I believe, as John Green1 stated in 1866, that astigmatic dials, properly used, are the most dependable practical devices yet discovered for measuring the amount and axis of astigmatism. Failure is due to faults of equipment or technic. Lancaster2 was too modest to say this in 1915 when he presented his paper on subjective tests for astigmatism, but if one had read between the lines or taken the trouble to test himself or his patients by this method, one would appreciate why this master of the art of refined refraction anticipated a rational response, namely, the general adoption of his dial or other astigmatic dials by ophthalmologists.
Twenty years later one finds earnest, conscientious, painstaking refractionists struggling without the satisfaction which astigmatic dials would afford or, perhaps, using only one dial—the clock-face or sunburst dial—with disappointing results. What is the reason? The chief reason is that