This document summarizes key aspects of perimetry testing. It defines the normal visual field and describes how perimetry can be used to detect functional vision loss and monitor disease progression. Two main types of perimetry are discussed: kinetic and static. Details are provided on testing strategies, stimuli brightness, interpreting results like total deviation and reliability indices. The document emphasizes the importance of perimetry in glaucoma and neurological diagnosis and management.

1. PERIMETRY
MODERATOR-
DR. BANAIT SIR
CONDUCTOR-
DR. CHANDAK SIR
PRESENTER-
DR. ROHIT AGRAWAL
06/08/2018

2. Normal Visual Field
• It is defined as the area that is perceived simultaneously by
a fixating eye.
• It is 60 superiorly and nasally, 75 inferiorly and 110
temporally.
• TRAQUAIR- described it as “island of vision in sea of
darkness”
• Island has a steep central peek
corresponding to the fovea.

3. • The visual field can be divided into :
1. Central field : Area from the fixation point to a circle 30° away.
The central zone contains physiologic blind spot on the temporal
side.
2. Peripheral field : Refers to the rest of the area beyond 30° to outer
extent of the field of vision

4. History
• Recognition of the visual field extends back more than 2,000 years to
the time of Hippocrates, who recognized a hemianopsia.
• Visual fields were frequently evaluated by confrontation visual.
• Quantification of visual fields was developed during the nineteenth
century by Jannik Bjerrum. This method of testing, known as the
tangent screen.
• The Amsler grid is another tool for measuring the central visual field
occupied by the macula.

5. Perimetry
• Is a subjective examination method for estimating the extent of
visual fields
• A decisive diagnostic technique for recognizing disturbance of
visual function/ functional loss of vision
• The threshold of perception of a test object, relative to its
background is measured.

6. When to do perimetry?
• To find out the extent of VF
• To diagnose and detect diseases as well as extent of damage caused in
VF by the disease
• To find out the progression of diseases
• To locate the possible lesion in neurological disorder

7. Types of Perimetry-
• Kinetic
• Static

8. KINETIC PERIMETRY-
• Stimuli is moved from a non-seeing area to a seeing area along a set
meridian.
• Aim is to find points in the visual field of equal retinal sensitivity.
• By joining these points ISOPTER is formed.
• Procedure is repeated using same stimulus along other meridians,
spaced 15º apart.
• Fixation is poor in this type of Perimetry.

9. • Stimulus used to plot an isopter are identified by a roman
numeral, a number and a letter.
• Goldman size 0 = 1/16 mm2
• Goldman size V = 64 mm2
• Examples-
• Lister perimeter
• Campimetry
• Goldman perimeter

10. STATIC PERIMETRY
• Intensity of the stimulus at the same pre-determined spot is varied.
• Helps to find threshold at that location
• More accurate as compared to kinetic Perimetry
• Gives a 3D picture of hill of vision
• Picks up field defects more accurately
• Stimuli appears in unpredictable fashion, therefore improves
fixation of the patient.
• HUMPHREYS VISUAL FIELD ANALYSER is most commonly used.

11. 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 but intensity is fixed
Stimulus is stationary but increases in
intensity(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
Detect when 40% damage VFD detect earlier with 20% defect
More error/Non Computerized Less error/Computerized
Non threshold Type Threshold Type

12. 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
Good for neurological.
It has ability to detect scotomas, particularly
small, shallow(flat), or fluctuating scotomas
but cannot correctly outline the border of
the defect
Good for glaucomatous and neurological
defects.
Eg. Confrontation perimeter, tangent
perimeter, Lister’s perimeter, Goldmann
perimeter
Eg. Automated perimeter, Goldmann
perimeter

13. BRIGHTNESS OF STIMULI
• Differential light sensitivity (DLS) is the degree by which luminance
of a target must exceed background luminance in order to be
perceived.
• Defined in terms of Decibels (Db) & Apostibs (abs).
• Decibels- it is negative logarithmic unit of change in stimulus
brightness, which is used in perimetry for scaling differential light
sensitivity
• 1db= 1/10th log unit
• Apostibs- bowl & target brightness is measured in apostibs
• 1abs= 1lumen/m2
• At 31.5 asb background luminance, fovea shows highest sensitivity
and is able to detect both the dimmest smallest targets

14. • Scotoma:A scotoma by definition is the depressed part of the field as
compared to the surrounding and not as compared to normals.
• An area of reduced light sensitivity surrounded by an area of normal
sensitivity – RELATIVE SCOTOMA
• An area of no light perception surrounded by normal sensitivity –
ABSOLUTE SCOTOMA

15. Threshold estimation- [BRACKETING STRATEGY]
• 4-2 STRATEGY algorithm is most commonly used
• STEPS-
Testing started with full threshold
Intensity of stimulus is decreased
by 4db Steps till stimulus is NO
longer seen
Now stimulus is increased by 2db
steps till stimulus is seen again

