Transcript 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 Bitemporal Relates to a lesion near or at the optic chiasm Homonymous Relates to a lesion in the parietal or temporal lobe 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 PERIPHERAL Predominantly fovea, cones (r/b/g) Predominantly peripheral retina, rods Predominantly Parvocellular Only Magnocellular Sustained Transient Focal Ambient What? Where? Cognitive 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 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 – Incorporate tints to spectacle correction – – – 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 24th Annual Multi-disciplinary Conference Renaissance Denver May 14-17, 2015 Denver, CO Website www.nora.cc Email: [email protected] CONTACT INFORMATION Carl Garbus, O.D. NORA Immediate Past President 28089 Smyth Drive Valencia, CA 91355 Office: 661-775-1860 Email: [email protected]