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Binocular vision YR 3 > investigation of concomitant exotropia > Flashcards

investigation of concomitant exotropia Flashcards

1
Q

what is a concomitant exotropia

A

a heterotropia that is a manifest divergent strabismus, where one or the other eye deviates outwards and the CR is nasal in the deviating eye

it can be an alternating exotropia where vision is fairly good in both eyes

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2
Q

what group of patients is an exotropia most common in and less common in

A
  • it is the most common form of childhood strabismus in asian races
  • less common than convergence in caucasians
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3
Q

what are the 3 types of exotropia

A
  • primary
  • secondary
  • consecutive
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4
Q

what are the 2 types of primary exotropia

A
  • constant (rare)

- intermittent (more common)

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5
Q

what type of secondary exotropia is there

A

usually a constant unilateral - due to poor vision in that eye

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6
Q

what is another name for secondary exotropia

A

sensory exotropia

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7
Q

what are the 2 types of consecutive exotropia

A
  • constant (usually)

- intermittent (maybe)

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8
Q

a patient with a primary constant exotropia has an exotropia…

A

all the time for all viewing distances

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9
Q

why should a constant childhood exotropia be examined carefully and at what age is most important

A

to exclude possibility of secondary strabismus especially under 2 years of age

the exotropia is most likely to be intermittent, but if there is a constant exotropia then you do need to exclude any pathology that is causing this exotropia

e.g. in a patient is under 1 years old, you must do a full cycloplegic fundus examination to rule out a retinoblastoma, which is the most common cause for a constant exotropia

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10
Q

what is a primary intermittent exotropia

A

The exotropia is only present under certain conditions of viewing distances e.g. for near or distance

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11
Q

what are the 3 basic types of an intermittent exotropia

A
  • distance exotropia
  • near exotropia
  • non-specific exotropia
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12
Q

what is a intermittent distance exotropia

A

when a patient has BSV on near fixation with intermittent or constant exotropia on distance fixation (or even when looking further than 6 metres)

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13
Q

which group of people is a intermittent distance exotropia most common of

A

all intermittent exotropias in children

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14
Q

what is a very rare symptom in a child who has a intermittent distance exotropia and therefore what normally occurs instead when the exotropia is manifest, also how is this demonstrated

A
  • diplopia very rare
  • suppression normally occurs when manifest
  • this (suppression) is demonstrated in bsv tests
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15
Q

what may a child with a intermittent distance exotropia do which is a sign

A

may close one eye especially in bright light as the eye drifts outwards (however don’t know the reason)

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16
Q

what are the 2 types of distance exotropia

A
  • true distance exotropia
    or
  • simulated distance exotropia
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17
Q

what is a true distance exotropia

A

BSV for near and exotropia for distance

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18
Q

what is a simulated distance exotropia

A

a controlled exophoria at near by either:
- accommodation (with high AC/A ratio)
or
- fusion

if you disrupt either the accommodation or the fusion, then you can break down the exophoria at near and this will show that the patient does not have a true distance exophoria.
but if we prevented them from using their fusion or accommodation and despite doing these two tests their near angle stayed exactly the same i.e. still controlled their exophoria, then that will be a true distance exophoria

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19
Q

how will you know if a patient is a true distance exophoria

A

if we prevented them from using their fusion or accommodation and despite doing these two tests their near angle stayed exactly the same i.e. still controlled their exophoria, then that will be a true distance exophoria

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20
Q

how will you test if a patient has a simulated distance exotropia caused by accommodation at near

A

by elimination of the accommodation using +3.00D lenses

this is done by doing a cover test and a prism cover test with +3.00DS lenses at near fixation.
you compare the results you get with the +3.00DS lenses to without using the +3.00DS lenses to see if their exophoria breaks down to a manifest exotropia with the +3.00DS lenses i.e. you disrupt their accommodation and therefore they will not be a true distance exotropia, but if by putting +3.00DS lenses they are still controlled to a exophoria, you need to see if you can prevent them from using their eyes as a pair by using a patch (fusion)

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21
Q

how will you test if a patient has a simulated distance exotropia caused by fusion at near

A

by putting a patch in front of one of their eyes/any eye for about 45 minutes, and when you do bring the eyes into fusion you need to do a prism cover test, but you need to make sure that they don’t go binocular, so as you remove the patch there needs to be an occluder over the other eye to prevent fusion.
so one eye must be covered all times during PCT and measure the deviation, if it gets larger then that means they were using their fusion abilities to maintain the exophoria and BVS = not a true distance exotropia

