This document describes three methods for binocular balancing: alternate occlusion, prism dissociated blur balance, and duochrome or bichrome balance. Alternate occlusion involves occluding each eye alternately and adding plus lenses until the patient reports equal clarity between the two eyes. Prism dissociated blur balance uses prisms to displace the images seen by each eye while plus lenses are added until equal blur is reported. Duochrome or bichrome balance uses a red-green chart split between the eyes and plus lenses are added until the same red-green endpoint is reported for both eyes.

1. BINOCULAR BALANCING
Methods
Alternate Occlusion
Prism Dissociated Blur Balance
Duochrome or Bichrome (Prism Dissociated Red-Green) Balance

2. ALTERNATE OCCLUSION
Procedure:
– ADD plus lenses binocularly till Px barely sees 20 /50 line(6/18) over the Rx you just
achieved from the monocular subjective refraction
– examiner performs slow alternate occlusion
– Px compares of letters between 2 eyes
– “I know this is blurry, I want you to tell me which image is clearer, or are they both
equally blurred.”
END POINT
– end point is equal acuity b/w 2 eyes
– If one eye clearer than
– Plus lenses added in + 0.25DS steps before clearer eye to equalize the blur
–
PRISM DISSOCIATED BLUR BALANCE
Procedure
– The two eyes will be dissociated by using the prisms in the technique
– Same amount of fog as last technique +1.00

3. – Same isolated line used 20/50
– Keep the prisms of 3 or 4 Δ BD in OD and 3 or 4 Δ BU in OS
– Equal and opposite
– BD prism will cause image to be higher (top)
– The image will be displaced towards the apex (point) of the prism Δ
– BU prism will cause image to be lower (bottom)
– BD for OD and BU for OS, therefore;
– EGNU5 seen by OD
– EGNU5 seen by OS
Patient instructions: “I know these images are blurred, I want you to take a few seconds and
look at the image on the top, and then take a few seconds and look at the image on the
bottom, tell me is one image clearer or are they equally blurred?”
– If the patient reports the top image clearer, add +0.25DS to the OD and repeat the
question
– If the patient reports the lower image clearer add +0.25DS to the OS and repeat the
question
– Now Px report both eyes see blur it means we balance the accommodation with
+0.25DS
– At the end remove prism and fog lenses that are use for the balancing and correct the
lenses

4. Duochrome or Bichrome (Prism Dissociated Red-
Green) Balance
• Bichrome test or Duochrome test
- Based on eye’s natural chromatic aberration
- Uses distance VA chart with black letters, splitted equally into two halves
- Letters on one half on red background
- Letters on other half on green background
- Similar to dissociated blur balance except fogging lenses are not added
- Instead of seeing two blurred charts, patient will see two relatively clear charts, with
each chart half red and half green
- Method of choice when maximum acuities for two eyes differ by several letters
-

5. -
Procedure
• Patient views the full size split R-G chart with 6/6 letters on the bottom
• Occlude both eyes and dissociate the chart using 3 ∆ BD in RE and 3 ∆ BU in LE
• The patient must be capable of perceiving diplopia
• Attention first on upper chart (seen by right eye )
• Asked to report which those on red or green side ; appear sharper , blacker or more
distinct
• Sufficient plus power is placed in RE till letters on red side are clearer
• Reduce plus power in 0.25 DS steps until both sides are equally clear (equality) OR
Green side first is clear (first green)
• Repeat the process for lower chart (left eye)

6. • The balance is complete when the patient reports the same red-green end point for
each eye (i.e. if the criterion used for lower chart is appearance of first green, same
criterion should be used for upper chart)
• It is not necessary for the upper and lower charts to be equally clear as long as both
have the same end point