14,15 - Binocular balancing

Question 2

TIB method of isolating foveal lines?
- What is it?
- Limitations?

Answer 2

Turville Infinity Balance:
Place an occluding septum on the mirror in the clinic so that RE can’t see left side of chart and vice versa. That way one eye sees one side of chart and other eye sees other side of chart.

Limitations:
- Must be precise
- Patient should keep head still
- Doesn’t work in our labs

Question 3

Humphriss Fogging Method of isolating foveal lines?
- What is it?
- Limitations?

Answer 3

Blur one eye with +0.75 or +1.00DS. This will force their attention to the unfogged eye.

Limitation:
- Has to be fogged enough that they don’t use the fogged eye but not too fogged where they suppress it.

Question 4

Prism Dissociation Method of isolating foveal lines?
- What is it?
- Limitations?

Answer 4

Single line of letters (duochrome). Separate by giving 3-4 BUR and 3-4 BDL prisms. Patient will see lower target with RE and vice versa.

Limitations:
- Not true binocular state
- Requires equal prism
- Px can adapt to prism

Question 5

How can polarisation be used to isolate foveal lines?
- Limitations?

Answer 5

Polarising lens with polarised image on unpolarised background. DIfferent images sent to LE and RE.

Limitations:
- Only some charts available.
- Reduced contrast
- Strong ocular dominance may make one letter darker than the other (interpret as clearer)

Question 6

Describe the plus to first blur technique

Answer 6

After isolating foveal lines,
- Offer +0.25DS to focusing eye
- Better or same = add lens and continue
- Worse = offer –ve now.
If using humphriss fogging, switch fog. Otherwise, redirect focus to other eye (other set of letters)

Question 7

Humphriss immediate contrast

Answer 7

After isolating foveal lines,
Offer +0.25DS then briefly offer –0.25DS and ask for which is clearer.

Question 8

Equal clarity under blur
- Limitations

Answer 8

Requires simultaneous image (not fog).
- Fog one eye with +1.00DS
- Adjust other eye with +0.25DS steps until both images are clear. Achieve reversal.
- Repeat other eye.
- Balance will be the difference between the two eyes.

Limitation:
- Good eye can become as bad as bad eye.

Question 9

How to do duochrome during binocular balancing?

Answer 9

Requires two simulatenous images (can’t fog)
Assume we used prism dissociation,
- Dim lights
- Introduce 4 diamonds on red green background
- Place prism
- Confirm they can see 4 sets of red green targets (RE should see lower image if BU is used)
- Tell patient to look at lower image and ask if red or green targets look clearer
- If red, add –0.25DS and if green, add +0.25DS. Repeat until equality then reversal (if no equality, aim for red clearer).
- Redirect attention to upper image and repeat.