Prism Therapy

Prism therapy

Optically, the prism bends light rays towards the base causing an apparent shift of the image towards the apex from the viewpoint of the observer. This provides a mismatch between the information received via the visual pathways and the information from the vestibular and proprioceptive pathways.5 Prism causes an object to appear at a different location in respect to its actual placement. The patient must attend to these sensory inputs simultaneously and make adjustments to perform the therapy tasks.

Prism is the ideal therapy tool. The goal of vision therapy is to engage the attention of the patient, provide feedback, and stimulate brain-based changes. The prism can do all of these.1 Getzell has espoused how prism in the therapy room can be used to create total “eye-mind-body” changes and improved perception of depth and space Prism produces changes in orientation with corresponding shifts in both eye movement and pelvic positions.3,4 They are a valuable tool in breaking down patterns that have developed over time that enable the patient to cope with their visual condition. This is especially true of higher powered prism . Optically, the prism bends light rays towards the base causing an apparent shift of the image towards the apex from the viewpoint of the observer. This provides a mismatch between the information received via the visual pathways and the information from the vestibular and proprioceptive pathways.5 Prism causes an object to appear at a different location in respect to its actual placement. The patient must attend to these sensory inputs simultaneously and make adjustments to perform the therapy tasks. For many patients, simply the novelty of the shifted image is enough to engage them in the tasks. For others, guidance from the optometrist and/or therapist is necessary to bring the changes induced to a conscious level. In both cases, the prism provides an ideal neurological stimulant to change the visual processing pathways of the brain. One of the more obvious advantages of using prism in the therapy room is the ability to perform activities in free space. Though there are many new “high-tech” instruments available, some restrict movement, periphery, or both. The use of prism glasses allows therapy to be performed while the patient is on their feet and moving. Bringing movement into play allows the patient to receive tactile, proprioceptive, and vestibular information. This adds a tremendous amount of information in addition to the visual stimuli. It results in a greater number of problems to solve and the need for the patient to develop flexibility and be cognitively involved in the learning situation created by the clinician. Since we live in an open, three-dimensional space world, this mode of therapy has tremendous carry-over to the real world. Conversely, the use of prism glasses allows the optometrist to observe the movements of the patient’s eyes during the procedures.

Besides the directional optical shift, prism provides many other changes unavailable in other optical and non-optical therapy instruments. The base of the prism has a net plus lens effect, with images being shifted further out in space from the observer. The apex of the prism does the opposite. It has a net minus power effect, with images being moved closer to the observer. As a result, there is a z-axis slant that is induced, resulting in even more visual-perceptual mismatches than a simple directional x-y axis shift. In addition, straight lines are curved in the direction of the prism’s base.6,7 These spatial warps provide even more stimulation of the neurology of the visual system. This requires greater attention from the patient and for them to attend to the total volume of space while performing the visual-motor tasks at hand.1 The subtle spatial shifts provide an opportunity to teach the patient to appreciate just noticeable differences (JNDs) in size, position, and orientation. The use of the prism in a free space setting allows asking open-ended questions to trigger greater and greater exploration of the visual environment. It has been said that the ideal vision therapy procedure stimulates convergence, accommodation, eye movements, and peripheral awareness

Prism Therapy Procedures

The following are three in-office procedures that are among the universal procedures that almost all of our patients experience. I hope that you will try them in your office and look for other ways to integrate the use of lenses and prism into your vision therapy programs. Materials Needed: The prisms referred to here are incorporated into six pairs of glasses. Two pairs are vertical dissociating prism: one with 5∆ base up in the right eye, and 5∆ base down in the left eye, the second dissociating prism glasses have the prism base down in the right and base up in the left. The other four pairs of glasses are yoked prism oriented as base up, down, left, and right. Though I prefer using 10∆, it is equally acceptable to use 8∆, 12∆, or 15∆. For variety, I also alternately use plano and curved prism. There are differences in the optical characteristics with the curved lenses having induced cylinder that is not present in the flat front lenses.4 The following are three of the many prism activities that take place in our therapy sessions. These are not performed only once in the therapy sequence as we return to them many times over. As the patient becomes more aware of their visual space world, they will be able to verb

Materials Needed The prisms referred to here are incorporated into six pairs of glasses. Two pairs are vertical dissociating prism: one with 5∆ base up in the right eye, and 5∆ base down in the left eye, the second dissociating prism glasses have the prism base down in the right and base up in the left. The other four pairs of glasses are yoked prism oriented as base up, down, left, and right. Though I prefer using 10∆, it is equally acceptable to use 8∆, 12∆, or 15∆. For variety, I also alternately use plano and curved prism. There are differences in the optical characteristics with the curved lenses having induced cylinder that is not present in the flat front lenses.4 The following are three of the many prism activities that take place in our therapy sessions. These are not performed only once in the therapy sequence as we return to them many times over. As the patient becomes more aware of their visual space world, they will be able to verb