aios 2010 presentation 1

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

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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


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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


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


Patient and examination data

Date of birth

RefractionQuestions, repetitions and

catch trials

Pupil sizeProgram and strategy


VA grey-scale degradation with age


Reliability check by:

Fixation losses catch trials


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.


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


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


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


Basic perimeter parameters


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


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)

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This table displays comparisons minus deviation

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RankingCO values

The cumulative defect (Bebie) curve


The CO values are sorted in size and displayed in order (ranking) from the smallest to the largest defect

Typical defect curves


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


Visual Field IndicesVisual Field Indices


Visual field indicesFor a quick assessment of the visual field it is helpful

to average all values in a few (global) indices


Index - mean sensitivity (MS)Index - mean sensitivity (MS)

Mean sensitivity MSMean sensitivity MS

Normal valuesNormal values

Measured valuesMeasured values

Average of all measured values


Mean defect (MD)Mean defect (MD)

Mean sensitivity MSMean sensitivity MS



Mean defect (MD) difference between average normal and MS


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


Loss variance (LV)

MSMS



MD

Loss variance (LV)Spread of measured values from MS

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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

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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

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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.



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.

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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


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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


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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



Same Patient comparison

Early Field Loss


Moderate Field Loss


Severe Field Loss


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


55 yr Male, LE DV post op 6 months


Field RELE


RE LE

aios 2010 presentation 1

Health & Medicine