To the Editor.
—I was pleased to read the recent article in the Archives entitled "Confirming a Change in Refraction With Assistance of a Programmable Calculator" by Davidoff and Duggan (1982;100:443-444).I am happy to see others using refractive techniques of the Phoroptor (refracter), even though what they describe is in a regressive form. Several ophthalmologists with whom I have discussed this article do not understand the difference between Phoroptor overrefraction and regressive Phoroptor overrefraction. Both techniques consist of placing the final refraction power at the plane of the patient's old lenses. It is only in this factor that the two techniques have similar characteristics.In regressive overrefraction, the vertex distance of the Phoroptor or trial frame simply designates the plane of the frame,1 thus patients with hyperopia are overcorrected and patients with myopia are undercorrected, due to the displacement (effectivity displacement error) of the back surface of the
Sims CN. Mathematical Approaches to Refractive Examination. Arch Ophthalmol. 1982;100(11):1854-1855. doi:10.1001/archopht.1982.01030040834028