| 释义 |
total diameter diameter, total (TD)The linear measurement (usually specified in millimetres) of the maximum external dimension of a contact lens. It is equal to the back optic zone diameter (BOZD) plus twice the width of each of the back peripheral optic zones (if any) or twice the width of the edge in a spherical lens. Formerly, it was called overall size (OS). See optic zone diameter; v gauge. |