Visual field testing and interpretation

VISUAL FIELD TESTING

AND INTERPRETATION

HIRA NATH DAHAL

PRESENTATION LAYOUT• INTRODUCTION ON VISUAL FIELD

• NORMAL LIMITS OF VISUAL FIELD

• SHORT OVERVIEW ON HISTORY OF VF

• TERMINOLOGIES RELATED TO VF

• VISUAL FIELD TESTING METHODS

• KINETIC, STATIC

• INTERPRETATION OF VF REPORTS

INTRODUCTION

VISUAL FIELD

• THE VISUAL AREA THAT IS PERCEIVED SIMULTANEOUSLY BY A FIXATING EYE.

RETINA VS VISUAL FIELD

Optic disc

Nasal to the fovea – Seen in temporal VF as a Blind spot

TRAQUAIRS FIELD OF VISION

HILL OF VISION

Normal limits of visual field

SHORT HISTORY OF VISUAL FIELD• IN B.C 150, PTOLEMY: USED SOME FORM OF PERIMETRIC

DEVICE TO MEASURE EXTEND OF VF

• FIRST CLINICAL INVESTIGATION OF VF DEFECT – HIPPOCRATES IN 5TH CENTURY, HEMIANOPIC FIELD DEFECT

• FINALLY IN 1604 KEPLER EXPLAINED THE PRINCIPLE OF SIGHT IN TERM OF AN INVERTED RETINAL IMAGE –

– AN STAGE FOR MODERN INVESTIGATION OF VF

HISTORY….• IN 1666, MARIOTTE DISCOVERED

PHYSIOLOGICAL BLIND SPOT

• IN 1801, YOUNG STATED THE NORMAL

EXTEND OF VF OF AN EYE

• VON GRAEFE MAPPED OUT BLIND SPOT,

CENTRAL SCOTOMAS, CONSTRUCTION OF

ISOPTER.

• INTRODUCED VF IN CLINICAL MEDICINE

FOR THE FIRST TIME

• UNTIL 1869, FOERESTER INVENTED ARC

PERIMETER, TILL THEN VF PLOTTED ON

FLAT SURFACE

Thomas Young

Von Graefe

HISTORY……• IN 1880, BJERRUM DEVELOPED

TANGENT SCREEN

• IN 1940, MARC AMSLER

INTRODUCED AMSLER GRID

• IN 1939 SLOAN DESCRIBED

STATIC PERIMETRY

• IN 1945 GOLDMAN

PERIMETER

• IN 1960 TUBINGER- MANUAL

TESTING OF BOTH STATIC AND

KINETIC PERIMETER

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FEW TERMINOLOGIES• THRESHOLD: THE WEAKEST TEST STIMULUS THAT IS JUST

VISIBLE IN A PARTICULAR LOCATION UNDER THE SPECIFIC

TESTING CONDITION.

• VARIES ACROSS THE VISUAL FIELD.

• SENSITIVITY: MOST SUBTLE CHARACTERISTICS OF A STIMULUS

THAT IS VISIBLE AT A SPECIFIC POINT IN SPACE.

• FIXATION: THAT PART OF VISUAL FIELD CORRESPONDING TO

FOVEA CENTRALIS.

TERMINOLOGIES…• ISOPTER:

• LINE CONNECTING ALL POINTS IN THE VISUAL FIELD WITH THE

SAME THRESHOLD ( FOR A GIVEN TEST SPOT)

• BOUNDARY BETWEEN AREA OF VISIBILITY TO THE AREA OF NON-

VISIBILITY FOR A PARTICULAR STIMULUS

TERMINOLOGIES…• SCOTOMA: LOCALIZED DEFECTS\DEPRESSIONS SURROUNDED BY

NORMAL VISUAL FIELD.

• ABSOLUTE: DEFECT THAT PERSISTS WHEN THE MAXIMUM

STIMULUS IS USED E. G BLIND SPOT.

