ask the labs

Tips and Tricks Of the Trade

Susan P. Tarrant

Q Is it necessary to take optical center (OC) height measurements for single-vision lenses today?

A Not on standard single-vision Rx's, but there are situations where it is helpful—even mandatory.

If an Rx has a notable difference in powers between the eyes, or if the patient's eyes sit significantly above or below the center of the frame, these measurements will enhance your lab's ability to more precisely process the Rx. Also, with the variables affecting visual performance in wraps and higher powers, these measurements add to a lab's ability to deliver the most accurate and cosmetically appealing Rx possible.

All “digital” Rx's should be submitted with OC heights. Digital lens fabrication is the future of our industry, and it represents the most advanced technological process available, designed to deliver truly customized eyewear with an unmatched degree of accuracy. The power of this technology, however, is only truly reached by incorporating the full scope of fitting parameters, including OC height measurements.

— Jeff Szymanski, vice president, Toledo Optical Laboratory, Inc., Toledo, Ohio

Q Can you provide some basic tips (or tricks) for tracing/edging high-wrap frames?

A Unless you have a tracer and edger designed for wrap frames, send it to a lab that has state-of-the-art tracing and edging equipment.

When we are not familiar with a frame, or the Rx is extreme, we make a single-vision poly lens in the base curve and Rx (including PD) of the job. We produce a test lens determining bevel type and placement, and then build a record in the edger for that frame. Once we have it stored, we just recall and produce the right lens. Depending on how extreme the wrap or Rx is, it can take several test lenses to produce the one that fits…or sometimes to determine that it is just not possible.

— Paul C. Zito, president, Encore Optics, LLC, South Windsor, Conn.