16. TESTING STRATEGIES
• Full threshold
• Threshold
• Supra threshold
• Fast Pac
• SITA standard
• SITA fast

17. • FULL THRESHOLD- Used to detect threshold
• THRESHOLD- threshold is found at pre-determined points
- Time consuming process
• SUPRATHRESHOLD- intensity of stimulus shown at a spot
much higher than threshold at the spot.
- mainly for screening
- picks up gross visual defects

18. • FAST PAC- decreased test time by 40%
- follows similar stair-stepping technique as in
full threshold
- but increment is 3db instead of 4db.
- crosses threshold only once
• SITA [SWEDISH INTERACTIVE THRESHOLD ALGORITHM]
standard- takes ½ time than full threshold technique
• SITA fast- takes ½ time than Fastpac

19. THRESHOLD TEST EXTENT OF VISUAL FIELD NO. OF POINTS
10-2 10º 68 POINT GRID
24-2 24º 54 POINT GRID
30-2 30º 76 POINT GRID
60-4 30º-60º 60POINT GRID
NASAL STEP 50º 14 POINT GRID
SCREENING TEST EXTENT OF VISUAL FIELD NO. OF POINTS
CENTRAL 40 30º 40 POINTS
CENTRAL 76 30º 76 POINTS
FULL FIELD 81 55º 81 POINTS
FULL FIELD 120 55º 120 POINTS
PERIPHERY 60 30º-60º 60 POINTS
MACULAR PROGRAMME 2º 16 POINTS

20. How to read a Perimetry?!

21. 1. Patient data
2. Reliability indices
3. Grayscale
4. Total deviation
5. Pattern deviation
6. Global indices
7. Glaucoma hemifield test
8. Numeric data
9. Gaze tracking

22. 1. Patient Data
• Name, Age & Sex
• Date
• Type of test/ Strategy
• Eye tested
• Visual acuity
• Pupil- ideal size is 2.5-3.5 mm
• Fixation target- central
• Spectacle correction for near
• Background illumination

23. 2. Reliability Indices
• Fixation losses-
• Indicates steadiness of gaze
• Presenting stimuli at blind spot
• Loss > 20% => test unreliable
• False positive-
• Trigger happy patients
• Response of audible stimulus when no target is
presented
• >33% => unreliable test
• False negative-
• Fails to respond to a supra-threshold stimuli
• Indicates fatigue & inattentiveness
• >33% => unreliable test
• Cloverleaf defect is seen due to high FN

24. • Foveal threshold-
• it should correlate with visual field.
• Good VA, Low foveal threshold => early foveal damage
• Low VA, Good foveal threshold => patient needs refraction before field test

25. 3. Grayscale
• Colour scheme of visual loss
• Provides overview of visual field loss
• BUT it cannot be relied upon
• Helps patients understand extent of visual field loss

26. P-value(probability value)
• (P < x%) indicates that less than x% of the normal
population has figure like this
• In other words there is an x% chance that the index
would be seen in normal.
• Lower the P value beside the global index the higher
chance of it being abnormal.
• If no P value is given beside a global index, it can be
considered normal.

27. 4. Total Deviation
• Comparison of patients response with
that to known normal patient of their
age.
• Representation is in both numbers and
probability plots

28. 5. Pattern Deviation
• Certain conditions like cataract cause a
generalised depression.
• This masks the actual field loss
• Pattern deviation factors out the generalised
deviation commonly caused by –
• Cataracts
• Miotic pupil
• Incorrect testing lens
• Confirms actual scotoma

29. 6. Global Indices
• Mean deviation (MD)
• Pattern standard Deviation (PSD)
• Short term fluctuation (SF)
• Corrected PSD

30. Mean deviation (MD)/mean defect
• Derived from averaging the total deviation values.
• Overall sensitivity of field.
• Negative (-) sign.
• A small localized defect will show a small MD, whereas a generalized or an
advanced defect will show a high MD.
• The value does not differentiate a generalized and a localized field loss. It
also does not give the location of the defect.
• Measures how much this patient’s overall function deviates from that of
age matched normal.

31. Pattern standard deviation(PSD)/Loss variance(LV)
• Measure of focal loss or variability within the VF
• Gives an idea about the resemblance of the patients’ field to the shape of
hill of vision.
• Positive sign
• Low PSD indicates a normal shape of the hill, whereas a high value indicates
a disturbed shape of the hill.
• Localized defect will give a high PSD, whereas a generalized defect will give a
low PSD.
• Improves with the generalization of the defect in advanced field loss.

32. Short term fluctuation(SF)
• Consistency of responses
• Intra-test variability
• Only with the full threshold
printouts.
• Ten preselected points are
thresholded twice and the variation
in the thresholds is represented as a
number
• SF > 3 indicates unreliable result

33. Corrected pattern standard deviation (CPSD)
• It is the PSD corrected for the SF
• Provides a measure of the irregularity of the contour of the hill of
vision that is not accounted for by patient variability (SF).
• Increased when localized defects are present .

