Transcript A Framework for Teaching the Use of Prisms

Framework for Teaching
the Use of Prisms
Low Vision Therapist and
O&M Specialist
Collaborate
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AER Cleveland, 2011 S. Barnard &
M. Beck
Training
• The Framework for Teaching the use of Prisms
is a Worksheet for checking and tracking the
introduction of skills needed for successful use
of Prism glasses.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Following the Framework Facilitates:
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Training in-office to functional settings
Collaboration between the LVT and COMS
Analyzing Post-training issues
Patient understanding through a hierarchy of
tasks
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AER Cleveland, 2011 S. Barnard &
M. Beck
Basic Training Components
• Traditional training components used in a
hierarchy
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AER Cleveland, 2011 S. Barnard &
M. Beck
Basic visual motor skills:
• Scanning: use of head and eye movements to
search for targets
• Tracing: follow stationary line
• Tracking: visually following a moving target
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Source: Geruschat, D. & Smith, A.J., (1999) Low vision and mobility In Blasch, B., Wiener, R., &
Welsh, R.L. (Eds.) Foundations of orientation and mobility, second edition (60-103) New York:
AFB.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Instructional program and
hierarchy for use of the prism
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Patient is stable; object is stable
Patient is stable; object is moving
Patient is moving; object is stable
Patient is moving; object(s) is/are moving
Source: Brilliant, R. (1999) Essentials of Low Vision. Boston: Butterworth Heinemann
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AER Cleveland, 2011 S. Barnard &
M. Beck
Why Do We Need Such A Long
Checklist?
Teaching New Behavior: Traditional Scanning
Techniques
Optical Device Training: Prism Therapy –
Adapting to Image Displacement
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AER Cleveland, 2011 S. Barnard &
M. Beck
Why Do We Need Such A Long
Checklist?
Patient Awareness of field loss
Assess Current Scanning Behavior
Head Movements
Eye Movements
Prism Education
Prism Adaptation
Safe Travel
Follow up
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AER Cleveland, 2011 S. Barnard &
M. Beck
Case Discussions
• Mr. A: Right Heminanopic Field Loss (HFL):
Occluding one eye which he believed was
blind
• Mr. C: Bilateral inferior field loss: None
• Mr. E: Left HFL: Avoids walking in congested
environments
• Mr. B: Incomplete right HFL: Repeatedly being
hit on the right side of his head by doors.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Complications
• Cognitive – Understanding & Retention
• Motivational – Learning new behavior and
time commitment
• Psychosocial Issues – Housing & Emotional
• Medical Conditions – HBP, Orthopedic issues,
etc.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Ophthalmic Prisms
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AER Cleveland, 2011 S. Barnard &
M. Beck
Ophthalmic Prisms
• This presentation discusses the use of prisms
for people with a hemianopic field loss for
which we use Full Field Prism Glasses.
• Relocates or shifts an image into an area of
residual vision
• The amount of prism is a measurement
describing the degree of shift or relocation of
an image.
• The higher the amount of prism, the more the
image is shifted.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Full Field Prism
With a hemianopic field loss, a full field prism
will have the base out towards the defect.
A person with a right hemianopsia will have
prism glasses with both bases right.
A person with a left hemianopsia will have both
bases left.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Base towards defect
This would be true of
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Full Field Prisms
Fresnel Prisms
Hemi Prism
Peli Prism
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AER Cleveland, 2011 S. Barnard &
M. Beck
Full Field versus Hemi Prism
The training of a full field prism differs slightly
from a hemi prism.
Full Field Prism
• Emphasis on adaptation through Reaching
Tasks.
Hemi Prism
• Emphasis on eye rotation and head turn
towards object.
7/17/2015
AER Cleveland, 2011 S. Barnard &
M. Beck
Reaching Tasks
• Emphasized with Full Field Prisms because the
person’s straight-ahead gaze is through a prism.
• The purpose is to educate and adapt to the shift
of the image (usually mid-line) of an object.
• The facilitator will hold objects in the peripheral
field and ask the person to point or grasp the
object until they perform the task with out error.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Eye Rotation and Head Turn
• With a Hemi Prism, the person’s straight-ahead
gaze is through a carrier lens without Prism.
• The Hemi Prism is accessed by an ocular turn into
the prism (placed in the area of the field loss)
creating an awareness that an object is there.
• Once the object is spotted, the person needs to
turn their head to view the image through the
carrier lens to get a clearer view of the image.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Benefits of Using Prisms
Our clinic has found that, with a number of
people, teaching of basic visual scanning skills
and instruction for using prism glasses,
decreased the reported number of critical
incidents.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Some Disadvantages
• Visual acuity is reduced when viewing
through a prism
• A Hemi prism creates a blind spot at the
edge of the prism. The higher the power of
the prism the larger the spot. It creates an
effect sometimes referred to as “jack-in-thebox” with the image suddenly appearing.