• RELATIVE : DEFECT THAT IS PRESENT TO WEAKER STIMULUS BUT

DISAPPEARS WITH BRIGHTER STIMULUS.

LOCATION OF VISUAL FIELD DEFECTS• CENTRAL

• 5 DEGREES OR LESS FROM THE POINT OF FIXATION

• PARACENTRAL

• >5 DEGRESS – 30 DEGREES

• CEACAL, PARACEACAL, PERICEACAL

• CENTROCECAL

• PERIPHERAL

• >30 DEGREES

DESCRIPTIVE COMPONENTS OF VF DEFECTS•MONOCULAR DESCRIPTIONS–DENSITY• ABSOLUTE (NO VISUAL SENSATION) OR RELATIVE (DEPRESSED

VISUAL SENSATION)

–AREA• GENERAL OR LOCAL

–SHAPE• SECTORIAL (HEMIANOPIC) OR NON-SECTORIAL (REGULAR OR IRREGULAR)

–EXTENT• TOTAL OR PARTIAL

–POSITION• RT. OR LT. . TEMPORAL, NASAL, SUPERIOR, INFERIOR

DESCRIPTIVE COMPONENTS OF VF DEFECTS

•Binocular description• Laterality•Unilateral or bilateral (homonymous/heteronymous)

•Equalness•Congruous or incongruous

•Additional description

•Awareness•Positive (defect perceived) or negative (defect not perceived)

SIGNIFICANCE OF VISUAL FIELD TESTING

• FIND OUT THE EXTENT OF VF

• TO DIAGNOSE AND DETECT DISEASES AS WELL AS EXTENT OF

DAMAGE CAUSED IN VF BY THE DISEASE

• TO LOCATE POSSIBLE LESION IN NEUROLOGICAL DISORDER

• TO FIND OUT THE PROGRESSION OF DISEASES

VISUAL FIELD TESTING METHODS/TOOLS

• CENTRAL

• AMSLER GRID: 200

• TANGENT (BJERRUM SCREEN): 300

• GOLDMANN

• AUTOMATED (OCTOPUS / HUMPHERY) :300

• PERIPHERAL

• CONFRONTATION

• GOLDMANN

• AUTOMATED 900 PROGRAMME

PERIMETRY

• SYSTEMATIC MEASUREMENT OF VF BY THE USE OF A

PERIMETER

• MODERN PERIMETER • CONSIST OF A BOWL POSITIONED AT A FIXED DISTANCE FROM

THE EYE,

• ENABLE THE CONTROLLED PRESENTATION OF STIMULI WITH IN THE BOWL

• ENABLES ASSESSMENT OF THE VISUAL FUNCTION THROUGH OUT THE VISUAL FIELD

• DETECTION & QUANTIFICATION OF DAMAGE TO THE VISUAL FIELD

• MONITORING THE CHANGE OVER A TIME

PERIMETRY TYPESKinetic Static

• measures extent of visual field by plotting isopters ( locus of retinal points having same sensitivity)

•Stimulus moves from non- seeing to seeing area.

•Result depends upon the experience of the operator.

• e.g, Goldman perimetry, confrontation, Tangent screen, Arc perimetry

• measures the sensitivity of each retinal points.

•The stimulus is stationary but increases in luminance.

• Mostly automatic, very little role of the operator.

•e. g, Automated perimetry, Goldman perimetry

GOLDMAN PERIMETRY

• THE MOST WIDELY USED INSTRUMENT FOR MANUAL

PERIMETRY.

• HAS A CALIBRATED BOWL PROJECTION INSTRUMENT

• WITH A BACKGROUND INTENSITY OF 31.5 APOSTILBS (ASB),

• TEST TARGETS: DOTS

• VARYING SIZE AND ILLUMINATION

PERIMETRY BOWL•BACKGROUND

LUMINANCE

31.5 ASB

RADIUS OF THE BOWL

30 CM Patient side

GOLDMANN TARGETS• THE STIMULI (DOT) USED TO PLOT AN ISOPTER DENOTED

BY

• ROMAN NUMERAL, A NUMBER, AND A LETTER.

