A change in vertex distance of eyeglasses compared to that of the trial lenses results in a change in the effective power of the eyeglasses. This becomes especially important when the eyeglass prescription is greater than a plus/minus four or five diopter correction.
Use this tool to measure distance from the patient's cornea to the lens of glasses or trial lenses in a trial frame. A circular conversion calculator is included with each distometer instrument. The distometer features a durable metal construction. Comes in a case.