Vergence Eye Movements and the ZCSBV (M2) Flashcards
What is the accommodative response for an 1D myope wearing no Rx at distance? 1. Near? 2. Amount of blur at distance? 3. Near? 4
- 0
- 1.50D
- 1.00D
- clear
What is the accommodative response for an 1D hyperope wearing no Rx at distance? 1. Near? 2. Amount of blur at distance? 3. Near? 4
- 1.00D
- 3.50D
- clear
- clear
How is the rate of accommodative convergence usually shown? 1. What are the two types of these? 2. What is a average value? 3
- AC/A (accom conv/accom)
- calculated (far-near) AC/A and Gradient AC/A
- 4 pd/D
What does placing prisms and lenses effect relative to the ZCSBV?
does not effect zone at all, only effects demand
What is the line measured from the phoria line to the right-hand boundary of ZCSBV?
positive fusional vergence (PFV)
What are the four components that combine to make the total convergence?
- fusional (disparity) vergence
- accommodative vergence
- proximal vergence
- tonic vergence
What are the average distance phoria values? 1. Average near phoria values? 2
- 1pd exo
2. 3pd exo
What is the latency of fusional vergence?
160ms
For an esophoria, what type of fusional convergence is used to compensate? 1. Exophoria? 2
- negative fusional convergence
2. positive fusional convergence
What do the vergence ranges mark?
zone of clear single binocular vision
What is the line measured from the phoria line to the left-hand boundary of ZCSBV?
negative fusional vergence (NFV)
What is the binocular oculocentric direction for each eye after uncovering the right eye during the unilateral cover test with the presence of a esophoria?
beta left = 0
beta right = phoria angle
What is the accommodative response for an 3D myope wearing -2.00D at distance? 1. Near? 2. Amount of blur at distance? 3. Near? 4
- 0
- 1.50D
- 1.00D
- clear
What are the theories of how the oculocentric directions are combined in binocular vision?
- dominant eye theory (one is suppressed) = not what happens
- cyclopean theory (betas averaged) = what actually happens
What is the idea that asymptomatic binocular vision occurs when the vergence demand is within the middle third of the total fusional vergence range? 1. Is this a better predictor of symptoms with esophoria or exophoria? 2
- Percival’s criterion
2. esophoria
What is the vergence position of the eyes in the absence of fusional vergence called?
phoria (dissociated phoria)
When patients have positive convergence deficiency, is the CA/C usually high or low?
high
What is the only information available to calculate and program the magnitude and direction of the required saccade when a person is monocular?
oculocentric direction (beta)
What happens when you decrease the convergence demand by putting a base in prism in front of a patient?
- negative fusional vergence creates negative conv accom
- negative conv accom can cause blur
- at limit of NFV, most patients will decrease accommodation in order to release accommodative convergence
- when run out of NFV and accom conv = double
What is the visual direction of an object specified relative to the line of fixation?
oculocentric direction (beta)
What is the accommodative demand equal to in general terms? 1. What also needs to be accounted for? 2
- 1/distance
2. refractive error and refractive correction
For what patients is the demand line never in the ZSCBV?
strabismic patients
What is the idea that asymptomatic binocular vision occurs when the compensating fusional reserve is at least double the magnitude of the phoria? 1. Is this a better predictor of symptoms with esophoria or exophoria? 2
- Sheard’s criterion
2. exophoria
What are the eye movements that occur when uncovering the right eye during the unilateral cover test with the presence of a esophoria?
- binocular disparity causes negative fusional vergence (divergence of both eyes)
- left now off target (oculocentric direction not 0) so rightward conjugate eye movement (saccade) required to maintain foveal fixation
- divergence to foveate