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OV2018 binocular vision > Sensory fusion > Flashcards

Sensory fusion Flashcards

1
Q

What is sensory fusion ?

A

whenever you look at an object you can see it with R and L eye
-if everything is normal- you will be able to fuse together the image seen from L and R eye in your (visual)cortex into one single image.

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2
Q

Whats worth’s 3 grades of BSV (binocular single vision)?

A

-Simultaneous perception
Ability to use both eyes at the same time-

-Fusion
Sensory fusion (THIS WEEKS Lecture)
Motor fusion

-Stereopsis
Use of BSV to see in 3D:

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3
Q

Why is BSV important?

A
  • important
  • more worths 3 grades of BSV the more better their vision is
  • want to reflect how good it i
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4
Q

What is the definition of sensory fusion ?

A
  • ‘Integration of two similar images, one formed on each retina into one image within the brain.’
  • Images must be similar in brightness, size and form in order to fuse and see as one image
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5
Q

When do we measure sensory fusion?

A

-consider when px has manifest stabrismus

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6
Q

Why do we measure sensory fusion for someone with developing manifest strab ?

A
  • it will test if they have:
    1. Confusion
    2. Pathological diplopia
    3. Suppression
    4. Abnormal Retinal Correspondence (ARC)
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7
Q

Who can you carry out sensory fusion with occasionally ?

A

with px with heterophoria to confirm they have normal BSV

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8
Q

What is confusion?

A

-uncommon in px

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9
Q

What happens if a px with R eSotropia (SOT) has confusion?

A
  • Their left eye is looking straight ahead at the image
  • However their right eye is deviated and looking towards the nose.
  • R.E would be looking elsewhere
  • As a result cant fuse image- can see overlapping images mixed up in the brain- which is why they are trying to put together in their visual cortex.- cyclopean eye sees superimposed tree and house.(e.g)
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10
Q

What happens if a px with R eXtropia (XOT) has confusion?

A
  • Their left eye is looking straight ahead at the image
  • However their right eye is deviated outwards away from the nose
  • and can’t fuse the images-therefore what they put in their cyclopean eye is a superimposed image of a (e.g tree and house) - overlapping of images.
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11
Q

What is pathological diplopia ?

A

-most common type of problem

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12
Q

What happens if a px with R eSotropia (SOT) has pathological diplopia?

A

-The left eye is looking straight ahead
-The right eye is turned into the nose
-therefore the image lands on the nasal retina
-know that nasal retinal ALWAYS projects temporally therefore they will see one image on the left with their left eye
and then see the image with their right eye to the right hand side.
-This is uncrossed double vision- as right eye is being seen on the right side.

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13
Q

What happens if a px with R eXotripia (XOT) has pathological diplopia?

A
  • Left eye is looking straight
  • Right eye is deviated outwards away from the nose
  • therefore the image lands on the temporal retina
  • know that temporal retina ALWAYS projects nasally therefore in their right eye they will see the image on the left hand side.
  • This is crossed double vision.
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14
Q

What to remember ?

A

X in eXotropia- for crossed double vision.

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15
Q

What is suppression ?

A

-begins in children under 8 years old

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16
Q

What happens if a px has a R eStrophia in suppression ?

A
  • px left eye is straight
  • right eye turned into nose
  • tree hits fovea of L eye
  • tree hits nasal retina of R eye
  • ordinarily what hthe px will see is 2 trees
  • however if you are under 8 years old when manifest strabismus develops we can do suppression
  • when both eyes are open we can suppress the unwanted image - the px will only ever see one image they will suppress the image infront of the manifest eye- R eye EsoTropic- suppress the right image.
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17
Q

What is suppression dependant on?

A
  • depends on the size of the manifest deviation
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18
Q

What is partial suppression ?

A
  • if you have a tiny trophia- you might only develop foveal suppression
  • however if you have a -larger angle - large area of retina will be suppressed.
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19
Q

What is intermittent suppression?

A
  • suppression in some circumstance. (for e.g in the distance only - normal at near)
  • otherwise diplopia or BSV
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20
Q

how do we investigate suppression ?

