WEEK 4: Binocular Balance and JCC

Question 1

What is the purpose of Binocular Balance (BB)?

Answer 1

1. Find the best BINOCULAR visual acuity
   - Reflects ‘normal’ vision i.e. binocular
   - Best binocular VA/vision may not require full monocular subjective Rxs
   - Occlusion may stimulate accommodation, may not have achieved actual MPMVA
   
   2. Equalise Accommodative demand
      
      • Activation/stimulation of accommodation in RE & LE are equal
        Balance vision at distance, to ensure equal accommodative demand/stimulation for each eye for binocular (near) vision

Question 2

What are the 4 types of BB methods?

Answer 2

Septum methods
Simultaneous Comparison Methods
Successive Comparison
Minimally invasive (Monocular Fogging Balance)

Question 3

skip

Answer 3

skip

Question 4

Prism Duo Chrome

Answer 4

1) Fog both eyes by +0.75DS
2) Present the duochrome chart
3) Using the Risley prisms, 3-4∆ BU is placed in front of the RE
and 3-4∆ BD is placed in front of the LE
4) Ask the px if they can see two of the duochrome, one up and
the other down? If doubling is not experienced, increase the
amount of vertical prism until double
5) Ask the px to look at the bottom chart only. “Ask which side
of the chart are the letters/figures clearer, red or green?”
6) Add lenses to the RE in accordance with the px’sresponse
until most positive equal or leave on red if reversal only
7) Once endpoint has been reached for RE, direct px to now
only look at the top duochrome chart
8) Add lenses to the LE in accordance with the px’sresponse
until most positive equal or leave on red if reversal only
9) Remove Risley prisms
10) Perform Binocular Addition

Question 5

Name the tests For Successive comparision methods and describe them

Answer 5

Alternative Occlusion

• Successive comparison techniques asks the px to compare the vision of a single target when two presentations are given consecutively
• Subjective refraction makes constant use of successive comparison techniques e.g. plus/minus or JCC
  The alternating occlusion method of binocular balance is a successive comparison technique that asks the px to compare the vision in the RE vs the LE, whilst both are under fog

Question 6

Modified Humphriss

Answer 6

Modified Humphriss

Fog one eye first with +1.00 or +0.75

1) On the unfogged eye, use the plus/minus technique
to find the MPMVA
oIf ≥ +0.50DS is required, this should also be
added to the fogged eye to maintain the fog
2) Procedure is repeated, swapping the fog to the other eye
3) Binocular Addition

Question 7

READ PRiSM DISSOCIATED DUOCHROME METHODS

Answer 7

READ PRiSM DISSOCIATED DUOCHROME METHODS

Question 8

READ ALTERNATING OCCLUSION

Answer 8

READ ALTERNATING OCCLUSION

Question 9

What are the common principles of dissociated techniques

Answer 9

1. Fog must be utilised
   
   2. The eyes are compared to each
      a. Except for duochrome
   3. Plus is added to the ‘clearer’ eye until equal blur is achieved
      If there is no equal, give clarity preference to the dominant eye OR allow the patient to express a preference based on comfort.

Question 10

READ HUMPHRISS IMMEDIATE CONTRAST METHOD

Answer 10

READ HUMPHRISS IMMEDIATE CONTRAST METHOD

Question 11

READ MODIFIED HUMPHRISS

Answer 11

READ MODIFIED HUMPHRISS

Question 12

READ CYL REFINEMENT FOR JCC

Answer 12

READ CYL REFINEMENT FOR JCC

Question 13

Why do you need to add +0.25DS when we increase the cyl by -0.50DC

Answer 13

• The COLC must be kept on the retina at all times when using the JCC i.e. mean spherical equivalent must remain the same at all times
  
  • For this to be achieved, for every 0.50 change to cyl, you must compensate with a 0.25 change to sphere.
  • EG. If you increase the cyl (add minus power)by 0.50 you must increase the PLUS power of the sphere by 0.25 (to balance)
    Likewise, if you decrease the cyl (which effectively adds plus power) by 0.50 you must decrease the plus power of the sphere (to balance