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Home » Colorado Vision Summit » 2022 Colorado Vision Summit Course: Prism, Prism, Prism!

2022 Colorado Vision Summit Course: Prism, Prism, Prism!

Flipper Friday Simonson

How Prisms are used in Patient Care:

  1. Compensatory – reduces work, moves the image to where the eye sees
  2. Therapeutic – increases work, moves the image to where we want the eyes to look

Therapeutic prism is used to challenge and build the visual system. The goal of these exercises is to use prism in order to improve sensory perception and oculomotor control.


  • Vision Therapy utilizing Prism:
    1. Monocular Prism
    2. Dissociating Prism (Bi-ocular training)
    3. Binocular Prism
    4. Yoked Prism
  • Definition of a prism: A transparent solid with sides that converge at an angle
    1. Prisms cause a deflection of a ray of light toward the thickest portion (the base) - this causes the image to appear toward the apex.
    2. Prism splitswhite light into its component colors
    3. A prism alters the apparent location of objects
    4. Develop functional understanding of a prism diopter:


  1. Prism Diopter: deviation of 1 cm at a distance of 1 meter
  2. Demonstration of prism optics
  • Demonstration of prism optics: Clinical: concomitancy Testing
  1. Demonstration of prism optics: Determining prism diopter power of unknown prism
  • Vision Training Techniques: Learn about therapy techniques that utilize prisms
    1. Stimulate eye movement toward apex of prism
    2. Stimulate convergence
    3. Stimulate divergence
    4. Decrease suppression
    5. Reorganize spatial perception: There are three dimensional perceptual shifts; the base expands space and the apex constricts space.
      1. May see BO prism cause images to appear SMALLER and CLOSER
      2. May see BI prism cause images to appear LARGER and FURTHER
  • Monocular Prism Therapy:
    1. Saccadic Accuracy in direction and amplitude (oculomotor)
    2. Just Noticeable Differences (sensory localization: direction and amplitude)
    3. Understanding spatial perception changes caused by viewing through prism
      1. Spatial Awareness: Robert Nurisio, COVT: The patient should have some awareness of the prism “moving the world” in the direction of the prism apex, as the light is bent towards the base of the prism.


  • Yoked Prism Therapy
  • Dissociating Prism Therapy:
    1. Bi-ocular Training using BU/BD prism or enough BI prism to create diplopia
    2. Motor Alignment
      1. Howell Phoria Card
      2. Voluntary Vergences
  • Prism Eye Rotations
  1. Accommodation and Vergence Relationships (the AC/A)
  1. Valenti Cross-Cylinder: adding cross cylinder lenses to engage both the accommodative and vergence systems
  2. G-560: adding plus and minus lenses to learn accommodative and vergence control and accuracy
  1. Adding tactile, auditory, and visually-guided motor activities to vision training
    1. Squinchel
    2. R-K Diplopia
  • Binocular Vision Therapy
    1. Prism Flipper
    2. Prism Rotations
    3. Loose prism and Prism Bar training
    4. Risley Prism use with stereoscopes
    5. BIM/BOP = Base-In with Minus/Base-Out with PlusRecommended Reading:
    1. Applied Concepts in Vision Therapy by Dr. Leonard Press (Editor) OEPF
    2. 2. The Vision Therapist’s Toolkit by Thomas Headline, Irene Wahlmeier and Vicki Bedes 3. Tools of Behavioral Vision Care: Prisms (Vision Therapist Vol 37, #4, 95/96)4. The Rationale for the Use of Prism in the Vision Therapy Roomby Dr. Rob Fox
    4. VT and Prism by Robert Nurisio, COVT
    5. Relieving Prism by Dr. Kelly Frantz

    Therapy Techniques using Prism

    1. MONOCULAR: Understand the purpose and techniques of monocular prism training
    2. Patch and Monocular Prism
      1. Monocular Saccades I
      2. Monocular Saccades II
    • Esotropia Manual: BI prism over esotropic eye
      • to change posture – stretch medial rectus, activate lateral rectus
      • sensory stimulation – stimulate light to fall on temporal retina of esotropic eye
    1. Demonstration and Practice session of Monocular Saccades activities
      1. BU/BD/BI/BO with 10 Δ
      2. BU/BD/BI/BO with 2 Δ
        • Direction
        • Amplitude
        • Accuracy
        • Field Expansion/Constriction
    • Therapeutic Yoked Prism: Reorganize spatial and oculomotor skills by using yoked prism during therapy activities
      1. Base-Left
      2. Base-Right
      3. Base-Down
      4. Base-Up
    1. BIOCULAR: Utilize bi-ocular vision training using dissociating prism
    2. Disassociating Prism– Using BU/BD or BI prism to create diplopia
    3. Howell Phoria Card
      1. Allows direct measurement of the distance and near phorias in real space. Any odd number (in yellow) shows esophoria while the even numbers (in blue) shows exophoria. An AC/A can quickly be determined with trial lenses.
      2. Voluntary vergences
        • Purpose: To develop the ability to voluntarily align the eyes in free space at all distances
          • Awareness of vision perception from each eye, anti-suppression
          • Biofeedback on eye position, motor alignment accuracy and stability
        • Near: Bi-Ocular Popsicle Sticks
          • Distance: Materials: Marsden ball, vertical prism glasses (6PD base up/6PD base down)
          • Demonstration and Practice Session of Voluntary Vergences at Distance and Near
    4. Valenti Crossed Cylinder Rock Technique
    5. Split Prism Ring Game
    6. G-560 Biocular activity
      • Demonstration and Practice Session of G-560
      • +2.00/-2.00, +2.00/-4.00
        • Size
        • Clarity
        • Distance
        • Alignment
        • Conscious Control
    1. Squinchel and R-K Diplopia
      • Group practice session
        • Tactile Match
        • Auditory Match
        • Visual-Motor Accuracy: Golf Tee and Loop
    1. Biocular Pursuits
    1. BINOCULAR: Understand how to build fusional vergence by using binocular prism techniques


    1. Prism Flipper Reading
      1. Base-Out
        • Binocular base out prisms stimulate vergence to keep the target single: Convergence
        • Must relax accommodation to keep accommodation at the plane of the target to achieve clear and single vision.
      2. Base-In
        • Binocular base in prisms relax vergence to keep the target single: Divergence
        • Must stimulate accommodation to keep accommodation at the plane of the target to achieve clear and single vision.
        1. Options:
          • One side BI/other BO
          • Both sides BI, but different powers
          • Both sides BO, but different powers
        2. Prism Recoveriesor Prism Rock
          1. Lollipop prism
          2. Loose prism (trial lens)
    1. Prism Rotations
      1. Horizontal and Vertical fusion ranges
    2. Prism Bar Training
      1. Demonstration and Group Practice with Marsden Ball
        • Building fusion – Left-Right gaze
        • Building fusion – Near-Far
        • Building fusion ranges – Orbit – all gazes and distances
      2. Prism Walk-Aways
      3. Prism with Stereoscope
        1. Add prism to other procedures to increase vergence skill

    In therapy we may need to start with compensatory lenses to encourage a fusion lock and then reduce power until not needed. Can do training OVER compensatory prism with the goal of reducing amount of compensatory prism in prescription