Understanding Visual Fields, Part I; Goldmann Perimetry

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J
ournal of O
p
hthalmic Medical Technolo
gy
Volume 2, Number 2
June 2006
www.JOMTonline.com
Understanding Visual Fields, Part I; Goldmann Perimetry
Inci Dersu, MD, Michael N. Wiggins, MD, Anne Luther, RN, Richard Harper, MD, and
Joseph Chacko, MD
Why is this important?
Visual field testing is a common procedure in almost every eye practice. Whether you
are the person performing the visual field or working up a patient who just had a visual
field, it is helpful to have background knowledge of this common test. This article is the
first of a four-part series designed to review the basic types of fields, how to perform
them and the reasoning behind selecting one type of visual field over another.
What are we testing?
A normal patient can see 60 degrees nasally, 110 degrees temporally, 75 degrees
inferiorly and 60 degrees superiorly1. And you might think that all visual fields are
designed to measure the total peripheral vision. In fact, most commonly ordered visual
fields only test the central portion of a patient's field of vision. The amount of the field
tested depends on which test you perform. Only a few tests, such as the Goldmann visual
field (GVF), truly evaluate the whole visual field.
Types of Perimetry
Static, Kinetic, Manual or Automated?
There are two basic types of visual field tests commonly used in the clinic. Depending
on whether or not the stimulus moves, the test can be classified as static or kinetic.
Goldmann perimetry is a common example of kinetic perimetry. The Humphrey Field
Analyzer™ (Allergan-Humphrey, San Leandro, CA) is a common example of static
perimetry. In fact, both perimeters have the capability of doing both static and kinetic
tests, but in practice, they are used as described above.
Perimeters can also be classified as manual or automated, depending on whether
the stimulus is moved by hand as in the Goldmann, or if the stimulus location is changed
by a computer, as in the Humphrey visual field (HVF).
Terminology: Perimetry is the name of the technique whereas perimeter implies
to the machine i
tself.

Manual Kinetic Visual Fields (i.e. Goldmann Perimetry)
How to perform Goldmann Perimetry
Both the patient and perimetrist affect the accuracy of the GVF. The patient must be able
to understand the test, maintain fixation and respond appropriately. The perimetrist must
be experienced. It is important to calibrate the stimulus and the background illumination
at least once a week to maintain consistency of lighting.
The patient should be comfortably seated. Make all preparations for testing before the
patient is positioned in the machine. Lenses used to test the central 30 degrees are
determined by the patient’s distance correction and Goldmann’s add for age (Table 1).
Use the spherical equivalent whenever the cylinder is 1.00 diopter or less. Myopia,
aphakia, pseudophakia or dilation may affect the choice of lens power. People with high
myopia or aphakia may require a contact lens for accurate testing. Place the correct lenses
in the holder. Insert the perimeter paper and lock into place. Be sure that markings on the
paper are aligned with the notches of the frame. Explain the test to the patient. Assess the
patient’s ability to push the button on the buzzer in response to the stimuli. Some patients
find it easier to respond verbally. Patch the eye that is not being tested: the eye must be
completely covered. If there is significant dermatochalasis, tape the excess tissue. If
there is ptosis, taping may not elevate the lid sufficiently. In this case, an assistant may be
asked to hold the lid during testing of the superior visual field. Move the chin rest to the
correct side of the bowl. Help the patient move onto the chinrest and position the
forehead against the forehead strap (Figure 1). Emphasize the need to maintain this
position during testing. Some machines have a head strap that will help keep the patient
in the proper position throughout testing. Turn out the room lights.
Table 1. Adds for GVF perimetry
Age years Add for perimetry
30-40 +1.00
40-45 +1.50
45-50 +2.00
50-55 +2.50
55-60 +3.00
60+ +3.25

