Binocular refraction

Question 1

what is binocular refraction

Answer 1

one in which the subjective part of the examination is carried out without an occluder being used.

The fogged eye has a central lock on it, but as theres peripheral stimuli around it, it allows the fogged eye to give input as well (but fogged eye makes less of the decision)

Question 2

what is binocular refraction a variation of and what does it aim to do

Answer 2

• It is a variation of the Humphriss Immediate Contrast Technique
• It aims to inhibit the fovea of one eye to control accommodation

Question 3

list 2 things a suitable patient must have to do binocular refraction on and what a patient definitely cannot have (as you can’t do it on everyone)

Answer 3

• Must be binocular (i.e. not on amblyopia px)
• Should have reasonably equal acuities
• Definitely not someone with a very dominant eye

Question 4

if the visual acuity of the eye being tested is 6/5, what va should the fogging eye be fogged to in order for it to be under foveal suppression and what va will push it to suppression which is not what we want

Answer 4

• 6/9 to 6/12 = foveal suppression with a +0.75/+1.00DS lens
• 6/18 = suppression

Question 5

list all the 6 steps of what you will do in binocular refraction, starting from just after ret

Answer 5

Step 1. After retinoscopy possibly carry out a quick monocular subjective check

Step 2. Fog left eye to 6/9 or 6/12
Usually requires a +0.75DS or a +1.00DS for Foveal Suspension

Step 3. Carry out your normal subjective routine on the right eye
BVS and X-cyl etc

Step 4. Fog right eye to 6/9 or 6/12
Usually requires a +0.75DS or a +1.00DS

Step 5. Carry out your normal subjective routine on the left eye

Step 6. Check sphere binocularly (+0.25DS) with fogging lenses removed
To see if px can see any better

Question 6

which result must be good before doing a binocular refraction

Answer 6

ret result as it has to be better than 6/12 if going to fog the other eye

Question 7

list 4 advantages of binocular refraction

Answer 7

• Provides an essentially normal visual environment
• Because of it providing an essentially normal visual environment, accommodation tends to relax as much as is possible during the subjective examination (binocular refraction helps to push for most plus)
• Cylinder axis is determined under binocular conditions
  You tend to get a difference cyl axis monocularly
• May save time
  No need to binocularly balance
  More stable accommodation

Question 8

for which types of patients does the advantage of binocular refraction provide more stable accommodation and give an example

Answer 8

Particularly helpful with “latent hyperopes”

For example
R&L +2.00DS on retinoscopy
Great reversal but “VA” after ret = 6/12

Question 9

what is the disadvantage of binocular refraction

Answer 9

The technique cannot be applied successfully to every patient

It follows that patient selection becomes most important with the ideal patient:

• Having a good standard of binocular vision
• Having reasonably equal right and left acuities