Download - The Visual Field for Technicians
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Dwight Thibodeaux, OD
THE VISUAL FIELD
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VISUAL FIELDS
Localized measurement of visual perception using manual or automated methods to determine normal status or to evaluate and track an ocular or neurological disease state.
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NORMAL FIELDS
• Visual Field - Roughly 140 degrees monocularly and just over 180 degrees binocularly
• Field of Gaze – Over 200 deg
• Field of View – Over 300 deg
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COMMON METHODS OF FIELDS TESTING
• Confrontation –gross target movement - in from periphery
• Manual kinetic central fields – Tangent screen, Autoplot
• Microperimetry – Amsler Grid, automated units
• Manual kinetic widefield perimetry – Goldmann
• Automated static perimetry – Computer algorithm, tester independent
Humphries HFA and FDT/Matrix
Haag-Streit Octopus
Oculus and others
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HISTORICAL FIELD TESTS
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CONFRONTATION FIELD TESTING
Technique
Targets
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GOLDMANN KINETIC FIELD TESTER
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GOLDMANN KINETIC PERIMETRY
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OCTOPUS AND OCULUS
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ZEISS/HUMPHRIES
HUMPHRIES
FIELD ANALYZER (HFA)
FDT and MATRIX
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TEST STRATEGIES
• Suprathreshold – usually full field - 60 degrees
• 24 degree central field 24-2
• 30 degree central 30-2
• 10 degree 10-2
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SUPRATHRESHOLD
• Targets set at moderate brightness
(above threshold) with wide field • Either seen or not seen• Useful for lid/ptosis evaluation• Two field tests, taped and untaped
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THRESHOLDING
• First stimuli presented in each of the 4 quadrants
• Lowered by 3-4 Db until not seen and vise versa
• Moves to different area and repeats process
• Cloverleaf pattern in poor pt.
management and cooperation
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SITA / SITA FAST (HFA)
Swedish Interactive Thresholding Algorithm
SITA 50% faster than standard, but 90% accuracy
SITA FAST 70% faster, 80% as accurate
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FDT/FDP
• Frequency Doubling Technology (Perimetry)
• For early detection of glaucoma
• Resistant to blur (Rx) and pupil size effects
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MATRIX FDT
• Hybrid of FDT and SAP
• Even more sensitive to early glaucoma defects
• Too hypersensitive for neuro field testing and poor for
tracking glaucoma progression
• Best for glaucoma suspects / pre-perimetric glaucoma
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SWAP – SHORT WAVELENGTH AUTO PERIMETRY
• Yellow background and large blue stimulus on HFA
• Catches early defects in pre-perimetric glaucoma
• Very time consuming and sensitive to media opacities
• Matrix now more commonly used
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30-2 VS 24-2
• 30-2 = 76 test locations
Most accurate, 0.2 sec.
stimulus vs. 0.25 sec
latency for eye movements
• 24-2 = 54 test locations
Used for the difficult patient
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HFA 10-2
• 10 deg. central field for macular toxicity and end stage glaucoma or RP
• Plaquenil – hydroxychloroquine
• OCT of macula also part of new protocol
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MICROPERIMETRY
• Amsler Grid
• Automated
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WHAT FIELD IS INDICATED?