A
  • diagnose the presence of suppression
  • need to know the size of the suppression scotoma
    • can use prisms to measure that
  • can be central suppression with peripheral fusion
  • need to know the density of the suppression
    • Measured with sbisa bar
    • Measured with NDF(neutral density filter) bar
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21
Q

How do we start investigating px suppression ?

A
  1. Start by measuring our patients area expression
  2. So we do this by putting up prisms infront of the deviated eye
  3. ask the px to look in the light
    or also might put red or green goggles on to to help measure this
  4. Keep increasing the strength of the prism infront of the deviated eye and ask them when they see double
  5. We can record for base up, base in, base down and base out
  6. therefore we can Measure the whole size of the suppression scotoma
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22
Q

What can you do to help the px with suppression ?

A

-can get cosmetic surgery to improve the look

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23
Q

What are some of the consequences of the cosmetic surgery for suppresion ?

A
  • tractable double vision
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24
Q

How can we test whether the px will or will not get diplopia after their surgery ?

A

post operative diplopia test

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25
Q

How do we measure their density of suppression ?

A
  1. Look at px first
  2. put the filter bar infront of the fixing eye (the good eye)
  3. Hold torch at 3rd of metre
    4.So now this px will be looking through a red bar essentially at a white light
    because of looking through the red bar the light will be coloured red
  4. Ask the px “ I want you to look at my light and tell eye what the colour is”?
  5. As you increase the colour of the bar strength , it will go from light to dark red colour , the further up the bar it goes the harder it is for the px to see with their good eye.
  6. Reach the point where they don’ t want to see from good eye and move to the deviated eye swinging in- the px will NOW report the red light is now changed to the white light
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26
Q

What are the 3 ways you can record the density ?

A
  • Could record the level before on the bar where that occurred.
  • or you can observe the px - and watch when the fixation swap)
  • or Lastly you can ask the px “tell me when it goes from being one light to two lights” - then record level of the bar before that occurred.
27
Q

What happens if the density recorded is less than 10 ?

A
  • stop any treatment such as patching for amblyopia
  • because although you can treat the px - the danger is at the risk of leaving them with tractable double vision
  • also find that the suppression will get weaker and weaker over time
  • so stop the patching
28
Q

Who does the px have to inform when they are seeing double vision?

A

-DVLA - px must stop driving immediately and tell them

29
Q

What are the consequences of not informing the. DVLA ?

A
  • can be fined up to 1000

- might be prosecuted if in an accident

30
Q

When can the px resume driving ?

A
  • IF DVLA have received confirmation that diplopia is controlled - e.g glasses or a patch (but note requirements for monocular vision above)
  • Exceptionally, a stable uncorrected diplopia endured for 6 months or more may be licensable with the support a consultant specialist’s report of satisfactory functional adaptation.
31
Q

What is ARC?

abnormal (anomalous) retinal correspondence

A
  • develop in children under 8 year olds with manifest strabismus
  • and happens with a real small angle- if its a big angle the pseudo fovea will be so far away from the real fovea but nothing useful would set up
32
Q

What happens in a px with ARC with a R eSotropia?

A
  • the object is hitting the pseudo fovea of the right eye - this is the most useful condition to develop
33
Q

Why is ARC the most useful condition to develop ?

A
  • as this Childs whole retina and brain to not want to use their real fovea when both eyes are open
  • they actually want to use their pseudo fovea
  • their whole brain is adapted to having a small angled trophia
  • these px behave like us (having stereopsis- motor fusion ) - despite having a manifest sstrabismus in their eye
34
Q

What would be an example where you cant determine whether px has sensory fusion or suppression?

A

The EXAMPLE IN This case would be :

  • an image of a house is being shown to the right and left eye
  • the px says that when they put both pictures together they saw one mental image of the house

so does this px have sensory fusion ?
-is the px using 2 eyes and fussing the image in the visual cortex to make one house or are they simply just suppressing one image.

35
Q

How do you determine whether the px has sensory fusion or suppression ?

A

-need controls to be sure the use of both eyes (binocular eyes) are being use to see the image.

36
Q

What are the controls used to determine whether the px has sensory fusion or suppression ?

A
  • placing a red filter infront of one eye
  • and placing a green filter infront of the other eye
  • In this e.g - WATCH the lecture at 24:20
37
Q

How else can determine sensory fusion instead of anything else?

