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.
- Measures distance from the patient’s cornea to the lens of glasses or trial lenses in a trial frame
- Circular conversion calculator is included
- Durable metal construction
- Comes in a case