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22
Q

what symptoms will a child with a simulated distance exo have as they get older

A

they will have near vision symptoms and headaches (more commonly compared to diplopia)

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23
Q

what is a intermittent near exotropia

A

when a patient has BSV on distant fixation with exotropia for near

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24
Q

which group of patients is a intermittent near exotropia more common in

A

in adults than in children

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25
Q

when will a patient more likely be aware of diplopia with a intermittent near exotropia

A

only when they are manifest

diplopia is unlikely with intermittent especially when they are young

26
Q

what may a px with an intermittent near exotropia complain of

A

problems for near work

in adult life the px may complain of asthenopic symptoms such as headaches and double vision etc

27
Q

what is a intermittent non-specific exotropia

A

Intermittent exotropia/BSV at any distance of viewing

28
Q

at what age group can a patient have a intermittent non-specific exotropia

A

at any age group

29
Q

what is an unlikely symptom of someone with a intermittent non-specific exotropia and why

A
  • diplopia is unlikely

- as usually suppression occurs

30
Q

what is a secondary exotropia

A

Exotropia following loss or impairment of vision (of that one eye) in patients of any age especially in older patients

there is no fusion, depending on what type of vision that manifest eye has got, but usually vision in that eye is extremely poor and they lost their fusional abilities where their eye has drifted outwards due to the poor vision

31
Q

what is a consecutive exotropia

A

Exotropia following previous esotropia/phoria

32
Q

what are the 2 types of consecutive exotropia, and which type of exotropia occurs in patients with no binocular function

A
  • intermittent or constant

- constant in patients with no binocular function

33
Q

what are the 2 possible aetiologies of a consecutive exotropia

A
  • Arises spontaneously with passage of time
    No binocular function
    Poor vision in one eye (amblyopia)
  • After strabismus surgery for correcting a eso deviation
    it can be when surgery has made the esotropia very small, so when the child puts on a hyperopic rx, they can get exotropic
34
Q

what 5 things needs to be done to investigate a patient with a exotropia

A
  • history
  • unicular visual acuity
  • establishing the type of exotropia
  • binocular functions
  • size of the deviation
35
Q

what 2 tests can you do to establish the type of exotropia a patient has

A
  • cover test

- eye movements

36
Q

why are binocular function tests carried out and what are the 2 types of tests

A

to prove they’re straight and binocular

  • fusion range
  • stereo acuity
37
Q

why is the size of the deviation measured on a patient with a exotropia

A

to determine their management and how big/small their exotropia is

38
Q

list the 7 things you will ask in signs and symptoms when taking a history of someone with a exotropia

A

onset: when did they first notice the exot

mode

frequency: how long was it noticed for and is it at a particular time of the day e.g. only out in bright sunlight are they closing one eye? at near or distance?

previous ocular history: if they have had a squint surgery before, and identify what direction their squint was before and if it has changed post operatively

family history: there is a stronger genetic link

general health

birth history

39
Q

when will a patient tend to get a significant level of amblyopia in a intermittent exotropia

A

if they’re decompensated and untreated in childhood

e.g. if they have a constant exotropia and its picked up a bit later on, then they may have some underlying amblyopia to begin with, so need to treat that in the first instance

40
Q

what are the visual acuity findings in a patient with consecutive and secondary exotropia

A
  • consecutive exotropia: often have amblyopia, as a result of initial underlying esotropia
  • secondary exotropia: reduced va from ocular pathology
41
Q

what are the 2 reasons to carry out a cover test on a patient with an exotropia

A
  • to differentiate the 3 basic types and diagnose

- to indicate the degree of control e.g. at different distances

42
Q

list the 8 things that need to be observed and noted in a cover test when investigating a exotropia

A
  • note position of corneal reflections
  • for near and distance and far distance
  • manifest/latent
  • rate of recovery
  • in bright light
  • estimate size
  • record fixing eye ? alternating
  • assess fixation – (may not be foveal if VA is poor)
43
Q

give an example of why it is important to note the rate of recovery when carrying out a cover test on a patient with a intermittent distance exotropia

A

i.e. they will be exophoric at near
when doing the cover test, when removing the cover, observe how well they recover and regain their bsv as a slow recovery = they do not have a good control at near

