Binocular Balancing

• What is the initial sphere adjustment used to assess monocular end point?

  +/- 0.25 sphere
• What principle should be followed when determining the best vision for a patient?

  Maximum plus power (or least minus) consistent with best vision
• What should a patient do when one eye is occluded during the vision test?

  View the smallest line of letters on the chart
• What question should be asked after adding +0.25DS to the other eye?

  Is it clearer, just the same, or actually worse with this lens?
• What should be done if the patient responds that the vision is clearer or just the same after adding +0.25DS?

  Add +0.25DS to monocular correction
• When should -0.25DS be tried during the assessment?

  When the response is "actually worse" with +0.25DS
• What question should be asked after adding -0.25DS to monocular correction?

  Is it clearer or just smaller and darker with this lens?
• What should be done if the patient reports that the letters are "just smaller and darker" after adding -0.25DS?

  Do not add -0.25DS; you have reached the spherical end point of monocular correction
• What should be observed about the patient during the assessment?

  If struggling, the lens probably makes visual acuity worse
• What should be communicated to the patient regarding their views?

  It is OK for both views to look the same
• What should be done if the patient is hesitant during the assessment?

  Show them again without hesitation
• What should be encouraged when determining astigmatic correction?

  Encourage the patient to select the best view
• What should be done if visual acuity (VA) is ≤ 6/9?

  Use a pinhole test
• What does improvement in pinhole visual acuity (PH VA) suggest?

  Most likely uncorrected refractive error
• What does no improvement in pinhole visual acuity (NIPH) indicate?

  Refraction is correct, possibly amblyopia or pathology
• Why might some patients seem uncertain about which lens gives the clearest vision?

  The depth of focus can add uncertainty to a finite end point
• How does pupil size affect depth of focus?

  Depth of focus varies with pupil size; it is larger for smaller pupils
• What is the purpose of the Red/Green Duochrome test chart?

  To utilize chromatic aberration of the eye to help determine monocular end point of refraction
• What should be done if the patient reports letters on the red side are more distinct?

  Add -0.25DS to equalize
• What should be checked if the patient reports equal distinctness on both sides of the duochrome test?

  Check that +0.25DS makes red clearer and -0.25DS makes green clearer
• What should be done if the patient reports letters on the green side are more distinct?

  Add +0.25DS to equalize
• What are the instructions for the Red/Green Duochrome test?

  • Reduce room illumination
  • One eye occluded
  • Ask if letters or circles are clearer on the red side, green side, or appear the same
• What should be ensured after changing the power during the assessment?

  Ensure that visual acuity has improved
• What should be noted if visual acuity changes by more than 0.50?

  Be cautious, especially in elderly, hyperopes, and pseudomyopes
• What is the purpose of the +1.00D blur check at the end of monocular refraction?

  To check that the eye blurs back to between ~6/12 - 6/15
• How much should +0.25D blur vision by one line?

  +0.25D will blur vision by one line
• What should be the expected outcome of a +1.00D lens in terms of visual acuity?

  It should blur the patient back approximately 4 lines
• What are the principles of binocular balancing?

  • Balance or equalize the accommodation of the two eyes, not the visual acuity
  • Aims to provide comfortable and clear binocular vision
• What is the theoretical basis of binocular balancing techniques?

  Ocular accommodation is a consensual reflex
• What can hinder binocular balancing?

  Functional binocular vision issues like strabismus or amblyopia
• What should be done when there is no active accommodation in elderly patients?

  Attempt to get the same response from both eyes using monocular endpoint refinement techniques
• What are the five basic techniques of binocular balancing?

  1. Successive alternate occlusion
  2. Vertical prism dissociation
  3. Blurring or fogging techniques
  4. Septum techniques
  5. Polaroid techniques
• What is the purpose of successive alternate occlusion?

  To compare vision between two eyes by flipping an occluder
• What should be done during vertical prism dissociation?

  Use equal power vertical prisms to vertically dissociate the images from the two eyes
• What should the patient report during vertical prism dissociation?

  If the letters are more distinct or easier to read on the upper or lower chart
• What should be done if the letters are not equally distinct during vertical prism dissociation?

  Add +0.25DS to the eye with clearer vision and repeat the test
• What is the purpose of the Humphriss fogging technique?

  • To equalize or balance accommodation
  • Fully relaxes accommodation
  • Simple and quick for patient and practitioner
• What should be done after completing monocular refraction in the Humphriss fogging technique?

  Fog one eye to suspend foveal vision
• What should be the level of fog achieved in the Humphriss fogging technique?

  Fog the other eye to 6/9 or 6/12, usually 2 to 3 lines
• What should be done if +0.25D makes the vision worse?

  Place -0.25D in front of the unfogged eye and ask about clarity