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KINETIC VS STATIC PERIMETRY, AUTOMATED PERIMETRY SURAJ CHHETRI B.OPTOMETRY 16 th batch

AVF by suraj chhetri

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Page 1: AVF by suraj chhetri

KINETIC VS STATIC PERIMETRY, AUTOMATED PERIMETRY

SURAJ CHHETRIB.OPTOMETRY16th batch

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Presentation layout Introduction to perimetry and visual field

Various terminologies Kinetic vs static perimetry Automated perimetry Difference between octopus and Humphrey Humphrey field analyzer o The hardware o Threshold testing strategies o Field locations for Humphrey o Single field analysis and interpretationo Learning effect and artifact in AVF o Point pattern of HFA

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Is the subjective examination method for estimating the extent of visual field.

Enables the assessment of: Visual function throughout the visual field Detection and quantification of damage to the

visual field. Monitoring the change over a time.

Perimetry

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Standard clinical perimetry tests the distribution of light difference sensitivity in the visual field.

Sensitivity reflects the capability of the eye to perceive a brightness difference between target and its background.

DLS=L1/L2-L1, where L1 is the background luminance and L2 is target luminance.

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5 The field of vision is defined as the area that is perceived simultaneously by a fixating eye

Ref:Becker- Shaffer’s Diagnosis and Management of Glaucoma, 8th edition.

VISUAL FIELD

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6

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7 Traquair defined visual field as island of vision in

the sea of darkness. Hill of vision is a 3D representation of the retinal

light sensitivity Sea represents the areas of no light perception

• Under photopic condition, the shape of hill of vision is closely related to the packing density of the cones and receptive field size.

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8 VARIOUS TERMINOLOGIES

Luminance: It is the intensity or ‘brightness’ of a light stimulus, measured in apostilbs (asb)

( inverse of sensitivity)

Isopter: All the locations where the stimulus is first seen have equal sensitivity, these locations can be connected to form a ring shaped locus of points

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Continue…..Threshold: : The minimum light energy necessary to evoke a visual response with a probability of 0.5, i.e. the observer can detect the stimulus 50% of the time it is presented Sensitivity which is reciprocal of threshold.

Sensitivity is presented in decibel(dB)

Higher db = lower intensity = high retinal sensitivity Lower db= higher intensity = lower retinal sensitivity

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Continue…. Anopia / anopsia : defect in visual field. e.g

hemianopia Absolute Scotoma : It is an area of total

(‘absolute’) loss of vision which is surrounded by a seeing area

Relative scotoma: It is an area of reduced (‘relative’) loss of vision which is surrounded by a seeing area.

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11

Kinetic vs. static perimetry

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A stimulus of same size and intensity moved from a non seeing area of the visual field a seeing

area along a set meridian to determine the extent of VF or VF

defects. The procedure is repeated with the use of the

same stimulus along other meridians, usually spaced every 15°: to plot an Isopter.

The hill of vision is found by approaching it horizontally.

Eg. Goldmann, Arc perimetry

Kinetic perimetry

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The size and location of the test target remain constant and measure the threshold of the retinal points

The threshold is determined exactly by increasing the luminance of an infrathreshold target as well as by decreasing the luminance of a suprathreshold targets, until the threshold has been determined.

Eg: Goldmann , Automated Perimetry

Static perimetry

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Principle difference is the way of detecting the differential light sensitivity.

The kinetic examination with moving test objects allows us to detect steep gradients or circumscribed scotomas especially well.

The static perimetry where the test target is stationary is a method especially suited to detect field defects with a flat gradient. e.gCircumscribed flat scotomas or a generalised depression of d. l. sensitivity

Comparison between kinetic and

static perimetry

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17

Eccentricity E

d.L

sens

itivi

ty

d.L

sens

itivi

ty

Eccentricity

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Continue….

If we find a steep slope in the visual field the kinetic principle with horizontal motion toward the hill of vision or toward the margins of the scotoma will provide a much sharper and well delineated threshold than the vertical approach.

If the slope is flat and if there is only a slightly inclined nearly horizontal gradient, the static method with vertical approach will be superior to the kinetic method

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Continue……

The physiologic distribution of differential light sensitivity with a relatively flat slope in the paracentral area and in the mid periphery make the static principle for central VF the method of choice.

