History of perimetry

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Humphrey Field Analyzer II/IIi
Introduction to Perimetry

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Module Objectives
When you have completed this Module, you should be able to:
 Understand the basic principles of Perimetery.
 Identify the historical methodologies of Perimetry
 Demonstrate an ability to identify the structures of the human
eye.
 Define Amsler Grid
 Define Confrontational Test
 Define Tangent Screen
 Define Goldmann Perimeter

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Additional information may be found in the Field
Analyzer User and Service Manuals.
??

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When would a Field test be indicated???

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A Field Test would be indicated for any patient:
With an elevated IOP (>21mmHg)
IIntrantra OOcularcular PPressureressure
Normal IOP = 12 – 22 mmHg

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IOP is defined as the pressure of the fluids within the chambers of the eye.
Increased pressure is caused when the normal drainage of the eye
chambers is somehow blocked. This increased pressure can restrict
blood flow to the Retina, which can in turn cause the Retinal cells to die.
The end result is a loss of vision.

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A Field Test would be indicated for any
patient:
 With an elevated IOP (>21mmHg)

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patient:
 With a history of visual field problem or defects.

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patient:
 With a history of visual field problem or defects
 With complaints of re – occurring headaches

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 With a medical history of Hypertension

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 With a medical history of Hypertension
 Who manifests HIGH Myopia (Nearsightedness)

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Boundaries of the
Visual Field
Normal vision is limited to the following
physical limitations:
1. Temporal (towards the temple) – 100 degrees
2. Nasal (towards the nose) – 60 degrees
3. Superior (towards the head) – 60 degrees
4. Inferior (towards the feet) – 75 degrees

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Normal Boundaries of the Visual Field
Temporal
100 degrees
Nasal
60
Degrees
Left EyeLeft Eye Right EyeRight Eye
Inferior 75 Degrees
Superior
60 degrees
Superior
60 degrees
Inferior 75 Degrees
Temporal
100 degrees

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Normal Boundaries of the Visual Field
Both EyesBoth Eyes
When the boundaries of both
the left and right eyes are
superimposed, a roughly
circular area is common to
both eyes. This is the area
known as Binocular Vision,
and approximately 120
degrees in size.

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Historical Methodologies of Perimetry TestingHistorical Methodologies of Perimetry Testing
Amsler GridAmsler Grid

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Historical Methodologies of Perimetry Testing
Amsler Grid
An Amsler Grid (Top) or a modified Amsler Grid
(Yanuzzi Card) (Bottom) can be used by the
patient for self – examination of gross
perimetry problems. They can be obtained
from an eye practitioner.
To administer the test:
1. Ensure adequate room lighting.
2. Glasses may be worn.
3. Close one eye and hold the grid at a distance
of approximately 14 inches.

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Amsler Grid
4.4. Fixate on the dot in the center of the grid.Fixate on the dot in the center of the grid.
5.5. Do not allow your gaze to drift from the fixationDo not allow your gaze to drift from the fixation
target.target.
Do any of the lines appear crooked or bent?Do any of the lines appear crooked or bent?
Do any of the boxes appear different in size orDo any of the boxes appear different in size or
shape from the others?shape from the others?
Are any of the lines blurry, wavy, or discolored fromAre any of the lines blurry, wavy, or discolored from
the others?the others?
If the answers to any of the above wereIf the answers to any of the above were YESYES, a further, a further
examination should be done by a physician. Thereexamination should be done by a physician. There
could be leaking or bleeding of the eye causingcould be leaking or bleeding of the eye causing
pressure on the retina.pressure on the retina.

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Amsler Grid
Sometimes a Patient could not see
the Central fixation dot. In those
cases, a grid with an X across the
grid was used to help the patient
fixate.

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Amsler Grid
Another type of Amsler Grid used red lines on a black
background. This was helpful to diagnose certain
Optic Nerve and Brain tumor type disorders.

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Amsler Grid
Here are some examples of the types
of distortions that patients would
report:
Scotoma
Chorioretinal
Scar
Arcuate
Scotoma
Macropsia
Micropsia
Metamorphasia

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Amsler Grid
Patients who experience ANY of
these types of distortions should
consult with their physician
IMMEDIATELY!
Scotoma
Chorioretinal
Scar
Arcuate
Scotoma
Macropsia
Micropsia
Metamorphasia

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Confrontation Test
The patient would sit or stand directly across
from the person administering the test. They
were asked to cover one eye, and fixate on a
point, usually the nose of the tester, with the eye
under test. The tester would then move a
stimulus, usually a flickering finger or a penlight
inwardly from a point outside the patient’s visual
field until the patient saw the stimulus.
Because of the relative distance between the
patient and the tester, the tester could compare
the patient response against their own visual
acuity.

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Confrontation Test
This test could effectively test gross visual
defects.
Because of its inherent possibilities for
error, the results were limited.

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Tangent Screen

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Tangent Screen
Made of a Black felt background with circular
stitching every 5 degrees, it was a simple
method of perimetry testing which tested out
to 30 degrees at one meter. It usually had
radial stitching every 22.5 degrees.
The Tangent screen was the standard test of
choice for many years, and is still considered
useful today with certain patients, such as
those afflicted with severe Arthritis.

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Tangent Screen
The patient was seated at a distance of 1
meter from the chart. A patch was worn over
one eye, and the chart was adjusted so that
the eye under test was level with the central
fixation point.
Wands with colored balls at the end of
varying sizes were introduced along a
meridian from beyond the patient’s field of
vision until the stimulus was seen. A pin was
inserted in the chart at that point.