Figure 1. Positioning of examiner and patient for Goldmann Perimetry
The perimetrist should adjust his/her seat for comfort. Look at the patient’s eye through
the observer’s tube (Figure 2). If the patient’s eye is not centered in the observer’s tube,
adjust the vertical and horizontal position of the chinrest with the knobs located below the
paper. After this adjustment, ask the patient if he/she is comfortable. Choose the size and
intensity of the first target. The most common stimuli are I4e for peripheral and I2e for
central visual field. Stimuli of other sizes and intensities may be used to give greater
detail to the visual field. A GVF is performed by using the pantograph handle to move
the stimuli from the non-seeing area into a seeing area at about 3-5 degrees per second.
Start with the peripheral field without the correction. After the peripheral isopter is
determined, place the corrective lens into position and proceed with plotting the central
field. The blind spot is outlined with the smallest target that easily encompasses it. Static
checks to test for scotoma are done after the isopters are completely outlined. To avoid
patient fatigue, the test should not exceed 10 minutes per eye. Allow any patient showing
signs of fatigue to have rest times during the test.
It is important to evaluate the patient’s ability to do visual field testing. Retesting areas
will give you information about the consistency of the patient’s responses. Occasionally,
turn off the stimuli and stop testing for a few seconds: the patient should not respond
during this time. Watching the patient’s eye through the observation tube while moving
the pantograph handle, allows evaluation of fixation. If responses are inconsistent or
fixation is poor, reinstruct the patient.

After testing the first eye, allow the patient to sit back and rest while preparations are
made for testing the other eye. Look over the completed test to verify all quadrants have
been tested sufficiently.
Figure 2. Recording the results during Goldmann Perimetry
Interpreting a Goldmann Visual Field
The Goldmann Visual field tests the entire visual field, one eye at a time, by plotting
points along circles known as isopters (Figure 3). Each isopter should be color-coded to
the size and intensity of the stimulus used. The size and intensity of the stimulus can be
adjusted. The stimulus size varies between 0 toV, and the intensity varies between 1 and
4 for each 5 dB (decibel) change and further differs between a-e for smaller (1 dB)
changes (Table 2). For example, a III 2e stimulus is larger and brighter than a I 2d
stimulus, but not as large or as bright as a IV 3a stimulus.

Figure 3. A normal GVF. Note that a dimmer stimulus (I 2e) is used centrally and a
brighter stimulus (I 4e) is used peripherally. This GVF is shown with two isopters: one
in red and one in blue. The physiologic blind spot is also seen para-centrally as a filled-in
blue circle.
Table 2. Options for the stimulus
Size: 0, I, II, III, IV, V : 0 is the smallest, V is the largest
Intensity: 1, 2, 3, 4 : 1 is the dimmest, 4 is the brightest
Intensity: a, b, c, d, e : a is the dimmest, e is the brightest
Unlike defects on most automated visual fields (which show up as dark areas), most
defects on a GVF are changes in the isopter. If the circle has an indented area (see the
blue circle in Figure 4 below), this represents an area of the visual field where the
stimulus was not seen. Additionally, the distance between the isopters is important. If
the defect is mild, the isopter will look indented towards the center, but will remain about
the same distance away from the other isopter. However, when the defect is more severe,
Terminology: Decibels are a way of comparing the intensity of light to the
maximum possible light intensity the machine can produce. It does not have a
value that can be measured somewhere other than in the machine, like meters or
pounds. 10 dB means the light is 1/10th as bright as the brightest light possible,
20 dB means the light is 1/100th as bright (it is based on log units). So, the
higher the number of dB, the dimmer the stimulus. For example, a I 2e stimulus
is 5 dB more (or dimmer) than a I 3e stimulus1.

