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Vision Science 5 > Lecture 5 > Flashcards

Lecture 5 Flashcards

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1
Q

Does fixation disparity affect the horopter property?

A

yes

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2
Q

Which horopter criterion belongs to fixation disparity?

A

identical visual direction horopter

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3
Q

The vergence angle of the eye, the angle between the visual axis, is slightly inaccurate
The fixation point does not coincide with the actual target in space.
“Fixation disparity should not be confused with binocular disparity: fixation disparity is a misalignment of the visual axes; binocular disparity is non-correspondence of the retinal regions stimulated by a target located
off the horopter.”

A

fixation disparity

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4
Q

When a subject has exo fixation disparity, what type of binocular disparity does the intended fixation target have?

A

crossed binocular disparity

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5
Q

what type of vergence does crossed binocular disparity stimulate?

A

CONVERGENCE

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6
Q

What type of binocular disparity does an eso FD cause?

A

uncrossed binocular disparity

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7
Q

What type of vergence does uncrossed binocular disparity cause?

A

divergence

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8
Q

________ is a small purposeful error in vergence

A

fixation disparity

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9
Q

FD and heterophoria is USUALLY correlated or uncorrelated?

A

correlated

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10
Q

exophoria pt usually has what type of FD?

A

exo FD

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11
Q

esophoria pt usually has what type of FD?

A

eso FD

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12
Q

FD and heterophoria always agrees. T/F

A

False

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13
Q

FD: test under binocular condition - what type of phoria?

A

associated phoria

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14
Q

heterophoria: test under monocular condition – what type of phoria?

A

dissociated

ex: cover test

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15
Q

The amount of prism needed to eliminate fixation disparity.

A

associated phoria

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16
Q

horizontal associated phoria is usually smaller than what?

A

horizontal dissociated phoria

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17
Q

associated phoria is a more reliable indicator for what?

A

successful prism prescription

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18
Q

seen by both eyes, has an angular

width of 1.5

A

binocular fusion lock

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19
Q

seen monocularly OD sees top line, OS sees bottom line

A

Two Nonius lines

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20
Q

Clinical measurement of FD

A

 Binocular fusion lock

 Two Nonius lines

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21
Q

most accurate way of measuring FD

A

sheedy disparometer

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22
Q

what uses the same method of sheedy disparomter?

A

saladin card

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23
Q

Wesson Card testing principle

A

 The polarized lines on the Wesson card are actually centered.
 The lines mark the intended fixation point but each eye’s visual
axis misses it.
 They appear deviated due to the fixation disparity.

24
Q

if pt has exo FD, what happens with wesson card test?

A

top eye image compared to bottom, is more towards left side

25
Q

wesson card: if arrow points to the right what type of FD?

A

exo FD

26
Q

wesson card: if arrow points to the left what type of FD?

A

eso FD

27
Q

sheedy: if bottom is to the left what type of FD?

A

exo FD

28
Q

sheedy: if bottom is to the right, what type of FD?

A

eso FD

29
Q

The sheedy disparometer marks the location of what?

A

visual axes of each eye; what doctor sees

30
Q

the wesson card shows what?

A

perceived location of the fixation point relative to each visual axis; what patient sees

31
Q

– The amount of prism needed to eliminate

fixation disparity

A

associated phoria

32
Q

how is prism use with associated phoria?

A

used to shift the images to match the visual axis

33
Q

Binocular rivalry can occur when very different images of exactly equal salience fall on corresponding points. T/F

A

False

34
Q

Wesson Card: bottom arrow points to the right side. Half way towards the first point. How do you record FD?

A

4.3 min of arc exo FD

35
Q

Saladin card: bottom vertical line is to the right.

How do you record FD?

A

Eso FD

36
Q

If BI prism is placed on two eyes, what type of disparity is created?

A

Uncrossed binocular disparity
stimulates negative fusional vergence
Eyes diverge to maintain bifoveal fixation

37
Q

uncrossed binocular disparity pt on sheedy test will see what?

A

top to the right

38
Q

BO prism stimulates what type of vergence?

A

positive fusional vergence (convergence)

39
Q

If we increase BI prism, what will happen to FD?

A

FD decreases

40
Q

What if we put too much BI prism?

A

visual axis no longer moves, but images move farther temporally outside of visual axis –> FD increases towards eso (oppositely)

41
Q

What axis for FVFD curve: amount of prism used to stimulate the vergence system

A

X axis

42
Q

What axis for FVFD curve: fixation disparity, how closely the visual axis keeps up with the stimulus

A

Y axis

43
Q

Y intercept on FVFD curve represents what?

A

FD (no prism)

44
Q

X intercept on FVFD curve represents what?

A

associated phoria (FD=0)

45
Q

Once we go beyond Panum’s fusional area, what will the patient experience?

A

diplopia

46
Q

A greater slope across the middle section would show

A

that fixation disparity is slowly changing with the addition of prism.

47
Q

When prisms stimulate vergence eye movements, the eyes tend to lag behind the prism, causing

A

a gradual change in the amount of fixation disparity. This is reflected in the slope.

48
Q

The flatter the slope, the better the eyes are able to maintain what?

A

their starting level of fixation disparity (better vergence adaptation).

49
Q

flatter and wider slope represents

A

a better system

50
Q

What type is most common and considered a normal response?

A

Type I

51
Q

eso FD when no prism, add BI increase the eso FD; add BO decrease eso FD till it becomes 0, then become exo FD.

A

Type I eso

52
Q

exo FD when no prism, add BI decrease exo FD till it becomes 0, then become eso FD; add BO increase the exo FD.

A

Type I exo

53
Q

What type curve is usually found in pt with large eso phoria?

A

Type II

54
Q

What type of patient will respond to prism correction well?

A

eso heterophoria pt

55
Q

What type of curve is usually found in pt with large exo phoria?

A

Type III

56
Q

What type of curve for patient that has a small exo FD.

A

type 4

Vision Science 5 (6 decks)

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