Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Strabismus 106 > BSV > Flashcards

BSV Flashcards

1
Q

How many components do binocular disparities have and what are they?

A

Horizontal = information on relative depths of objects which is the basis for stereopsis
Vertical = useful info on eye positions that partly determine disparity size and is used to compute eye position and so distance to fixation and gaze angle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is correspondence in relation to BSV?

A

Cortical function enabling fusion of images from each eye. ARC occurs when constant manifest strabismus where cortical changes allow correspondence from retinal elements that normally wouldn’t correspond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is panoramic vision?

A

Those with large-angle exotropia can appreciate the images in the peripheral field with both eyes simultaneously which presents a benefit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What age does stereopsis emerge?

A

3-4mo with abrupt and rapid onset. Due to IPD so the eyes get a different image in each eye which is called ‘parallactic angle’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is ‘parallactic angle’?

A

The fact that each eye gets a slightly different image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is linear perspective?

A

It’s the illusion of depth on a flat surface where parallel lines converge in a single vanishing point on the horizon = objects with a constant size appear to subtend at smaller angles as they recede from the subject

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is ‘interposition’?

A

It’s the overlay of contours where the object is seen as in front

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are all the monocular cues?

A
  • Linear Perspective
  • Interposition
  • Highlights & Shadows
  • Aerial Perspective
  • Relative Size
  • Texture Gradient
  • Height in Plane
  • Motion Parallax
  • Size Constancy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the binocular cues?

A
  • Binocular Disparity
  • Binocular Convergence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does highlights and shadows refer to with monocular cues?

A

Elevations and depressions for depth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is aerial perspective?

A

A monocular cue where depth is depicted where distant objects are seen as paler, less detailed and usually bluer than near objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is relative size?

A

A monocular cue where more distant images are smaller on the retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is texture gradient?

A

A monocular cue where object texture is less apparent than further away

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is Height in Plane?

A

A monocular cue where distant objects tend to appear higher on our visual fields than close objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is motion parallax?

A

A monocular cue where apparent motion of object is relative to use when we move our heads side-to-side objects are closer than our fixation point appear to move in the opposite direction to head movement whereas those further in fixation move in the same direction and slower than the nearer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is size constancy?

A

A monocular cue where perception of size of objects are relatively constant despite size on retina varying with distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is BSV?

A

The ability to use both eyes simultaneously to contribute to a common single vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is stereopsis?

A

Fine judgements with respect to the relative positions of objects in space like with threading a needle. Facilitates manipulation, reaching and balance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What constitutes normal BSV?

A
  • Normal anatomical development of the eyes
  • Brain & orbital parts of the skull
  • Overlapping visual orbits
  • Nasal fibres cross at optic chiasm (decussation)
  • Retinal correspondenceW
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is ‘fovea avascular zone’?

A

0.5mm wide with no blood vessels
The fovea is 1.5mm wide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the horopter?

A

Arch shade, anywhere on this we see single images as they stimulate corresponding points at the same distance to the fovea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is Vieth-Muller?

A

Defined as a circle but discovered to be flatter on the top

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is Panum’s fusional space?

A

Within a narrow band around the horopter it stimulates disparate retinal elements that transmit the impression of single vision. Disparities of 2-3” can be fused. Fixation disparity is when a minute image displacement of 2-3” of arc occurs within Panum’s fusion space is maintained.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is retinal rivalry?

A

When dissimilar contours are presented to corresponding retinal areas so fusion isn’t possible leading to retinal rivalry
Binocular rivalry is when disparity is too great on the retina
Actively suppress one eye for single signal to be perceived

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What’s an empirical horopter (Hering & Hillebrand)?

A

Characteristics of the horopter for each individual vary within certain limits and thus is a personal horopter

26
Q

What is homonymous (uncrossed) physiological diplopia?

A

A form of physiological diplopia. When near is fixated on the distant object appears as double. Image uncrossed as hitting nasal retina = temporal space. Behind the horopter.

27
Q

What is heteronymous (crossed) diplopia?

A

A form of physiological diplopia. When distant object is fixated on the near object appears as double. Image crossed as hitting temporal retina = nasal space. In front of the horopter.

28
Q

What’s the retinomotor value of the fovea?

A

Zero. No incentive for ocular rotation and thus the fovea is the retinomotor centre or retinomotor zero point

29
Q

What is simultaneous perception?

A

Ability to appreciate 2 images at the same time with 1 image formed on each retina

30
Q

What is sensory fusion?

A

The ability to perceive 2 similar images, one on each retina and interpret them as one. Have to stimulate corresponding retinal areas, be of similar size, colour, luminosity and focus otherwise retinal rivalry occurs

31
Q

What is motor fusion?

A

The ability to maintain sensory fusion through a range of vergence movements so to maintain fusion when moving or the object is moving.

32
Q

What are the symptoms of being unable to motor fuse?

A

Headaches, eye strain and diplopia

33
Q

What is the vertical range for motor fusion?

A

Vertical range is 2 - 4

34
Q

What is the horizontal range for motor fusion?

A

Horizontal range is 34

35
Q

How often does conscious perception switch in binocular rivalry?

A

Every few seconds but depends on eye dominance

36
Q

What is stereopsis?