the isopters will be much closer together2. Dense central defects on GVF are generally
shaded in, similar to automated tests (Figure 5).
Advantages and Disadvantages er stimuli are used for testing the very center of vision
en, it is
might
e
ganic)
dications to use a Goldmann Visual Field ated visual field. Some patients fall ated
. The full extent of the visual field needs to be tested. A GVF can be a reliable, of time.
. A visual field defect found on an automated visual field needs to be confirmed. In f
t l
During Goldmann perimetry, dimm
with the intensity increasing as more peripheral portions of the field are tested.
Some patients might prefer it because there is human interaction. By the same tok
very much examiner dependent1. It may not be reproducible by another examiner, and it
does not have the advantages of a computerized system for storage and comparison to
normative data. Additionally, kinetic perimetry may not be as sensitive as static
perimetry in detecting early glaucoma defects3. However, Goldmann visual fields
reveal scotomas that were missed between the testing points in static perimetry4. The
shape of the defects may also be more impressive in Goldmann perimetry1. With sever
vision loss (vision worse than 20/200), test-retest variability might be better in
comparison to automated static testing. In addition, it shows functional (non-or
defects on visual field testing better than automated testing.
In
1. The patient cannot reliably perform an autom
asleep or may become disinterested in participation if left unmonitored during autom
testing. Goldmann perimetry cannot be performed without an examiner, so constant
patient monitoring is present.
2
reproducible test for the full field and can usually be performed in a short amount
3
routine practice, the automated field is usually just repeated in these cases. However, i
the results must be confirmed on the same day as the original automated field and the
patient is tired, then a GVF may be appropriate. Additionally, a new visual field defec
found on automated testing that also manifests on GVF testing is more likely a true visua
field defect than an artifact of the test (Figure 4).

Figure 4. Side by side comparison of a GVF and a HVF. Note
the missing area (upper left portion) of the blue I 2e isopter on
the GVF corresponding to the black shaded area in the upper
left quadrant on the HVF. Also note that the lower left
quadrant of the HVF also shows a visual field defect, but the
GVF does not.
Specific Uses of Goldmann Visual Fields
Low Vision
Goldmann visual field testing is preferred over automated visual field testing for low
vision patients with central scotomata for the following reasons: 1) fixation is easier to
monitor when a human perimetrist is performing the test since they can provide direction
and encouragement to the patient and 2) also due to difficulties with fixation, a human
perimetrist is better able to map the size and shape of the central scotoma. The size and
shape of the central scotoma can be helpful in guiding the patient and therapist during
eccentric viewing training in locating a preferred retinal locus. Other less common
indications would include patients with isolated peripheral islands of remaining visual
field and patients who are unable to provide reliable automated visual field responses.

Figure 5. Note the large central scotoma in this patient with low vision.
Neuro-Ophthalmology
Goldmann visual fields (GVF) are essential to the practice of Neuro-Ophthalmology. In
fact, ophthalmic techs with training in GVFs are widely sought-after. First of all, the
GVF is used when patients are unable to perform a Humphrey visual field (HVF). This
may be due to fatigue, slower cognitive skills, low reliability, poor fixation, or decreased
vision. Secondly, the GVF is helpful when the visual defect is located or extends beyond
the central 30 degrees (peripheral visual field defect). Lastly, the GVF is extremely
useful in patients with functional visual loss. These patients have no organic basis for
their decreased vision. They run the gamut from malingerers (to feign for gain) to the
psychologically depressed (subconscious loss of vision). Certain visual field defects are
indicative of functional patients. These include spiraling isopters (Figure 6), crossing of
isopters, and severely constricted fields (Figure 7).

Figure 6. Spiraling of Isopters. Note both isopters constrict as the test progresses.
Figure 7. Constricted Visual Fields OU which improve to normal one month later
with reassurance that no organic lesion exists.

Summary
Goldmann visual field testing is an invaluable test to detect and follow the progression of
scotomas in a variety of ocular diseases, especially when performed by an experienced
tester. However, the ease and other advantages of using computerized systems has
relegated GVFs to mostly a second choice test. Although older, it still has value in our
clinics and should be understood by all ophthalmic personnel. Its newer sibling,
automated perimetry, will be visited in part II of our four part series on understanding
visual fields.
This work was supported in part by an unrestricted grant from Research to Prevent
Blindness and the Pat & Willard Walker Eye Research Center, Jones Eye Institute,
University of Arkansas for Medical Sciences (Little Rock, AR).
References
1. Alward, W. Glaucoma the requisites in Ophthalmology. Krachmer, J editor; Mosby,
St Louis; 2000; p57-61.
2. Anderson DR. Testing the Field of Vision. Mosby, St.Louis; 1982.
3. Katz J, Tielsch JM, Quigley HA, Sommer A. Automated perimetry detects visual field
loss before manual Goldmann perimetry. Ophthalmology 1995;102(1):21-6.
4. Choplin NT, Edwards RP.Visual Field Testing with the Humphrey Field.2nd ed. New
Jersey: SLACK;1999.