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(B)
Determine Trial Lens
If you are not using the automatic trial lens calculation refer to the following guidelines for selecting
manual trial lenses.
Guidelines for Trial Lens Selection
1. Ignore cylinders of 0.25 D or less.
2. For cylinder errors of up to 1.75 D use the spherical equivalent. Use the full cylinder correction
for cylinder errors of 1.75 D or more.
3. Refer to
Table B-1
for hyperopic or emmetropic patients, or
determine the power of the spherical trial lens needed.
4. Verify that the patient can see the fixation light clearly through the trial lens before beginning
testing. Young myopes may need additional minus power if the target appears blurry to them,
prior to beginning testing. Many 30–40 year olds may not need the full trial lens correction.
How to Calculate the Spherical Equivalent
The spherical equivalent is equal to half of the power of the cylinder (DC) correction. For example,
the spherical equivalent of +1.00 DC is +0.50 D. The spherical equivalent of –0.50 DC is –0.25 D.
Add the spherical equivalent of the cylinder power to the original spherical power to get the overall
spherical equivalent.
Age
Hyperopic Distance R
Under 30 Distance R
only
x
30 –39
(Dist. R
) + (1.00 D) = trial lens
x
40–44
(Dist. R
) + (1.50 D) = trial lens
x
45–49
(Dist. R
) + (2.00 D) = trial lens
x
50–54
(Dist. R
) + (2.50 D) = trial lens
x
55–59
(Dist. R
) + (3.00 D) = trial lens
x
60 & Over (Dist. R
) + (3.25 D) = trial lens
x
Table B-1 Spherical Trial Lens Correction for Central Visual Field Testing of Hyperopic and
Emmetropic Patients
HFA3 Instructions for Use
Determine Trial Lens
Table B-2
is Greater than Zero
Emmetropic Distance R
x
No correction
+1.00 D trial lens
+1.50 D trial lens
+2.00 D trial lens
+2.50 D trial lens
+3.00 D trial lens
+3.25 D trial lens
2660021166131 Rev. A 2018-11
B-1
for myopic patients, to
is Zero (Plano)
x
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Troubleshooting
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slow and lagging
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How to turn the Blue Yellow Parameter from off to on
To enable the Blue Yellow Parameter on the Zeiss Humphrey Field Analyzer 3, set the Blue Yellow parameter to "On." When enabled, this setting provides a yellow bowl and a Blue Size V stimulus, with illumination from a yellow lamp at the top of the bowl.
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