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OP2204- BV Lectures > 1 & 2. Intro To Binocular Vision & BV problems > Flashcards

1 & 2. Intro To Binocular Vision & BV problems Flashcards

1
Q

Benefits of binocular vision

A
  1. Increased field of view.
  2. Compensation for the phycological blind spot.
  3. Binocular summation
  4. Stereopsis (depth perception)
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2
Q

What is the term used to describe double vision?

A

Diplopia

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3
Q

What causes double vision?

A

When the eyes are not lined up, different images fall on each fovea in both eyes (this is called confusion). This 2 images are superimposed leading to double vision- because the 2 images are seen together at the same time.

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4
Q

How is alternating vision caused? And it can lead to ?

A

Due to double vision, the brain uses image from 1 eye at a time causing an alternation between the 2 images, leading to loss of peripheral vision.

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5
Q

What is stereopsis?

A

Depth perception or 3D vision

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6
Q

What do we need to have binocular vision?

A

Two eyes with overlapping visual field

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7
Q

What 4 factors are important for optimal binocular vision?

A

Good VA
Roughly equal VA
Roughly equal sized images
Clear media- no cataracts

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8
Q

Where does binocular visual processing take place pathway and why does it need to be intact?

A

Processing takes place in the cortex (brain) hence needs to be intact.
BV processing takes place in the brain and not they eye.

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9
Q

What ocular conditions are caused if binocular vision pathway isn’t intact?

A

Albinism -not all information cross optic chiasma it stays on the same side of the brain.

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10
Q

What motor aspect is important for BV?

A

Positioning of the eyes to look at an object and maintaining alignment at the object

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11
Q

What voluntary and involuntary muscles play a role in motor aspects of BV?

A

Voluntary- extraocular (extrinsic) muscles
Involuntary- ciliary muscles (Accommodation) and pupils (sphincter and dilatory)

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12
Q

Is binocular vision present at birth?

A

NO

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13
Q

Binocular vision develops at what age?

A

It first rapidly develops over the first 6 months of life and continues for 8/9 years of life

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14
Q

At what age is binocular vision the most malleable?

A

Up to 5/6 years, maybe up until 8/9 years, very difficult to change after this

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15
Q

Where does binocular vision processing occur?

A

In the brain (in V1 of the occipital cortex and subsequently in the higher centre) and this route is provided by the retina to co-ordinate information

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16
Q

Describe how binocular vision processing occurs in relation to ganglion cells and the cortex

A

Info from ganglion cells at corresponding points in each eye are processed together in the cortex to extract binocular information. Decussation of nerve fibres at chiasm allows this.

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17
Q

Define principal visual direction/ visual axis/ line of sight?

A

(When looking at an object), the image falls on the fovea and lies on the visual axis.

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18
Q

Define secondary visual direction

A

Image does not fall on the fovea. (Surrounding objects)

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19
Q

Define oculocentric localisation

A

Position of objects relative to principal visual direction in monocular vision.

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20
Q

Define egocentric localisation

A

Understanding position of objects relative to our bodies. (using both eyes and proprioceptive clues).

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21
Q

Define primary visual direction and it is determined by?

A

It is determined by the eyes rotation. Image will fall on the fovea even if that object is not at the centre of the scene.

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22
Q

Multiple objects in the same visual direction are perceived as?

A

Being behind or in front of each other.

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23
Q

Difference in images between 2 eyes is called?

A

Retinal Disparity

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24
Q

Define Horopter

A

Imaginary plane for a fixation point. All objects on this plane perceived as single.

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25
Q

Define Panum’s area

A

Region behind and in front of horopter where objects can still be fused, but are seen in depth.

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26
Q

We don’t see images as diplopic because?

A

Our brains suppress the image from the non-dominant eye. This is called as physiological diplopia.

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27
Q

Can patients with diplopia drive?

A

No

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28
Q

What is congenital or infantile BV problems?

A

Either present at birth or develop within the first 6-12 months

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29
Q

Childhood BV problems onset?

A

Typically 2-5 years onset

30
Q

How are BV problems acquired in life?

A

Trauma, cranial nerve palsy or decompensation of existing heterophoria

31
Q

What are complains reported by adults with non-specific BV problems?

A

Eye strain when using computers

32
Q

Squint synonyms?

A

Strabismus or heterotropia

33
Q

What are congenital BV conditions? what kind of deviations do they produce?

A

This conditions are present at birth however, may not be diagnosed until later. They often produce INCOMITANT deviation.

34
Q

What are incomitant deviations?

