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Karlen McLean, ABOC, NCLC

Power POINTERS

As an optician working the floor, I was always on the lookout for lens dispensing guidelines. It was easy when the choices were glass and plastic. Then came polycarbonate, mid-index, high index, and now free-form and wraps.

With so many variations in vision correction, it's best to view guidelines as a basic starting point. Here are what prescription powers are typically recommended for lens types.

HIGH INDEX

Recommend high index in Rx's starting at +/− 2.50 or 3.00D, and strongly recommend high index in prescriptions over +/− 4.00 or 5.00D. Use AR technology on high index lenses, since they can block 10 to 12 percent of the light that enters the eye, and AR can increase transmittance to 99.5 percent.

RIMLESS

Rimless—especially drill-mount styles—generally should go no higher than +/− 2.50 to 300D. Some opticians advocate fitting higher powers in semi-rimless frames if patients' PDs are narrow (around 58mm or less) and in high index material. For the most part, rimless lenses are polycarbonate, 1.67, Trivex, or other high impact-resistant lens material.

FREE-FORM

Almost everyone can benefit from free-form produced lenses, as they can be customized for the patient's frame, viewing habits, prescription specifics, and more.

Most ECPs agree that the patients who get the most “wow” factor from their free-form lenses are those in the range of +/− 2.50 and higher (see a 2.50 trend?). Patients with high cylinder also are more likely to have an impressive free-form result.

WRAPS

Current wrap power ranges are from around +4.00 to −6.00D, offered in 8 to 8.25 base curves. Prescriptions in this power range are most common, and the wearer's visual results are best when kept within these parameters. EB

Frame Fit Factors

Pleasing customers takes a simple formula that adds up to great results.

Follow these four basics to ensure the best frame fit and lens performance results:

1 Always pre-adjust frames before taking measurements.

2 Pay special attention to pantoscopic/retroscopic tilt. Average pantoscopic tilt is 10 to 12 degrees. Fit the frame with minimum vertex distance (as close to the face as possible). Does the frame touch eyebrows or cheekbones? Consider how the frame will sit once Rx lenses are installed.

3 Cut corners on high-minus lenses. Fit frames that are small and roundish to cut down on edge thickness.

4 Generally, smaller is better. Fit the smallest frame possible that still allows all-around visual acuity, especially peripherally and for correct PAL, bifocal, and multi-focal fitting. The smaller you go, the thinner and more lightweight the lenses will be.

Senior editor Karlen McLean has been in the optical industry for 35 years. She has spent half of that time in the dispensary. In this monthly column, Karlen shares her own experiences, and hopes you'll share yours. Contact her via email at karlen.mclean@wolterskluwer.com.