Binocular Balancing CSA

Question 1

What is the purpose of binocular balancing?

Answer 1

To balance the accommodative effort between the two eyes.

Question 2

What is asthenopia?

Answer 2

Asthenopia is more commonly known as eyestrain or ocular fatigue. It’s a common condition that occurs when your eyes become tired from intense use.

Question 3

Why bother with binocular balancing?

Answer 3

The accommodative effort is not always the same under monocular conditions as it is under binocular conditions.

• When both eyes are working together, they accommodate by the least amount needed to maintain a clear image.
• This can cause accommodation to be unstable and can result in asthenopia.

Question 4

When should you do binocular balancing?

Answer 4

After subjective monocular refraction.

Question 5

How do you carry out binocular balancing?

Answer 5

There are several techniques but the one we concentrate on in labs is called Humphriss Immediate Contrast test.

[Another noted one is Turville’s Infinity Balance Test]

Question 6

Which patients should you binocularly balance?

Answer 6

All patients with binocular vision and good acuity in each eye

Question 7

Which patients should you not binocularly balance?

Answer 7

Px with:

• Squint
• Amblyopia
• Monocular
• VA differences of 3 or more lines
• Presbyopes (60 years or over)

Question 8

What are the general concepts behind the Humphriss Immediate Contrast Test?

Answer 8

• Uses a fogging lens between the powers +0.75 and +1.25D to fog one eye to 6/12 (although usually the power is +0.75/+1.00D).
• Over fogging an eye (e.g. +2.00D) can cause it to become monocular.
• Many clinicians use +1.00D and leave it in situ after the +1.00 blur test as they already know how much it fogs the patient by.

Question 9

What are the reasons for fogging?

Answer 9

Relaxes accommodation

• Central Vision suppressed i.e. fovea
• Peripheral Vision maintained
• Very similar to normal binocular viewing conditions

Question 10

What are the three methods of carrying out the Humphriss Immediate contrast test?

Answer 10

• Comfort method
• Clarity method
• Duochrome method

Question 11

What does the Humphriss Immediate Contrast comfort method involve?

Answer 11

So basically once you have found the monocular Rx (imagine it’s 6/5 in both eyes) you are going to go ahead and fog an eye.

Let’s imagine in this case you fog the left eye. The left eye would be fogged using a +0.75/+1.00D lens (whichever lens is needed to get VA to 6/12).

[At this point the Px would view line of letters close to the acuity of their non fogged eye - so in this case 6/5 would be the Best Corrected Visual Acuity (BCVA)].

You would then place a +0.25D lens in front of the non-fogged eye (so our right eye in this case). This would be done for only 1 second. Then you would place a negative lens, -0.25D in front of the eye for half a second, and then go back to the +0.25D lens.

Then proceed to ask the Px are the letters more COMFORTABLE with lens 1 (the positive lens) or lens 2 (the negative lens).

[Do not offer the Px the choice of no lens].

You then add whatever lens they have said is more comfortable and repeat the procedure of asking which lens makes the letters more comfortable until they pick the lens opposite to the last lens they choose (i.e. if they previously picked lens 1 - our positive lens, then if they next pick lens 2 - our negative lens, you have reached reversal and vice versa). You are looking to find the point of reversal - (so when adding the same type of lens doesn’t make the letters any more comfortable to read).

Question 12

Why in the Humphriss Immediate Contrast Comfort Test is the minus lens only allowed to be placed in front of the non-fogged eye for half a second?

Answer 12

Because the Px will accommodate if the minus lens is left in place for too long.

Question 13

What do you do if in the Humphriss Immediate Contrast COMFORT Test the Px says that lenses one and two are the same?

Answer 13

Keep pushing the positive lens. -so add on the +0.25D lens and do the next round of adding lens 1 and lens 2 and asking which one is more comfortable.

Just double-check though that the negative lens isn’t just making the letters smaller and blacker by asking.

Question 14

What’s the theory around reaching reversal in the Humphriss Comfort Contrast test?

Answer 14

• A plus lens that relaxes accommodation (no change in clarity), or a minus lens that makes vision clearer should both be more comfortable.
• A plus lens that blurs vision or a minus lens that makes the eyes accommodate (letters smaller and blacker) should be less comfortable.

Question 15

What’s a con of the Humphriss Immediate Contrast Comfort Test?

Answer 15

Not all Pxs understand the concept of comfortable thus you might have to use the Clarity Method to follow up or just the duochrome.

Question 16

What is the clarity method and how do you carry it out?

Answer 16

So the patient has got to the point where they can’t tell whether the lens is making the letters more comfortable or not. If position 2 was more clearer/comfortable than position 1:

First ask “is it definitely clearer or just smaller or blacker?”

