Brainscape's Knowledge GenomeTM

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


See full index

OV2018 binocular vision > manifest and latent strabismus > Flashcards

manifest and latent strabismus Flashcards

1
Q

what is manifest strabismus known as ?

A

heterotropia

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

what is latent strabismus known as ?

A

heterophoria

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

what is no tropia?

A

.both foveas simultaneously looking at the object

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

what is manifest strabismus/tropia?

A

. both foveas are not simultaneously looking at the object

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

what are the different types of manifest strabismus?

A

. left esotropia (LSOT)
. left exotropia ( LXOT )
. left hypertropia ( left eye is higher )
. right hypertropia
. L incyclotropia- eye is turned in an anti-clock wise towards the nose
. L excyclotropia - eye is turned in a clock-wise fashion

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

why can’t you always diagnose a strabismus by looking at the appearance of the eye?

A

. not all tropias large enough to be cosmetically noticeable

. smaller angle tropias can appear normal

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

what to test to use to determine if a px has a tropia?

A

. cover test required to determine if they have tropia or not

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

what is a pseudostrabismus ?

A

. gives the appearance of a tropia when normal
. cover test required to determine if they have tropia or not
-can see from the corneal reflex in the eyes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

why can a pseudostrabismus occur in young infants ?

A

. this is due to the skin around the nose , extra skin around the nose happens in young infants because their nose hasn’t fully formed yet
. therefore infants end up with a lot of skin around their nose , this gives a rise to the appearance of a squint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the reasons for the appearance of a pseudostrabismus ?

A

. epicanthal folds ( skin around nose - most common types

. different lids position

. wide interpupillary distance

. unilateral myopia or exopthalmos

. facial asymmetry

. variation of angle kappa

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

what is angle kappa?

A

. angle between optical axis and visual - not coincident

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

why does angle kappa give rise to pseudostrabismus?

A

. instead of corneal reflections being right in the centre of the pupil, because most people’s fovea is temporal to the posterior pole
. the corneal reflection will be slightly off centre from the pupil, thus giving rise to pseudostrabismus

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

what is the the angle of kappa in a normal eye?

A

. normal position of corneal reflexes positive kappa angle of 3deg, this is because the fovea lies temporally to the posterior pole
-so corneal reflections will be nasal
. exotropia is observed

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

what happens when the fovea is coincident with the posterior pole?

A

. angle kappa is zero

. eye look completely central

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

what happens when fovea lies nasally to posterior pole?

A

. rarely fovea lies nasally to posterior pole and corneal reflex is temporal. resulting in a negative angle kappa
. esotropia is observed

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

how to detect pseudostrabismus?

A

. corneal reflections - hold pen - torch 30cm for patient’s eye and look to see if they are symmetrical

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

when to use corneal reflections when detecting pseudostrabismus?

A

. useful in uncooperative children and adults
. can only be used in moderate large deviations
. small deviation need cover test

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

what does it mean if corneal reflection is temporal ?

A

eye is esotropic

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

what does it mean if corneal reflection is nasal?

A

eye is exotropic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is a cover test used to decide?

A

used to decide:
. pseudostrabismus
. latent (phoria)
. manifest ( tropia ) deviation

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

what can a cover test be broken into?

A
  1. cover/uncover test
    - used as a test to detect manifest strabismus ( tropias)
  2. alternating cover test
    - best test to detect heterophorias as it fully dissociates ( makes the deviation as large as possible )
22
Q

how is a cover uncover test carried out?

A

. carried out:

  1. 1/3 m - near
  2. 6m
  3. > 6m if deviation increases distance

. need to carry out the cover test with an accommodative target ( with tiny letters)

  • line above worst V-A
  • the beak of the bird

. need to carry out the cover test with light

. with and without spectacle prescription
- this is because spectacle prescription will influence size of deviation

. with and without head posture

23
Q

why do we carry cover test with and without spectacle prescription?