A

Sensory fusion of 2 slightly different images resulting in the perception of depth with relative depth of objects on the basis of ‘binocular disparity’

37
Q

What are Bagolini Glasses?

A

Striated glasses over the nose that cause the fixation light to turn into a line running in the opposite directions to the striation itself
It’s a gross test of simultaneous perception
33cm both c/gls and s/gls

38
Q

How do you carry out Bagolini glasses?

A
  • Ask how many lights are seen
  • If any lines are seen
  • How many lines?
  • What shape the lines make
  • If an ‘x’ response ask if they go through the centre

Can turn the lights off or ask them to draw their response. Check the response by occluding each eye or turn glasses around.If diplopia, check their response with correcting prism.

39
Q

How do you check diplopia response with bagolini?

A

Check response with correcting prism

40
Q

Bagolini glasses, what does homonymous diplopia look like?

A

\ /

41
Q

Bagolini glasses, what does heteronymous diplopia look like?

A

/ \

42
Q

Bagolini glasses, what does R and L suppression look like?

A

\ = Right
/ = Left

43
Q

What is Worth Lights? How is it carried out?

A

A measure of sensory fusion. Can be conducted at 6m, 3m and 33cm.
Red before Right, Green over Left
Ask how many they see & what colour

If 5 lights, ask the side the red ones are on compared to the green and check response with a prism

44
Q

What can Worth Lights tell us?

A

Presence of BSV, diplopia, response to correcting prisms, peripheral retinal suppression and which eye. It’s only meaningful in conjunction to cover test.

45
Q

What are the disadvantages of Worth Lights?

A

Eyes can be easily dissociated with red-green glasses so may get a suppression response if having unstable but functional BSV
Doesn’t assess presence of bifoveal fusion and so even with deviation with ARC they could get a normal BSV response.

46
Q

What does homonymous diplopia look like with Worth Lights?

A

Uncrossed. Same side as deviation with red over right eye so the red is the same side as the right eye.

47
Q

What does heteronymous diplopia look like with Worth Lights?

A

Crossed. Different side as the deviation with red over right eye so the red is the other side as right eye (left eye).

48
Q

What does right suppression look like with Worth Lights?

A

3 green lights as red is over right

49
Q

What does left suppression look like with Worth Lights?

A

2 red lights as red is over right, green over left

50
Q

How is the Polaroid 4-Dot Test conducted?

A

Done at 6m, uses polarisation as a means of dissociation testing bifoveal BSV. Can move forward to test peripheral fusion.

51
Q

What does Bagolini glasses test for?

A

Presence of gross BSV
Presence and type of diplopia
Response to correcting prisms
Suppression (and which eye)

52
Q

What is the 4PD Prism Test?

A

A test of motor fusion
It’s an objective test for the presence of bifoveal BSV and is used in assessment of microtropia (small angle strabismus <10PD)

53
Q

How do we complete the 4PD prism test?

A

We can estimate the extent of a suppressions scotoma. As we increase prism strength the patient will eventually report diplopia as the fixation will go out of the suppression scotoma area into an area that is not habitually suppressed.
Use a base-out prism (BO) looking for biphasic movement in the fellow eye. However, in microtropia it may only shift to an area of abnormal retinal correspondence so will not show a corrective eye movement.

54
Q

What’s the Prism Reflex Test? How do you complete this?

A

A test of motor fusion. They’re asked to fixate at near and then introduce the prism base-out (20BO). With BSV the eye under the prism moves in and the eye that isn’t under the prism moves out and then back in. Held at 33cm.

55
Q

What are the Prism Fusion Ranges?

A

Distance - 15BO - 5-7 BI
Near - 35BO - 15 BI
Vertical - 3BU - 3BI
Cyclo - 3 Excyclo - 3 Incyclo (motor + large sensory amplitude)

56
Q

What can the synoptophore test for?

A

Simultaneous perception
Superimposition
Sensory & Motor Fusion
Stereovision

57
Q

What’s the Sbisa Bar? How do we test this?

A

Density of Suppression
Tests the amount of dissociation required to disrupt BSV and promote diplopia
Placed over the dominant eye
Done via a series of red filters of increasing density in a ladder up to 6-8 layers to make one aware of the images perceived by the deviated eye, reducing the retinal illuminance until the patient sees double
The greater the number of layers the deeper the suppression

58
Q

How do you complete the Prism Fusion Range?

A

33cm, introduce decreasing strength BO prism in front of one eye with increasing prism strength and record the last prism the image is kept single

  • May report blurring image
  • Person to say when they are experiencing diplopia
  • Encourage effort to ensure maximum prism fusion range
  • At break point will reduce to ascertain fusion, watch eyes as they may not appreciate diplopia but obvious one eye is no longer looking
  • Repeat with BI prism and record range
  • Repeat with BU and BD prisms
59
Q

How do you complete the Lang 2 Pen test?

A

Do it BEO and Monocularly to get a judgement on depth with one eye or the other. If they have the same performance with both eyes it could mean they’re suppressing one eye = no stereoacuity. If 1 eye is worse than 2 eyes it suggests some stereopsis. This is just a gross judgement.

Move around the pen to get a judgement on depth

Vertical pen (orthoptist) to pen (patient)

Quick, reflexive action

60
Q
A

Strabismus 106 (35 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions