Methods for Determining Near Insets for Ophthalmic Lenses

Grant Hannaford BSc SLD (Hons) FBDO BA (Hons) While the facial measurements used in dispensing are well established, the derivations and purpose driving the measurements are often poorly understood. This article looks at inter pupillary distances (PD’s), specifically the difference between distance and near pupillary measurements. We will also identify three of the methods by which these numbers are determined. This discussion will consider the problem in the context of spherical design lenses. All references to PDs and centration are monocular unless stated.