Comparison of dioptric power.

The important formal process of inferring properties of populations from statistics of samples requires a method by which variables can be compared or ranked. A suitable method of comparing dioptric powers is described. The method recognizes the essentially four-dimensional nature of dioptric power and is sufficiently general to allow for comparison of powers (for example, equivalent powers of general thick bitorics) that cannot be represented in the usual manner, sphere/cylinder x axis.