Simplified analysis of meridional refraction data

An eye may be refracted by making independent measurements of spectacle correction in 3 or more preselected meridians. This paper presents a method for calculating sphere power, cylinder power, and axis, from meridional data taken in evenly spaced axes (such as 45, 90, 135, and 180 deg). The formulas given are equivalent in accuracy to a method previously published and are simpler to apply. Meridional techniques can simplify the patient's task in a subjective refraction and are therefore more suitable for automation than the traditional subjective techniques using crossed cylinders. Methods that might usefully be coupled with this technique include laser and stenopaic slit refraction and streak retinoscopy.