binocular balancing

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Binocular Balancing

Binocular BalancingSahira tayyab Bsvs 3rd year

Binocular balancing

The final important step of subjective refraction is to make certain that accomadation has been relaxed equally in the 2 eyes is known as binocular balancing.PURPOSE : To Equalize accommodation between the two eyesNot to equalize the best corrected visual acuity between the two eyes:CANNOT BE PERFORMED WHEN:px suppresses one eyestrabismus existspx has only one eye

Why?Pre-presbyopic patients can accommodate during the distance monocular refractionPatients may actually accommodate different amounts in the left and right eyes

Methods for binocular balance technique: There are various methods that may be employed to perform binocular balancing of a prescription . These include:1 Successive Alternate Occlusion2Vertical Prism Dissociation3Blurring or fogging (Humphriss Immediate Contrast)4 Polarized or Vectographic5 Turville Infinity Balance (Septum technique)

1.Successive 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 refractionexaminer performs slow alternate occlusionPx 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 thanPlus lenses added in + 0.25DS steps before clearer eye to equalize the blur

2.Vertical Prism Dissociation:

Procedure:The two eyes will be dissociated by using the prisms in the techniqueSame amount of fog as last technique +1.00Same isolated line used 20/50Keep the prisms of 3 or 4 BD in OD and 3 or 4 BU in OS Equal and oppositeBD prism will cause image to be higher (top)The image will be displaced towards the apex (point) of the prism 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

Contd!!!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 questionIf the patient reports the lower image clearer add +0.25DS to the OS and repeat the questionNow 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

3.Fogging method / humphriss immediate contrast test:Procedure:Place +0.75DS/+1.00DS fogging lens before the LE Fogging verified lens should blur 3_4 lines on chart Present +0.25DS lens ( lens 1)over RE , replace with _0.25DS lens (lens2)and once again revert to +0.25DS (lens1)Px asked to compare lenses 1 2 and 1 Px must report which lens makes target clearer sharper and comfortable to look If px reports lens 2 better then add _0.25DS lens Present lenses 1 2 and 1 again END POINT:Px reports view through both lenses is the same ReversalOnce RE Rx balanced fog RE and perform procedure on LE

4.Polaroid Technique /(Vectographic)Polaroid Filters are used to partially dissociate the two eyes

FZBD FZBD

While wearing polaroid filters (P in phoropter knob), each eye sees a separate line and the rod in the middle serves as a fusion lock

Polaroid TechniqueFog by +1.00 OD and OSSame technique as the vertical prism dissociationMake appropriate adjustmentsMost natural binocular balance technique as diplopia and prism are not introduced

5.Septum Technique:Separate the visual fields with a septum in the refracting laneEach eye sees part of the lineFog by a +1.00 DSSame instruction set as vertical prism dissociation

Reference :American academy Zadnik InternetNotes