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PPO 1 > Cover Test for Screening > Flashcards

Cover Test for Screening Flashcards

1
Q

Where does the cover test get its name from?

A

An occluder is used to cover one eye.

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2
Q

What is the purpose of the cover test?

A

To identify a “misalignment” of the eye.

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3
Q

Why is the cover test important?

A

Eye misalignment has the potential to lead to amblyopia in children.

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4
Q

True or False: When a person is alive, the eyes line up with the midline of the bony orbits, causing eyes to look away from each other by more than 45 degrees.

A

False. Only when a person is dead.

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5
Q

True or False: When a person is alive and lacks any alignment anomalies, the eyes point “straight ahead” and the “line of sight” of each eye is directed at the same point in space.

A

True.

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6
Q

For each eye, where does the “image” of an object fall on?

A

The fovea of each retina.

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7
Q

When the line of sight of each eye is directed at the same point in space it is called what?

A

Bifixation.

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8
Q

What does bifixation simply mean?

A

That each eye is fixating (looking at) the same target.

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9
Q

What causes the eyes to line up in life but to look outwards in misalignment in death?

A

Muscle tone in the extra ocular muscles and the brain to make up what the muscle tone does not achieve.

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10
Q

True of False: Muscle tone pulls the eyes towards the straight ahead position by exact right amount.

A

False. Often not by exact right amount. Need to brain to make up the rest.

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11
Q

The neural circuitry that controls the EOMs has how many parts?

A

3.

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12
Q

Name the 3 neural circuitry components that controls the EOMs.

A

Sensory (afferent),
Central (processing),
Motor (efferent).

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13
Q

What structure in the eye is involved in the sensory mechanism that leads to alignment of the two eyes?

A

Retina in each eye.

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14
Q

The neural signal from each retina remains mostly segregated until it reaches what part of the neocortex?

A

Primary visual cortex or striate cortex.

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15
Q

In order for the brain to cause alignment of the eyes, the sensory signal from both eyes must what?

A

Reach the brain, be of good quality, and be nearly identical in OD and OS.

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16
Q

True or False: If the brain receives good sensory signals from both eyes, it does not have to have the ability to put the two signals together into a single perception.

A

False. It ALSO has to have that ability.

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17
Q

The neural process of combing the sensory signal from two eyes into a single percept is called what?

A

Fusion.

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18
Q

Where does fusion take place?

A

Neocortex in the central processing part of the fusional system.

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19
Q

During fusion, the brain has to perceive that the information coming from the two eyes is coming from where?

A

Be coming from the same visual target and coming from the same location.

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20
Q

True or False: During fusion, the retinal images and the neural signals they cause must be very similar.

A

True.

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21
Q

True or False: During fusion, if retinal images are the same, but something is wrong with the retina or optic nerve in one eye, neural signals reaching the brain will still remain the same and the brain will perceive very similar images.

A

False. Neural signals reaching the brain will differ and the brain will perceive difference and will fail at sensory fusion.

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22
Q

True or False: If the neural signals are dissimilar enough, even if the retinal images are the same, the brain may not fuse the images.

A

True.

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23
Q

How does the brain know where something is located? What is it called?

A

Brain interprets the object’s location according to the location of the object’s image on the retina. Local sign.

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24
Q

If the image falls on the fovea, the brain interprets the object to be _________. In other words, the Local Sign of the fovea is “________________”.

A

Straight ahead. “Straight ahead viewing”.

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25
Q

True or False: Local sign is never referenced to straight ahead.

A

False. Always.

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26
Q

If the image falls on the retina above the fovea, the brain interprets the object to be _________ than straight ahead.

A

Lower.

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27
Q

What three conditions have to be met in order for sensory fusion to work?

A

Brain mechanism for fusion have to be healthy, the brain has to perceive that the information coming from the two eyes is coming from the same visual target and coming from the same location (corresponding points).
(Brain healthy, same target, same location).

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28
Q

In order for the brain to perceive that the information is coming from the same location, the images on the two eyes must have the same what?

A

Local Sign.

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29
Q

When the retinal images in the two eyes have the same Local Sign, we say that the images are falling on what?

A

“Corresponding Points”

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30
Q

True or False: The fovea of each eye are corresponding points when the image of the same object falls on the fovea of each normal eye, it is “fused” or perceived to be a single object, and its location is “straight ahead”.

A

True.

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31
Q

In the fusion system, do images have to be exactly alike and exactly corresponding?