Similarly, the steep gradients of the peripheral VF make the kinetic principle superior to the static one.

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20 Kinetic perimetry

Static perimetry

Measures the extent of visual field by plotting the isopters

Measures the sensitivity of each retinal points

Stimulus moves from non seeing to seeing area

Stimulus is stationary but increases in luminance until seen

Stimulus size can be varied

Constant

2D measurement of hill of vision

3D assessment of height of predetermined areas of hill of vision

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21 Kinetic perimetry

Static perimetry

Results depend upon the experience of the operators

Though it depends but has very little role of the operator

Can rapidly evaluate the peripheral VF, plot deep defects.Can accurately plot steep bordered defects and useful for localization, characterization of neurological defects

It has ability to detect scotomas, particularly small, shallow, or fluctuating scotomas but cannot correctly outline the border of the defect

Eg. Confrontation perimeter, tangent perimeter, Arc perimeter, Goldmann perimeter

Eg. Automated perimeter, Goldmann perimeter

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22 A moving stimulus will be detected more readily

in the periphery than a static stimulus because of successive lateral spatial summation.

As the stimulus moves across the visual field, spatial summation of receptive fields adjacent to the receptive field over which the stimulus is placed occurs.

Thus, the detection of the stimulus will be influenced by normal areas of visual field, in addition to any damaged areas, which could lead to shallow focal loss in the visual field being missed.

Continue…

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23 Automated perimetry Is merely a computer assisted examination (and

not a fully automatic test) since the results depend on the patient’s collaboration and the accuracy of the answers.

Field testing strategy mainly static field testing

Test target is placed at a preselected field position, and intensity gradually raised until the patient detects it.

e.g Humphrey ,octopus , dicon ,Topcon perimeters

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24

OCTOPUS 300 HUMPHREY 700BOWL TYPE Direct projection A spherical bowl

(1/3m)

Background luminance

31.4 asb 31.5 asb

Stimulus size Goldmann III and V Goldmann I-VDuration 100ms 200msLuminance for 0 dB

4800asb 10000asb

Measuring range 0 – 40 dB 0-40dBTest strategies 4-2-1dB bracketting

Dynamic strategyTOP

4-2dB brackettingSITA NormalSITA Fast

Normal values Age correction per yr of age

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HUMPHREY FIELD ANALYZER

The hardware: consist of following parts

The bowl : HFA|| aspherical or bullet shaped surface

Distance from eye to center of bowl is 30 cm Bowl surface is textured perfectly matte finish

known as Lambertian surface The optical system: stimuli presented by

aiming a particular location to be tested

1. The bowl or projection system2. The optical system3. Central processor4. The patient interface

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Continue…..

The central processor : it fulfills many functions commonly seen in desktop computers

must control optical system Split second strategy adjustment based upon

the each patient response The patient interface : consists of Chin rest, forehead rest , trial lens holder,table

and chair Trial lens holder use to hold 37mm ophthalmic

trial lens which is never used for testing outside 30 degrees because lens and holder will produce an area of deep artifact

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THRESHOLD TESTING STRATEGIES

1) Old threshold strategy Suprathreshold strategy Full threshold strategy

2) newer threshold strategies Fast PAC SITA standard SITA fast

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Time saving strategy Screen for the presence of a defect, and

roughly localize it (SCREENING STRATEGY)

Two type: Single intensity static suprathreshold

strategy/ One-level suprathreshold strategy

Gradient- adapted threshold strategy/Two level suprathreshold test

Suprathreshold strategy

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Continue…

A stimulus that is 2 to 6 db brighter (suprathreshold) than the expected hill of vision is used to test multiple locations in the visual field

Stimulus luminance is automatically modified to be brighter at more peripheral locations and dimmer centrally, thus suprathreshold level will take into account the normal shape of hill of vision.

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DLS determined by use of 4-2 bracketing strategy (Staircase method )

Computer determines threshold first at one primary point per quadrant. (9 degree away from vertical meridian and horizontal meridian for 30-2 program)

Staircase consist of 4db decrements in light intensity until the patient fail to respond(first reversal), then 2db increment until the patient sees the light again(second reversal). This final level is the sensitivity recorded

Full threshold/Normal strategy

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Uses 3 db step size.

