18
11625-101-Rev. L
Instructions for Use
(continued)
Optical Corneal Aligning Device
(continued)
14. The scale reading of the Corneal Aligning Device is used with the Correction Factor Table to deter-
mine the correction factor for the power reading.
Note:
The correction factor is always added to the Phoroptor reading as a plus quantity.
Example:
• If the Phoroptor
reading is +8.00D and the Corneal Aligning Device scale indicates an addi
-
tional 4 mm, the correction factor according to the table is +0.27. Therefore, the power of the
correcting lens is obtained by 0.27 to +8.00 diopters, which 8.27 diopters,
when the spectacle lens is worn at 13.75 mm from the cornea.
• If the Phoroptor reading is -11.50D, and the Corneal Aligning Device indicates an additional
5 mm, it is necessary to interpolate to obtain the correction factor. Interpolating between
-11.00 and -12.00, the correction factor according to the table is +0.62. Therefore, the power
of the correction lens is obtained by 0.62 to -11.50, which equals -10.88 diopters,
when the spectacle lens is worn at 13.75 mm.
15. T
he tables can also be applied in the case where the spectacle lenses are to be worn at one dis-
tance, the test is made at another distance, and neither distance is at 13.75 mm.
Note:
First, assume the Corneal Aligning Device indicates an additional 4 mm; that the spectacle
lenses are to be worn at 12 mm instead of 13.75 mm; and that the Phoroptor
reading is +13.00
diopters. In this case, fitting distance of 12 mm is subtracted from the refracting distance of
17.75 mm (13.75 mm plus 4 mm), the result being 5.75 mm. In the table for plus Phoroptor
readings at the horizontal row corresponding with +13.00 diopters, the value of 5.75 falls be
-
tween the 5 mm and 6 mm columns. By interpolation, the addition is found to be 1.05D. Hence,
the power of the spectacle lens should be +13.00 plus +1.05 for a total of +14.05 diopters.
