Binocular refraction

Question 1

What is binocular refraction

Answer 1

• Where the subjective part of the examination is carried out without an occluder being used.
• Instead a +0.75D or +1.00D blurring lens is used to fog the eye

Question 2

What technique does binocular refraction include:

Answer 2

• It is a variation of the Humphriss Immediate Contrast Technique
• Which aims to inhibit the fovea of one eye to control accommodation and maintain peripheral and paracentral areas
• Uses a +1.00 or +0.75 lens to blur one eye

Question 3

Which sort of px’s can you do binocular refraction on:

Answer 3

• Must be binocular and suspend their fovea – cant do on amblyopes cause even though fog better eye, they will still look through that
• Should have reasonably equal VAs
• Not someone with a very dominant eye
• Cant do it on someone with NO accommodation
• If you have a patient with cataract in one eye (6/12) and IOL in the other eye (6/5) you cant do binocular balancing

Question 4

Explain how binocular refraction works:

Answer 4

• If you are testing the RE, you fog the LE.
• Most of the information will come from the RE
• But the LE has a central lock on it but the peripheral vision is still there… allowing you to use both eyes

Question 5

What is the Humphriss Immediate Contrast (HIC) technique used for:

Answer 5

To balance accommodative effort following monocular refraction but does not attempt to equalise visual acuities

Question 6

How does Humphriss Immediate Contrast (HIC) technique work:

Answer 6

• It makes use of the psychological septum, which is the inhibition of the fovea one eye to favour the other, whilst retaining paracentral and peripheral vision.
• This state is achieved by the use of a low power positive fogging lens +0.75 or +1.00 DS
• This reduces the acuity of the fogged eye to about 6/12 Snellen.

Question 7

Why do we do binocular refraction:

Answer 7

To control accommodation

Question 8

What VA would you need to blur to in binocular refraction

Answer 8

If you want to do a binocular refraction by blurring the LE……
- If you reduce the LE VA to 6/6, this is not enough as they are still binocular i.e using both eyes
- So you cannot correct the VA of the RE because you will be using influence from the LE.
- So not good to blur to 6/6 = no effect on binocularity
- You need the VA to be down to 6/9 or 6/12 before there is foveal suspension.
- If blur to 6/18 = too much plus = cause suppression = suspend fovea AND periphery
- If the LE is suppressing, it is like putting an occluder in front of the eye = happens if blur back to 6/18
- The eye that is being fogged needs to have a VA of 6/9 or 6/12.
- SO BLUR TO 6/9 – 6/12 = create foveal suspension – not using fovea but will be using paracentral and peripheral areas of fusion

Question 9

What happens if you don’t blur enough:

Answer 9

You are not suspending fovea

Question 10

What happens if you blur too much:

Answer 10

Cause suppression

Question 11

What should the eye be fogged to and why

Answer 11

6/9 or 6/12
For foveal suppression

Question 12

What is the routine for binocular refraction:

Answer 12

1.Put fogging lens LE ( +0.75 ) to obtain foveal suppression – might have to use +1.00D
2.Fog eye to 6/9 or 6/12 = MAKE SURE TO CHECK WHAT LINE THEY ARE READING WHEN PUTTING FOGGING LENS IN – WANT 6/9 OR 6/12
3.Do BVS with plus lens only and say is it just as clear or better without…
*Add +0.25DS in front
*Ask if it is any worse or does it remain the same?
*If it remain the same, add the +0.25
*If its worse then don’t add the +0.25.

Question 13

How does retinoscopy result affect binocular refraction:

Answer 13

*If you have a poor ret result, you will not be able to do a binocular refraction
*Because you want the patient to be fogged to 6/9 or 6/12.
*If you are getting the patient to read 6/36 after ret then this is not going to allow you to do binocular refraction.

Question 14

What do you do in binocular balancing:

Answer 14

*Add +0.25DS in front of both eyes.
*Ask if it is any worse or does it remain the same?
*If it remain the same, add the +0.25
*If its worse then don’t add the +0.25.
*Important to remove the fogging lens
*ONLY USE PLUS

Question 15

Advantages of binocular refraction:

Answer 15

Provides an essentially normal visual environment
Accommodation tends to relax as much as is possible during the subjective examination
Cylinder axis is determined under binocular conditions
May save time
- No need to binocularly balance
- More stable accommodation
Particularly helpful with “latent hyperopes”

Question 16

Disadvantages of binocular refraction:

Answer 16

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

Question 17

What is important when swapping lenses in binocular refraction:

Answer 17

*If you have a patient who needs to go from +3.50 to +3.25, always add the +3.25 before removing the +3.50
*Otherwise you are changing the accommodation.
*Because + lenses relax the accommodation.
*As soon you take the + lens out, the patient starts accommodating again.
*You have lost the process of fogging the patient.