Staircase terminates when it has crossed the threshold once

Threshold is recorded as the last seen stimulus Time saving – 1/3rd of time of standard full threshold.

Drawback: short term fluctuation more and increased threshold error, thus reducing the reproducibility.

FASTPAC

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Comparison between standard full threshold and FASTPAC

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Ideal threshold algorithm

Estimate threshold with high precision within minimum time

Also uses the staircase method to determine threshold like the standard threshod.

But, it compares the threshold of patient with the recorded normal and abnormal values and make sophisticated statistical analysis and give probability plotting.

SITA(Swedish Interactive Threshold Algorithm)

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Unlike, other threshold algorithms used in perimeters, SITA adapts the stimulus presentation speed to the reaction times of the patient, which in most cases reduces test time.

Available in two forms :SITA Standard and SITA Fast

The difference between the two is the chosen level of accuracy for the threshold estimation.

That is SITA Fast more faster with less accuracy than the SITA Standard.

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Accuracy

SITA Standard is equivalent with full/ standard threshold consuming less time.

SITA Fast is equivalent with FASTPAC consuming less time.

Comparison of SITA algorithm with other threshold strategy

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TIME TAKEN BY STRATEGIES

30-2 SITA fast takes 5.5 min to estimate threshold

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37Examination programs

OCTOPUS 300G1/G2

PROGRAM 32

M1/M2

HUMPHREY 700

CENTRAL ZONE

PERIPHERAL ZONE

FULL FIELD

SPECIAL DESIGNS

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Field location options for Humphrey

ZONE SCREENING THRESHOLD TEST

AREA OF FIELD COVERED

CENTRAL FIELD ONLY

Central 40 pt orCentral 80ptCentral 76pt orCentral 166pt

MaculaCentral 10-2Central 24-1Central 24-2Central 30-1Central 30-2

0-4°0-10°0-24°0-24°0-30°0-30°

PERIPHERAL FIELD ONLY

Peripheral 68 pt

Peripheral 30/60-1Peripheral 30/60-2

30-60°30-60°

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`ZONE SCREENING TEST AREA OF FIELD

COVEREDFULL FIELD Full field 120 pt

Full field 246 pt0-60°0-60°

-1 version start their point on the horizontal and vertical meridians whereas -2 version place test locations flanking the meridians

- 2 better for detemining nasal and hemianopic steps.1

1 field of vision: a manual and atlas of perimetry by Barton and Banetar

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Statistical analysis of patient’s result is done and the this package available in Humphrey is called STATPAC.

Greatly simplifies VF interpretation by differentiating between normal and

abnormal VFs

by identifying significant change in the series of visual fields.

Also determines whether the patient VF results fall within the range normal for his/her age.

Printing results

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The analysis of the data acquired, is presented in following formats

Single field analysis Change analysis Overview glaucoma change printout

Single field analysis is devoted to analysis of a single field

Change analysis and overview are used to interpret multiple fields obtained at different times.

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Single Field Analysis and Interpretation VF Printout consists of following regions:

1. Patient data/ Test data/Demographic data 2. Reliability indices/foveal threshold 3. Raw data 4. Grey scale 5. Total Deviation Numerical Plot (TDNP) 6. Total Deviation Probability Plot (TDPP) 7. Pattern Deviation Numerical Plot (PDNP) 8. Pattern Deviation Probability Plot (PDPP) 9. Global indices (MD, PSD, CPSD, SF) 10. Glaucoma Hemi-field test (GHT)

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1: demographic data Name, age/gender Birth date Pupil size (at least 2.5 to 3 mm) Visual acuity Refractive error Test performed ( strategy) Stimulus size and color Fixation target

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2:Foveal threshold Reliablity parameters

Fixation loss False positive error False negative error Test duration Foveal sensitivity

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Monitered by three methods

Observation of perimetrist(manual): perimeter has video system to project an image of the eye on monitor and perimetrist has to detect fixation shifts and faulty head positioning.