44
Q

list 3 things that need to be observed and noted when observing ocular movements

A
  • Versions and Ductions (common for limitations to be found if previous strabismus surgery)
    to be done with both eyes open and then one eye at a time
  • May vary looking up or down (alphabetic patterns A, V, X, Y)
  • Near point of convergence
45
Q

why is it important to record any alphabetic patterns e.g., A, V, X, Y when carrying out ocular movements

A

e.g. if you do find the eyes diverging more at a location e.g. down at depression and they control to an exophoria then that means they have a V pattern exophoria and if its a big difference e.g. 50 prism dioptre at elevation and 6 prism dioptre at depression, then this can change our management plan regarding surgery as may need to do further surgery to reduce the pattern

46
Q

why is it important to measure near point of convergence when carrying out ocular movements

A

it is an important indicator of control for near, with someone with an intermittent distance exotropia
if these patients have good convergence, then this means they have good control of their exophoria and a good recovery at an alternating cover test = good control at near fixation

47
Q

what 2 things would imply you to do a binocular functions test

A
  • when taking history

- the results of a cover test

48
Q

what is the best way to do a pct at elevation and depression to look for a V pattern exo

A

get the patient to look at a distance target at 6 metres and ask the patient to put their chin down, do the pct and do the same with the patient’s head straight up with the eyes in depression, the head must not be tilted

49
Q

at which distance will you carry out tests of someone with intermittent deviations

A

at the distance at which the deviation is controlled

50
Q

name 2 tests you will carry out on a patient with an intermittent exotropia for distance (where their deviation is controlled)

A

Need to look at their binocular control at distance by doing:

  • FD2 distance stereotest (frisby)
  • Fusion range for distance
51
Q

name 2 tests you will carry out on a patient with an intermittent exotropia for near (where their deviation is controlled)

A
  • Lang, Randot, TNO (stereopsis)

- Fusion range for near

52
Q

so as well as doing a cover test to prove that e.g. if someone has a intermittent distance exotropia, we need to prove that they’re binocular at near, as to make sure they can turn into an exophoria, we have had to look to see if their convergence is in normal levels. what else do we need to look at to make sure this is true

A

their fusion and stereopsis

53
Q

what 2 things do you have to after testing someone who is found to have constant deviations

A
  • correct the deviation with: prisms, synoptophore, botulinum toxin
    then
  • assess: binocular vision and the risk of post operative diplopia
54
Q

why would you want to correct the deviation when assessing someones constant deviation and what 3 things will you use to do this

A

the purpose is to put the eye into the straight position and look for any binocular potential and after that to see if with these tests if they can use both eyes together

can use:

  • prisms
  • synoptophore
  • botulinum toxin
55
Q

after putting the eyes in the straight ahead position when assessing someone with a constant deviation, why do you want to check their binocular vision

A

because if they have no potential for BSV at their angle of deviation we need to look at their post operative diplopia test to see whether if we do correct their underlying exotropia that they got in primary position, if we corrected that completely then are they likely to get double vision because the brain is used to the eye being slightly diverged and so if we alter that position, there is a chance they can become symptomatic and get double vision.

therefore it is also easy to put fresnel prisms on a child and check their BSV after

56
Q

how will you measure the deviation in patients with good VA and central fixation

A

a prism cover test (PCT) in primary position at 1/3m, 6m and 6m+ (to prove that the further away the px looks, the bigger the deviation gets) up and down gaze at 6m if indicated

57
Q

how will you measure the deviation in patients with poor VA i.e. less that 6/60 vision in one eye

A

prism reflection test

  • krimsky
  • Hirschberg CR’s

shine the light into the patient’s eye and use a prism bar infront of their eyes to align the corneal reflections in the exotropic eye (which will initially be nasal)

58
Q

as a prism reflection test can only be done at near on a patient with poor VA’s less than 6/60 vision in one eye, how will you check prism reflection test at distance

A

by using a synoptophore

59
Q

when differentially diagnosing a patient with having a true or simulated intermittent distance exotropia, with someone with a high AC/A ratio (accommodation) using a +3.00DS lens, what distance and target should you use and what should you ensure in clear

A
  • done at a 1/3rd of a metre
  • using the reduced snellen chart
  • make sure the 6/6 letter is clear

if its a true exo, then thee should be no change in angle with the PCT at a 1/3rd of a metre

60
Q

if the degree of exophoria doesn’t increase with either a +3.00DS lens or after 45 minutes of occlusion, then the patient has a…

A

true distance exotropia

Binocular vision YR 3 (20 decks)

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