A
  • equipment
    -see image in-front of the right eye is a donkey with a saddle
    image infant of left eye is a donkey with a tree in it
  • the px says they see when they see with both eyes when they fuse together in their visual cortex is one donkey (both eyes being used as they said they can see the saddle and the green tree)- so therefore is sensory fusion
38
Q

What is the first type of sensory fuse test ?

A

synoptophore

39
Q

What is the synotophore test ?

A
  • it is based on total dissociation

- this means that R eye and L eye see 2 totally different images

40
Q

What is another type of sensory fuse test?

A
  • can use partial dissociation - to make sensory fusion tests
  • same single target seen in both eyes
  • parts of it only L eye can see and parts of it R eye can see and there are parts that Both eyes can see together
41
Q

What can we do to dissociate this partial dissociation test ?

A
  • can use red / green glasses
  • Diffraction
  • polarisation
42
Q

What is the worths lights ?

A

-red / green glasses to dissociate

43
Q

What is the bagolini lenses?

A

-diffraction to dissociate

44
Q

What is the mallet unit ?

A

polarisation to dissociate

45
Q

How do we conduct the Worth 4 dot test/ Worths light ?

A

-Px needs to wear red and green goggle
- R- always has Red filter infront
- L eye- always has Green filter
-red filter cant see green images and green filter cant see any red images
-There are 4 dots placed on the screen and looking at it through the red and green goggles
-In the example in the powerpoint= the px in the right eye will see the top red dot and bottom dot as red (but is white)
-with their left eye - they will see 2 green dots horizontally and a green dot on the bottom (but is white)
-

46
Q

What does the px see if they have normal vision in the Worth 4 dot test ?

A
  • they will be able to see all the 4 dots but the bottom dot will alternate between red and green
  • the white circle sits in the fovea of L and R eye - we know both fovea’s are corresponding therefore the common white circle they see with both eyes they would see as single because they would be fused together and the bottom circle will alternate between red and green
47
Q

What does a px with a R eSotropia see with the worth 4 dot test ?

A
  • px right eye is turned in towards the nose
    -px left eye - will see both green dots horizontally and the bottom white dot will appear as green - proving the L eye is working properly
    -R eye- the top red control dot will hit nasal retina and nasal retina always projects temporally therefore the top red dot the see in the right eye they will see to the right hadn’t side
    -the px will also see the bottom white light - but it is hitting the nasal retina - and the nasal and fovea do not correpspond - therefore this white light is not gonna be single or fuse - it will project temporally - so R eye will see top control dot and the white dot on the right hand side (but white dot seen as red)
    -in total px will say they see 5 lights
  • uncrossed double vision
    no sensory fusion
    EXAMPLE - 32:00
48
Q

What is the treatment for R eSotrophia?

A
  • lenses - the eye is in so want to ease it out
    -want to relax accommodation and therefore convergence
    -to relax accommodation need + lenses
    -we can give base out prism
    -exercise
    -refer (HES)
    surgery
    second opinion
49
Q

What does a px with a R eXotropia see with the worth 4 dot test ?

A
  • px right eye is turned outwards
  • l eye is straight and looking through green filter- same s before sees 3 green dots
  • R eye will see top red dot - the image is hitting temporal retina which projects nasally therefore this top red dot will be seen in the left hand side
  • px will aslo see the bottom white light on the left hadn’t side as it hits the temporal retina - and the white dot will. be seen as red.
  • see 5 dots
  • fovea of the L eye and R eye retina do not fuse= therefore see 5 dots
  • crossed double vision
50
Q

what is the treatment for exotropia?

A
  • give maximum minus / minimum plus - lenses - stimulate accommodation and convergence to pull them in
  • give prisms
  • exerciseS
  • refere to HES
51
Q

What happens when px has left suppression ?

A
  • see 2 red dots
52
Q

What happens if px has right suppression ?

A
  • they will see 3 green dots on left eye
53
Q

What is the management/treatment for suppression ?

A

have no diplopia - dont need to pull them in with lenses or stop

-Constant suppression
Leave alone as no symptoms
Cosmetic Surgery

-Central suppression
Microtropia
Usually no treatment needed except for amblyopia
Be aware BSV slightly inferior to normal

54
Q

What happens with a px with R esotropia ARC in the worths 4 dot test ?

