Visual field assessment

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Visual field assessment

  1. 1. VISUAL FIELD ASSESSMENT STATIC PERIMETRY BY DR. ANAND SUDHALKAR Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 1
  2. 2. Situations demanding Field Test  Glaucoma Diagnostic Triad with IOP and Disc changes.  IOP > 21mm Hg.  Significant Cupping with/without high IOP  Strong Family History, Myopia, Diabetes  Narrow Angles/Int. IOP  Normal “Other” Eye of the glaucoma patient 9/22/2010
  3. 3. What are we testing? Actual visual field Tested visual field 60° Fixation Blind  The central 30° field spot represents 66% of the ganglion cells and 83% of the visual cortex  Nearly all pathologies can be 60° 30° 90° associated with loss of retinal sensitivity in the 30° visual field Nasal field Temporal field  If in doubt, it is recommended 70° to repeat the central field rather than test the periphery Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 3
  4. 4. What are we looking for?  Is the visual field reliable?  Pattern of defects  Significance of defects  Normal or Glaucoma  Clinical correlation Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 5
  5. 5. Reading the chart Patient and examination data Measured values and greyscale GHT Defect Curve Comparison values VF Indices Probability plots Eye fixation Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 6
  6. 6. Patient and examination data Program and strategy Pupil size Date of birth Questions, repetitions and catch Refraction trials Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 7
  7. 7. VA grey-scale degradation with age Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 8
  8. 8. Reliability check by:  Fixation losses  catch trials Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 9
  9. 9. Reliability check by catch trials Positive Catch Trials  With the positive catch trials, the perimeter produces a stimulus sound although NO light is projected - the patient should not respond.  With many positive mistakes, the patient is a “happy trigger” patient. Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 10
  10. 10. Reliability check by catch trials Negative Catch Trials  With the negative catch trials, the perimeter projects its brightest spot where a less intense stimulus was seen before - the patient must respond!  With severely depressed fields, the patient usually makes more mistakes. This is normal. Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 11
  11. 11. Reliability check by catch trials Evaluation  The Reliability Factor is the number in percent of the positive and negative catch trial mistakes.  Whenever this factor exceeds 15-20% the results must be evaluated with caution. Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 12
  12. 12. Value table and VA grey-scale The measured values are the The VA grey-scale presents a base for all further calculations comprehensive summary of and graphics the visual field Foveal Threshold Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 13
  13. 13. Octopus Humphrey comparisons Measuring range in Decibel (dB) d.l. sensitivity luminance in Decibel (dB) in Apostilb (asb) Perimeter models 101 300 HFA 40 dB - 0.1 asb 0.4 asb 1 asb 30 - 1.0 4.0 10 20 - 10 40 100 10 - 100 400 1’000 0 - 1’000 4’000 10’000 Background (asb) 4 31.5 31.5 Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 14
  14. 14. Basic perimeter parameters Parameter OCTOPUS 101 OCTOPUS 300 HFA Bowl type Spherical bowl Direct projection A-spherical bowl 42.5 cm 18-30 cm Background - Luminance 4 asb 31.4 asb 31.5 asb (1.27 cd/m²) (10 cd/m²) (10 cd/m²) Stimulus - Size Goldmann I - V Goldmann III, V Goldmann I - V - Duration 100 ms 100 ms 200 ms - Luminance 1’000 asb 4’800 asb 10’000 asb for 0 dB Measuring range 0 - 40 dB 0 - 40 dB 0 - 40 dB Test strategies 4-2-1 dB bracketing 4-2-1 dB bracketing 4-2 dB bracketing Dynamic strategy Dynamic strategy SITA Normal TOP TOP SITA Fast Normal values Age correction per year of age Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 15
  15. 15. Comparison table and CO grey-scale:(difference (comparison) between the age-corrected normal data and the actual measured results) Actual Value table Age matched comparison Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 16
  16. 16. Corrected comparisons table: depicts local defects relative to the mean diffuse depression In the “corrected” comparisons table the deviation value is taken into account to highlight pathological changes without the effect of any preretinal interferences(mean diffuse depression of 8db) This table displays comparisons minus deviation 9/22/2010 18
