ask the labs

Alternative Lens Paths

Susan Tarrant

EXTREME HIGHS

Q For extremely high prescriptions, such as −/+15.00 or more, should I go right for the highest-index material, or would something else work better? Are lenticular lenses a viable option?

A When you get into a high Rx range, there are a few problems that you will face. Either the lens blanks aren’t thick enough, or there isn’t a high enough base curve for the Rx. Using a higher-index material may overcome some issues, but not all. Plastic will often be used because it’s easier to get extra thick or in very high base curves.

The ideal for combining the best vision with the most attractive look would be to use the smallest frame possible, preferably plastic, as the thicker rims will help to conceal some of the thickness of the lens. If a patient doesn’t want to be limited to small frames, there are two other options: high-index or lenticularization.

Our primary free-form provider, Indizen Optical Technologies (IOT), has developed a lenticularization process that we do at FEA that takes a regular lens and blends the peripheral, creating a central viewing zone. When most people hear ‘lenticular’ (assuming they’ve ever seen one) they assume an ugly brick. This new process allows for the creation of lenticularized lenses for not just single vision, but also lined bifocals and progressives.

No special lens blanks are needed for this, as digital surfacing equipment allows labs to do some pretty extreme curves on any base we want. This means I can lenticularize a six or eight base lens with a very strong prescription.

This new technology takes a frame trace and creates a fully-compensated lenticularized free-form design for that specific frame shape and measurements. My own Rx is extremely high (OD: -12.00 +0.50 x 180, OS: -14.75 +0.75 x 180), and I have it in a six base wrap frame with a wrap angle of 22 degrees. Pictures of my glasses may be viewed at lenticular.feaind.com.

— Bill Heffner, IV, IT and marketing director, FEA Industries, Morton, PA

SPORT PAL OPTIONS

Q For patients who really want their PAL in sport sunwear, can I—or should I—manipulate the add at all?

A Single vision would work best, but lowering the fitting height (if they do not need to read a lot) would help their distance vision while giving them some reading area. The exception may be high power/cyl power. Getting too far away from OC could affect their distance vision.

Depending on the Rx and intended activity, there are several options. For reading at the pool or boating, leave the fitting cross at the pupil. For golf, try a Rd. 22 golf seg turned toward the lower temporal corner of the golfer’s back shoulder lens.

— Robert Hughbanks, ABOC, HFOAA, manager of training and development, Expert Optics, Inc., Shorewood, IL