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Auto perimetry

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  • 1. INTERPRETATION OFAUTOMATED PERIMETRY
  • 2. © Thomas RAutomated perimetry
  • 3. © Thomas RAutomated perimetryI. Perimetry logicII. Identifying field defectsIII. Criteria for glaucomatous defectsIV. Detecting glaucomatous progressionV. Advanced field defects
  • 4. © Thomas RBracketing strategyBA
  • 5. © Thomas RNormal thresholds• Mean threshold in disease-free fields• In a given age group• At a given location in the visual field• Mean normal values are stored in theautomated perimeter and comparedagainst patient data
  • 6. © Thomas RComputers and ease ofinterpretationSensitivity+Simple set of rulesComputerDiagnosis
  • 7. © Thomas RPerimeter logic (1)• Sensitivity determined at each location• Normal range developed• Normal range is arbitrary– Includes the values of 95% of thenormal population
  • 8. © Thomas RPerimeter logic (2)• ‘Abnormal’ values include the lowest5% of those in normal individuals• Therefore, 5% of normal individualswill be labelled abnormal‘Abnormal’ is not the sameas diseased
  • 9. © Thomas RPerimeter logic (3)• General population – 100 tested• 1% glaucoma; 99% normal• Six will have abnormal tests:• 1 glaucoma patient• 5 normal individuals
  • 10. © Thomas RPerimeter logic (4)• Clinic population – 100 tested• 30% glaucoma; 70% normal• 33 will have abnormal tests• 30 glaucoma patients• 3 normal individuals
  • 11. © Thomas RInterpretation is not child’s playAutomated perimeters still need interpretation
  • 12. © Thomas RBefore interpretation …… a few principles
  • 13. © Thomas RRely on threshold tests• First real evidence of glaucoma• Detect scotoma• Detect depression of the ‘hill’ of vision• May predict visual loss
  • 14. © Thomas RScreening tests• Screening• Fishing• Fatigue
  • 15. © Thomas RInterpreting decibel values isjust half the challenge …• False positives• False negatives• Fixation• Fluctuation• Strategy• Experience• Technicians• Artefacts
  • 16. © Thomas R
  • 17. © Thomas ROptimising patient performance• Choose the most appropriate investigation– Test pattern and strategy• Ensure the patient is comfortably positioned– Support feet, back and arms– Adjust chin rest– Cover the other eye fully• Provide careful instructions prior to the test• Support the patient during the test• Give feedback on test performanceSEAGIG. Asia Pacific Glaucoma Guidelines. 2003–2004.
  • 18. © Thomas RA word about the grey scale• Never use the grey scale alone forinterpretation• It is useful to educate the patientand to identify false-positiveand false-negative errors
  • 19. ‘White’ scotomas associatedwith false positives© Thomas R
  • 20. © Thomas R
  • 21. ‘Clover leaf’ pattern associatedwith false negatives© Thomas R
  • 22. © Thomas RUsing the grey scale• To educate the patient• White scotomas with false positives• Clover leaf pattern with false negatives• Never interpret using the grey scale alone
  • 23. © Thomas RQuestions• Is there a field defect?• Is it due to glaucoma?• Is the defect progressing?
  • 24. © Thomas RIs the field abnormal?• Without obvious defects, it is difficultto make a decision based on thefirst field• Repeat examinations providedefinitive information• Never make a diagnosis based onthe visual field alone
  • 25. Interpret the fieldsystematically usingzones 1–8© Thomas R
  • 26. 2© Thomas RAGE 57 2FIXATION LOSSES 0/24FALSE POS ERRORS 0/14FALSE NEG ERRORS 1/13QUESTIONS ASKED 449FOVEA: 33 DBTEST TIME 13:59
  • 27. • Just glance at thegrey scale and moveon to zones 4 & 5• Never interpret usingthe grey scale alone3© Thomas R
  • 28. © Thomas R• Point-by-point difference from theexpected value for age-relatednormal individuals• Reveals generalised depression• Cannot confirm a scotoma• Look at the number and patternof symbolsZone 4: total deviation
  • 29. © Thomas R180° 0°40 dB030201090 60 30 0 30 60 90Normal ‘hill’ of vision
  • 30. © Thomas R180° 0°40 dB030201090 60 30 0 30 60 90Generalised depression
  • 31. © Thomas R180° 0°40 dB030201090 60 30 0 30 60 90Generalised depression with‘hidden’ localised scotoma
  • 32. © Thomas R180° 0°40 dB030201090 60 30 0 30 60 90Pattern deviation plot: scotoma revealedafter adjusting for generalised depression
  • 33. © Thomas R• Reveals focal defectsafter adjusting foroverall depression(or elevation) of thehill of vision• Confirms a scotoma::::Zone 5: pattern deviation
  • 34. Examples of total and patterndeviation plots in different situations
  • 35. © Thomas RNormal ‘hill’ of vision
  • 36. © Thomas R‘Normal’ hill of vision withlocalised scotomaSEAGIG. Asia Pacific Glaucoma Guidelines. 2003–2004.180° 0°40 dB030201090 60 30 0 30 60 90‘Normal’ hill of vision withlocalised scotoma
  • 37. © Thomas RGeneralised depression with‘hidden’ localised scotoma
  • 38. © Thomas RGeneralised depression
  • 39. © Thomas R
  • 40. © Thomas RMD –2.18 dBPSD 4.63 dB; p < 1%SF 1.24 dBCPSD 4.44 dB; p < 0.5%• All the informationfrom all the pointstested is reduced tosingle numbersGlobal indicesMD, mean deviation; PSD, pattern standard deviation; SF, short-term fluctuation;CPSD, corrected PSD.
