2. Visual Field
• The visual field is the total area in which objects can be
seen in the peripheral vision while the eye is focused on a
central point
• The most peripheral portions of the visual field are least
sensitive ; objects must be large and bright to be visualized.
• Outside the borders of the visual field, no visual perception
occurs
4. Kinetic Perimetry
• In kinetic perimetry,stimulus is presented in
the non seeing periphery & moved towards
the point of fixation until the patient first
perceives it.
• The procedure is repeated with the use of
same stimulus along other meridians,usually
spaced every 15degrees.
• By joining these areas an isopter is formed.
5. Static Perimetry
• A stimulus is presented at a known location
for a known duration with varying luminance
to find local threshold.
• The stimulus is not moved as in kinetic
perimetry.
• This is a stationary target.
7. CONFRONTATION TECHNIQUE
• Preparing the patient for the test:
• Examiner and patient should sit facing each
other about 1m apart.
• Test should be in good lighting which comes
from behind the patient and uniformly
illuminates the patient’s visual field.
• Plain background should be in front of the
patient , to allow detection of the stimulus
more reliably.
8. • Patient is instructed to look directly into the
examiner’s eye.
• When testing the right eye , the patient’s left
eye should be occluded.
• The visual field of the patient’s right eye will
correspond to the visual field of the
examiner’s left eye.
9. Indications
Field examination by neurologists on the bed
side.
By optometrists &ophthalmologists as a rapid
screening visual field test.
Only way to evaluate visual field in bedridden
patients
Patient with lack of attention & morbid
patient who cannot undergo longer test.
11. Apostilb & Decibel
Luminance can be indicated in units called as
apostilb(asb).
Apostilb is an absolute value & remain constant
from machine to machine.
Decibel scale is a logarithmic scale that is
reciprocally related to the intensity of light.
asb & dB values go in opposite directions.
In humphrey test,
-10asb=30dB
-100asb=20dB.
12. AUTOMATED PERIMETRY VARIABLES
• Stimulus Size:
• *5 Sizes(I-V),
• *Stimulus Size III is Commonly Used.
• *Distance from Eye 30 cm.
• Stimulus Duration:0.2 Sec
• Stimulus intensity: 0(max) to 50(min) dB
• Background illumination:31.5asb
13. Procedures
• Setting up the perimeter
– Enter patient data and examination data
– Typing error in the birth year results in a uniform artifact depression
– Calibrate the unit
– Apply the trial lenses before seating the patient
• Instructing the patient
– Maintain comfortable position. Do not move
– Always Look straight ahead at the fixation target
– Blink regularly to avoid discomfort
– Press the button only when the stimulus is seen as not all
stimuli are visible
14. • Instructing the patient
– If uncomfortable, may close eye for a moment. The test is
interrupted and only continues after eye opens
-To ask for assistance, keep the button pressed
• Setting up the patient
– The patient seated comfortably on a height-adjustable
chair with a back rest
– The patient is asked to press the button a few times and
occluder is applied making sure the patient can blink freely
15. • Refractive errors
– If patient does not have sharp image of the
stimulus, the d.l. sensitivity values are reduced
-For direct projection type perimeters (OCTOPUS
300) far correction is required
-For cupola perimeter near correction (42.5cm) is
needed
• Refraction and trial lenses
– Cylinder correction
17. Single-level suprathreshold test
• Stimulus 2-6 dB higher than threshold or expected hill
of vision
• Result: seen (normal) or nor seen (defect)
2-Level suprathreshold test
• 3 categories: Normal, relative defect, absolute defect
• Done as per single-level but abnormal spots are tested
with 0 dB attenuation: Threshold-Related Strategy
(Humphrey
18. Factors influencing result
Age
Pupil size
Clarity of ocular media
Refractive error & retinal blur
Concentration
Fixation
Alertness
Fatigue effects
19. THRESHOLD STRATEGY
1.Suprathreshold Perimetry
2.Threshold Perimetry-
a.Threshold:
Full Threshold-30-2(Total Point 76,Field 30)
24-2(Total Point 54.Field 24)
10-2(Total Point 68,Field 10)
Macular(Total Point 16,Field 5).
Full Field(120 Degree).
b.Fast pac
c.SITA fast
d.SITA Standard
20. Supra threshold Static Perimetry
Stimulus brighter than the anticipated normal
value for the corresponding retinal locations.
Mainly used for screening purposes.
Only provide information about depth &
contour of field defect.
21. Threshold Perimetry
Full threshold periemtry
• Measure the retinal threshold at 70-80 points
within the central 24-30degrees.
• Determines the threshold value at each point by
the bracketing technique
• Appropriate for a patients first test as it helps in
determining the future data points.
22.
23. ADVANTAGES OVER MANUAL
PERIMETRY
• 1. STANDARDIZATION OF TEST CONDITION
• 2. ESTIMATION OF PATIENT RELIABILITY
• 3. COMPUTERIZED ANALYSIS OF FIELD
• 4. EASY FOLLOW-UP
24. Sources of error
Poor performance
Uncorrected refractive error
Spectacle rim artefact
Miosis
Media opacities
Ptosis
Inadequate retinal adaptation
26. Reliability indices
• False Positive (FP):
– Sound cue without light source or subthreshold
stimulus
– SITA: FP = response within the patient’s response time
• False Negative (FN):
– No response to a 9 dB brighter stimulus at a location
that had a measurable threshold earlier.
– “Clover leaf” pattern with fatigue
27. • Fixation Losses (FL):
– Heijl-Krakau method of periodic testing of the
blind spot
– Video monitor ± IR camera to detect pupil
movement
– Pseudofixation losses
28. Grey scale
• It provides only a semiquantitative
assessment of the visual field, with
interpolated values printed between tested
points, and are insufficient for full analysis.
• Gives the idea of retinal threshold at a glance.
– Darker means lower retinal sensitivity
– Alarming sign Beware!!
29.
30. Total Deviation Plot
• Represents the deviation of the patient’s result from the
age matched controls.
• The upper numerical display illustrates the difference in
decibel and the lower display exhibits these differences in
grey symbols.
• Deviation from age matched controls even less than 4
decibel is shown.(differ. from Octopus)
31. PATTERN DEVIATION PLOT
Derived from the total deviation plot
Gives an idea about the resemblance of
patients visual field to the shape of the hill of
vision.
Localized defects
34. GHT
• 5 sectors in the upper field are compared to
five mirror images in the lower
• If value in two sectors differ to an extent that
found in
– <0.5% of the normal population ( highly sensitive)
– <1% of normal population (outside normal limit)
– <3% of the normal population (Boderline)
– <5% of the normal population ( can be a normal
plot)
35.
36.
37. Criteria
Pattern deviation plot
- ≥3non edge points with p>5%
-one point with p>1%
-Cluster in arcuate area
CPSD or PSD
-depressed with p>5%
Abnormal GHT