• ROMAN NUMERALS = 0 TO V (SIZE)

• NUMBER = 1 TO 5 (LUMINANCE) USE OF FILTER

• ALPHABET = A TO E ( ‘’) USE OF FILTER

V4e , I4e, IV3e

GOLDMANN PERIMETRY: ROMAN NUMERAL

• SIZES OF STIMULI [0...V SCALE]

• EACH SIZE INCREMENT EQUALS

• A TWOFOLD INCREASE IN DIAMETER AND A FOURFOLD

INCREASE IN AREA.

Diameter (mm) Area (mm2)

0 0.28 1/16

I 0.56 ¼

II 1.13 1

III 2.26 4

IV 4.51 16

V 9.03 64

TARGET ILLUMINATION

• LUMINANCE SETTINGS

• EXPRESSED IN UNITS CALLED APOSTILBS (CANDELA/M2)

• 2 SETS OF FILTERS – 5 EACH • 10 STEPS

• STANDARD VS FINE SETTINGS

• (1...5 AND A...E SCALES)

• 1, 2, 3, 4 SETTINGS REPRESENT 0.5 LOG UNIT CHANGES = 5 DB

• A, B, C, D AND E SETTINGS REPRESENT 0.1 LOG UNIT CHANGES = 1DB

TARGET RANGE IN GOLDMANN

• MORE THAN 100 COMBINATIONS OF SIZE AND INTENSITY OF TEST

TARGETS ARE POSSIBLE

• BUT ONLY A FEW ISOPTER ARE NEEDED TO DEFINE THE VISUAL FIELD.

• SIZE “0” GENERALLY IS OMITTED

• BECAUSE RESULTS OF THE PLOTS ARE INCONSISTENT.

• THE FINE-INTENSITY FILTER IS USUALLY SET TO THE LETTER “E”

• WHICH ELIMINATES THE SMALL-INCREMENT LIGHT FILTERS.

• TEST TARGET : DENOTED BY – SIZE + (STD. + FINE) LUMINANCE

• EG: V4E, I4E, II3E

SOME INTERESTING FACTS• A CHANGE OF ONE NUMBER OF INTENSITY

– IS ROUGHLY EQUIVALENT TO A CHANGE OF ONE ROMAN

NUMERAL OF SIZE I.E. III4E = IV3E

• ISOPTER PLOTTED WITH TARGETS OF EQUAL SUM OF

–ROMAN NUMERALS (SIZE) & NUMBER (INTENSITY)

• ARE CONSIDERED EQUIVALENT.

–FOR EXAMPLE,

• THE I4E ISOPTER IS ROUGHLY EQUIVALENT TO THE II3E ISOPTER.

• I + 4 = 5, II + 3 = 5

STANDARD VF PLOT OF RE

REQUIRED EQUIPMENT FOR VF MAPPING

•GOLDMANN BOWL PERIMETER

•LENS HOLDER

• RECORDING PAPER

•COLORED MARKERS

•PATCH FOR MONOCULAR TESTING

GOLDMANN PERIMETER

Pantoscopic handle

Horizontal cut

Patient Side (Bowl)

GOLDMANN PERIMETER

Patient Side (Bowl)

Fixation target

Chin rest

Head rest

Len Holder

GUIDELINE TO PLOT

• FIRST DEMONSTRATE THE PROCEDURE TO PATIENT

• BY STATICALLY PRESENTING LARGE TEST

GENERAL RULES FOR PLOTTING “ISOPTERS”

• AN ISOPTER IS MAPPED FOR THE PARTICULAR STIMULUS SIZE AND INTENSITY

• MOVE FROM NON-SEEING TO SEEING WHILE PRESENTING STIMULUS

• MOVE AT A RATE OF 5 DEGREES PER SECOND INSIDE

• PRESENT KINETICALLY EVERY 15 DEGREES INTERVAL

GUIDELINES FOR PLOTTING

• BEGIN IN THE FAR PERIPHERY AND KINETIC PLOT ISOPTER IN ALL

MERIDIANS

• USE A V4E, I-3E , I-2E OR TARGET (DEPENDING UPON AGE

• PLOT THE BLINDSPOT

• ONLY 4 MERIDIANS ARE REQUIRED( MORE IF IRREGULAR OR

LARGE)