  • 41. • Both MD and PSDare derived from thetotal deviation plot• However, theyprovide differenttypes of information© Thomas R
  • 42. © Thomas R• Average of all the numbersin the total deviation plot• Indicates overall deviationof the visual field fromnormal• Positive numbers indicatean ‘elevated’ field• Negative numbers indicatea ‘depressed’ fieldGlobal indices: mean deviation (1)MD –2.18 dBPSD 4.63 dB; p < 1%SF 1.24 dBCPSD 4.44 dB; p < 0.5%
  • 43. © Thomas R• Provides similarinformation to totaldeviation• Cannot confirm thepresence of a scotomaGlobal indices: mean deviation (2)MD –2.18 dBPSD 4.63 dB; p < 1%SF 1.24 dBCPSD 4.44 dB; p < 0.5%
  • 44. © Thomas R• Also derived from thetotal deviation plot• Indicates the degreeto which the numbersdiffer from each other• Highlights ‘roughness’or ‘pot-holes’ in the hillof visionGlobal indices:pattern standard deviation (1)MD –2.18 dBPSD 4.63 dB; p < 1%SF 1.24 dBCPSD 4.44 dB; p < 0.5%
  • 45. © Thomas RGlobal indices:pattern standard deviation (2)MD –2.18 dBPSD 4.63 dB; p < 1%SF 1.24 dBCPSD 4.44 dB; p < 0.5%• Provides similarinformation to thepattern deviation• Calls attention toscotomas
  • 46. © Thomas R2828 29 33 32 32323030333229 31283029292921262728293332312429313029282629292726262528 29 32 32 32322930323129 312528292520272627280343432293233303032252729282329(31)(32)(32) (30)(31)(30)(33)(30) (31)(33)• Intra-test error inthreshold determination• Standard deviation of10 predeterminedpoints that are eachtested twiceGlobal indices:short-term fluctuation
  • 47. © Thomas RGlobal indices: correctedpattern standard deviation• CPSD is PSD corrected for the SF– If SF is due to unreliability,then CPSD is better– If SF is due to pathology,then PSD is better
  • 48. © Thomas RMDTotaldeviation plotPSDPatterndeviation plotGeneralised depressionCan suspect a scotomaReview of key pointsLocal irregularityConfirms scotoma
  • 49. Glaucoma Hemifield Test© Thomas R
  • 50. © Thomas RZone 7: Glaucoma Hemifield Test44 5321
  • 51. © Thomas RGHT, Glaucoma Hemifield Test.
  • 52. © Thomas R
  • 53. 8© Thomas R
  • 54. • Never rely on thegrey scale alone tomake a diagnosis• Never rely on thevisual field alone tomake a diagnosis• Always correlatewith the clinicalfindings© Thomas R
  • 55. © Thomas RQuestionsIs there a field defect?• Is it due to glaucoma?• Is the defect progressing?
  • 56. © Thomas RGlaucomatous defects• Characteristics of glaucomatous defects:– Asymmetrical across the horizontal midline*– Located in the mid-periphery*(5–25 degrees from fixation)– Reproducible– Not attributable to other pathology– Localised– Correlating with the appearance of the optic discand neighbouring areas* Applicable to early/moderate cases.SEAGIG. Asia Pacific Glaucoma Guidelines. 2003–2004.
