optical

Going Digital

Measuring systems provide benefits for digitally surfaced progressive lenses.

DAVE ZIEGLER, O.D.

Many optician make their measurements manually with a PD stick and a Sharpie to place the optical centers of progressive lenses. However, these measurements have great variability from one staff person to another. Even when a pupillometer is used, the potential still remains for different monocular PD measurements between two opticians.

Today’s digitally surfaced progressive lenses require measuring systems to properly deliver on their optical properties. Here is some of the information being gathered by these systems and how to get started utilizing this technology in your practice:

1. Eye rotation center

The interpupillary distance is a static measurement acquired in the primary position. The center of rotation is the point in the eye at which the eye rotates. It varies slightly with the direction of gaze and refractive error. It reflects the dynamic nature of our eyes in motion, since two eyes looking in the same direction may look through two different points on the lens.

2. Head cape

The head cape is our natural head posture and refers to the difference between where our eyes are looking and our head is pointing. Head cape is a habitual slight turn of the head to the right or left shoulder that many people exhibit.

3. Fitting heights

Imaging computers provide accurate fitting height measurements, while allowing the patient to be in a natural position when being measured rather than leaning across a dispensing table.

4. Pantoscopic tilt, wrap and vertex distance

These measurements have not been traditionally measured, but, in my practice, patients have experienced better vision after we have made these adjustments. Prescriptions for digital lenses can be compensated for these measurements to enhance visual acuity and lens performance.

5. Head and eye movement behaviors

Each person has his/her own ingrained pattern of viewing the world with a combination of eye and head movements. Because we all do it somewhat differently, it affects the area of the lens that we look through on peripheral gaze. Personalized digital lenses can result in improved side vision.

Getting started

To start using this technology, contact the manufacturer of the progressive lens that you prescribe most. Ask them which instrument they prefer, and have them train your staff in its use.

I recommend using the instrument on all patients, even single vision patients where many of the measurements aren’t necessarily needed. It gets your staff used to using this as the new way of measuring for lenses and impresses your patients with the technology from your office.

Going digital

Several measuring systems are available, many of which acquire either still images or a video stream to make the measurements. (See “List of Devices,” below.)

Something to consider: One of the national optical chains now uses (and advertises) their digital method of capturing eyeglass measurements. Imagine what your patients think when they see commercials for these instruments while you do not offer this technology. OM

DR. ZIEGLER IS THE SENIOR PARTNER IN A GROUP PRIVATE PRACTICE IN MILWAUKEE, WISC., AND A FELLOW OF THE AMERICAN ACADEMY OF OPTOMETRY. E-MAIL HIM AT DZIEGLER@AMERITECH.NET, OR SEND COMMENTS TO OPTOMETRICMANAGEMENT@GMAIL.COM.