• USE THE I-4E FOR THE BLIND SPOT

• WITHIN ISOPTER OF I-2E OR I-3E

GUIDELINES•CENTRAL STATIC TEST WITH I-2E

• EXPLORE FOR ANY SCOTOMAS

• KINETIC PLOT WITH I-3E STIMULUS ONLY IN SUSPECTED DEFECT AREA

•STATIC TEST BETWEEN I-3E AND I-2E ISOPTERS

WITH THE I-3E STIMULUS (SCOTOMA SEARCH)

GUIDELINES

• SPECIAL CASE PLOTS

• GLAUCOMA SUSPECTS

• PLOT MORE POINTS ALONG THE NASAL EDGE OF THE ISOPTER

• PLOT APPROXIMATELY

• EVERY 3-5 DEGREES,

• 15 DEGREES ABOVE AND BELOW THE HORIZONTAL RAPHE

REPEAT FOR CENTRAL, INTERMEDIATE AND PERIPHERAL PLOTS

• SUSPECTED NEUROLOGICAL LESIONS

• PLOT MORE POINTS ON EITHER SIDE OF THE VERTICAL MERIDIAN

• REPEAT FOR CENTRAL, INTERMEDIATE AND PERIPHERAL PLOTS

RECORDING

• ALL RECORDING SHOULD BE DONE ON THE GOLDMANN RECORDING PAPER

• PATIENT NAME,

• DATE,

• RX USED,

• PUPIL SIZE,

• EYE TESTED AND

• PATIENT COOPERATION / FIXATION

• INDICATE THE TARGET SIZES USED IN THE BOTTOM RIGHT HAND BLOCK (COLOR MARKER)

COLOR CODING OF ISOPTERS

• I-2E BLUE

• I-3E ORANGE

•I-4E RED

•II-4E GREEN

•III-4E PURPLE

•IV-4E BROWN

•V-4E BLACK

EXPECTED FINDINGS FOR NORMAL ISOPTERS • PATIENTS UNDER 50 YEARS OF AGE

I. PERIPHERAL I-4E (SIZE=SAME, BRIGHTER LUMINANCE)

II. INTERMEDIATE I-3E

III. CENTRAL I-2E (SIZE=SAME, DIMMER LUMINANCE)

EXPECTED FINDINGS FOR NORMAL ISOPTERS• PATIENTS 50 YEARS OR OLDER

I. PERIPHERAL II-4E (SIZE=LARGER, BRIGHTER LUMINANCE)

II. INTERMEDIATE I-4E

III. CENTRAL I-2E OR I-3E (SIZE=SMALLER, DIMMER LUMINANCE)

INTERPRETATION

• THE VISUAL FIELD IS CONSIDERED ABNORMAL IF:

– THE THRESHOLD VALUES ARE SIGNIFICANTLY BRIGHTER (0.5

LOG UNITS OR MORE) THAN THE EXPECTED VALUES

AND / OR

– SCOTOMAS OR DEPRESSIONS ARE PRESENT

SOME VISUAL FIELD DEFECTS

SOME VISUAL FIELD DEFECTS

BITEMPORAL HEMIANOPIARight eye Left eye

AUTOMATED PERIMETRY ( STATIC)• MACHINE CONSTRUCTED ALONG THE BASIC LINES OF A

GOLDMAN PERIMETER + SOPHISTICATED SOFTWARE

PROGRAMS.

• KEY REASON FOR INCREASED INTEREST IN AUTOMATED

PERIMETRY HAS BEEN DUE TO THE STANDARDIZATION

AUTOMATED PERIMETRY ALLOWS.

