Using Trial Lenses; Spherical Trial Lens Correction For Central Visual Field Testing - Zeiss HUMPHREY 720i User Manual

SETTING-UP TESTS

USING TRIAL LENSES

Table 3.4: Spherical Trial Lens Correction for Central Visual Field Testing
Distance
Rx Greater
than Zero
Age
Use Hyperopic
Under 30 Distance Rx
30 to 39 Dist. Rx + 1.00
40 to 44 Dist. Rx + 1.50
45 to 49 Dist. Rx + 2.00
50 to 54 Dist. Rx + 2.50
55 to 59 Dist. Rx + 3.00
60 and over Dist. Rx + 3.25
REV. B 02/03 PN 51680-1
All patients requiring near vision correction should use trial lenses while taking central field
tests and the central portion of full field tests. For your convenience, the HFA II automati-
cally calculates the proper trial lens for your patient, if you know the patient's distance
prescription and date of birth (refer to "Entering Patient Data" earlier in this section).
If you are not using the automatic trial lens calculation, refer to the following guidelines for
selecting trial lenses.
GUIDELINES FOR TRIAL LENS SELECTION:
1. Ignore cylinders of 0.25 D or less.
2. For cylinder errors up to 1.25 D use the spherical equivalent. Use the full
cylinder correction for cylinder errors of 1.50 D or more.
3. Refer to Table 3.4 to determine the spherical power to be used.
Distance Distance Distance
Rx Equals Rx is: Rx is:
Zero (Plano) -0.50 -1.00
Spherical Trial Lens to Be Used
• • •
+1.00 +0.50 •
+1.50 +1.00 +0.50
+2.00 +1.50 +1.00
+2.50 +2.00 +1.50
+3.00 +2.50 +2.00
+3.25 +2.75 +2.25
• means no spherical trial lens needed
The following are examples of trial lens corrections using Table 3.4:
Example A.
For an emmetropic (plano) 70 year-old patient, follow the Distance Rx Equals Zero (Plano)
column to the 60 & Over row. The trial lens correction for this patient is +3.25 D.
Distance Distance Distance
Rx is: Rx is: Rx is:
-1.50 -2.00 -2.50
• • •
• • •
• • •
+0.50 • •
+1.00 +0.50 •
+1.50 +1.00 +0.50
+1.75 +1.25 +0.75
HUMPHREY FIELD ANALYZER II -
3-19
Distance Distance
Rx is: Rx is:
-3.00 > -3.00
Myopic
•
Dist. Rx + 3.25
•
Dist. Rx + 3.25
•
Dist. Rx + 3.25
•
Dist. Rx + 3.25
•
Dist. Rx + 3.25
•
Dist. Rx + 3.25
•
Dist. Rx + 3.25
i
series