7/17/2015
AER Cleveland, 2011 S. Barnard &
M. Beck
Some Disadvantages
• There are reflections – some described
seeing colors –especially yellow
• There is a reduction in contrast
• And, finally the reason we created a
Framework: Lots of Patient Education and
Training.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Goals of Training
• Adapting to a hemianopic field loss using an
optical device that shifts images into the
residual field
• Measures of Success:
• Percentage of time they wear the device
• Correction of functional complaints (i.e. being
hit by doors, avoiding certain environments)
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AER Cleveland, 2011 S. Barnard &
M. Beck
Hemianopic Field Loss
• Patients don’t always understand the nature
and functional limitation of their vision loss.
• Mr. A. Reported occluding his right eye,
reporting that there is “no vision in this eye”
and the left eye is unaffected.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Static Training
• Correct any misconceptions the patient has
about his field loss.
• Design a visual pattern that can reinforce the
degree of field loss
• Introduce basic visual skills
• Introduce Prism Glasses
• Begin Adaptation exercises
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AER Cleveland, 2011 S. Barnard &
M. Beck
The Advanced Low Vision Clinic at the VA NY Harbor
Health Care System
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Static Visual Field Assessment –
1. Understanding the Field Loss
Pt. understanding of Field loss:
Diagrams, simulators
Near tasks using deck of cards
Occlusion – Evidence that both eyes have some vision
Designing a pattern of visual targets to practice head turns
and eye turns- Evidence that the patient is missing some
information
e. Discuss measuring the head turn in relationship to a shoulder
f. Record observations for COMS
7/17/2015
AER Cleveland, 2011 S. Barnard &
M. Beck
The Advanced Low Vision Clinic at the VA NY
Harbor Health Care System
2. Describe and Record head movements:
a. Observation of head movements: no movement
slow movements quick movements
b. Pointing to objects in the outer most field
(highest, lowest, left, right)
c. Estimate of degree of head turn to find “missing
objects”
d. Describe head turn in relationship of head to
shoulder
7/17/2015
AER Cleveland, 2011 S. Barnard &
M. Beck
The Advanced Low Vision Clinic at the VA NY
Harbor Health Care System
Describe visual scanning pattern used – Looking for
signs and numbers (Circle appropriate description):
• Static head posture: downward upward left right
• Scanning: None
occasionally
• Pattern: Random
Systematically
• Time: quickly
timely
slowly
AER Cleveland, 2011 S. Barnard &
M. Beck
frequently
Introduce prism glasses to patient:
Reaching Tasks
Observing Displacement
Assess Adaptation
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AER Cleveland, 2011 S. Barnard &
M. Beck
What Is Adaptation?
• They demonstrate this by accurately pointing,
reaching and touching stationary then moving
objects.
• We consider adaptation occurring when the
patient consistently demonstrates accurate
object dislocation while wearing prisms.
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AER Cleveland, 2011 S. Barnard &
M. Beck
Dynamic Training
• Begin in a quiet location, such as a hallway
• Locate targets placed in the patient’s field
deficit; they must move their head to locate the
object
• Progress to more complex environments
• Reinforce compensatory scanning strategies
• Patient GOAL: turn head into the field loss
• Scanning may reduce the blind area formed
from the placement of the prism
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AER Cleveland, 2011 S. Barnard &
M. Beck
Dynamic Training continues…
• Moving displacement and relocation;
identifying by scanning
• It is like using the side mirror on a vehicle
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AER Cleveland, 2011 S. Barnard &
M. Beck
Long cane
• The long cane can be used to enhance visual
efficiency.
• The COMS teaches goal-specific visual
scanning behaviors (gridline, perimeter, etc.).
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AER Cleveland, 2011 S. Barnard &
M. Beck
Case Discussions
7/17/2015
AER Cleveland, 2011 S. Barnard &
M. Beck
Framework for Teaching
the Use of Prisms
Questions?
7/17/2015
AER Cleveland, 2011 S. Barnard &
M. Beck
Sources
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Blasch, B., Weiner, W., & Welsh, R. (Eds.). Foundations of Orientation and Mobility, 2nd edition. New York:
AFB Press, 1997.
Brilliant, R. (1999). Essentials of low vision. Boston: Butterworth Heinemann.
Cicerone, K. D., Dahlberg, C., Kalmer, K., Langenbahn, D. M., Malec, J. F., Bergquist, T. F. et al. (2000).
Evidence-based cognitive rehabilitation: recommendations for clinical practice. Archives of Physical
Medicine Rehabilitation, 81, 1596-1615.
Houston, K., Eldred, K., & Mennem, T. (2010). EnVision Conference Proceedings, Sept. 22, 2010, Workshop
on prism adaptation therapy for left hemispatial neglect after stroke or brain injury. San Antonio, TX.
O’Neill, E.C. , Connell, P., O’Connor, J. C., Brady, J., Reid, I. & Logan, P. (2011). Prism therapy and visual
rehabilitation in homonymous visual field loss. Optometry and Vision Science. 88, 263-268.
Perez, A. & Jose, R. T. (2003). The use of Fresnel and ophthalmic prisms with person with hemianopic
visual field loss. Journal of Visual Impairment and Blindness, 97, 173-176.
Chadwick Optical (2011). How Prisms Work. Retrieved May 2011 from
www.hemianopia.org/index_files/Howprismswork.htm
7/17/2015
AER Cleveland, 2011 S. Barnard &
M. Beck
7/17/2015
AER Cleveland, 2011 S. Barnard &
M. Beck