Binocular Balancing 1 and 2 - Week 2

Question 1

When do you perform Binocular Balancing?

[from sharpen your subjective refraction technique pdf I found online]

Answer 1

Once the monocular subjective refraction has been completed for each eye

(start by fogging the eye)

Question 2

True or false: Binocular Balancing is only done when the visual acuity is different between the 2 eyes

[from sharpen your subjective refraction technique pdf I found online]

Answer 2

False.

Binocular balancing is mainly done when the V.A is RELATIVELY EQUAL between the 2 eyes

(If unequal use Duochrome target)

Question 3

State the purpose of Binocular Balancing

Answer 3

To balance or equalise the ‘accommodation’ of the 2 eyes

Question 4

What happens if accommodation is not balanced?

Answer 4

This will lead to symptoms and uncomfortable vision

Question 5

What is the theoretical basis of binocular balancing techniques? What does this mean?

Answer 5

ocular accommodation is a consensual reflex

• this means that any active accommodation occurring in one eye will induce the same amount of accommodation in the other eye

Question 6

After JCC, how do you assess monocular end point?

Answer 6

By adding +/-0.25DS and getting them to read the letter chart
– note: add +ve first, keep going if ‘clearer’
(then you do blur check etc)

Question 7

What principle should you adhere to when assessing monocular end point?

Answer 7

Maximum plus power (or least minus) consistent with best vision – i.e. be more +ve/less -ve

Question 8

When assessing monocular end point, what if V.A is worse than 6/9 still?

Answer 8

Try using pinhole (PH)
If PH improves V.A: 
- could be uncorrected refractive error (most likely)
- could be a paracentral media opacity (e.g. cortical cataract)
If PH does NOT improve V.A:
- refraction correct
- could be Amblyopia
- could be Pathology

Question 9

What’s the abbreviation for when pinhole gives you no improvement?

Answer 9

NIPH

Question 10

why do some patients seem uncertain as to what lens gives the clearest vision?

Answer 10

The depth of focus can add uncertainty to a finite end point
- hence if px undecided, follow the maxim of maximum +ve power
Depth of focus also varies with pupil size
- is larger for smaller pupils

Question 11

(revision) in relation to the retina, during chromatic aberration, where are shorter and longer wavelength brought into focus for an emmetropic eye when accommodation is relaxed?

Answer 11

Shorter wavelengths (blue) brought into focus in front of retina
Longer wavelengths (red) behind retina

Question 12

How can we use the nature of chromatic aberration to help determine monocular end point of refraction?

Answer 12

Duochrome

• if green clearer, add +ve (0.25)
• if red clearer, add =ve

Question 13

In what cases may duochrome incorrectly suggest a change of more than 0.50DS from previously determined refraction?

Answer 13

• elderly

- hyperopes and pseudomyopes

Question 14

In what cases is Binocular Balancing not productive?

Answer 14

When the patient does not have any functional binocular vision - could be due to: strabismus, amblyopia, pathology

When there is no active accommodation (elderly >60yr)

(in each case, attempt to get same response from both eyes - use techniques as for monocular endpoint refinement)

Question 15

List the 5 basic techniques of binocular balancing.

in order of increasing sensitivity from 1 to 5

Answer 15

1. Successive alternate occlusion
2. Vertical prism dissociation
3. Blurring or fogging techniques
4. Septum techniques
5. Polaroid techniques

Way to remember:
** Success in vertical blurring of the septum involves polaroids

Question 16

Which of the following are NOT binocular techniques:
A) Successive alternate occlusion
B) Vertical prism dissociation
C) Blurring or fogging techniques
D) Septum techniques
E) Polaroid techniques

Answer 16

A and B.

Successive alternate occlusion and Vertical prism dissociation

Question 17

Explain Successive alternate occlusion

Answer 17

Px reads smallest line they can with both eyes. PD occluder is alternated from one eye to the other, and px is asked to compare.