Automatic fixation: either signals the perimetrist when fixation wanders or repeat the stimulus presentation.

Fixation loss

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Heijl Krakau method: Blindspot is localised though not

necessarily plotted, early in the testing process.

Stimuli is then periodically presented in the presumed blind spot.

Light seen by patient in this area means fixation loss.

Fixation loss >20% are considered unreliable test.

Continue…

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In case of HFA, there is gaze tracking/monitor at the bottom of the single field analysis printout.

Here, the distance between a corneal light reflex and the center of the pupil is measured. Thus eye rotations can be judged.

Errors are indicated by upward deflections from the baseline. i.e upward deflections indicate deviations due to eye movement.

Downward deflections indicate that the patient blinked when a stimulus was present.

Continue…

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This is a positive response by the patient even in absence of stimulus

Also called positive catch trials

In case of SITA algorithm, the number of anticipatory response made too soon to light stimulus than expected are labelled as false positive.

False positive up to 20% is acceptable.

False positive error

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A fairly bright suprathreshold target is flashed in a region previously tested with fainter targets. If the patient fails to indicate its presence, this is recorded with false negative.

Called as negative catch trial. High false negative implies inattention or

fatigueness of patient. Acceptable upto 20%. High false negative value is indicated by XX

beside the abberant value and a printed statement of low patient reliability in upper left corner.

False negative

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3: Raw data It is exact retinal sensitivity expressed in db units

Raw data used by different strategies differs so always use same strategy for follow ups

Normally (<) sign is seen only in front of zero(0). But if (<1) then, maximum intensity of light projected by field analyzer is not 10,000 asb units but 9500 asb.

So, (<) sign in any digit other than zero ‘0’ indicate that the light is becoming dim and it’s time to replace bulb or it requires calibration)

Visual field threshold decline with age about 0.5 to 1 db per decade

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4:Gray scale/half tone/color scale

Numerical values from raw data are presented

graphically according to a grey scale form,

Grey scale doesn’t give definitive diagnosis .it only help doctors to explain status of visual field to patients

• Areas of high sensitivity are denoted by lighter shades and area of low sensitivity are denoted by darker shades

Never ever use gray scale solely for diagnosis ( we examine 76/54 points but gray scale form by upto 2000 points )

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The numeric value of threshold ( raw data) is compared with the age matched normative data and the difference in value at each points is printed in numbers.

Lower than normal value is printed with minus sign whereas points higher than normal value is printed without any sign.

Draws attention towards overall sinking of hill of vision (media opacities like cataracts, refractive errors, corneal opacities and miosis)

5: Total deviation plot

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Depicted by two plots: Total deviationnumerical plot ( TDNP) and Total deviation probability plot(TDPP)

Numeric plot: has numeric value showing point to point difference in the patient ‘s threshold from those expected in age corrected normal

Probability plot: gives the probability of each deviation being normal or abnormal.

All dots are considered as normal, whereas all other symbols, denotes the different p-value.

Darker the symbol, more chances of being abnormal.

Continue…

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Probability/ P- value P- value doesn’t say if loss of sensitivity is normal

or abnormal but only say percentage that on how many people the defect is seen.

STATPAC only calculates P-value where there loss of sensitivity but not for the points where retinal sensitivity is better than normal.

If no P value is given beside a global index, it can be considered normal.

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Gives the total deviation plot after correcting it for the generalized field defect which may be due to cataract , vitreous haemorrage , miosis of pupil, uncorrected refractive error and optic atrophy

The localized defect will be more prominent in this plot.

Probability plot of pattern deviation plot: depicts the probability of pattern deviation plot being abnormal.

6: Pattern deviation

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continue

Depicted by two plots: pattern deviation numeric plot (PDNP) and pattern deviation probability plot (PDPP)

Pattern deviation plot is created to now the pattern and extent of the deep sootomas, masked by generalized depression in the Total Deviation Probability Plots.

Pattern Deviation Probability Plots never shows generalized depression. ( as generalized depression is removed)

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7: Global indices: Provide grand summary that captures something

about the field in a single number.

All are printed as sensitivity measures in db, along with p-value

Are useful in sequential follow up.