  • 57. © Thomas RCriteria for glaucomatousdefects (1)Pattern deviation plot• ≥ 3 non-edge pointswith p < 5%• One point with p < 1%• Cluster in arcuate area
  • 58. © Thomas RCriteria for glaucomatousdefects (2)CPSD or PSDdepressedwith p < 5%
  • 59. © Thomas RCriteria for glaucomatousdefects (3)Abnormal GHT
  • 60. © Thomas RThree criteria for glaucomatousdefects*1. Pattern deviation plot– ≥ 3 non-edge pointswith p < 5%– One point with p < 1%– Cluster in arcuate area2. CPSD or PSDdepressed with p < 5%3. Abnormal GHT*Anderson DR, Patella VM. Automated Static Perimetry. 2nd Edn. St Louis: Mosby, 1999.
  • 61. • Try interpretingthis visual field,going fromzones 1–8© Thomas R
  • 62. 22Visual acuity should correlatewith the foveal threshold© Thomas R
  • 63. • Continueinterpretingthis visual field:zones 3–8• Remember:no more than aglance at thegrey scale© Thomas R
  • 64. © Thomas RRevision: typical cataract
  • 65. © Thomas RRevision: typical glaucoma
  • 66. © Thomas RRevision: glaucoma and cataract
  • 67. © Thomas RDoes this patient haveglaucoma? (1)Only if the defects are repeatable and correlate with disc and clinical findings
  • 68. © Thomas RDoes this patient haveglaucoma? (2)Only if the defects are repeatable and correlate with disc and clinical findings
  • 69. © Thomas RQuestionsIs there a field defect?Is it due to glaucoma?• Is the defect progressing?
  • 70. © Thomas RPrinciple• Is there a field defect?• Is it due to glaucoma?• Is the defect progressing?– Compare to selected baseline– Discard learning fields from baseline– Recognise ‘false’ progression
  • 71. © Thomas RFalse progression• Learning curve• Long-term fluctuation• Artefacts• Patient factors• Pupil size
  • 72. Pupil: 1 mm© Thomas R
  • 73. Pupil: 2.5 mm© Thomas R
  • 74. © Thomas RDetecting change• Change analysis – box plot• Overview programme• Glaucoma progression analysis™(GPA™)1. Select appropriate baseline2. Discard learning fields from baseline
  • 75. © Thomas ROverview programme• Sequential series of fields for the samepatient over a period of time• Has all the single field information,including total and pattern deviation plots• Tells us at a glance what is happeningand allows us to deduce WHY it ishappening
  • 76. Fluctuation over time© Thomas R
  • 77. Overview: the patient developed a cataract, which wasextracted. Note that the pattern deviation plot remains clear.© Thomas R
  • 78. Overview: glaucoma is progressing. Both the total and patterndeviation plots show worsening.© Thomas R
  • 79. © Thomas ROverviewprogramme showsprogressionFull thresholdSITA standardSITA, Swedish InteractiveThreshold Algorithm.
  • 80. © Thomas ROverviewprogramme showsprogression• SITA is differentfrom full threshold• Cant compareapples to oranges• Fields may fluctuate
  • 81. © Thomas RGlaucoma Progression Analysis™*• GPA™ is now in clinical use• Change is based on the pattern deviation plot• Compatible with both SITA and full threshold(baseline only)*Carl Zeiss Meditec.
  • 82. © Thomas R
  • 83. GPA™Right eye:baseline© Thomas RGPATM, Glaucoma ProgressionAnalysisTM.
  • 84. GPA™Right eye:follow-up© Thomas RGPATM, Glaucoma ProgressionAnalysisTM.
  • 85. © Thomas R3 or more points deteriorate in at least 2 consecutive tests© Thomas R
  • 86. 3 or more points deteriorate in at least 3 consecutive tests© Thomas R
  • 87. GPA™Left eye:baseline© Thomas RGPATM, Glaucoma ProgressionAnalysisTM.
  • 88. GPA™Left eye:follow-up© Thomas RGPATM, GlaucomaProgressionAnalysisTM.
