Understanding BIM/BOP Understanding BIM/BOP & Degrees of Freedom Understanding BIM/BOP Degrees of Freedom

Understanding BIM/BOP & Degrees of Freedom Degrees of freedom refers to the amount of separation available between vergence (aiming) and accommodation(focusing) within the visual system. 

Understanding BIM/BOP & Degrees of Freedom Normal Viewing This diagram illustrates vision in a “normal” state of rest. If we were having our patient perform Vectograms, this illustration shows where their vision would be when we are on the zero setting. As you can see, vergence (illustrated by the orange star), and accommodation (illustrated by the green star) are both settled on or near the plane of regard (a.k.a. “the target”) as we achieve clear and single vision.

Understanding BIM/BOP & Degrees of Freedom Base In Viewing This illustrates vision under Base In, or divergent, conditions.   As you can see, vergence (illustrated by the orange star) is behind the plane of regard (POR), and accommodation (illustrated by the green star) has settled on or near the POR to achieve clear and single vision.  The dotted line illustrates the current degrees of freedom, or separation between the two systems. As the demand is increased (we move the Vectogram further into the alphabet) the point of divergence would get further from the POR.  In order to maintain a clear and single image, the patient must hold accommodation on the POR.  Patients who struggle in this situation may either report single and blurry because divergence is appropriate, but accommodation cannot relax back to the POR – or double and clear, which would indicate accommodation is appropriate, but vergence cannot properly align.

Understanding BIM/BOP & Degrees of Freedom Minus Lenses To challenge the patient and build Degrees of Freedom we use: Causes image to appear smaller and closer which means that the patient would need to focus more.

Understanding BIM/BOP & Degrees of Freedom Minus Lenses Introduced – Eyes converge and target doubles as accommodation is stimulated by the minus lens

Understanding BIM/BOP & Degrees of Freedom Minus Lens Resolved- The patient must relax vergence in order to obtain a single target The patient must accommodate (focus) more while maintaining relaxed vergence. If the minus lens is resolved while vergence behind the target is maintained then the target will appear clear and single.

Understanding BIM/BOP & Degrees of Freedom Base Out- Eyes aim in front of the target but accommodation must happen at plane of regard.

Understanding BIM/BOP & Degrees of Freedom Plus Lenses Causes image to appear larger and further away which means that the patient would need to focus less.

Understanding BIM/BOP & Degrees of Freedom Plus Lenses Introduced – Eyes continue to aim in front of target, accommodation is moved further away.

Understanding BIM/BOP & Degrees of Freedom The patient must relax their focusing while maintaining convergence (eyes turning in). If the plus lens is resolved while vergence in front of the target is maintained then the target will appear clear and single.

Ways to use BIM/BOP in Therapy Understanding BIM/BOP & Degrees of Freedom Ways to use BIM/BOP in Therapy Vectograms with Plus/Minus Lenses SART/DART with Plus/Minus Lenses Fusion Cards with Plus/Minus Lenses