A
  • px wants to look with their pseudo fovea
  • l eye is fixing eye- see 3 green dots- hitting fovea
  • Red dot is hitting pseudo fovea in the right eye - that is where the brain is rewired to - the px wants to use the pseudofovea-
  • with this arrangement because its hitting their ideol spot that is fovea with the left eye and pseudo fovea with the right eye are corresponding because their brains are rewired
  • R eye they will see top red circle and bottom white circle (as red) because they are looking through red filter
  • they will fuse together because their brains are rewired
  • their full fovea with their L eye to pair with the pseudo fovea with the right eye - px will see 4 dots
  • with bottom circle alternating red and green and they will see this despite having esotrophia in the R eye
55
Q

What is the management for ARC?

A

-Do not treat
- Be aware that BSV slightly inferior
Therefore monitor

56
Q

What is striated lens partial dissociation ? (diffraction)

A
  • these are the bagolini lenses- can make them

- controls: line of light the px sees is perpendicular to the striations

57
Q

How are the controls managed in the striated lens partial dissociation ?

A
  • e.g px R eye - see striations on lens are running 45 degree angle- the px will see the light at 135 degrees- that’s the control for the R eye- know it is working
  • In front of the L eye you can see the striations are running in 135 degrees- the px will report that the line of light at 45 degree- know that the l eye is working
58
Q

How to know is normal in striated lens partial dissociation test ?

A
  • Spot light pen torch
  • px sees last: the pen torch - the common thing seen in R and L eye- use fovea fovea - know its corresponding- fuse image from L and R eye together- will see one pen torch- see a perfect X
  • if not corresponding- px reports double - pen torch is double
59
Q

How do we check for diffraction of Bagolini glasses?

A
  • Fixate a spot light
    Near or distance fixation
    Easiest with a bright pen torch
    Striations before RE placed perpendicular to striations before LE
    Normally 135° and 45°
    -Ask patient to report on how many lights they see
    -Ask them to draw the pattern they sees
    -Are there any gaps in the centre near the light?
60
Q

What happens if a px has a right esotropia in the bagolini test for diffraction ?

A
  • r eye turned towards nose
  • the pen torch is going to hit nasal retina
  • L eye- striations run at 135 - line of light at 45- see one spot light on L eye
  • fovea of left eye and nasal retina of right eye are not coreesponding- won’t see one pen torch
  • R eye- pen torch hits nasal retina and projects temporally so will see pen torch on the right hand side
  • uncrossed double vision
  • R eye- 45 degrees striations- line of light at 135 degrees
  • px sees 2 lights indicating double vision
  • px sees A
61
Q

What happens if a px has a right eXotropia in the bagolini test for diffraction ?

A
  • L eye- striations 135 degrees - lien fo light at 45 - one pen torch
    -R eye- hit temporal retina- fovea of l eye and temporal retina of R eye do not fuse- see 2 pen torches
    -temporal retina projects nasally- the pen torch they see on right eye , will see on the left hand side
    -crossed double vision
    r eye- striations at 45 degrees- - line of light at 135
    -px sees a v pattern- double vision
62
Q

What happens if px sees right suppression in bagolini test fro diffraction ?

A
  • fovea of L eye fixing - one pen torch
  • R eye- pen torch hits nasal retina- projects temporally
  • uncrossed double vision
  • fovea and retina does not correspond
  • but under 8 years old when this happensed
  • so px will now suppress
  • so when L eye is covered yes will use R eye- when both eyes open the px brain just ignores the other image
  • extrememly useful - both eyes open got right suppression- px will see what the left eye sees- one pen torch light
63
Q

What happens when you just have central suppression of the eye in R esotrophia? (diffraction test)

A
  • sees image in L eye- one pen torch
  • see image in R eye- one line - one light
  • little suppression- so will see little gap in the middle -the deviation is so small- the px will see one light but will have a little gap in the line infront of the right eye
64
Q

What happens in px with ARC R esotrophia in diffraction test ?

A
  • want to use pseudo fovea
  • if behave normally- see one light in L eye and R eye too.
  • R eye - light will be fused - striations at 45 deg- line of light at 135- so see one light
  • not normal- have right esotrophia however have ARC so see one light

OV2018 binocular vision (15 decks)

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