ABSTRACT It is possible to refract an eye by determining the power of the correcting lens along at least three preselected meridians. It is shown that measurement errors place severe restrictions on the reliability of this technique. A mathematical method of overcoming this problem is presented which involves measurement of four or more meridional powers at any convenient pre‐selected orientations. The method predicts the final prescription and gives estimates of the errors in sphere power, cylinder power, and cylinder axis, while providing the refractionist with an indication of which meridional measurements should be re‐evaluated if the estimated accuracy is imadequate.
William F. Long (Mon,) studied this question.