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binocular vision > lecture 2 - strabismus, latent and manifest > Flashcards

lecture 2 - strabismus, latent and manifest Flashcards

1
Q

heterotropia is… strabismus

A

manifest or squint

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2
Q

Heterophoria is …. strabismus

A

heterophoria

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3
Q

tropia

A

both fovea aren’t looking at the same object

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4
Q

can you always see a strabismus

A

no - need to do cover test

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5
Q

what causes psuedostrabismus

A 
epicentral folds
wide inter pupillary distance 
unilateral myopia or exophthalmos 
facial asymmetry 
large angle kappa
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6
Q

what is angle kappa (K)

A

the angle between the centre of pupil and corneal reflection

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7
Q

in normal people what is angle kappa (K)

A

3 - temporally to posterior pole

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8
Q

in central corneal reflexes what is angle kappa

A

0

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9
Q

if the fovea lies nasal to the posterior pole what is angle kappa

A

negative - as corneal reflection is temporal

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10
Q

how to detect pseudo strabismus

A

use corneal reflection and see if they are symmetrical

use cover test

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11
Q

what is cover test used for?

A

pseduostrabismus
latent (phobia)
manifest (tropia) deviation

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12
Q

what is cover/uncover test used for?

A

used as a test to detect manifest

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13
Q

what is alternating cover test for?

A

best test to detect Heterophoria as it fully dissociates

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14
Q

if you find esotropia at near …

A

also use a light

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15
Q

why do you always use corneal reflections initially?

A

easier to do with young children and adults with learning difficulties and can determine if someone has eccentric fixation

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16
Q

when you are not using your fovea for central fixation

A

eccentric fixation

17
Q

what is the accommodative target for cover test

A

line above worst VA or toys for infants

18
Q

cover test is only as good as…

A

patients fixation

19
Q

what is the largest reason for misdiagnosis

A

poor fixation

20
Q

how do you control a px’s fixation

A

ask them questions about it - eg, when looking at bird, ask what colour the beak is, how many legs is he standing on etc

21
Q

when do you look at the eye on cover/uncover

A

as you are covering one eye you observe the movement of the other

22
Q

COVER/UNCOVER:

if eye moves out

A

esotropia

23
Q

COVER/UNCOVER:

if eye moves in

A

exotropia

24
Q

COVER/UNCOVER:

if eye moves up

A

hypotropia

25
Q

COVER/UNCOVER:

if the eye moves down

A

hypertropia

26
Q

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

27
Q

what does constant tropia mean

A

both eyes uncovered the patient will always go back to fix with one eye

28
Q

what do you record when recording results for tropia

A
  • which eye is affected
  • what distance it was measured at
  • degree of movement
  • target used
29
Q

minimal deviation is

A

<10 prism dioptres

30
Q

small deviation is

A

10-20 prism dioptres

31
Q

moderate deviation

A

20-40 prism dioptres

32
Q

large deviation

A

> 40 prism dioptres

33
Q

Heterophoria

A

when the eyes are dissociated the eyes deviate from the fixation point

34
Q

orthophoria

A

no phoria or tropia

35
Q

when do you look at the eye on alternating CT

A

watch the eye as you remove the cover

36
Q

movement on alternating: esophoria

A

eye moves out

37
Q

movement on alternating: exophoria

A

eye moves in

38
Q

recording results for phoria

A
  • direction of deviation
  • degree of deviation
  • speed of recovery
  • distance
  • target
  • whether specs were worn
39
Q

how to analyse cover test?

A
  1. is it cover/uncover or alternating
  2. what does the uncovered eye do to take up fixation
  3. if it moves out then it was Esophoria
  4. if it moves in it was eco
  5. if nothing found and it moved out on alternating then it was SOP

binocular vision (10 decks)

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