34. 7. Glaucoma Hemifield test
• 5 set of points above
horizontal meridian
• Compared to mirror image
below horizontal meridian
• It gives one of the 4 results-
• Within normal limit
• Borderline
• Outside normal limit
• Generalised reduction in
sensitivity

35. • Outside normal limits- Either the values between upper and lower
clusters differ to an extent found in <1% of the population or any
one pair of clusters is depressed to the extent that would be
expected in <0.5% of the population.
• Border line- When the difference between any one of the upper
and lower mirror clusters is what might be expected in <3% of
population.
• General reduction in sensitivity- If the best part of visual field is
depressed to an extent expected in <0.5% of the population.
• Within normal limits- When none of the above criteria is met.

36. 8. Numeric Data
• Numerical display:
• Gives the threshold for all points checked
• Value in () indicates that the point has
been tested twice

37. 9. Gaze tracking
• It is present newer Humphreys field analysers
• The distance between corneal light reflex and the centre of the
pupil is measured
• Upward deviations on the gaze graph indicates deviations due to
eye movements
• Downward deviation indicates that the patient blinked when the
stimulus was present.

38. Sources of Error-
• Miosis:
• decreases the threshold sensitivity in peripheral field
• Increases the variability in central field
• Uncorrected refractive errors:
• Threshold sensitivity appears less
• Hyperopic patient with contact lens:
• Defect gets magnified
• Spectacles can cause rim scotomas
• Ptosis :
• Suppression of superior visual field

39. Glaucomatous defects
• Characteristics-
• Asymmetrical across horizontal midline
• Located in mid-periphery
• Reproducible
• Localised

40. Andersons criteria
• This criteria is to confirm that the scotoma is due to glaucoma
• It has 3 criteria-
1. pattern deviation plot:
• 3 non-edge points with p<5%
• One point with p<1%
• Cluster in arcuate area
2. PSD
• Abnormal with p<5% on 2 consecutive occasion
3. Abnormal GHT

41. Few Examples-

42. I
II
III

43. I
GRAYSCALE
LOOKS LIKE THAT
OF A ARCUATE
SCOTOMA
TOTAL
DEVIATION ALSO
REVEALS A
SCOTOMA
BUT, ON
PATTERN
DEVIATION…..NO
SCOTOMA
CATARACT

44. II
GRAYSCALE S/O
VISUAL FIELD
DEFECT
ARCUATE DEFECT
SEEN ON TOTAL
DEVIATION
ON PATTERN
DEVIATION
DEFECT REMAINS
CONSTANT
GLAUCOMA

45. III
GROSS VISUAL
DEFECT ON
GRAYSCALE
COMPLETE
SCOTOMA ON
TOTAL DEVIATION
BUT, ON PATTERN
DEVIATION
ARCUATE
SCOTOMA IS SEEN
S/O CATARACT + GLAUCOMA

46. • PATTERN
DEVIATION
S/O???

47. BUT…… PUPIL SIZE=1MM !!

48. • Same patient’s Perimetry
when repeated with 2.5mm
pupil size is normal
PUPIL SIZE= 2.5MM

49. • ADVANCED FIELD DEFECT-
• BUT…..LOOK AT THE PATTERN
DEVIATION
• IT SHOWS NO DEFECT

50. NOT ENOUGH POINTS
WITH SENSITIVITY TO
PRODUCE PATTERN
DEVIATION

51. REPEAT WITH 10-2……
• Enough sensitive
points to produce
pattern deviation
plot.

52. Does this Perimetry suggest
glaucoma?
• According to Anderson
criteria…..YES IT IS A
GLAUCOMATOUS FIELD
• BUT
• NEVER Diagnose on the basis of
visual field alone
• CORRELATE with clinical fundus
findings.

53. Some non-glaucomatous visual field defects:

54. Alternatives of standard automated Perimetry
Short-wavelength automated perimetry (SWAP){BLUE ON YELLOW}:
• SWAP utilizes the koniocellular pathway and selectively measures the short
blue wavelength function by projecting a blue stimulus on a yellow
background.
• SWAP has been found to identify early glaucomatous damage in ocular
hypertensives, glaucoma suspects, and patients with glaucoma.
• Detects glaucomatous changes 3-5 years earlier than SAP.
• Has high fluctuation rates.

55. Frequency doubling technology (FDT):
• A combination of low spatial frequency and high temporal frequency
preferentially targets ganglion cells of the magnocellular pathway.
• Due to selective uncovering of functional deficits in the ganglion cells, FDT has
been shown to have high sensitivity(97%) and specificity for early detection of
glaucoma

56. Flicker Perimetry:
• Flicker perimetry is a visual field test procedure that evaluates an observer’s ability
to detect light/dark stimulus alternations (flicker) at various locations in the field of
view.
Micro Perimetry/Scotometry:
• The scanning laser polarimetry can visualize a particular area of retina and test its
sensitivity to visual stimuli, thereby generating a map of seeing and non-seeing
areas. If central vision is lost, patient can potentially be trained to use an adjacent
retinal site to substitute for central VF.

57. Thank you…

58. Next PG activity- 07/08/2018
• Case presentation
• Presenter- Dr. Arjan Singh
• Moderator- Dr. Sune sir
• Conductor- Dr. Archana madam