What is the definition of convergence ?
simultaneous rotation of the eye inwards
What are the 2 methods you can use ti measure near point of convergence ?
Pen to nose
An inaccurate technique
Provides an estimate of the n.p.c.
RAF rule
Dot provides a fixation point
Single high contrast line helps recognition of diplopia
Use cm scale for measurement
What method do we use in the UK to measure near point of convergence ?
RAF rule
- line with a dot in it, bring it closer and closer to the px and ask when that line turns into 2 - get diplopia
- then will read off the cm scale
Will the px be asked to wear their correction or not ?
- rule of thumb is : if they are a high hyperopia, presbyope , moderate to high myopes should all wear glasses.
- If px required to wear spectacles to see clear at near then ask them to put them on.
How do you measure using RAF rule ?
line with dot
- hold RAF rule in a slightly depressed angle.
- then going to bring the target closer and closer till they can see double
- you will move it very slowly at about 1-2cm per second and record where double occurs
- once double occurs then you can pull it back and ask when it turns into single
What would you do if px may have convergence and fatigue?
would repeat the RAF rule 3 times as the first time could be normal but then 2nd and 3rd may be reduced
What is normal near point convergence ?
-if you are pre-presbyopic - expect to get a normal near value of 10cm or less
what can you get your convergence down to if you are a pre-presbyope ?
-get down to 5cm before your convergence breaks and recovery is at 7cm
(happens when using the budgie stick or pen torch and not the Raf rule - anything 10cm or below is normal)
What is normal near point value for presbyope px ?
15cm
What are the 2 ways to test convergence ?
objectively
subjectively
Why do we test objectively the most ?
- for children
- because if you ask a child to tell when it goes double - they will think that’s the correct answer and will tell you double
How do we test subjectively ?
-ask the px when the line goes double- reports diplopia
How do we test objectively ?
-watch where the point where one eye or both eyes diverges and then note the distance where that occurs and ask when they may be able to report diplopia
How do you write down the results for when testing objectively ?
e.g
RAF conv with Rx : binocular 10/15/20cms RE diverged with diplopia
What is the definition of accommodation ?
Is the ability to change the convexity of the crystalline lens in order to obtain a clear image of a near object
What are the 3 assessments of accommodation ?
- Accommodative amplitude or range
- Near point- with RAF rule
- use Minus lenses also - Accommodative facility
- measure using Flipper lenses - Accommodative lag or lead
- using Dynamic retinoscopy- Monocular Estimation Method
- Nott Method
How do you measure the near amplitude or range ?
-using RAF rule
- the target for reading- ask px to read the smallest sentence they can read - e.g N5 so they would use that as target
-Test monocularly and binocularly
-Ensure FULL distance Rx is worn
Maximum +ve or least -ve
- Find nearest point of clear vision
- measure in cm and convert to dioptres
- use dioptric scale
- bring it closer and closer to the px and ask the px tor report when the lines get blurred.
-Target
N5 or smallest visible print or target
What do we have to ensure when doing any accommodation test ?
- make sure the px is wearing the full distance rx
- this is because if px was hyperbole and wasn’t wearing correction - they would accommodate to see so would have to make sure they are fully corrected before testing for accommodation.
What is the technique for measuring near point amplitude using RAF rule ?
-push up target until patient reports target blur
-Pull back until patient reports target as clear
-repeat push up / pull back
if difference < 1D record mean
if difference > 1 D record range
What happens to px amplitude when presbyopic ?
low amplitude of accommodation
What do we recommend in presbyopic px with less than 2D ?
- as their accommodation is low - include a binocular near addition of +2.00 infront of both eyes and subtract this at the very end from their final near amplitude
- if you were to get 5D then you would subtract 2D = 3Dioptres
What does amplitude of accommodation vary with ?
age
- the older you get the lower it gets
- the normal values are on the RAF rule table for specific ages
How to write down the amplitude of accommodation results ?
-first what test you are doing
E.G RAF or AoA Binocular with Rx: 10 D x3 or Monoc with Rx RE:8D x 3 and LE 8D x 3
How can you measure near amplitude of accommodation using minus lenses ?
- Full refractive correction
- hold Target near card at 40cm
- One eye occluded
- slowly put Negative lenses are placed in front of eye
- Increased in 0.25Ds steps
- can take px 10sec to accommodate in to these lenses hence would take long
- Encourage patient to make the print clear
- End point when letters can not be cleared and the print is blurred
- Repeat for other eye and binocularly
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introduction to binocular vision49
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manifest and latent strabismus51
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Sensory fusion64
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Motor Fusion51
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stereopsis49
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measurement of ocular deviations33
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Accommodation and convergence54
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extraocular muscles 158
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Extraocular muscles 268
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extraocular muscle 329
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extraocular muscle 451
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fixation disparity34
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investigating eye movement systems56
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EOM- cell biology and pathology32
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Ocular motor nuclei nerves0