• Glaucoma suspect or pre-perimetric pt.• Established glaucoma patient with field loss• Neuro patient• Ptosis patient• High risk meds patient
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GLAUCOMA SUSPECT
• Minimal or no nerve head cupping – Matrix/FDT
• Obvious nerve damage – SITA Standard 30-2
• Difficult patient w/ damage– SITA Fast 24-2
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ESTABLISHED GLAUCOMA
• SITA Standard 30-2
• Difficult / older patient
SITA Fast 24-2
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NEURO FIELDS
• SITA Fast 30-2• Used for unexplained
vision loss or
neuro signs• Matrix oversensitive
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PTOSIS OR BLEPHAROCHALASIS
• Suprathreshold automated or kinetic fields
• Wider field to catch more peripheral defects
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HIGH RISK MEDSSITA 10-2
• For subtle central defects from retinal toxicity
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INTERPRETATION
• Quality measures and errors
• Plots
• Glaucoma Hemifield Test
• Global indices
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QUALITY MEASURES
• Fixation losses – targets blind spot, need <15%, ? misaligned
• False positives – positive response when no target is shown, need < 20%
• False negatives – <33%
• Gaze tracker - camera notes eye movement
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COMMON ARTIFACTS AND ERRORS
• Ptosis
• Prominent brows
• Lens holder positioning—ring scotoma
• Patient positioning—high FL, ring scotoma
• False positives based on patient expectations of stimulus timing
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GREY SCALE PLOT
• Quickly identifies overall depressions
• Good for patient education
• No comparison for age related normals
• No adjustment for media opacities
• Under represents shallow gen. depression and overemphasizes midperipheral non-significant defects
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TOTAL DEVIATION PLOT
• Graph and numeric representation
• Compared to age-matched normals
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PATTERN DEVIATION PLOT
• Probably the most important data
• Takes total deviation and filters out overall depression (cataracts)
• Looks for focal damaged areas pertinent to glaucoma
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GLOBAL INDICES
• Mean Deviation (MD)
• Positive Standard Deviation (PSD)
• Glaucoma Hemifield Test (GHT)
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GLOBAL INDICES
• Single number representations of the visual field
• Overall guidelines to help assess the field
• Probability values when numbers reach significant levels
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MEAN DEVIATION (MD)
• Overall level of sensitivity compared to age-matched normals
• Not corrected for generalized depression from media opacities
• Important for following diffuse loss in glaucoma
• MD of -2.00 or worse is suspicious
• Mild damage at <-6
• Moderate at -6 to-12 severe >-12
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PATTERN STANDARD DEVIATION (PSD)
• Sensitive measurement of localized loss
• Especially useful in glaucoma evaluation/progression
• The higher the number, the greater the loss
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GLAUCOMA HEMIFIELD TESTGHT
• Compares top and bottom half of field
• General reduction in sensitivity
• Abnormally high sensitivity
• ONL – difference not found in 99% of patients without glaucoma
• Borderline – difference not found in 97% of normals
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VISUAL FUNCTION INDEX (VFI) AND PROGRESSION ANALYSIS
Seen in newer units
VFI similar in meaning to MD but easier to conceptualize--100% is normal
75-80% is approaching significant loss = -6 or worse on MD
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COMMON GLAUCOMA SCOTOMAS
• Arcuate
• Nasal step
• Temporal wedge
• Localized paracentral
• Generalized depression
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ARCUATE OR NERVE FIBER BUNDLE DEFECT
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NASAL STEP
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LOCALIZED PARACENTRAL SCOTOMAS
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SECTOR OR WEDGE DEFECTS
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GENERALIZED DEPRESSION
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FUNCTIONAL VISION LOSS
• Most common in young girls
• Emotional trauma
• Also called hysterical fields
• Spiral and variable in nature
• Treat with education of parents and counseling
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NEURO FIELDS
Unilateral – usually involves the retina or optic nerve
Bilateral – involves both nerves or the optic chiasm/tract/brain
Homonymous – alike, same side on both eyes
Heteronomous – different, opposite sides
Congruous – symmetric in both eyes
Hemianopia – defect respects vertical midline
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MRI CHIASM
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HOMONYMOUS
• Hemianopsia – homonymous, congruous, points to cerebral cortex lesion such as stroke
• Quadranopsia or sectoranopsia– cerebral cortex (congruous) or lateral geniculate nucleus
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HETERONOMOUS
Hemianopsia- bitemporal, congruous- points to chiasmal lesion such as a pituitary tumor
Quadranopsia- very rare, points to different area of chiasm
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BINOCULAR FIELDS
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ALTITUDINAL
• Almost always unilateral
• Associated with AION – stroke at the optic disc
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CENTRAL SCOTOMA
• More commonly unilateral
as in:
optic neuritis
macular degeneration
early AION, cerebro-vascular
blood loss
retinal dystrophy
Bilateral – toxic, nutritional, heriditary optic neuropathy and
maculopathy
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QUESTIONS? [email protected]