Automated perimetry - explained in brief. how to read the print out and its interpretation.

1. AUTOMATED PERIMETRY
DR INDEEVAR V MISHRA
MM JOSHI EYE HOSPITAL,
HUBLI.

2. BASIC CONCEPTS
• TRAQUAIR'S HAS DEFINED THE VISUAL FIELD AS BEEN A HILL
ISLAND OF VISION IN A SEA OF DARKNESS TESTING ALONG X-Y
AXES OF THIS 3 DIMENSIONAL AREA DETERMINES THE LOCATION
IN THE VISUAL FIELD AND ALONG THE Z AXIS IDENTIFIES THE
VISIBILITY THRESHOLD.
• AUTOMATED PERIMETRY - " DIFFERENTIAL LIGHT THRESHOLD –
ABILITY TO DIFFERENTIATE AN ILLUMINATED TARGET AGAINST
AN ILLUMINATED BACKGROUND."

3. BASIC CONCEPTS
--- CONTD
THRESHOLD
• LUMINANCE OF STIMULI THAT IS SEEN 50% OF TIMES IT IS
PRESENTED
• LOGARITHMIC UNIT DB ( DB PROP. 1 / BRIGHTNESS )
• BRACKETING STRATEGY ( 4 - 2 - 2 ALGORITHM )
• SUPRA THRESHOLD - 95 % CHANCE A STIMULUS IS SEEN.
• INFRA THRESHOLD - 5% CHANCE A STIMULUS IS SEEN.

4. BASIC MACHINE DESIGN
• ILLUMINATED HEMISPHERICAL BOWL 33 CM
AWAY WITH TARGET OF FIXATION
• STIMULI - SPOT OF LIGHT - LED / PROJECTION
SYSTEM / COMP. VIDEO MONITOR
• HFA - II ( 700 SERIES ) ASPHERICAL BOWL 30 CMS
AWAY ,SMALLER ,MORE ERGONOMIC STIMULI IN
PERIPHERY MORE CLOSER,

5. FIXATION CONTROL
• CC TV MONITOR
• HEIJL - KRAKAU BLIND SPOT METHOD
• GAZE TRACKER
• FULL TIME TWO VARIABLE GAZE MONITOR
• IMAGE ANALYSIS
• ERRORS - UPWARD / DOWNWARD
• FIXATION CHECKED 100 % OF STIM. TIME
• NO TESTING TIME FOR FIXATION CHECK

6. PARAMETERS RECOMMENDED
FOR TESTING
• FOVEAL FIXATION TARGET – SMALL AND LARGE
DIAMOND WITH YELLOW LIGHTS.
• GOLDMANN SIZE III TARGET FOR STIMULI & BLIND
SPOT CHECK. IF EXCESSIVE FIXATION LOSS IT CAN BE
DECREASED TO II OR I OR IF VISION LESS THAN 6/36
THAN IT CAN BE INCREASED TO V.
• WHITE STIMULUS COLOUR
• NORMAL TESTING SPEED. CAN BE SLOW DOWN IF
PATIENT IS SLOW TO RESPONSE.
• FOVEAL THRESHOLD - ON / OFF

7. THRESHOLD TESTS
• CENTRAL 30-2 – 76 POINTS ARE TESTED . EACH
POINT 6 DEG APART. STRADDLING THE
HORIZONTAL AND VERTICAL AXIS SO THAT THE 2
INNER MOST TEST POINTS ARE 3 DEG FROM
FIXATION POINT.
• CENTRAL 24-2 – 56 POINTS ARE TESTED . AVOIDS
RIM ARTIFACTS.
• CENTRAL 10-2 – 68 POINTS SPACE 2 DEG APART.
USEFUL IN ADVANCE DISEASE WITH SPILT
FIXATION.
• MACULAR THRESHOLD TEST – SQUARE GRID OF 16
POINTS EACH 2 DEG APART , WITH EACH POINT
THRESHOLDED 3 TIMES.

8. 30 – 2 24 – 2 Macular threshold

9. INTERPRETATION
FACTORS FOR CONSISTENCY IN TESTING
• BEST REFRACTIVE CORRECTION USED. CONTACT
LENS TO AVOID RIM ARTIFACTS.
• PUPIL DIAMETER – AT LEAST 3.5 MM IN SIZE.
• VISUAL ACUITY
• DATE & TIME OF TESTING
• AGE-FOR COMPARISON WITH NORMATIVE DATA
• SHORT TERM FLUCTUATION-FLUCTUATION
OCCURRING WITHIN THE TEST. SHOULD BE <3DB.

10. INTERPRETATION ----CONTD.
FIXATION LOSSES: 10/12 XX
FALSE POS ERRORS : 0/7
FALSE NEG ERRORS :0/6
TEST DURATION : 16:20

11. STATISTICAL GLOBAL INDICES
• MD – MEAN DEVIATION – SENSITIVE TO TOTAL LOSS
• PSD – PATTERN STANDARD DEVIATION – SENSITIVE TO LOCALIZED
LOSS.
• CPSD – CORRECTED PATTERN STANDARD DEVIATION – PSD
CORRECTED FOR SHORT TERM FLUCTUATION. VERY SENSITIVE
INDEX.

12. GLAUCOMA DEFECT WITH AUTOMATED
PERIMETRY- ANDERSON'S
CRITERIA
• 3 OR MORE CONT.NON EDGE
POINTS WITH >= 5 DB LOSS
• 2 OR MORE CONT. NON EDGE
POINTS WITH >=10 DB LOSS
• DIFF. OF 10 DB ACROSS
NASAL HOR. MERIDIAN AT 2
OR MORE ADJ. POINTS
( NASAL STEP.)
• GHT - ONL
• PSD PLOT - >= 3 PTS , P< 5%
OF WHICH ONE < 1%
• CPSD ( P <5% ) GHT ONL

13. SWAP
• TESTS SUBSET OF GANGLIONS AFFECTED EARLIER &
SELECTIVELY -- BLUE / YELLOW
• REDUCES THE REDUNDANCY OF RESPONSIVENESS TO
STIMULI
• INTENSE YELLOW BACKGROUND - BLEACHES GREEN /
RED CONES
• BLUE STIM. ( 440NM ) - ISOLATES BLUE CONES
• ADAPTATION - 3 MTS. ROOM ILLUMINATION - MINIMAL
• STIMULUS SIZE & BS CHECK SIZE V
• MEAN THRESHOLD VALUES LOWER THAN SAP - GRAY
SCALE DARKER
• STAT PAC PROBABILITY PLOTS MORE RELIABLE

14. SWAP -- CONTD
• FIELD DEFECT PRECEDES SAP BY >= 3 YRS
• ONCE ABNORMAL - REMAIN ABNORMAL ( NO RECOVERY
OF DAMAGED BLUE CONES )
• NO ROLE IN ADVANCED POAG / ADVANCED LENTICULAR
CHANGES / COLOUR VISION ABNORMALITIES
• MOST USEFUL IN YOUNGER GLAUCOMA SUSPECTS,
OHT , POAG WITH MILD TO MOD.DAMAGE
• TIME CONSUMING - SITA OPTIMISED FOR SWAP / FAST
PAC CAN BE USED