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04/12/2023Sudhalkar Eye Hospital, Baroda, Gujarat 1
SINGLE FIELD ANALYSISBY
DR. ANAND SUDHALKAR
AIOS 2010, Kolkatta. Instruction course no. 82 [IC76] GLAUCOMA –Basic Sunday, 24-1-2010
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
04/12/2023
What are we testing?
Actual visual field Tested visual field
Temporal field
Nasal field
60°
90°
70°
60° 30°
Fixation
Blind spot
The central 30° field represents 66% of the ganglion cells and 83% of the visual cortex
Nearly all pathologies can be associated with loss of retinal sensitivity in the 30° visual field
If in doubt, it is recommended to repeat the central field rather than test the periphery
04/12/2023Sudhalkar Eye Hospital, Baroda, Gujarat 3
04/12/2023
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 5
Reading the chart
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Patient and examination dataPatient and examination data
Measured values and greyscaleMeasured values and greyscale
VF IndicesVF Indices
GHTGHT
Comparison valuesComparison values
Defect CurveDefect Curve
Eye fixationEye fixation
Probability plotsProbability plots
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Patient and examination data
Date of birth
RefractionQuestions, repetitions and
catch trials
Pupil sizeProgram and strategy
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VA grey-scale degradation with age
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Reliability check by:
Fixation losses catch trials
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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.
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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.
Reliability check by catch trials Negative Catch Trials
Reliability check by catch trials Negative Catch Trials
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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.
Reliability check by catch trials Evaluation
Reliability check by catch trials Evaluation
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Value table and VA grey-scale
The VA grey-scale presents a comprehensive summary of
the visual field
The measured values are the base for all further calculations and graphics
Foveal Threshold
Octopus Humphrey comparisonsMeasuring 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
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Basic perimeter parameters
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Parameter OCTOPUS 101 OCTOPUS 300 HFA
Bowl type Spherical bowl Direct projection A-spherical bowl42.5 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 bracketingDynamic strategy Dynamic strategy SITA Normal
TOP TOP SITA Fast
Normal values Age correction per year of age
Comparison table and CO grey-scale:(difference (comparison) between the age-corrected normal data and the actual measured results)
Actual Value tableAge matched comparison
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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)
04/12/2023
This table displays comparisons minus deviation
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RankingCO values
The cumulative defect (Bebie) curve
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The CO values are sorted in size and displayed in order (ranking) from the smallest to the largest defect
Typical defect curves
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Normal visual fieldNormal visual field
Suspect field:• incorrect date of birth
or trial lens• small pupil • cataract• early glaucoma
Suspect field:• incorrect date of birth
or trial lens• small pupil • cataract• early glaucoma
Focal defectFocal defect e.g. Early glaucomae.g. Early glaucoma
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Visual Field IndicesVisual Field Indices
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Visual field indicesFor a quick assessment of the visual field it is helpful
to average all values in a few (global) indices
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Index - mean sensitivity (MS)Index - mean sensitivity (MS)
Mean sensitivity MSMean sensitivity MS
Normal valuesNormal values
Measured valuesMeasured values
Average of all measured values
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Mean defect (MD)Mean defect (MD)
Mean sensitivity MSMean sensitivity MS
Normal valuesNormal values
Measured valuesMeasured values
Mean defect (MD) difference between average normal and MS
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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
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Loss variance (LV)
MSMS
Normal valuesNormal values
Measured valuesMeasured values
MD
Loss variance (LV)Spread of measured values from MS
26
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
04/12/2023Sudhalkar Eye Hospital, Baroda, Gujarat
Probability of defects
Probability plots helpful to signal the significance
of a local defect
04/12/2023
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
28
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.
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Diagnostic field defects in glaucoma
Locations on chartThe visual field below demonstrates a cecocentral scotoma and superior nasal step and inferior nasal step with some extension into the acruate bundle.
30
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
04/12/2023Sudhalkar Eye Hospital, Baroda, Gujarat
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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
04/12/2023Sudhalkar Eye Hospital, Baroda, Gujarat
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Criteria for glaucomatous lossAdvanced Stage
MD > 12dB More than 30 points affected with p < 5%
and more than 15 points below p < 1% level
04/12/2023Sudhalkar Eye Hospital, Baroda, Gujarat
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Same Patient comparison
Early Field Loss
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Moderate Field Loss
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Severe Field Loss
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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
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55 yr Male, LE DV post op 6 months
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Field RELE
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RE LE