Download MBBS (Bachelor of Medicine and Bachelor of Surgery) 3rd Year (Third Year) Opthalmology Perimetry Topic Handwritten Notes
of the visual fields
It is the measurement of visual functions of the
eye at topographically defined loci in the visual
field.
HISTORY
1970- Octopus perimeter was first introduced
1982 ? Humphrey field analyser first displayed at
AAO
1983 ? Michael Patella showed first clinical trial
1984 ? Became popular
Visual field
Visual field is a three-dimensional area of a
subject's surroundings that can be seen at any
one time around an object of fixation.
Traquair described it as an "island of vision
surrounded by a sea of darkness"
Island of vision
visual field division
central
peripheral
central
an area from the fixation point to a circle 30?
away.
The central zone contains physiologic blind spot
on the temporal side.
Peripheral field
The rest of the area beyond 30? to outer extent
of the field of vision
Isopter
a contour line in a representation of the visual
field around the points representing the macula
that passes through the points of equal visual
acuity.
each isopter can be defined as a threshold line
forming points of equal sensitivity on a visual field
chart
Scotoma
an area of loss of vision totally (absolute
scotoma) or partially (relative scotoma) in the
visual field.
It is the depressed part of the field as compared
to the surrounding and not as compared to
normals.
Perimetry
Kinetic versus static perimetry
Peripheral versus central field charting
Manual versus automated perimetry
Kinetic
In this the stimulus of known luminance is moved
from a peripheral non seeing point towards the
centre till it is perceived to establish the isopters.
confrontation method
Lister's perimetry,
tangent screen scotometry
Goldmann's perimetry.
confrontation method
Lister's perimetry
Goldmann's perimetry
Goldmann's perimetry
Static perimetry
This involves presenting a stimulus at a
predetermined position for a preset duration
with varying luminance in the field of vision
Goldmann perimetry
Friedmann perimetry
Automated perimetry.
Friedmann perimetry
Automated perimetry- Humphrey field
analyser
Automated perimetry- octopus field
analyser
Peripheral field charting
Confrontation method
Perimetry: Lister's, Goldmann's and automated
Central field charting
Campimetry or scotometry
Goldmann's perimetry
Automated field analysis.
MANUAL PERIMETRY
Confrontation method
Lister's perimeter
Campimetry (scotometry)
Goldmann's perimeter
Confrontation method
This is a rough but rapid and extremely simple
method of estimating the peripheral visual field.
Assuming the examiner's fields to be within the
normal range
Confrontation method
The patient is seated facing the examiner at a
distance of 1 metre. While testing the left eye, the
patient covers his right eye and looks into the
examiner's right eye. The examiner occludes his left
eye and moves his hands in from the periphery
keeping it midway between the patient and himself.
The patient and the examiner ought to see the hand
simultaneously, for the patient's field to be
considered normal. The hand is moved similarly from
above, below and from right and left.
Lister's perimeter
It has a metallic semicircular arc, graded in
degrees, with a white dot for fixation in the
centre.
Campimetry (scotometry)
Bjerrum's screen of either l metre or 2 metres
square is used
not used now-a-days
Goldmann's perimeter
The test conditions and the intensity of the target
are always the same.
It permits greater reproducibility.
AUTOMATED PERIMETRY
The automated perimeters automatically test
suprathreshold and threshold stimuli and
quantify depth of field defect
The problem of subjectivity of perimetrist was
eliminated by automation which began in the
1970s
Automated perimetry improved the uniformity
and reproducibility of visual fields
Lister's perimeter
Octopus Field Master
Humphrey field analyser
Octopus Field Master
Humphrey field analyser
Advantages of automated perimetry
flexibility, precision and consistency of test
method
data storage capability, ease of operation, well
controlled fixation, menu driven software and on
line assistance
compare results statistically
compare with previous tests of the same
individual
Automated perimeter variables
Background il umination
Stimulus intensity
Stimulus size
Stimulus duration
Testing strategies and programmes
The normal threshold is defined as the mean
threshold in normal people in a given age group
at a given location in the visual field.
range of 0?50. 50(db) -dimmest
0 db is the brightest illumination.
the higher the decibel value, the higher is the
sensitivity
Suprathreshold testing
Threshold testing.
Suprathreshold testing
targets that are well above the brightness
screening procedure to detect gross defects
It should not be used to monitor glaucoma.
Screening central > 6 points
Full field 120 points
Threshold testing.
Ful threshold testing.
Fast Pac
SITA
Test programmes -HFA
Central field tests
Peripheral field tests
Speciality tests
Custom tests
Evaluation of Humphrey single-field Statpac
printout
I. Patient data and test parameters.
I . Reliability indices.
I I. Gray scale simulation
IV. Total deviation plots
V. Pattern deviation plots.
VI. Global indices
VII. Glaucoma hemifield test (GHT)
VII . Actual threshold values
I. Patient data and test parameters.
Patients data (name, date of birth, eye (right/
left) pupil size, visual acuity).
Test parameters (test name, strategy, stimulus
used, background).
I . Reliability indices.
reliability indices and test duration
Unreliable if three or more of the fol owing reliability
indices have below mentioned values:
? Fixation losses > 20%,
? False positive error > 33%,
? False negative error > 33%,
? Short-term fluctuations > 4.0 dB,
? Total questions > 400.
I I. Gray scale simulation
The darker the printout, the worse is the field
do not make a diagnosis based on the grey
scale
IV. Total deviation plots
provide the deviation of patient's threshold
values from that of age corrected normal data.
? Numeric value plot represents the differences
in decibels.
? Zero value means that the patient has the
expected threshold for that age.
? Positive numbers reflect points that are more
sensitive than average for that age; whereas
? Negative numbers reflect points that are
depressed compared with the average.
? Probability plot (grey scale symbol plot). In the
lower half of part of zone IV of the printout, the
darker the graphic representation the more
significant it is.
V. Pattern deviation plots.
numeric pattern deviation plot and probability
pattern deviation plot
Statpac software has corrected the results for
the changes caused by ?
Cataract, small pupil, refractive error, etc
VI. Global indices
To provide overall guidelines to help the
practitioner assess the field results as a whole
rather than on point-to-point
1. Mean deviation (MD).
2. Pattern standard deviation (PSD).
3. Short-term fluctuation (SF).
4. Corrected pattern standard deviation (CPSD).
VI . Glaucoma hemifield test (GHT)
compares the five clusters of points in the upper
field (above the horizontal midline) with the five
mirror images in the lower field.
Outside normal limits.
Border line.
General reduction in sensitivity
Abnormally high sensitivity
Within normal limits.
VI I. Actual threshold values
may be inspected for any pattern or scotoma
when clinical features are suspecious
even if all the seven other parts of the printout
are normal
This post was last modified on 11 August 2021