The orientation of the prisms over the eyes affects how space is perceived. Prisms can be
positioned in a variety of ways. They can be yoked meaning both prisms are oriented
with the base in the same direction. In other words base left refers to prisms whose base is
oriented to the persons left side. The left eye prism base orients laterally while the right eye
prism base orients temporally, thus both prism bases orient toward the persons left side.
Prisms can be yoked in a variety of ways such as base left, base right, base up, or base
down. Prisms refract or bend light thus changing the line of sight of the eyes and can result in the
eyes moving into a more correct alignment to enable binocular vision. They can change
postural tone by influencing head/neck and body alignment in relation to the vertical and
horizontal planes of space. Yoked prisms are used to influence postural tone, postural
reactions, and balance. By changing the perception of midline they facilitate the person
shifting their weight, thus increasing proprioceptive input from the base of support through
the entire body side. The head/neck and body realign and reinforced the visual, vestibular,
and somatic reorganization of midline.