• if both views are equally clear, good
• if not, add +0.25DS to the eye with clearer vision

Question 18

On what type of patients do you perform successive alternate occlusion?

Answer 18

Px with poor binocularity

Question 19

is vertical prism dissociation a binocular technique? why/why not?

Answer 19

No. Because you totally suspend fusion and therefore do not stimulate binocular vision

Question 20

Explain Vertical prism dissociation

Answer 20

Add 2-3diopters BU in one eye, and BD in other eye, then ask them to compare a line of letters (6/9 line) on the letter chart (ask if top or bottom perceived line is clearer).

• if both lines the same, good
• if not, add +0.25DS to the eye with clearer vision

Question 21

True or False: Vertical prism dissociation can be performed using duochrome as the target

Answer 21

True

Question 22

How much should you fog the eye when doing Humphriss Fogging Technique? Why?

Answer 22

Fog the open eye by at least 2 lines, to be certain this eye is not being used for critical vision (generally we fog 2-3 lines)

Question 23

When fogging the eye, should you tell the patient?

Answer 23

No

Question 24

What are the advantages of the Humphriss fogging technique?

Answer 24

• it fully relaxes accommodation, therefore there is little need to do binocular addition afterwards
• Is quick and simple for both px and practitioner
• is relatively accurate

Question 25

What is the Humphriss Immediate Contrast (HIC) technique, and how does it differ from the normal humphriss fogging?

Answer 25

Is almost identical except that +0.25DS (1sec) and -0.25DS (0.5sec) are immediately presented one after the other

• and the px is asked if lens 1 or 2 is more ‘comfortable’
• note: only add -0.25 if px immediately reports that this lens is better

Question 26

What does the fog do in Humprhis fogging?

Answer 26

The fog is used to suspend foveal vision in one eye but allows paracentral and peripheral vision to act as a binocular lock

Question 27

What are the 6 major tests in practice that employ either the septum or a polaroid technique?

Answer 27

Turville - septum
Freeman - septum
Wilmut - polaroid
Cowan/Mallet - polaroid
Grolman - polaroid vectograph

note: the names on the left are the inventors

Question 28

How do polaroid techniques work?

Answer 28

Use polaroid filters before both eyes (oriented at 90deg) with 2 similar test charts (also polarised at 90deg) to be seen by each eye separately

• direct px to 6/9 line, ask px which side is clearer
• • if equally clear, good
• • if not, add +0.25DS to the eye with clearer vision

Question 29

How does septum differ from polaroid technique?

Answer 29

It’s basically the same except for septum, the view is split into 2 by something physically in your field of view (rather than through polarised light filtering)

Question 30

After binocular balancing, is px accommodation fully relaxed? What should you perform at the end of your routine?

Answer 30

Not necessarily, therefore you should always attempt binocular addition at the end of your routine.

Question 31

Explain the technique of Binocular Addition

Answer 31

Ask px to view smallest line and place +0.25DS in front of both eyes simultaneously
ask px are the letters “clearer, just the same, or actually worse”
If better or same, continue adding +0.25DS

i.e. it’s basically just BVS but you are doing it on both eyes at once, and you’re only adding 0.25

Question 32

What are Binocular Refraction techniques? Do you need to binocular balance after this?

Answer 32

It’s when you refract under binocular conditions throughout your subjective refraction routine.
Negates need for binocular balancing at end

Question 33

What type of patients is binocular refraction useful for?

Answer 33

younger patients and latent hyperopes

Question 34

When fogging in binocular refraction, do you occlude the other eye?

Answer 34

No, you fog other eye by +0.75DS/+1.00DS rather than occluding, then you perform normal monocular refraction routine on other eye

Question 35

True or False: When doing ‘binocular’ refraction techniques, you must first do retinoscopy?

Answer 35

True

Question 36

List errors in Rx (4)

Answer 36

• incorrect prescribing
• failure to adjust prescription
• ocular pathology
• communication