Consist of Mean Deviation(MD) Pattern Standard Deviation(PSD) Short-term fluctuation(SF) Corrected pattern standard deviation(CPSD)

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Mean deviation(MD) Mean Deviation index signifies the average of oveall

severity of field loss i.e average of all numbers of TDNP except two points in area of blind spot.

Difference of MD index between both eyes should be taken as a serious clue in confirming the diagnosis of glaucoma.

1 db MD difference means , 52 db difference in 2 eyes in 24-2 point pattern.( 54 points in 24-2)

It is the most important index to asses field defect progression ( expected change in MD per yaer is 0.08 db

MD can be increased due to reasons that cause generalized field defect.

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continue Negative value- represent depressed field

and positive value represent elevated field.

MD between +/- 2 db is normal mild defect if MD -2 to -6 db moderate defect if MD -6 to -12 db sever defect if MD greater than -12 db

Loss of sensitivity is distributed equally to all the points If depression of field is not significant, MD will be a simple number without P-value.

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Pattern standard deviation Expresses dissimilar deviation values in the Total Deviation

Numerical Plot whether it is smooth or rough.

The roughness of hill of vision can be either due to the loss of sensitivity or due to the measured sensitivity being better than normal values.

PSD doesn’t carry either “+” or “-“ sign in front of it. It will just be a simple number.

If roughness of slope is not significant, PSD will be a simple number without P-value.

If the deviation of slope is significant it will be represented by P-value. So, PSD with significant P-value indicates the numbers in TDNP are not similar to each other.

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Continue…

PSD is higher in localized or irregular generalized field defect but lower in uniform generalized field defect.

PSD pick up localized scotoma. So, useful in early glaucoma but once glaucoma is diagnosed PSD have very minimal role in management of glaucoma.

PSD less than 6 consider as normal

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Short term fluctuation (SF)

SF is an index of intra test variation The result of 1st series of the test will be calculated

with second series of threshold values at these points .

Difference between them is calculated and expressed as a Root Mea Square (RMS) of the standard deviations estimated at these locations.

SF is usually < 3db i.e between 1 to 2.5 db, value higher than this shows an index of unreliability or pathology.

Short term fluctuation and corrected Pattern Standard Deviation will be calculated by full threshold or FAST PAC strategies. (SITA strategies do not calculate SF and CPSD)

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Corrected pattern standard deviation(CPSD)

PSD corrected for SF.

Since moment to moment variability(SF) may cause a patient to fail to respond sensitively in a particular region, generating a local depression adversely affecting PSD. Thus, CPSD adjust for SF and separate real deviations from deviations due to variability.

Normally CPSD should be less than 4

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65 8: Glaucoma Hemifield Test

Five sectors in upper field are compared with five sectors in lower field which are mirror images.

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Continue……

There can be five result of GHT 1. Outside Normal Limit Indicates that one of two conditions has been met a) When the scores in upper zones are compared with

those of lower zones, at least one sector pairs’ sore difference must exceed that found in 99 % of normal population.

b) The individual zone scores in both members of any zone pair exceed that found in 99.5 % of normal population.

2.Borderline In comparing the upper zone with lower zones, at

least one zone pair difference exceeds that found in 97% of normal individuals.

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Continue….. 3.General Reduction in sensitivity This message appears only if neither of conditions for

“outside normal limit” message is met, but general height calculation shows the best part of field to be depressed to a degree that occurs in fewer than 0.5% of normal population.

4. Abnormally high sensitivity The general height calculation shows the overall

sensitivity in the best part of the field to be higher than that found in others.

In phase of abnormally high sensitivity, the comparison of upper zones with lower zones is not made.

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Continue….

Within normal limits This message appears if none of above four

conditions are met. 30-2 outer sets are not included in GHT test

except the two outer points on nasal side)

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Visual field index (VFI) Is a single number that summarizes each patient’s

visual field status as a percentage of the normal age-corrected sensitivity.

Originally designed to approximately reflect the rate of ganglion cell loss.

It is derived from PD and is centre weighted, considering the high density of the retinal ganglion cells in the central retina.

