VD....... Vertex Distance
Last week I saw and used a Distometer for the first time. Before the high tech programs on tablets and iPads the Distometer was used to measure a patient's vertex distance. Without accurate measurements (frame A,B DBL, ED, wrap, frame tilt) and the prescription the patient would not get to completely optimize the new digital technology that's currently saturating the industry. And the debate continues on the process, accuracy and end benefits for some patients.
The Distometer is heavier than it looks. To use it place the instrument between the patients eye and their lens. Ask the patient to close their eyes, you press the plunger (like if you were giving a shot) which causes the two balls on the other end to open. One of the balls will touch the lid and the other the lens in their frame, read the gauge add one millimeter for the lid and this is their Vertex Distance.
Sometimes I do enjoy the old school devices.