  17. 17. The cumulative defect (Bebie) curve The CO values are sorted in size and displayed in order (ranking) from the smallest to the largest defect CO values Ranking Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 18
  18. 18. Typical defect curves Suspect field: • incorrect date of birth Normal visual field or trial lens • small pupil • cataract • early glaucoma Focal defect e.g. Early glaucoma Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 19
  19. 19. Visual Field Indices Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 20
  20. 20. Visual field indices For a quick assessment of the visual field it is helpful to average all values in a few (global) indices Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 21
  21. 21. Index - mean sensitivity (MS)  Normal values      Mean sensitivity MS    Average of all measured values  Measured values Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 22
  22. 22. Mean defect (MD)  Normal values      Mean sensitivity MS    Mean defect (MD) difference between average normal and MS  Measured values Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 23
  23. 23. Normal range of MD = -2 to +2 dB  The Mean Defect MD represents the average defect of the entire visual field  MD reacts strongly on diffuse (homogeneous) depression  Localized (topical) defects have practically no influence on MD  MD is the index for uniform loss of sensitivity Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 24
  24. 24. Loss variance (LV)  Normal values      MS    MD Loss variance (LV) Spread of measured Measured values values from MS  Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 25
  25. 25. Normal range of LV = 0 to 6 dB2  The index Loss variance (LV) is sensitive to the irregularity of the visual field  Normal visual fields have an LV of 0 .. 6 dB2  LV (or sLV) = standard deviation (sd)  Normal visual fields have an sLV of 0 .. 2.5 dB  An elevated LV (or sLV) is an indication that the field has localized defects exceeding the normal local variability Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 26
  26. 26. Probability of defects Probability plots helpful to signal the significance of a local defect P<0.5 means that less than 0.5% of the normal population shows a defect of this size at this location – Therefore this defect is a significant defect 9/22/2010 28
  27. 27. What are we looking at? Established glaucomatous damage  Nasal and upper hemifield defects  Classic arcuate Bjerrum scotoma  Nasal Step respecting the horizontal raphe  Differentiate between generalized or diffuse against localized deep defects.  Increased fluctuations in retinal sensitivity in those specific areas. Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 28
  28. 28. Diagnostic field defects in glaucoma The visual field below demonstrates a cecocentral Locations on chart scotoma and superior nasal step and inferior nasal step with some extension into the acruate bundle. Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 29
  29. 29. Criteria for glaucomatous loss Early Stage  MD > 3 < 6dB  Fewer than 15 points affected with p < 5% and fewer than 8 points below p < 1% level Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 30
  30. 30. Criteria for glaucomatous loss Moderate Stage  MD > 6 < 12dB  Fewer than 30 points affected with p < 5% and fewer than 15 points below p < 1% level Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 31
  31. 31. Criteria for glaucomatous loss Advanced Stage  MD > 12dB  More than 30 points affected with p < 5% and more than 15 points below p < 1% level Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 32
  32. 32. Early Field Loss Same Patient comparison Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 33
  33. 33. Moderate Field Loss Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 34
  34. 34. Severe Field Loss Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 35
  35. 35. Pearls  Check field for reliability  Look for glaucoma specific losses/neurological  Correlate with disc cupping, NFL loss and IOP, complete fundus examination.  Repeat fields : 1. If in doubt  2. Follow-up Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 36
  36. 36. Thank You Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 37
  37. 37. 55 yr Male, LE DV post op 6 months Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 38
  38. 38. Field RE LE Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 39
  39. 39. Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 40
  40. 40. RE LE Sudhalkar Eye Hospital, Baroda, Gujarat 9/22/2010 41

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