抄録
As a measure to confirm the accuracy of astigmatic correction, using a fan-dial chart, there is a technique of shifting the cylinder axis back and forth purposely.
Expanding this technique, a table was completed which enables to read off possible errors in both power and axis simultaneously, from the directions of darker lines noticed in shifting the axis +10 and -10 degrees respectively.
This method, tentatively called “the Double-shift Method”, is described in detail, explaining the use of the table and its application in determining astigmatism.