AUTOMATED PERIMETRY

• VISUAL THRESHOLD IS MEASURED AT A SERIES OF FIXED POINTS IN THE VISUAL FIELD.

• THE BRIGHTNESS OF THE TEST SPOT IS VARIED, BUT NOT ITS LOCATION.

• THRESHOLD IS USUALLY PLOTTED RELATIVE TO NORMAL FIELDS, TO REVEAL DEFECTS

AUTOMATED PERIMETRY

AUTOMATED PERIMETRY

• HUMPHREY:

• OCTOPUS:

THRESHOLD DETERMINATION

Frequency of seeing curve

THRESHOLD DETERMINATION

28dB

24 dB

32 dB

30 dB29 dB

0 dB brightest stimulus

THRESHOLD DETERMINATION

• AGE MATCHED NORMAL DATA ARE USED TO COMPARE

PATIENT’S DATA

• NORMAL RANGE DETERMINED BY

• SENSITIVITY OF EACH RETINAL POINTS 10,000 INDIVIDUALS

• UPPER 95% AS NORMAL

• LOWER 5% AS ABNORMAL

TESTING STRATEGIES

• OCTOPUS

• NORMAL

• DYNAMIC

• TOP ( TENDENCY ORIENTED PERIMETRY)

• HUMPHREY

• SITA (SWEDISH INTERACTIVE THRESHOLD ALGORITHM)

• SITA FAST

• FULL THRESHOLD

DIFFERENCE BETWEEN OCTOPUS AND HUMPHREY (TEST PARAMETERS)

FACTORS AFFECTING AUTOMATED PERIMETRY• BACKGROUND LUMINANCE

• STIMULUS SIZE

• FIXATION CONTROL

• REFRACTIVE ERRORS

• CATARACTS AND OTHER MEDIA OPACITIES

• MIOSIS

• FACIAL STRUCTURE

• FATIGUE

• EXPERIENCE OF A PERIMETER

VALIDITY OF THE TEST

• FALSE POSITIVE RESPONSE

• > 20% UNRELIABLE

• FALSE NEGATIVE

• >20% UNRELIABLE

• SHORT TERM FLUCTUATION

• 1-3 DB NORMAL FLUCTUATION

• FIXATION LOSS

• >33% UNRELIABLE

CHOOSING AN APPROPRIATE PROGRAM

EXAMINATION PROCEDURE

TEST PROGRAM(G1, G2, 32, M2)

+

TEST STRATEGY (NORMAL, DYNAMIC, TOP)

+

PERIMETRY METHOD( W/W, FLICKER, B/Y, KINETIC)

PROGRAMS

G1/G2

• CENTRAL 30 DEGREE

• GLAUCOMA SCREENING

• 59 POINTS

• LOCATIONS MORE CLOSELY WITH TOPOGRAPHY OF RETINA

(IN AREAS OF CONCERN OF GLAUCOMA)

• 2.8 DEG SPACING

PROGRAMS 32 ( GENERAL EXAMINATION)= 30-2 IN HUMPHREY

• INTRODUCED WITH EARLY AUTOMATED PERIMETRY

• 76 TEST LOCATIONS

• WIDE SPACING (6 DEGREES) ( NOT APPROPRIATE FOR

GLAUCOMA)

PROGRAMS

MACULA PROGRAM(M2)

• CENTRAL AND PARACENTRAL VISUAL DEFECTS IN

NEUROLOGICAL AND MACULAR PROBLEMS

• CENTRAL 10 DEG

• 56 TEST LOCATIONS

• SPACING 2 DEGREES

• 0.7DEG SPACING IN THE MACULA

PROGRAMS

LVC (CENTRAL LOW VISION)

• TO TEST HOW MUCH SENSITIVITY IS REMAINED IN THE

CENTRAL FOVEAL AREA.

