handout 1
Carl Garbus, O.D., F.A.A.O.
Neuro Vision Rehabilitation Institute
Valencia, CA
FUNCTIONAL VISUAL FIELD
ASSESSMENT AND MANAGEMENT
INTRODUCTION
Visual fields provide the most important information that we have to help us with functional vision (daily living skills)
The visual system uses parallel processing to combine information along specialized visual pathways
If working properly, the brain quickly tells us where an object is in space and what it is
INTRODUCTION
Course Objectives
Learn how to do a confrontation field
Understand the importance of visual fields
Have the awareness of different types off visual field tests
Learn about the application of prisms in field loss
DEFINITIONS OF VISUAL FIELD
That portion of space in which objects are simultaneously visible to the steadily fixating eye
Visual space that can used for activities of daily living
Awareness of the spatial world around us
NORMAL FIELD LIMITS
The normal visual field extends 40 to 60 degrees nasally to 65 to 100 degrees temporally
The normal visual field extends 30 to 60 degrees above horizontal midline and 50 to 75 degrees below horizontal midline
The actual extent of the field is related to the size of the test object and the testing distance
MEASURING VISUAL FIELDS
PERIMETRY
Kinetic perimetry- test target moves
Static perimetry- test target is stationary
Automated (computerized)
Manual
Test target is a point of light which could be white or a color
FIELD INSTRUMENTATION
Goldmann Visual Fields
Manual and automated
Great for detecting defects over larger areas
Stroke, retinal degeneration and tumors
Humphrey Visual Fields
Automated
Great for glaucoma detection and follow-up
Great for central field defects
FIELD INSTRUMENTATION
Tangent Screen
Manual
Great for monitoring attention
Campimeter
Manual
Used for mapping out functional fields
Amsler Grid (hand held)
Quick check on the macular area
CONFRONTATION FIELDS
Quick and easy to administer
Can be done with a fingers or wand
The examiner and patient sit across from each other eye to eye
Goal is to find matching fields with patient and examiner
Demonstration of two different confrontation fields
COMMON PROBLEMS
WITH FIELD LOSS
Frequently bumps into objects like door-frames
Difficulty moving crowded areas
Unsteady balance in walking
Problems finding objects on desks
AREAS OF FUNCTIONAL PERFORMANCE
MOST AFFECTED BY VISUAL FIELD DEFECT
Reading: omissions, line skipping, difficulty navigating a page
Activities of Daily Living: self care and mobility
Independent Activities of Daily Living: grocery shopping, driving
Balance and coordination
Judging distance and speed of objects
PRIMARY VISUAL PATHWAY
TYPES OF VISUAL FIELD DEFECTS
Altitudinal
Relates to a lesion in the parietal or temporal lobe
Bitemporal
Relates to a lesion near or at the optic chiasm
Homonymous
Most common defect from stroke and encompasses portions of one side of the field
Central Scotomas
Glaucoma and other retinal diseases
FUNCTIONAL VISUAL FIELD DEFECTS
In the Field of Syntonics Functional
Visual Fields are done with the campimeter
The field is mapped with four different test objects, white, blue, red and green
Each color will elicit a different size field
Largest is the white field, then blue, red and white
When colors overlap expect visual dysfunction
FUNCTIONAL VISUAL FIELD DEFECTS
When an individual is under stress or is fatigued the functional field usually constricts
Field constriction is a common sign of traumatic brain injury, autism, stroke and neurological disease
With proper therapeutic techniques it is possible to improve and open up a constricted visual field
The therapy program may use syntonic filters, as neuro vision rehabilitation
HOMONYMOUS HEMIANOPSIA
Homonymous Hemianopsia is a common visual field deficit present with many stroke and tumor patients
It is present in 30% of stroke patients
Hemianopsia is not black half to the vision
Missing vision is simply gone
Like the area behind us
SPONTANEOUS RECOVERY
254 patients with homonymous hemianopsia were evaluated with formal visual field
The longer period after the insult, the less likely the improvement will occur
Spontaneous seen in about 50% of patients with the first month
Most improvement within three months
After six months minimal improvement
HOMONYMOUS HEMIANOPSIA
CAUSES
Most common vascular lesions are in the posterior cerebral or middle cerebral arteries
Study showed causes:
Stroke 69.5%
Trauma 13.6%
Tumor 11.3%
Brain surgery 2.4%1.4%
Demyelination
GANGLION CELLS
• Midget ganglion cells (P-cells)
>70% cells that project to LGN
Origin of Parvocellular pathway
• Parasol ganglion cells (M-cells)
10% of all cells projecting to LGN
Origin of Magnocellular pathway
• Bi-stratified ganglion cells
Lateral Geniculate Nucleus
8% of all cells projecting to LGN
Blue/Yellow color signals
WHERE IS IT? WHAT IS IT?
Magnocellular pathway (aka where)
Ambient System
Transmits information about motion and spatial analysis, stereopsis, and low spatial frequency contrast sensitivity
Spatial vision
Parvocellular pathway (aka what) Focal
System
Relays color and fine discrimination information, shape perception, and high spatial frequency contrast sensitivity
Object vision
VISUAL PROCESSING SEMANTICS
PARALLEL PROCESSING
CENTRAL
Predominantly fovea, cones (r/b/g)
Predominantly Parvocellular
Sustained
Focal
What?
Cognitive
PERIPHERAL
Predominantly peripheral retina, rods
Only Magnocellular
Transient
Ambient
Where?
