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3. Adjusting the Corneal Distance
3-1. Adjusting the Corneal Distance by Normal Measurement
For normal measurement, set the comeal distance of the patient to the position shown in
Figure 3-3 while observing the OT-8A comeal distance window.
Make sure line 12 is on
=> Turn the forehead rest
=> Adjust the position of the
the triangle base mark
adjustment knob while
comeal distance to line 12
watching the comeal
(At this time, the corneal
distance position of
distance is 12 mm)
patient
Figure 3-1
Figure 3-2
Figure 3-3
If comeal (wearing) distance is different for the test and for the dispensed spectacles,
convert the test result (if more than 5 diopters) according to the diopter conversion table
in Section 3.2 (pages 9 and 10).
Example:
When SPH-9.00D was obtained with the comeal distance of 12 mm, and spectacles are
dispensed for a wearing distance of 15 mm, the prescription is as follows.
(1) "(-) lens" because it is -9.00D. "3 mm away" because 12 mm -» 15 mm
(2) Follow the line of "test result 9.00D" rightward.
(3) Select the column "(-) lens distance by 3 mm."
(4) SPH -9.25D is the prescription for the spectacles.
9
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