A

No, images need to be similar and fall nearly on the corresponding points.

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32
Q

What 3 things control the contraction of the EOMs to assure that the eyes are physically lined up?

A

Central Nervous System, Cranial Nerves (III, IV, VI), and the muscles (EOMs) themselves.

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33
Q

True or False: If something is malfunctioning in the motor fusion system, (example) OS will rotate by the wrong amount and OS will not be aligned on the object of interest as it should be.

A

True.

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34
Q

What are two things that may happen if one eye is not aligned with the other?

A

Patient will either see double (diplopia) or the brain will suppress the input from the unaligned eye.

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35
Q

What is the condition called when an eye is misaligned?

A

Strabismus or tropia.

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36
Q

True or False: Strabismus can result only from a deficit in the sensory part of the system necessary for fusion.

A

False. All three. Sensory, processing, motor.

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37
Q

What will happen if a suppression in one eye is prolonged?

A

Becomes permanent and the eye will have reduced VA.

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38
Q

True or False: Prolonged suppression will result in reduced VA in an otherwise healthy eye even with the best refractive correction in place.

A

True.

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39
Q

What is the most common cause of reduced VA in young children?

A

Amblyopia.

40
Q

Is amblyopia ever preventable?

A

Yes, when caught early.

41
Q

What test is used as our first line of defense in detecting strabismus?

A

Cover Test.

42
Q

What do we look for in a vision screening to try to prevent the development of amblyopia?

A

Strabismus.

43
Q

The cover test is broken up into two parts. What are they called?

A

Unilateral or “Cover-Uncover Test” and Alternating Cover Test.

44
Q

Is cover test performed at near and at distance?

A

Yes, 20 ft and 16 in (or 40 cm).

45
Q

Should patient look at fine detail during both of the cover tests?

A

Yes, anything with fine visual detail.

46
Q

An eye moves in order to fixate because it was not already fixating is what law?

A

The First Law of the Unilateral Cover Test.

47
Q

In the First Law of the Unilateral Cover Test, on a cover test, an eye moves in order to _____ because it was not already_______.

A

fixate; fixating.

48
Q

True or False: Because OS moved when OD was covered, the patient has strabismus or a tropia OS.

A

True.

49
Q

What will happen to a normal OD eye on the unilateral cover test if we cover an OS?

A

OD will not move because it was already fixating the target.

50
Q

True of False: On a cover test, if an eye does not move, it wasn’t fixating on a target and this patient does have strabismus.

A

False. If an eye does not move, it was already fixating on a target and this patient does not have strabismus.

51
Q

What does the Second Law of Cover Test say?

A

If an eye does not move, it was already fixating.

52
Q

True or False: When you cover an eye and the other eye moves, it does so in order to fixate because it was not already fixating. That means that the eye that moved is normal.

A

False. The eye that moved has a tropia.

53
Q

True or False: If OS is covered and OD moves, OD has tropia. If the OD is covered and OS does not move, OS has tropia because OD has tropia.

A

False. Since OS did not move when OD was covered, OS is normal and does not have a tropia despite what OD has.

54
Q

How long should you keep an eye open and occluded during an unilateral cover test?

A

2-3 seconds.

55
Q

If OD is covered and OS is observed, OS did not move means________.

A

No tropia for the left eye.

56
Q

If OD is covered and OS is observed, OS moved means________.

A

Tropia for the left eye.

57
Q

Say if both eyes move during a unilateral cover test that’s done on both eyes, what is this action interpreted as?

A

Alternating tropia or alternating strabismus.

58
Q

Should tropia be passed or referred?

A

Refer

59
Q

What’s the difference between esotropia and exotropia?

A

Exotropia is when one eye moves in when the other eye is occluded. Esotropia is when one eye moves out when the other eye is occluded.

60
Q

What is the main goal for the unilateral cover test?

A

To detect the presence or absence of strabismus.

61
Q

The alternating cover test allows us to check for what?

A

Phoria.

62
Q

A misalignment of the eyes that is present only when fusion is broken is called?

A

Phoria.

63
Q

True or False: For fusion to take place images on the retinas of the eyes have to be very similar.

A

True.

64
Q

True or False: If a patient does not have a tropia or strabismus, then it is unlikely for the patient to have a phoria.

A

False. Eyes that are normally aligned (no strabismus) may become misaligned when fusion is broken and when fusion is broken, the eyes go their “phoria position”.
If there is no strabismus, there is often a phoria present.