Visuomotor
VISUAL PROCESSING SEMANTICS
PARALLEL PROCESSING
PERIPHERAL CENTRAL
Conscious Pathway
Retino-calcarine Pathway
Predominantly ON -> LGN (4P/2M) ->
V1 (80%) ->
Ventral Stream—”What”? (4P) to IT
.......or ->
Responsible for object identification
Color, high spatial frequency, low temporal frequency, high contrast
Relatively slow system
Sub-cortical Pathway
Tectal Pathway
Predominantly ON -> SC -> parietaloccipital (20%)—only Magnocellular
Dorsal Stream—”Where?” (2M) to
PIP
Responsible for object localization
Low spatial frequency, high temporal frequency, low contrast, motion
Much faster / “reflexive” system
HOW TO ISOLATE EACH PATHWAY
•
Magnocellular (M) pathway (where?)
–
Motion discrimination
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–
–
–
–
Critical flicker fusion
Stereopsis
Contrast sensitivity (low contrast is sensitive to rapid movement and is monochromatic)
Frequency doubling technology (FDT) or motion automated perimetry
Visual evoked potential (VEP)
HOW TO ISOLATE EACH PATHWAY
•
Parvocellular (P) pathway (what?)
–
–
Visual acuity
Color discrimination (sensitive to red-green)
–
–
Contrast sensitivity (high spatial frequency)
Visual Evoked Potential
MAGNOCELLULAR PATHWAY
Plays an important role in visual motion processing, controlling vergence eye movements, and reading
Provides general spatial orientation
Contributes to balance, movement, coordination and posture
VISUAL SPATIAL INATTENTION
A deficit in attention to and awareness of one side of space
The patient’s eyesight is fine, but half his visual world no longer seems to matter
Most common is left sided neglect
Patient’s more prone to bumping into things on one side and won’t attend to things on one side
VISUAL SPATIAL INATTENTION
As you can see from the drawings, mental images are half too, its not related to how well the patient sees. It is a problem with consciousness.
The neglect results from damage to processing areas (on the opposite side of the brain)
Treatment: prisms with base in direction of neglect
i.e.. Left spatial inattention, use base left yoked prisms
MAGNOCELLUAR DEFICITS
•
Disorders that involve difficulty in learning to read
•
•
Causes problems with reading comprehension and poor reading fluency
Complaints that small letters tend to blur and move around when trying to read
MAGNOCELLUAR DEFICITS
•
•
Notoriously are clumsy and uncoordinated, and balance is poor
Magnocellular theory:
–
–
–
If patient has binocular instability and visual perception instability, then reading will be effected
Possible trouble processing fast incoming sensory information
Combination of visual, vestibular, auditory and motor functions
TREATMENT FOR CONSTRICTED VISUAL FIELDS
Neuro Vision Rehabilitation
Address peripheral system with lenses, prisms and binasals
Lenses (plus lenses help to stabilize the vestibular ocular systems)
Prisms (typically base in or yoked base down)
Binasals (eliminates binocular confusion)
LENS TREATMENTS FOR CONSTRICTED FIELDS
•
Filters
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Incorporate tints to spectacle correction
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–
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Green combined with blue helps with photosensitivity
Blue reduces ocular pain with eye movements
Yellow reduces blue light from passing through the lens and helps with computer and fluorescent lighting
THERAPY PROGRAM PRISMS
Prisms- what can they do?
Affect can change the spatial orientation of the patient
Can expand space or constrict space
Are used in therapy and/or a full time prescription in glasses
Need to be prescribed by a doctor
THERAPY PROGRAM SPECIAL PRISMS
Peli Prisms
Primarily to locate objects outside the patient’s visual field
Peli prism is placed on the lens of the temporal field defect
Upper and lower are 40 or 57 diopter press-on prisms
Expand upper and lower fields by about 22 degrees
PELI PRISMS
May fit upper first if there are adaptation problems
Never look through the prism
If object is seen peripherally on the field loss side, use head turn to locate object
Scanning is still needed
Reach and touch training
Practice walking and use of stairs
THERAPY PROGRAM SPECIAL PRISMS
Sector Prisms
Prism power is in the range of 15 to 20 diopters
Placed on the temporal aspect of the lens on the side of the field loss
Increased visual field awareness by 6-19 degrees
Success rate depends on training
THERAPY PROGRAM PRISMS
Yoked Prisms
Usually 3 to 8 diopters prism base to the side of the field loss
Ground in Prism
Patient can experience improvement in posture and gait when it is prescribed correctly
Visual field enhancement
THERAPY PROGRAM
MOVEMENT ACTIVITIES FIELD ENHANCEMENT
Bilateral Movements in Space
Motor Equivalents
Interactive Metronome
Extension and Rotation
Movement into the area of field loss
Weight shifting (seated, standing)
Balance
THERAPY PROGRAM
MOVEMENT ACTIVITIES FIELD ENHANCEMENT
Obstacle
Course
Scanning
Turning
Fixations
Eye Movements
Full Length Mirrors
THERAPY PROGRAM
VISUALIZATION-
FIELD ENHANCEMENT
Peripheral Visualization
Patient is to scan into the side of the field loss
Ask patient to remember as many objects to the side as possible
Looking straight ahead visualize those objects
Now have the patient point to the area where the object were seen
While the patient is still pointing have them turn their head, so they can view the missing field
NEURO OPTOMETRIC REHABILITATION CONFERENCE
24 th Annual Multi-disciplinary Conference
Renaissance Denver
May 14-17, 2015
Denver, CO
Website www.nora.cc
Email: noraoptometric@yahoo.com
CONTACT INFORMATION
Carl Garbus, O.D.
NORA Immediate Past President
28089 Smyth Drive
Valencia, CA 91355
Office: 661-775-1860
Email: cgarbusod@gmail.com
