Vergence Flashcards
What units are used to measure vergence?
Prism diopters, which is the prism power necessary to deviate a ray of light one cm over a distance of one meter.
What is the equation used to calculate vergence demand?
V = pd in cm/target distance in meters.
Does base in prism increase or decrease vergence demand?
It decreases vergence demand (stimulates divergence).
Does base out prism increase or decrease vergence demand?
It increases vergence demand (stimulates convergence).
What is the primary stimulus for vergence adjustment?
Binocular retinal image disparity.
What are the Maddox categories that contribute to total vergence?
Tonic, fusional, accommodative, and proximal.
What is tonic vergence?
Vergence that occurs in the absence of a target.
What is fusional vergence?
Vergence that occurs in response to a target further or closer than the current target.
What is accommodative vergence?
Vergence that occurs in response to a change in accommodation.
What is proximal vergence?
Vergence that occurs in response to thinking that a target is near.
On the Alternating Cover Test, what type of eye movement would you see for an exo patient?
You would see an inward (with the paddle) eye movement, since the eye was turned out and now has to turn in to take up fixation.
On the Alternating Cover Test, what type of eye movement would you see for an eso patient?
You would see an outward (against the paddle) eye movement, since the eye was turned in and now has to turn out to take up fixation.
What three factors must be considered to properly assess vergence?
Amplitude, facility, posture.
What test is used to measure vergence amplitude?
NPC, or prism bar vergence ranges.
What test is used to measure vergence facility?
BI/BO prism flippers.
