with symbol)?
relative disparity (η or eta)
What are important factors in determining the stereothreshold?
1. target type/size
2. length of vertical lines (better for longer lines)
3. luminance of targets (better for more luminance)
4. Exposure duration of targets (more time means better threshold)
What is the minimum relative disparity required for stereopsis called?
What is the average stereothreshold for the Howard-Dolman?
What is the alternating shutters/images device that is able to achieve dichoptic presentation?
synchronous shutter stereoscope
What is the equation to calculate the relative disparity for dioptic stimulation?
η = (β(1L) - β(1R)) - (β(2L) - β(2R))
η = φ(L) - φ(R)
**** η(rad) = PD*Δd/d^2**** know this one
What is the movement that adjusts eye position so object of regard is imaged on both foveas?
What position is unimportant in terms of relative disparity?
Is an object inside the Vieth-Muller circle positive or negative in value?
What is normal diplopia resulting from retinal disparity called?
What is the image presentation of a target seen simultaneously by both eyes called? 1. What are examples of this in clinic? 2
1. dioptic stimulation
2. standard VA charts, near point cards, etc
Which type of fusion is not required for stereopsis?
Does monocular or binocular blur increase (worsen) the stereothreshold more?
When looking at cards with a white background and red lettering, what color lens would be able to see the lettering? 1. What color lens wouldn't be able to see it? 2
1. green lens
2. red lens
What are the clinical methods to find the stereothreshold?
1. Howard-Dolman Apparatus
2. Verhoeff Stereopter
3. Brewster stereoscope
What is the disparity range that permits stereopsis called?
the region of depth
What type of stereopsis is where the depth sensation is linearly proportional to disparity?
What type of stereopsis is where the depth sensation has a non-monotonic relationship to disparity?
What is present over most of the region of depth?
What type of target is the Worth's first degree? 1. Second degree? 2. Third degree? 3
1. non-identical targets (non-fusible)
2. identical targets (fusible)
3. contain stereo (disparity) features
What is a common (30% of pop) deficiency of stereopsis that is limited to crossed or uncrossed disparity called? 1. What type of stereopsis is altered? 2
2. coarse stereopsis
What are the six classes of cortical disparity detectors?
3. tuned zero
4. tuned inhibitory
5. tuned far
6. tuned near
Is fine stereopsis a transient or sustained response? 1. Parvocellular or magnocellular units? 2. More or less defects in population than coarse? 3
Is coarse stereopsis a transient or sustained response? 1. Parvocellular or magnocellular units? 2. More or less defects in population than fine? 3
What is the stereopsis called when relative disparity is processed independently for each local target pair? 1. What is an example of this? 2
1. local stereopsis
2. simple line targets
What is the stereopsis called when relative disparities are processed interactively over a large region of the binocular field? 1. What is an example of this? 2
1. global stereopsis
2. Random dot stereogram or highly structured environments
What is the significance of random dot stereograms?
1. stereopsis does not require monocularly identifiable contours
2. RDS is useful in detecting the presence of stereopsis