65
Q

True or False: If a phoria is present, either eye behind the occluder does the deviating for its own fixation.

A

False. Regardless of which eye is covered, the eye behind the occluder does the deviating for both eyes.

66
Q

True or False: A phoria is a property of one eye or the other just like strabismus.

A

False. Phoria is shared by the two eyes.

67
Q

If the phoria has a size of zero, its type is called what?

A

Orthophoria.

68
Q

What does orthophoria mean?

A

Even with fusion broken, the eye behind the occluder continues to point at the target, even though it can’t see the target through the occluder. Essentially, the eyes remain aligned with each other.

69
Q

If the phoria has a size other than zero, its type is called what?

A

Heterophoria.

70
Q

What does heterophoria mean?

A

With fusion broken, the eye behind the occluder is no longer pointing directly at the target and the eye are misaligned with each other when fusion is disrupted.

71
Q

The left eye is occluded and is not turned in (converged) enough to be pointing at the target. This kind of deviation is called an _____ deviation.

A

Exo.

72
Q

The left eye is occluded and is turned in (converged) too much to point at the target. This kinda of deviation is called an _____ deviation.

A

Eso.

73
Q

An eye that is deviated upward has a ______ deviation and an eye that is deviated downward has a _____ deviation.

A

Hyper; hypo.

74
Q

True or False: Unlike horizontal deviations, when describing vertical deviations, you always specify both the direction and the eye.

A

True.

75
Q

True or False: When the deviation is a phoria rather than a tropia, by convention, we always specify the hyper eye.

A

True.

76
Q

Say if OD is hyperphoria and OS is hypophoria, what is this condition called?

A

Right hyperphoria.

77
Q

True or False: In the case of tropia, you must indicate which eye has the tropia.

A

True.

78
Q

Is it correct to specify one eye as having a phoria?

A

No because in the case of phoria, the deviation is shared by both eyes.

79
Q

When should you refer patients with phoria?

A

Refer when phoria is large and is vertical.

80
Q

The Unilateral Cover Test or Cover-Uncover Test detects what?

A

Strabismus or tropia.

81
Q

Phoria are detected by using the second part of cover test, which is what?

A

Alternating cover test.

82
Q

What should you do during an alternating cover test?

A

Place occluder over patient’s OD and quickly move the occluder from OD to cover the OS. Always look at the eye that gets uncovered.

83
Q

OD moves inward towards the nose once occluder is removed. What type of phoria is this?

A

Exophoria because eye was deviated outwards.

84
Q

During an alternating cover test, should you look at the eye that not occluded or the eye that is occluded?

A

Eye that is occluded.

85
Q

Direction of eye movement as eye is uncovered: Inward.
Direction of the eye’s deviation was:
Outward.
Then this type of phoria is what?

A

Exophoria.

86
Q 
Direction of eye movement as eye is uncovered:
No movement. 
Direction of the eye's deviation was:
None.
Then this type of phoria is what?
A

Orthophoria.

87
Q 
Direction of eye movement as eye is uncovered: 
Outward. 
Direction of the eye's deviation was:
Inward.
Then this type of phoria is what?
A

Esophoria.

88
Q 
Direction of eye movement as eye is uncovered: 
Downward. 
Direction of the eye's deviation was:
Upward.
Then this type of phoria is what?
A

Hyperphoria.

89
Q 
Direction of eye movement as eye is uncovered: 
Upward. 
Direction of the eye's deviation was:
Downward.
Then this type of phoria is what?
A

Hypophoria.

90
Q

True or False: The alternating cover test distinguishes a tropia from a phoria.

A

False. Does not.

91
Q

The alternating cover test is used to identify what?

A

If phoria is present.

92
Q

True or False: There is no such thing as a right or left phoria.

A

True.

93
Q

Phoria is present only when fusion is what?

A

Broken.

94
Q

On the unilateral cover test, when you cover your patient’s OD, his OS does not move. When you cover his OS, his OD does move. What kind of deviation does he have?

A

Right tropia.

95
Q

During an alternating cover test, when you move you occluder quickly from the OD to OS you see the OD move inward. When you move your occluder quickly from the OS back to the OD, you see the OS move inward. What does this patient have?

A

Exophoria.

96
Q

True or False: During a cover test, patient’s ocular deviation is the same at distance and near.

A

False. Ocular deviation can be different at distance and near; any combination is possible.

PPO 1 (7 decks)

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