• 77 LOCATIONS

• 30 DEGREES

• END STAGE GLAUCOMA

STRATEGIES

• NORMAL STRATEGY

• STANDARD

• 4-2-1 BRACKETING PROCEDURE

• 10-15 MIN

• EARLY AND SHALLOW DEFECTS

• YOUNGER PATIENTS ( GOOD CONDITION IN ANSWERING THE

QUESTION TILL THE END OF A LONG PROGRAM)

STRATEGIES

• DYNAMIC STRATEGY

• ONE THRESHOLD CROSSING

• SMALL STEPS IN REGIONS WITH NORMAL SENSITIVITY AND

LARGE TOWARDS DEPRESSED FIELD

• TEST DURATION REDUCED BY TWO

• ESPECIALLY WHEN FOCAL DEFECTS ARE EXPECTED

STRATEGIES• TOP ( TENDENCY ORIENTED PERIMETRY)

• LIGHT SENSITIVITY OF THE RETINAL IS INTERRELATED RATHER

THAN HAVING AN INDIVIDUAL VALUE

• 2 MINUTES

• FOR PATIENTS WITH DEPRESSED FIELDS, FOR CHILDREN, ELDERLY

ONES WHO ARE NOT CAPABLE OF FINISHING A LONGER

EXAMINATION

INTERPRETATION OF RESULTS

DIFFERENT ZONES

GREYSCALE

VALUE TABLE

COMPARISON /CORRECTED COMPARISON(TOTAL AND PATTERN DEVIATION)

PROBABILITY PLOTS

CUMULATIVE DEFECT CURVE

GLAUCOMA HEMIFIELD TEST

• 5 SECTORS IN THE UPPER FIELD ARE COMPARED TO FIVE

MIRROR IMAGES IN THE LOWER

• IF VALUE IN TWO SECTORS DIFFER TO AN EXTENT THAT FOUND

IN

• <0.5% OF THE NORMAL POPULATION ( HIGHLY SENSITIVE)

• <1% OF NORMAL POPULATION (OUTSIDE NORMAL LIMIT)

• <3% OF THE NORMAL POPULATION (BODERLINE)

• <5% OF THE NORMAL POPULATION ( CAN BE A NORMAL PLOT)

GLOBAL INDICES OCTOPUS

•MEAN SENSITIVITY (MS)

•MEAN DEVIATION (MD) (–2DB TO +2DB)

• LOSS VARIANCE (LV) (0-6DB)

•CLV(0-4DB)

• SF (1.5DB- 2.5DB)

•RF < 15%

HUMPHREY

• GHT

• MEAN DEVIATION

• PSD

• CPSD

• SF

OCTOPUS CRITERIA FOR VISUAL FIELD DEFECT§

HFA CRITERIA FOR VF LOSS

• PATTERN DEVIATION PLOT

RECENT ADVANCES IN AUTOMATED PERIMETRY• GOLDMAN KINETIC MODULE• HIGH-PASS RESOLUTION PERIMETRY - USES THIN RINGS INSTEAD

OF SPOTS• SHORT WAVELENGTH SENSITIVE PERIMETRY - BLUE ON YELLOW

FOR S CONES• FLICKER PERIMETRY - FLICKERING TARGETS INSTEAD OF STATIC

FLASHES• AULHORN'S SNOW FIELD CAMPIMETRY - USES TV “SNOW” AND

POINTING• MOTION PERIMETRY - DETECT MOVING TARGETS INSTEAD OF

FLASHED ONES• RAREBIT PERIMETRY- USES VERY SMALL, BRIGHT SPOTS• PUPIL PERIMETRY - MEASURES PUPIL RESPONSES INSTEAD OF

SUBJECTREPORTS• MULTIFOCAL VEP - MEASURES CORTICAL EVOKED POTENTIALS

INSTEAD OFSUBJECT REPORTS

SUMMARY

• PRINCIPLE OF KINETIC AND AUTOMATED PERIMETRY

• APPROPRIATE SELECTION OF VISUAL FIELD TESTING FOR A

PARTICULAR PATIENT

• ACCURATE INTERPRETATION OF VF REPORTS