visual field examination
TRANSCRIPT
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VISUAL FIELD EXAMINATIONAND
INTERPRETATION OF AUTOMATED PERIMETRY IN GLAUCOMA
DR PAAVAN KALRADEPARTMENT OF OPHTHALMOLOGY
S P MEDICAL COLLEGEBIKANER
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VISUAL FIELD• That part of environment wherein a steadily fixating eye can
detect visual stimulus.
• BASIS - presence of Photoreceptors and corresponding visual pathways upto the periphery of retina away from point of fixation i e fovea.
• IMPORTANCE – Reflects topographic sensitivity of various foci on retina and corresponding visual apparatus.
Resolution – Acuitydifferential light sensitivity and contrastcolourflickermotion
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PHYSIOLOGICAL BASIS
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VISUAL ACUITY
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DIFFERENTIAL LIGHT SENSITIVITY
Basis of most modern visual field examination methods
TRAQUAIR – “HILL OF VISION IN THE SEA OF DARKNESS”
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FACTORSApparent size of spot – real size
-- distance from eyeDuration of stimulus Background illumination Stimulus intensityContrast ColourPatient factorsLight / dark adaptationVisionRefractive statusEducation , attentiveness, cooperation
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Stereoscopic field
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PHYSIOLOGICAL BLIND SPOT
Corresponding to optic nerve head
15 deg temporal to point of fixation
Span – 5 deg horizontal -- 7 deg vertical
Two thirds below the horizontal meridian
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COLOUR FIELD
• Point at which passing from periphery to centre, the colour first becomes evident
• Peripheral to the limit, the object is perceptible but appears grey
• First red and green are used followed by blue and yellow
• Extent of field for objects of same size and intensitywhite > yellow > blue > red > green
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VISUAL FIELD DEFECTS
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• SCOTOMA : focal region of abnormally decreased sensitivity surrounded by an area of normal sensitivity
ABSOLUTERELATIVE
POSITIVENEGATIVE
• DEPRESSION : is an area of reduced sensitivity without a surrounding area of normal sensitivity
appears as denting of isopters
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• Generalized depression(both peripheral and central contraction)
e g cataract
• Peripheral Contraction – retinitis pigmentosa
• Temporal contraction - age
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• Hemifield defect :B/L - Hemianopias
homonymous heteronymous
• Altitudinal defect
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• Central scotoma• Pericentral • Centrocaecal scotoma
• Arcuate scotomasSeidel scotomaparacentral scotomaBjerrum scotoma
• Nasal step• Ring – double arcuate• Split fixation• Barring of blind spot
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EXAMINATION METHODOLOGY
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KINETIC• Test object of particular size and intensity is passed from
non seeing area to seeing area along a particular meridian at the rate of 3 – 5 deg per sec
• Repeated every 15 – 30 deg• To find points in the visual field of equal sensitivities –
ISOPTER (Groenouw) marking• Intensity and size of stimulus is varied to mark various
isopters• Thus 2 D Contour map of the hill of vision is made• Extent of scotomas and blind spot marked from inside
out
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STATIC• The location, size and duration of stimulus is kept constant
and the luminance is gradually increased until seen• Actual estimation of sensitivity ( THRESHOLD ) of each
point is made out• SUPRA THRESHOLD stimulus used for screening
-------------------------------------------------------------------------------IMPORTANT :
one eye is tested at a time, other is occluded
fixation of the patient has to be steady and is monitored throughout the test
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CLINICAL METHODS GROSS DEFECTS
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PROJECTION OF LIGHT
In patients with very poor vision –> HM + to PL +e g dense cataracts
-dark room, other eye occluded-patients are constantly instructed to look straight to avoid
tendency to deviate eye towards light source-light shown onto 4 quadrants from 30-50 cm and switched
on and off-Patient tells about the direction of light source
Accurate in all quadInaccurate in some quadInaccurate in all quad