A

This are deviations that change in size in different direction of gaze.

35
Q

What are comitant deviations?

A

This is when deviations are same in all direction of gaze

36
Q

What are potential BV issues?

A

Problems with convergence, accommodation and extra-ocular muscles, convergence insufficiency (unable to maintain convergence)

37
Q

What is gaze palsies?

A

This is BV potential issue, this is a lesion in the brain that causes eye movement problems

38
Q

How is recovery tested in cover test?

A

It is assessed on how well fusion is restored.

39
Q

Describe the recovery of eyes with a tropia

A

The eye doesn’t recover, since the eyes are unable to fuse at the end of the cover test.

40
Q

What is the purpose of cover test and why is it done at distance and near?

A

Purpose: to assess ocular alignment. It is done at both distances cause it may vary.

41
Q

Why is cover test done with glasses on and off?

A

To identify if glasses are making vision better, worse or same. This also helps identify existing BV problems

42
Q

What target is used for cover test?

A

1 line above normal V/A on snell chart and if vision is poor use of spot light

43
Q

Can cover test be useful for highly myopic eyes?

A

No, target needs to be visible by both eyes

44
Q

What is Nystagmus?

A

If the patients eyes can remain still- involuntary eye movement

45
Q

Before cover test is performed what observations are made?

A
  1. Are the eyes straight?
  2. Is the head straight?
  3. Are the eyes still?
46
Q

What will be seen in patients with unequal Rx in both eyes?

A

Unequal phoria

47
Q

What are the preliminary observations taken before performing cover test?

A
  1. Mobility/ navigation
  2. One eye covered?
  3. Facial structural characteristics?
  4. Abnormal head posture?
  5. Ocular alignment?
  6. Nystagmus?
  7. Does the patient have an existing Rx?
48
Q

What is suspected in patients with one eye higher then the other?

A

Vertical deviation

49
Q

What is suspected in patients with high interpupillary distance?

50
Q

What is suspected in patients with a small PD?

51
Q

How can epicanthic folds mislead into BV problems?

A

If folds are large, it can give the illusion of esotropia

52
Q

What can be determined by eyelids: Angle of lid fissure?

A

Abnormal slope may indicate high astigmatism.
Asymmetry might indicate unilateral high astigmatism

53
Q

What is proptosis?

A

Forward bulging of the globe, e.g Grave’s disease

54
Q

What is pseudoproptosis?

A

Retraction of the upper eyelid causing the appearance of ptosis. e.g, graves disease

55
Q

What is ptosis?

A

Dropping of eyelids e.g, myasthenia gravis, 3rd nerve palsy. OM can be affected

56
Q

What is pseudoptosis?

A

False appearance of drooping eye lids of eyes.

57
Q

Describe Abnormal Head Posture (AHP)? what kind of deviation does it produce?

A

Usually found in incomitant deviation. It develops to improve BV problems. And occasionally this condition increases diplopia

58
Q

What are the common face movements caused by AHP?

A

Head/ face turn
Head/ face tilt
Chin up/ down

59
Q

How do you know if your patient has AHP?

A

Sit directly in front of the patient and ask the patient to fixate on a target. Assess heterotropia with and without AHP

60
Q

What conditions can give the appearance of AHP?

A
  1. Nystagmus null point
  2. Homonymous hemianopia
  3. Musculo- skeletal issues affecting the back and neck
61
Q

What is the optometrists responsibility to the patient?

A
  1. Identify any problems
  2. Resolve any problems or refer (Recognize your own limits)
  3. Communicate effectively with your patients
62
Q

Which ocular pathology can be presenting as BV problem?

A

Retinoblastoma - can be represented as a convergent squint

63
Q

Is it true that the target in the cover test needs to be seen by both eyes?

64
Q

Is phoria or tropia alternating?

65
Q

If a patient has a phoria, what is being observed about the movement between the 2?

A

The equality between the movements

66
Q

Asymmetry in angles of lid fissure may indicate? And patients with this are at high risk of?

A

Unilateral astigmatism- high risk for amblyopia

67
Q

Importance of corresponding points?

A

They send information to the brain

68
Q

Retinoblastoma can be represented as?

A

Convergent squint

69
Q

What is binocular visual field?

A

Combination of right and left visual fields.

70
Q

Define confusion in terms of diplopia

A

Differing images falling on the fovea seen simultaneously, overlying each other.

71
Q

Fusion of images from both eyes leads to extraction of information related to?

A

Depth perception

72
Q

Images fall on which part in the retina?

OP2204- BV Lectures (4 decks)

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