6 - Fixation Disparity

Question 1

What is fixation disparity?

Answer 1

the small angle of misalignment of the eyes under binocular conditions

Question 2

units of fixation disparity?

Answer 2

minutes are arc

Question 3

Difference between heterophoria and fixation disparity?

Answer 3

heterophoria is under dissociated conditions

Question 4

eso - _ converging, fixation ahead of target

Answer 4

over

Question 5

eso - visual axes are _ - _ disparity

Answer 5

crossed, uncrossed

Question 6

exo - _ converging, fixation behind the target

Answer 6

under

Question 7

exo - visual axes are _ - _ disparity

Answer 7

uncrossed, crossed

Question 8

with fixation disparity, it is still within PFA, and fusion is _

Answer 8

not sacrificed

Question 9

What does fixation disparity do to the horopter?

Answer 9

moves it from middle of Panum’s to the edge

Question 10

if esophoria, they will most likely have _ fixation disparity

Answer 10

eso

Question 11

fixation disparity is _ error

Answer 11

purposeful - keeps brain stimulated

Question 12

what makes fixation disparity different from Von Grafe phoria testing?

Answer 12

there is a binocular fusion lock with FD testing, FD is done under natural conditions (vs dissociated)

Question 13

forced vergence fixation disparity curve graphically represents how a change in vergence demand (with prism) changes _

Answer 13

fixation disparity

Question 14

sequence for disparity curve:

Answer 14

no prism, 3 BI BO, 6 BI BO, until patient can no longer maintain fusion

Question 15

x-axis is:

Answer 15

prism amount in prism diopters

Question 16

y axis is:

Answer 16

magnitude of fixation disparity

Question 17

x - intercept is:

Answer 17

associated phoria - amount of prism needed to reduce fixation disparity to 0

Question 18

y - intercept is:

Answer 18

magnitude of fixation disparity with NO prism

Question 19

What is the method of choice when determining amount of prism to put in glasses?

Answer 19

associated phoria from curve

Question 20

slope between 3 BO and 3 BI represents:

Answer 20

ability to adapt to prism, flat= good ability

Question 21

center of symmetry is _

Answer 21

area where adaptation occurs most readily, slope closest to 0

Question 22

if patient has type 1 graph and is symptomatic, patient is best suited for _

Answer 22

vision therapy

Question 23

patient with type 1 curve _ to prism

Answer 23

adapts well

Question 24

type 2 curve is flat on _ side

patient adapts well to _

Answer 24

BO

BO (and +), shifts graph to right

Question 25

type 3 curve is flat on _ side

pt adapts well to _

Answer 25

BI

BI (or -), shifts graph to right

Question 26

patient with type 4 graph is like _,

patient has _

Answer 26

flat Z

poor sensory/motor fusion

Question 27

patient with type 4 graph are usually/usually not symptomatic? do well with VT?

Answer 27

usually are, yes

Question 28

_ is best method to determine amount of prism to rx,

less is more

Answer 28

fixation curve