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Anderson and patella’s criteria diagnostic of glaucoma field

1.Cluster of 3 or more points on pattern deviation plot abnormal at P < 5% level, at least one at the P < 1% level in an expected area of the visual field

2.Pattern standard deviation abnormal at P < 5% level.

3.GHT outside normal limits.

If any one of the above criteria is met, glaucoma should be suspected provided that the visual field defect is repeatable on a second visual field test in a similar location and is not attributable to other pathologic findings such as nonglaucomatous optic neuropathy or chorioretinal disease.

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71Glaucoma progression

We compare the baseline visual field with the follow up visual field.

Proper baseline visual fields should be done usually 2-3 (more if required).

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72 Changes detected by:

Change Analysis-box plot

Overview programme

Glaucoma progression analysis

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73Overview programme

Sequential series of fields for the same patient over a period of time.

Has all the single field information including total and pattern deviation plots

Tells us at a glance what is happening and allows us to deduce why it is happening

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74Glaucoma Progression Analysis

GPA is now in clinical use Change is based on the pattern deviation plot It compares the current visual field with a

baseline composed of 2 separate visual field tests.

The operator must choose the 2 baseline visual fields.

As a result, if progression occurs, a new baseline must be established for future analysis.

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75

Each of the 3 visual fields shown demonstrates progressive loss compared with the same baseline. The black triangles designate points with a probability (P < .05) that the value is worse than the baseline value.

Progression of glaucomatous damage

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76Progression

The following are reasonable guidelines: Deepening of an existing scotoma is suggested by

the reproducible depression of a point in an existing scotoma by >or=7 dB.

Enlargement of an existing scotoma is suggested by the reproducible depression of a point adjacent to an existing scotoma by > or =9 dB.

Development of a new scotoma is suggested by the reproducible depression of a previously normal point in the visual field by > or=11 dB, or of 2 adjacent,previously normal points by > or =5dB

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Learning effects and artefacts in automated perimetry

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Learning effects

Patients performance improves with learning and experience , this phenomenon is termed as ‘ learning effect’

learning effect greater for peripheral rather than for central stimulus locations.

To minimize learning effects, it is advisable to conduct a practice test procedure in “demonstration”

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PUPIL SIZE: Testing with a pupil of size less than 2.5mm in diameter can produce artifact.

Size of pupil should be kept constant from test to test. Pupil size can affect retinal illumination and influence

visual field sensitivity

constricted pupil dims both the intensity of the stimulus and that of the background.

Mydriasis has less influence on the visual field and it may only reduce peripheral threshold sensitivity.

Miosed pupil

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Media opacities

Opacity of ocular media reduces the brightness of test stimuli and background equally, so overall depression of retinal sensitivity

This is reflected in changes to the total deviation plot and global indices

E.g corneal opacity , cataract , vitreous hemorrhage

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Fatigue effect Difficulty in maintaining attention. This becomes

more pronounced as the examination time increases

‘clover leaf pattern’ in which the patient performs well at the beginning of the test but becomes inattentive with time and fails to respond to the stimuli

It may also be associated with a high false negative rate.

Patient fatigue usually begins approx after 3 min. Longer the duration of examination more the sensitivity decreases.

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usually located between 25 and 3o degree.

So lens should not be used in measuring VF larger than 30 degrees

Lens should place as close as possible to eye without touching eyelashes

Lens Rim Artifact:

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Uncorrected Refrative error Uncorrected error defocus the target thus

reduces the luminance of the stimulus on the retina.

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Continue……. High myopic errors can create areas of retinal blur

that appear as a vertical wedge–type defect and may be confused with glaucomatous field loss

A rule of thumb would be to correct refractive error even as low as 1.00D.

significant cylindrical defocus being induced when astigmatism is greater than 1.00D.

In case of presbyopia Humphrey visual field analyzer uses age-matched data to aid in determining the appropriate correction.

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Eyelid and facial features

Superior lid ptosis – superior VF defect

Large nose can mimic defect as inferior nasal steps

Overhanging brow and deep set eyes can lead to superior peripheral artefactual field defects

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Head position The head must also be placed against the

headrest, in order to prevent an artefactual altitudinal defect from forming (as a result of the patient not being able to see stimuli presented in the inferior visual field).

