History of perimetry

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Humphrey Field Analyzer II/IIiIntroduction to Perimetry

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Module ObjectivesWhen 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)

IIntra ntra OOcular cular 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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With an elevated IOP (>21mmHg)


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With an elevated IOP (>21mmHg) With a history of visual field problem or defects.


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A Field Test would be indicated for any patient: With an elevated IOP (>21mmHg) With a history of visual field problem or defects With complaints of re – occurring headaches


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A Field Test would be indicated for any patient: With an elevated IOP (>21mmHg) With a history of visual field problem or defects With complaints of re – occurring headaches With a medical history of Hypertension


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A Field Test would be indicated for any patient: With an elevated IOP (>21mmHg) With a history of visual field problem or defects With complaints of re – occurring headaches 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

DegreesLeft 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 GridAn 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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Historical Methodologies of Perimetry TestingAmsler Grid4.4. 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 fixation Do 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 or Do 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 from Are any of the lines blurry, wavy, or discolored from the others?the others?

If the answers to any of the above were If the answers to any of the above were YESYES, a further , a further examination should be done by a physician. There examination should be done by a physician. There could be leaking or bleeding of the eye causing could be leaking or bleeding of the eye causing pressure on the retina.pressure on the retina.


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Amsler GridSometimes 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 GridAnother 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 GridHere 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 GridPatients 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 TestThe 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 TestThis 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 ScreenMade 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 ScreenThe 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 ScreenThe 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 PerimeterAlthough 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

The The CorneaCornea is the is the transparent, dome shaped transparent, dome shaped window which covers the window which covers the front of the eye. It is a front of the eye. It is a powerful refracting powerful refracting surface, providing 2/3 of surface, providing 2/3 of the focusing ability of the the focusing ability of the eye.eye.


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IrisThe The IrisIris is the colored is the colored portion of the eye. It portion of the eye. It controls light levels in the controls light levels in the eye. It contains muscles eye. It contains muscles which dilate (widen) or which dilate (widen) or constrict (narrow) to constrict (narrow) to control the amount of light control the amount of light entering the eye. The entering the eye. The opening at the center is opening at the center is known as the known 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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LensThe The LensLens provides provides 1/31/3 of of the focusing ability of the the focusing ability of the eye, and serves to focus eye, and serves to focus light entering the eye to light entering the eye to the the FoveaFovea. It is . It is suspended in the eye and suspended in the eye and held in place by tiny “guy held in place by tiny “guy wires” called wires” called 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

The The Optic NerveOptic Nerve transmits transmits electrical impulses from electrical impulses from the the RetinaRetina to the brain. It to the brain. It connects to the back of connects to the back of the eye near the the eye near the MaculaMacula. . The visible portion of the The visible portion of the Optic NerveOptic Nerve is known as is known as the the 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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FoveaThe 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 COLORCones are most highly concentrated in the FoveaThe eye contains approximately 125 million RodsRods are spread equally throughout the RetinaRods work best in dim lightRods give us our vision.night


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The Optic Chiasm

The Optic Nerve

The Optic TrackOptic 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 ChiasmThe 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 TestOn a piece of paper, draw a cross and a dot as below.Hold the paper in your right handCover your left EyeFixate (stare) at the crossWhile fixating on the cross, pull the paper inward.What happens?


Entertainment & Humor

History of perimetry