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HAND IDENTIFICATION
Other eye is occluded
Patient fixates on the nose of examiner
Examiner keeps both hands on either side of eye 50 cm away
One hand absent or indistinct – hemianopic defect
Either palms or fingers of both hands missing / faint – altitudinal defect
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FINGER COUNTING
Varying no of fingers are held in each quadrant, 1 m and 45 deg from fixation
If unable to count, fingers are brought closer to fixation, until patient sees (kinetic)
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RED DESATURATION
Can be confirmed kinetically
Patient has to indicate when color appears to change
Can also be used to compare the two eyes in case of optic neuropathy
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CONFRONTATION(kinetic)
Patient’s and examiner at same level
Compares the visual field of eye of patient with opposite eye of the examiner in a plane perpendicular to line of gaze
Red pin is particularly useful for neurological cases
GROSS PERIMETRY (kinetic)
Follows facial contour
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AMSLER GRIDFor Central 10 deg ( static )
Other eye occluded
Near correction given
Chart at held 28-30 cm – each small square subtends angle of 1 deg
Patient fixates at central dot – tells whether all corners are seen simultaneously and about lines- parallel, distorted, missing
Can be used for mapping blind spot – patient fixates at edge of grid
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EQUIPMENTS
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PERIMETRY
Examination and quantification of visual field by using stimulus of various sizes, intensities and colours
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ARC PERIMETERS eg LISTER’s PERIMETER
• Only kinetic• Peripheral charting
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BJERRUM’s SCREEN ( CAMPIMETRY)
• Patient sits at 1 or 2 m from flat screen• Kinetic and static• For central 30 deg only• Done under subdued lighting
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GOLDMANN’s PERIMETER
• Bowl type• Standardization• Both kinetic and static• Peripheral as well as central
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AUTOMATED PERIMETRYstandard automated perimetry
HUMPHREY FIELD ANALYZER OCTOPUS
• STATIC perimetry
• Measurement of threshold values
• STATPAC (HFA)- Comparison to normative data
• Inbuilt program for analysis – diagnosis and progression
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ADVANTAGES• Removal of examiner variability• More sensitive to subtle field defects• Reproducibility• Retests abnormal points automatically• Gives reliability parameters like
fixation monitoring – HEIJL KRAKAU methodGaze trackingFalse positiveFalse negative
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SHORT COMINGS• EXPENSIVE• Learning curves• Difficult to follow by older debilitated patients especially
neurological problems• Not infallible – only 1 % of field is actually examined• Diagnosis and management decisions based on
correlation with other clinical findings
A well performed tangent screen examination is better than poorly carried out automated perimetry
In neurological patients, clinical methods may be the only possible assessment techniques
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• WHITE ON WHITE
• BACKGROUND ILLUMINATION - 31.5 asb
• STIMULUS SIZE – GOLDMANN - III
• DURATION OF SPOT EXPOSURE 0.2s
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PROGRAMS / PATTERNS30-2 – gold standard24-210-2MACULARNasal step program – additional 12 locations upto 50 deg
nasalperipheral 60 and 60-4 progEstermann test – for binocular 120 deg field
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MACULA PROGRAM :16 locations within the central 5° with 2° spacing. Each location is tested three times
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STRATEGIES
SUPRATHRESHOLD – screening
Fixed suprathreshold
contour suprathreshold
3 zone suprathreshold
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FULL THRESHOLDBRACKETING STRATEGY( staircase)
– GOLD STANDARD
FASTPAC
Estimation of SHORT TERM FLUCTATIONS at 10 prefixed points
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SWEDISH INTERACTIVE TESTING ALGORITHM (SITA)
SITA STANDARD ( Bracketing strategy based)
SITA FAST ( FASTPAC based)
Analyzes patients response and responds accordinglyDecreases overall no of stimuli presented, hence test
durationPaces the test according to patients speedDoesn’t estimate Short term Fluctuations