  • 89. © Thomas R
  • 90. © Thomas RDiagnosis of visual fieldprogression• Different for research purposes– Set criteria in isolation• Clinical follow-up scenario– Other criteria (IOP, disc changes) to consider– A corresponding repeatable change is sufficient– If in doubt, REPEAT• Baseline fields are not constant– Select accordingly
  • 91. Don’t forget to discard‘learning’ fields frombaseline© Thomas R
  • 92. © Thomas RFollow-up of advancedfield defects
  • 93. Advanced field defectWhy is the patterndeviation plot notshowing a defect?© Thomas R
  • 94. Not enough points withsensitivity to produce thepattern deviation plot© Thomas R
  • 95. Follow-up with a 10–2 programme –now there are enough sensitive pointsto produce a pattern deviation plot© Thomas R
  • 96. Advanced defectand/or low sensitivities –follow-up with a size VtargetDisadvantage: we losestatistical help forinterpreting the total andpattern deviation plots© Thomas R
  • 97. © Thomas RMore advanced defects: followwith macular programme
  • 98. Macular programme inadvanced glaucoma© Thomas R
  • 99. Size V target: macular splitMacular split (0 dB) next to the foveawith a size V target may predict ‘wipe out’© Thomas R
  • 100. © Thomas RRecent developments: SITA• Asks smart questions• Gold standard• More abnormal points on patterndeviation• Shallower defects• Significant because of less variability
  • 101. SITA is interpreted inthe same 8 zones aspreviously described© Thomas RSITA, Swedish InteractiveThreshold Algorithm.
  • 102. SITA uses the samecriteria to identify aglaucomatous fielddefect© Thomas RSITA, Swedish InteractiveThreshold Algorithm.
  • 103. Applying the skillsDoes this field fulfilthe criteria for aglaucomatous defect?Does this patienthave glaucoma?© Thomas R
  • 104. Not unless the fielddefect correlates withclinical findingsNever diagnosebased on the visualfield ALONE© Thomas R
  • 105. © Thomas RAutomated perimetry: warningSophisticated techniques and elaboratedata printouts should not seduce us intoa false sense of security or a misplacedbelief in the validity or reliability ofautomated perimetry**Zalta AH. Ophthalmology 1989; 96: 1302–11.
  • 106. INTERPRETATION OFOCTOPUS FIELDS
  • 107. © Thomas RTest parameters – Octopus vs.HFA4–2 dB bracketingstrategySITA standardSITA fast4–2–1 dB bracketingstrategyDynamicTendency orientedperimetry (TOP)Test strategies0–40 dB0–40 dBMeasuring rangeGoldmann I–V200 ms10,000 asbGoldmann III and V100 ms4800 asbStimulus sizeStimulus durationLuminance for 0 dB10 cd/m2 (31.5 asb)10 cd/m2 (31.4 asb)Background luminanceAspherical bowlDirect projectionBowl typeHFA 700 seriesOctopus 300ParameterFankhauser F et al. Automated Perimetry: Visual Field Digest. 5thEdn. Köniz: Haag-Streit AG, 2004.
  • 108. [[Credit line to be added]]ProbabilityplotsComparisontablesGrey scalePatient dataand refractionStrategy andtest parametersActual valuesBebie (defect)curveDeviationGlobal indicesRP: permissionrequested
  • 109. © Thomas ROctopus global indices• MS Mean sensitivity– Average of all measured values• MD Mean defect– Average of all values corrected for age• LV Loss variance– Equivalent to PSD• SF Short-term fluctuation• CLV ‘Corrected’ loss variance– Equivalent to corrected PSD• RF Reliability factor
  • 110. © Thomas RIs the visual field abnormal?• Octopus criteria for a visual field defect1– MD greater than 2 dB– LV greater than 6 dB– At least 7 points with sensitivity decreasedby ≥ 5 dB, three of them being contiguous• How do these compare to HFA criteria?1. Morales J et al. Ophthalmology 2000; 107: 134–42.
  • 111. © Thomas RHFA criteria for glaucomatousdefects*1. Pattern deviation plot– ≥ 3 non-edge pointswith p < 5%– One point with p < 1%– Cluster in arcuate area2. CPSD or PSDdepressed with p < 5%3. Abnormal GHT*Anderson DR, Patella VM. Automated Static Perimetry. 2nd Edn. St Louis: Mosby, 1999.
  • 112. Comparison of Octopus andHFA fields from a single patient© Sihota R
  • 113. © Thomas RPatient data, strategy and testparameters© Sihota R
  • 114. © Sihota RGrey scale
  • 115. © Thomas R© Sihota ROctopus: comparison tablesPhase I Phase 2 Mean# 59 59 59MS 21.8 18.6 20.2MD 6.8 10.1 8.5LV 46.6 73.2 51.0CLV 42.2SF 4.9RF 3.1
  • 116. © Thomas R© Sihota RGHT Outside normal limitsMD –7.58 dB; p < 0.5%PSD 6.30 dB; p < 2%SF 2.27 dB; p < 10%CPSD 5.75 dB; p < 1%HFA: total and pattern deviation