A
  • this is because spectacle prescription will influence size of deviation
  • convex lenses relax accommodation and therefore will relax convergence
  • convex lenses makes an eco deviation better and exo deviation worse - important to do with and without posture
24
Q

what are some cover test tips?

A
  1. always light and always use corneal reflections
  2. always use accommodative target
    - infant use small toys
    - older child ( knows letter ) line above worst VA
  3. your cover test is only as good as your patients fixation
25
Q

why might someone not move eye during cover test but still have manifest deviation ?

A

. this might be due to a visual impairment

. young children and adults with learning difficulty may not move eye because they don’t understand what you’re asking them to do

. they have eccentric fixation- not using fovea

26
Q

what does it mean by always using an accommodative target?

A

. check what either eye can see and then you always choose the line above the worst VA

. if their worst VA was the 6/9 line , then you would use 6/12

27
Q

why is your cover test only as good as your patients fixation ?

A

. poor fixation is the biggest reason for misdiagnosis

28
Q

how do you control a patients fixation ?

A

. ask the px questions about the target

. if you get correct response you know px fixation is good

29
Q

what is the main reason for cover/uncover test?

A

to look for manifest deviation

30
Q

explain the cover/uncover test?

A
  1. ensure head straight and still
  2. cover the right eye and observe left eye
  3. if left eye is deviated, it will move to take up fixation
    if it moves:
    - out, it was convergent= left esotropia
    - in, it was divergent = left exotropia
    - down, it was elevated= left hypertropia
    - up, it was depressed = left hypotropia
  4. repeat by covering left eye and observing right eye

. you look at the right eye as you’re covering the left
. always look at how the uncovered eye is moving to take up fixation

31
Q

what is hering’s law ?

A

. when a muscle in one eye contracts a muscle in the opposite eye also contracts in order for both eyes to work together

32
Q

what happens when right eye is straight( fixing on the target) is covered and left eye esotropic (L SOT) ?

A

. when the right eye is covered, the left uncovered and eye moves out ( to left ) to take up fixation

. hering’s law means that the right eye will also move to the left

. when the cover is removed the left eye moves back in to the right

. the right eye also moves back in ( to the right ) to become straight again

33
Q

what happens when you cover the left esotropic eye and the right straight eye is uncovered?

A

. when you cover the left eye

. right eye straight ( fixing ) no movement

34
Q

what happens when right eye is straight and covered and left eye is elevated L HYPERTROPIA?

A

. right eye is covered
. left uncovered eye moves down to take up fixation
. right eye also moves down behind the occulder ( becomes right hypo phoria ) because of hering’s law

. when the right eye is uncovered
. left eye move up ( returns to L hypertropia )
. right eye also moves up ( now straight )

35
Q

what happens when straight right eye is uncovered and left eye is elevated and covered ?

A

right eye will not move

36
Q

what happens when we have right straight eye covered and left esotropia ? the px also has alternating esotropia

A
  1. right eye covered so the left uncovered eye moves out ( to the left ) to take up fixation ( its now straight )
  2. right eye behind the occluder also moves to the left due to hering’s law ( R eso deviation )
  3. when the occluder is removed the right eye stays in toward the nose due to alternating esotropia
  4. alternated from being a left esotropia to right esotropia
  5. when left is eye covered , right uncovered eye must move out to the right to take up fixation
  6. the patient may show a preference to fix with one eye
  7. record as Alt SOT if no preference or L SOT if there is a preference
37
Q

how to record results?

A

. need to say it was cover test you are carrying out

. which eye ?
- right, left or alternating

. did px wear glasses?

.what distance was it measured ?
- distance (D), near ( N) , far distance ( FD)

  • degree of movement
    . minimal, small, moderate or large

. is there double vision?

  • target used
    . accommodative or no accommodative ( light )
38
Q

how to record deviation?

A

. minimal
. small
. moderate
. large

39
Q

what is heterophoria/ latent strabismus ?