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• Selection of adequate test• Proper environment• Comfortable sitting position• Adequate size of pupil >3mm• Adequate Near correction• Proper explanation – running of demonstration• Reassurance – not all points will be seen
- test can be paused by keeping the response button pressed
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Patient data• Name, DOB, eye• Vision, refraction,• Pupil diameter
Test data• Date and time• Program and strategy• Background
illumination• Test size, color,
duration, interval
ZONE 1 : REPRODUCIBILITY
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ZONE 2 : RELIABILITY• Fixation monitor• Fixation target – central, small diamond,
large diamond, bottom LED• Test duration
• Reliability indicesFixation losses ( Heijl Krakau) <20 %Gaze tracking
False positives < 33%(trigger happy)
False negatives < 33 %
Foveal threshold
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ZONE 3 : GREY SCALE• Based on actual threshold values at each location• General identification• Patient information
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ZONE 4 :TOTAL DEVIATION PLOT
• Numerical plot – indicates by how much decibels is each point depressed compared to mean value in normal population of similar age
• Probability plot- grey scale indicates the probability of occurrence of the deviation in normal population
Generalized depression due to media opacities, refractive error, miosis may hamper appearance of a pattern
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ZONE 5 : PATTERN DEVIATION PLOT
• Numerical - calculated by adjustment for generalized depression or elevation of visual field
• Thus brings out pattern• Probability plot • Significance - ANDERSON’S CRITERIA
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ZONE 6 : GLOBAL INDICESsingle numbers to denote whole field
• MEAN DEVIATION : average loss of sensitivity from normal age matched population along with probability
calculated from total deviation plot
• PATTERN STANDARD DEVIATION : range over which change of sensitivity at all the points has occurred, along with probability
compensates for effect of generalized depression or elevation of field on mean deviation value
local defects affect PSD > MD
• SHORT TERM FLUCTUATIONS• CORRECTED PATTERN STANDARD DEVIATION
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ZONE 7 : GLAUCOMA HEMIFIELD TEST
• PLAIN ENGLISH LANGUAGE MESSAGE
• Comparison of 5 clusters of points in superior hemifield with mirror images in inferior hemifield
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OUTSIDE NORMAL LIMITSall cluster pairs differ @ p < 1% OR1 cluster pair differs @ p < 0.5%
BORDERLINEhemifields differ @ p < 3%
GENERAL REDUCTION OF SENSITIVITYoverall field depressed @ p < 0.5%
ABNORMAL HIGH SENSITIVITYoverall field elevated( best 15 % points) @ p < 0.5 %
WITHIN NORMAL LIMITS
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ANDERSON and PATELLA CRITERIA• 3 or more congrous ‘non edge points’ in typical arcuate area
on 30-2 program
depressed @ p< 5 % with at least one point @ p<1 %
•PSD / CPSD @ p< 5%
•GHT – outside normal limits
Must be demonstrated on 2 field tests
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CLINICAL CORRELATION : MUST
DISC and NERVE FIBRE LAYER
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OVERVIEW
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CHANGE ANALYSIS
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GLAUCOMA PROGRESSION ANALYSIS
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ARTEFACTS• OBSTRUCTION
RIM ARTEFACTSPTOSISMEDIA OPACITIESANGIOSCOTOMA
• MIOSIS
• REFRACTION ARTEFACTS• High power plus and minus lenses
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NEWER METHODS
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SHORT WAVELENGTH AUTOMATED PERIMETERY“BLUE ON YELLOW”detects glaucomatous defects 3-5 years earlier than SAPhigh fluctuation rates
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FREQUENCY DOUBLING PERIMETRY
Based on frequency doubling illusion
Test stimulus – series of white and black bands flickering at 25 Hz ( low spatial frequency & high temporal frequncy)
Detects damage to Magnocellular Ganglion cells
C – 20 17 points – screening
N – 30 19 points – diagnosis n management
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RANDOM DOT MOTION PERIMETRY
Patient has to tell direction in which dots are moving
HIGH PASS RESOLUTION PERIMETRY
Test resolution and not mere threshold detection
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THANK YOU