ask the labs

Getting it Right

Susan P. Tarrant

AVOIDING SCRATCHES

Q Would you provide some tips on avoiding flaking the coating/treatment or scratching the lens when installing a three-piece mount?

A First off, it goes without saying that CAUTION needs to prevail at all times when working with a three-piece mount. A trick that I use is to hold the lens with tissue paper. I wrap it with either tissue paper or the little lens protective “wrap” that most lenses are shipped with, securing it in place with Scotch tape. Then I use either tissue paper or paper towel to hold the lens. I leave the area I need to work on exposed.

Again, I use a lot of caution. Also, I would advise that you never work on a three-piece mount when in a hurry. Give yourself the time to go slowly and carefully.

— Steven Lantz, general manager,
Eyear Optical, McAllen, Texas

SPECIAL CONSIDERATION

Q If a patient has a high-plus or high-minus Rx, which frame characteristics should be taken into consideration to ensure it will work best with the lenses?

A When working with a patient with a high-plus or high-minus lens Rx, say over four or five diopters in total power, the following tips can help:

In general, rounder and smaller shapes are best for reducing edge thickness. One key factor in reducing edge thickness is picking a frame that requires the least amount of decentration. Decentration is the natural enemy of high-power lenses, as decentration increases, so does edge thickness. Another way to look at it: The closer the geometric center of each eye is to the pupil, the less edge thickness there will be.

Of course, other aspects of frame choice also have a role to play. A frame that hides more of the lens edge will help improve aesthetics— with plus lenses the thickness will tend to be in the nasal, with minus lenses it will be the temple edge. Be careful with drills and rimless groove frames; instead consider zyl or metal frames with thicker eyewires.

As for wraps, they are designed for lower powers, typically from -3.00D to +3.00D, and can become risky above this range. For wraps in general, we strongly recommend consulting the frame manufacturer to determine the lens range the frames were designed to accommodate.

— Swen Carlson, vice president,
operations, VSP Optics Group,
Columbus, Ohio

If you have a question you'd like to have answered in Ask the Labs, send it to Susan P. Tarrant. Email: Susan.Tarrant@Springer.com. An archive of past Ask the Labs columns can be found on the Eyecare Business website at eyecarebusiness.com.