Vergence Flashcards
maddox’s 5 components of vergence are:
- tonic
- proximal
- voluntary
- accommodative
- disparity
the response in the absence of stimulus is called _____ vergence
tonic
tonic vergence is about ____ prism diopters of convergence
2-4 prism diopters of convergence
_____ convergence is driven by perception of nearness of an object (less than 3 meters)
proximal convergence
_____ vergence is driven by voluntary effort (on purpose)
voluntary
____ vergence is driven by accommodation and an important component of the near response
accommodative vergence
AC/A ratio is
accommodation convergence per unit of accommodation (in prism diopters / diopter)
______ AC/A ratio assumes a perfect response to accommodation
stimulus
______ AC/A ratio is more accurate
response
_____ AC/A ratio is usually 10% less than the ______ AC/A ratio
response is 10% less than stimulus
accommodative convergence can provide over _____ of the required convergence at near
a half
high AC/A ratio means
AC can provide much more
-eso at near
low AC/A ratio means
AC can provide much less
-exo at near
(more common)
AC/A ratio is responsible for patient’s ____ ______
near phoria
______ vergence is driven by binocular disparity, and has closed-loop negative feedback control
(also called fusion or reflex)
disparity
uncrossed retinal disparity requires _____ for fusion
divergence
crossed retinal disparity requires _____ for fusion
convergence
object images on the foveal have ____ disparity
0
_____ is responsible for the patient’s near phoria
AC/A ratio
_____ is responsible for the patient’s distance phoria
tonic vergence
phasic controller element is the:
fast component of disparity vergence
tonic adaptive controller element is the:
slow component for disparity vergence
problems with what can lead to asthenopia (eye strain)?
tonic adaptive controller element (slow component to disparity vergence)
negative fusional vergence uses ___ prism and tests ____
base in (BI) to test divergence
positive fusional vergence uses ___ prism and tests _____
base out (BO) to test convergence
adding ___ prism stimulates accommodation therefore accommodation must relax
BO (convergence)
adding ___ prism inhibits accommodation therefore accommodation must stimulate
BI (divergence)
what does the blur point represent?
the fusional vergence without the effects of accommodation
what kind of fusional vergence amplitudes are associated with less asthenopia?
larger fusional vergences
why are larger fusional vergences associated with less asthenopia?
they can compensate for larger phorias
the break point is a measure of
the amount of fusional vergence that is not independent of accommodation
the total demand on the fusional vergence system is the:
phoria plus the compensating vergence
interval between 0 and the blue point (or break if no blur occurs) = ______ vergence
relative
interval between the phoria and the blue point in the opposite direction = ______ vergence
fusional
blur point is from _____ vergence only
fusional vergence only
vergence independent of accommodation
what does accommodation do after blur?
after blur, accommodation contributes to the vergence response
when can you analyze using Morgan’s data?
if no or low phoria (1EP-1XP at far) or (0-6XP at near)
PFV compensates for:
XP
NFV compensates for:
EP
right infravergence compensates for
right hyperphoria
Sheard’s criterion states that
relative vergence reserve needs to be at least twice the demand
Sheard’s criterion is a good predictor of symptoms in
moderate to high XP
Percival’s criterion is a better predictor of symptoms in cases of
esophoria
moderate
Percival’s criterion states
the lower magnitude vergence should be at least 1/2 of the higher magnitude vergence
using prism as a treatment option causes:
decreases the vergence demand
what is the net result from using prism as a treatment option
smaller phoria and larger compensating ranges
what prism would be used for esophoria
base out prism
what prism would be used for exophoria
base in prism
addition lenses at near would be a useful treatment option for:
esophoria at near
addition lenses at near can cause:
decreases accommodative demand which then decreases accommodative-convergence