• If just smaller and blacker, STOP.
• If definitely clearer, add the lens and repeat the procedure until reversal obtained (i.e. they choose a lens opposite to the previous lens) OR they say they can’t tell the difference between the two lenses in which case just give them the positive lens (to their Rx) and call it a day.

Question 17

What’s the difference between the Humphriss Immediate Contrast Test carried out the British way as a pose to it carried out the American way?

Answer 17

Exactly the same except you only show a +0.25DS lens, never a -0.25DS lens

Question 18

What’s the benefit of using a duochrome to conduct Humphriss Immediate Contrast (HIC) Test?

Answer 18

Pxs do not need to understand the concept of comfortable vision.

Question 19

What is the end goal for HIC using a duochrome?

Answer 19

• Identical end point should be achieved in each eye i.e. if RE = red so LE must also be left on red.

Question 20

What are problems associated with the HIC Test?

Answer 20

• Eye fogged too little
• Eye fogged too much
• Fogging lens left in trial frame and optometrist incorporates into final result

Question 21

What are important things to remember with the HIC test?

Answer 21

-Remember always push plus

• Only give more minus if it is definitely more comfortable and VA is better
• Do not repeat +1.00 blur test after binocular balancing.

Question 22

How does Turnville’s Infinity Balance (TIB) test work?

Answer 22

• Septum placed on mirror to occlude vertical section in central field of each eye.
• Remainder of field still seen by both eyes, hence binocularity maintained.
• Can use duochrome, letters, concentric circles on white background.

Question 23

What is the method for TIB?

Answer 23

• Ask patient to look at circles on the right and ask if circles appear darkest against red or green background or about the same.

If the patient says:

–Red=Green i.e. about the same Then stop and repeat for other eye

—If Red better Then add minus to balance (-0.25 steps). If balance not possible leave at “red better” and do the other eye.

–If Green better then add plus to balance (+0.25). If balance not possible leave at “red better” and do the other eye.

Question 24

What is your end goal for TIB?

Answer 24

• Endpoint must be same for each eye:

i.e. RE red = green, LE red = green

OR RE = red, LE = red

OR

RE = green, LE = green (this is done is special circumstances)

Question 25

In what cases would you want both the right and left eye to be left on green when conducting TIB using a duochrome?

Answer 25

You might want to over minus if e.g. they do a lot of night driving

Question 26

When should you use the duochrome?

Answer 26

On Pxs who respond well to the duochrome

Pxs who have unequal VAs

Question 27

When would you not use the duochrome?

Answer 27

Patients who always see either red/green better

• When it has not been possible to achieve same end point in each eye
• Px with Media opacities - as it produces a red bias
• Very small pupils

Question 28

What is an alternative to using the duochrome in TIB and how would you carry this out?

Answer 28

What would you use:

You would use letters/ concentric circles on a white background.

What you do:

Ask patient to compare clarity of images on right and left side of the chart

What would you based on results?

• If one of the circles/ letters is missing check septum
• If still missing or there is a misalignment of circles/letters this could indicate significant heterophoria
• If one of the circles/letters is clearer that the other, perform best vision sphere assessment of eye with least clear vision
• If circles/letters are still not equally clear, perform best vision sphere on other eye - Always start off with +0.25

[Best to use 2 letters- one seen by RE and other seen by LE. The letters ‘F’ and ‘L’ are usually used although may not be found in CS lab]

Question 29

What do you do after you have finished binocular balancing and how would you carry this out?

Answer 29

You need to do binocular addition.

How?

• Direct patient to smallest line. Add +0.25 to both eyes and ask if’ letters are just as clear, with or without’

. • If VA remains unaltered, add +0.25 binocularly.

• Repeat until further addition of +0.25 causes reduction in acuity.
• No need to offer -0.25 unless binocular VA less than monocular VA and you feel you have under minused.
• Best done with flippers.

[Note that young pxs should never be encouraged to accept more minus]

Question 30

Are there any alternatives to binocular balancing?

Answer 30

Yes you can do Binocular refraction - this is an alternative to the whole process of finding monocular VA then binocularly balancing it.

It’s very quick and easy to use but you need ACCURATE ret results.

Question 31

How do you carry out binocular refraction?

Answer 31

• Rather than occluding fellow eye, fog fellow eye (with +1.00DS) and perform subjective routine

Question 32

What are some indications for carrying out binocular refraction?

Answer 32

• Anisometropia
• Latent Hyperopia
• Pseudomyopia
• Unequal Visual Acuities due to pathology/ amblyopia
• Significant horizontal or vertical phorias
• Latent Nystagmus

Question 33

What is the order of tests after retinoscopy?

Answer 33

1. Monocular subjective refraction
2. +1.00DS blur test
3. Binocular balancing
4. Binocular add