Distortion of the Image by Prisms

The distortion of the image formed by a prism, principally an ophthalmic prism, is shown to be adequately described quantitatively by five parameters. Expressions are derived which relate the physical constants of the prism and the position of the prism before the eye to these five parameters. Comparisons of measurements and theory are given. This theory is useful for the study of this distortion and for designing prisms with a minimum of certain aspects of this distortion.