If the head is turned temporally, the nose may present a considerable obstacle, even to a central 30° plot

If the head is tilted, the blind spot may be elevated

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Trigger happy field Some patients, particularly if they are anxious,

will be eager to see most or even all of the stimuli during a test.

will press the response button as often as possible, resulting in large numbers of false positive errors.

“trigger-happy” field is characterized by patches of abnormally light white areas in the greyscale plot due to abnormally high thresholds.

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Hysterical visual field loss and malingering

Hysteria and malingering are examples of ‘functional visual field loss’

Such visual fields plots are best assessed using kinetic techniques (e.g. Goldmann bowl perimeter)

Typically yield a constricted visual field or spiral defects

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Point pattern of Humphrey field analyzer Two most commonly used pattern in management

of glaucoma

Group 1: used in suspected and established glaucoma

30-2 point pattern 24-2 pont pattern Nasal step

Group 2: used in advanced cases in glaucoma 10-2 point pattern Macular programming point pattern Custom test

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Group 1: used in suspected and established glaucoma

To reduce the number of points, a bare area of 3⁰ around fixation point is planned in 30-2 and 24-2 point patterns as macula will be affected last.

30-2 point pattern VF extent = 30⁰ radius There are no points on both the horizontal and vertical axis. Distance between two points: 6⁰ 76 points measured 3⁰ bare area 24-2 point pattern - Similar to 30-2 except VF extent is 24⁰ and points measures is

54 points

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Continue…… In 24 -2 point pattern extra 2 points above and

below horizontal on nasal side is taken making it 27⁰ at nasal field

Thus 24-2 pattern is not circular and extra points indicates area where there is high possibility of VF loss

Nasal step pattern It is peripheral test pattern that explores from 30⁰

to 50⁰.

The nasal step test points provide 2 points above and 2 points below the horizontal axis of 30⁰,40⁰ and 50⁰ as well as 2 eccentric central points.

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Group 2: used in advanced cases in glaucoma

10-2 point pattern VF tested= 10⁰ No points in horizontal and vertical axis Distance between points=2⁰ 68 points tested Bare area= 1⁰( extra 12 points are checked inside 3⁰ )

Macular point pattern 3 ⁰ VF tested in 10-2 pattern No points in vertical and horizontal axis Distance between points= 2⁰ 16 points are checked in 3⁰ area

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Continue… Custom test 6-2 point pattern Subset of 10-2 program VF extent= 6⁰ Distance between points= 2⁰ 24 points measured Bare area= 1⁰

In advanced glaucoma, use 10-2 pattern, but, if sensitivity loss is from 10-25 db then normal we should go for macular program.

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why24-2 point pattern is test choice than 30-2? The outer set of 30-2 are not considered while

selecting the 7th best sensitivity point of TDNP ( Total Deviation Numerical Plot)

The outer set of 30-2 are not included in five zones of GHT (Glaucoma Hemi-field Test)

The outer set of 30-2 are not considered in the Anderson’s criteria to pick up early field defects due to glaucoma.

The outer set of points of 30-2 are tested last. The patient may be fatigued and there is chance to get high fixation losses, high false –ve errors.

The average normative data value of peripheral points have a wide range.

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95 Conclusion It is important to correlate changes in the

visual field with those of the optic disc.

If such correlation is lacking, other causes of visual loss should be considered, such as ischemic optic neuropathy, demyelinating or other neurologic disease, pituitary tumor, and so forth.

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96 This consideration is especially important

in the following situations: The patient's optic disc seems less cupped than

would be expected for the degree of visual field loss.

The pallor of the disc is more impressive than the cupping.

The progression of the visual field loss seems excessive.

The pattern of visual field loss is uncharacteristic for glaucoma- for example, it respects the vertical midline.

The location of the cupping or thinning of the neural rim does not correspond to the proper location of the visual field defect.

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97DIAGNOSIS IS MADE ONLY IF THE DEFECTS ARE

REPEATABLE AND CORRELATE WITH DISC AND CLINICAL FINDINGS.

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INFERIOR NOTCHING OF NRR WITH SUPERIOR VF DEFECT

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References

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