6 - Fixation Disparity Flashcards
What is fixation disparity?
the small angle of misalignment of the eyes under binocular conditions
units of fixation disparity?
minutes are arc
Difference between heterophoria and fixation disparity?
heterophoria is under dissociated conditions
eso - _ converging, fixation ahead of target
over
eso - visual axes are _ - _ disparity
crossed, uncrossed
exo - _ converging, fixation behind the target
under
exo - visual axes are _ - _ disparity
uncrossed, crossed
with fixation disparity, it is still within PFA, and fusion is _
not sacrificed
What does fixation disparity do to the horopter?
moves it from middle of Panum’s to the edge
if esophoria, they will most likely have _ fixation disparity
eso
fixation disparity is _ error
purposeful - keeps brain stimulated
what makes fixation disparity different from Von Grafe phoria testing?
there is a binocular fusion lock with FD testing, FD is done under natural conditions (vs dissociated)
forced vergence fixation disparity curve graphically represents how a change in vergence demand (with prism) changes _
fixation disparity
sequence for disparity curve:
no prism, 3 BI BO, 6 BI BO, until patient can no longer maintain fusion
x-axis is:
prism amount in prism diopters
y axis is:
magnitude of fixation disparity
x - intercept is:
associated phoria - amount of prism needed to reduce fixation disparity to 0
y - intercept is:
magnitude of fixation disparity with NO prism
What is the method of choice when determining amount of prism to put in glasses?
associated phoria from curve
slope between 3 BO and 3 BI represents:
ability to adapt to prism, flat= good ability
center of symmetry is _
area where adaptation occurs most readily, slope closest to 0
if patient has type 1 graph and is symptomatic, patient is best suited for _
vision therapy
patient with type 1 curve _ to prism
adapts well
type 2 curve is flat on _ side
patient adapts well to _
BO
BO (and +), shifts graph to right