A

. when both eye uncovered, the visual axis are directed towards the fixation target

. when an occluder is put in place, the eye behind the occluder deviates away from the fixation point

40
Q

what is orthophoria ?

A

. with both eye uncovered, the visual axis are directed towards the fixation target

. when the eyes are dissociated ( i.e covered by an occluder ) the visual axis are still directed towards the fixation target

41
Q

what are the types of heterophoria ?

A

. SOP ( nesophoris )- turns in towards the nose
. XOP ( exophoria ) - turns out towards the temple
. L hyperP- turns upwards
.R hyper P
.incycloP - twisted in anti-clock
.ExcycloP- twisted clock wise

42
Q

what test to use for heterophoria ( latent strabismus)?

A

. you must always carry out a cover uncover test initially to confirm no manifest deviation before moving onto alternating cover test

. if on cover uncover test , you find a manifest deviation then it is not a heterophoria

43
Q

what is the best method for heterophoria ( latent strabismus)?

A

. alternating cover test is the best method to detect heterophoria as it fully dissociates ( makes the deviation bigger)

44
Q

how to carry out alternating cover test?

A

. patient sits with their head erect

. patient fixates a suitable target
. alternate the occluder between the two eyes

. the patient must never be able to see the target with both eyes

. continue alternating the occluder until the deviation no longer increases in size

. move the cover at an appropriate speed
- the slower the better

45
Q

how to look at the eye during heterophoria- alternating cover test?

A

. the movement of the uncovered eye is noted as you move the occluder between eyes

. at the end of the alternating cover test watch as you remove the occluder

. when you remove the occluder from both eyes , you must note the recovery - how quickly the eye takes to move back up to a straight position

46
Q

what does it mean if the eye does not move back to take up fixation?

A

it is manifest strabismus

47
Q

what happens when both eye have no manifest deviation and you cover them and carry out alternating cover test ?
esophoria in RE

A

. when we cover right eye and it’s an esophoria
. the eye behind occluder will turn in towards the nose
. alternating cover test- occluder moved from RE to the LE
. the uncovered eye moves outwards to the right to take up fixation
. as the eye moves outwards to take up fixation then it was inwards to begin with ( esophoric )
. the eye behind the occluder moves in towards nose to take up fixation

48
Q

what happens when both eyes have no manifest deviation and an alternating cover test is carried out ?
exophoria

A

. when an occluder is placed in front of RE fusion is suspended and the eye behind the occluder moves out

. when the cover is moved from RE to the left. uncovered right eye moves inwards to take up fixation

. as the eye needs to move inwards to take up fixation then it was outwards to begin with ( exophoric )

. the LE now behind the occluder ( fusion suspended ) then LE moves out

49
Q

what happens when no manifest deviation and an alternating cover test is carried out?
right hyperphoria

A

. occluder placed in front of RE, RE elevates
. cover moved from RE to the left eye, the right uncovered eye moves downwards to take up fixation
. as the eye needs to moves downwards to take up fixation it was elevated to begin with ( right hyperphoria )

. LE now occluded- as RE moved down to fixate due to hering’s law the left eye also moved down ( it is a left hypophoria )

. if you were to move occluder from LE to RE then LE would move up ( left hypophoria )

50
Q

how to record results in latent deviation?

A
  1. record direction of deviation
    - esophoria not right or left esophoria
  • exophoria not right or left exophoria
  • right hyperphoria
  • left hyperphoria
  1. record degree of deviation
    - minimal, small, moderate or large
  2. speed of recovery
    - rapid recovery(r.r), noderate recovery(m.r.) or slow recovery(s.r.) or to blink
  • the speed of recovery is important as the faster the speed of recovery, the better the control of the deviation
  1. distance
    - distance, intermediate or near
  2. target
    accommodative or non-accommodative
  3. whether spectacle worn
51
Q

When do you look at each eye to check for manifest deviation ?

A
  • check when cover one eye then look at the other eye
    if no movement- then no trophia .
  • only look when one eye is covered

OV2018 binocular vision (15 decks)

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