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Tangent Screen
The Tangent Screen was more sophisticated
and certainly much more accurate than the
Confrontation Test, but it too had its
disadvantages:
The tester would have to constantly monitor
the patient fixation.
Relied on ambient light being constant at 7
foot candles
The tester had to move the stimulus at a
constant speed.

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Goldmann Perimeter

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Goldmann Perimeter
Although rudimentary in the number of
different tests it could perform, and
relatively large in size compared to
modern day Perimetry equipment, the
Goldmann Perimeter set the standards
which are still used today for the
diagnosis of glaucoma and related
diseases of the eye.

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A Review of the Anatomy of the Eye

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The Conjunctiva is the
thin, transparent tissue
that covers the outer
surface of the eye. It
begins at the outer edge
of the Cornea, covers the
visible portion of the eye,
and lines the inner surface
of the eyelid.
Conjunctiva

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Cornea
TheThe CorneaCornea is theis the
transparent, dome shapedtransparent, dome shaped
window which covers thewindow which covers the
front of the eye. It is afront of the eye. It is a
powerful refractingpowerful refracting
surface, providing 2/3 ofsurface, providing 2/3 of
the focusing ability of thethe focusing ability of the
eye.eye.

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Iris
TheThe IrisIris is the coloredis the colored
portion of the eye. Itportion of the eye. It
controls light levels in thecontrols light levels in the
eye. It contains muscleseye. It contains muscles
which dilate (widen) orwhich dilate (widen) or
constrict (narrow) toconstrict (narrow) to
control the amount of lightcontrol the amount of light
entering the eye. Theentering the eye. The
opening at the center isopening at the center is
known as theknown as the PupilPupil..

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Pupil
The Pupil is the black
opening in the center of
the Iris. Under the control
of the Iris, it opens and
closes to control the
amount of light which is
allowed to enter the eye.
PupilPupil

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Lens
TheThe LensLens providesprovides 1/31/3 ofof
the focusing ability of thethe focusing ability of the
eye, and serves to focuseye, and serves to focus
light entering the eye tolight entering the eye to
thethe FoveaFovea. It is suspended. It is suspended
in the eye and held inin the eye and held in
place by tiny “guy wires”place by tiny “guy wires”
calledcalled ZonulesZonules..

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Retina
The Retina is a very thin
layer of tissue which lines
the inner surface of the eye.
It functions much like film
in photography, capturing
the light rays entering the
eye.

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Macula
The Macula is located in
the approximate center of
the Retina, temporal
(towards the temple) to
the optic nerve. It is a
small and highly sensitive
area of the retina
responsible for detailed
central vision.

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Optic Nerve
TheThe Optic NerveOptic Nerve transmitstransmits
electrical impulses fromelectrical impulses from
thethe RetinaRetina to the brain. Itto the brain. It
connects to the back ofconnects to the back of
the eye near thethe eye near the MaculaMacula..
The visible portion of theThe visible portion of the
Optic NerveOptic Nerve is known asis known as
thethe Optic DiscOptic Disc..

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Optic Disc
The Optic Disc has no
sensory receptors. This is
the area known as the
“blind spot”.

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Sclera
The Sclera is the tough,
opaque tissue known as
the “white of the eye”.
It serves as the eyes
protective outer coat.

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Choroid
The Choroid lies between
the Retina and the Sclera,
and is composed of layers
of blood vessels which
nourish the back of the eye.

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Fovea
The Fovea is the very
center of the Macula and
is the most highly
sensitive area of the eye.
The Fovea also has the
highest concentration of
RodsRods and CCoonneess

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Rod and Cones facts:Rod and Cones facts:
The Retina contains approximately 6 million Cones.
Cones function best in bright light.
Cones help us to appreciate COLOR
Cones are most highly concentrated in the Fovea
The eye contains approximately 125 million Rods
Rods are spread equally throughout the Retina
Rods work best in dim light
Rods give us our vision.night

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The Optic Chiasm
The Optic
Nerve
The Optic Track
Optic Track Visual
Field Impairments
Optic Chiasm Visual
Field Impairment
Optic Nerve Visual
Field Impairment
The Human Optical PathThe Human Optical Path
Tumors

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The Optic Chiasm
The Optic Chiasm is located at the base
of the brain. Approximately half of the
nerves in the Optic Nerve bundle from
each eye cross over to the other
hemisphere of the brain.
As a result, pathologies that develop at
the Chiasm, or at the Optic Track, can
affect BOTH eyes, while damage to the
Optic Nerve will affect only ONE eye.
Knowing the nature of visual field issues
can help to determine the source of the
pathology.

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Detection of possible Brain tumor
using Field Analysis
The example shown below illustrates how Field Analysis tests can be
utilized to detect not only visual defects of the eye itself, but also possible
brain tumor pathology.
Left EyeLeft Eye Right EyeRight Eye

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You should now have a basic understanding of the
History of Perimetry, the different types of
methodologies used in Perimetry testing, and a
knowledge of the structure and function of the
human eye.
In subsequent presentations, you will apply this
knowledge to understanding the operation of the
Humphrey Field Analyzer HFAII and HFAIIi.

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A Simple Field Test
On a piece of paper, draw a cross and a dot as below.
Hold the paper in your right hand
Cover your left Eye
Fixate (stare) at the cross
While fixating on the cross, pull the paper inward.
What happens?
 

History of perimetry

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