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Ask The Labs

Q: I’ve heard that heat may crack/craze AR lenses when adjusting glasses in the bead pan or hot air warmer. How can I avoid this happening?

Anti-reflective lenses should not be exposed to extreme temperatures, such as those found in most frame adjustment devices, which may reach temperatures over 150F. Lens substrates such as CR-39, polycarbonate and high-index are more susceptible to heat expansion than the materials found in anti-reflective surfaces. As a result, when AR lenses are exposed to extreme heat, the substrate expands to a greater degree than the AR surface, resulting in fissures across the lens surface. Consider a balloon covered with an extremely thin layer of plaster. When air is added to the balloon, the balloon expands but the plaster does not, and the plaster cracks. To avoid heat crazing AR lenses when adjusting frames, remove lenses prior to adjusting frames in a heating device then re-insert lenses after adjusting the frame.

Pete Hanlin, ABOM, LDO, Training and Development Manager
Essilor Lens Group

Q: What are the steps in a basic eyewear bench alignment?

For all frames, make sure nose pad arms flow along edges of lenses and temples are parallel to each other. Right side up 4-point stance: bottom of each lens, tip of each temple. Upside down 3-point stance: across top of lenses and top of each temple at point of bend. Temples should be tight and lenses should be tight in the frame. There should be no marks on the frame, no lens warpage or distortion, and no gaps between lens and frame. The frame should be completely clean. For plastic frames, ensure there are no rolled frame grooves, heat marks or burns. For metal frames, there should be no gaps at the closure or temple to end-piece junction, no damaged screws, and no sharp screw edges. Screw style, size and color must match the frame and each other. On rimless frames, ensure there’s no dirt in the groove or monofilament. Grooves must be even and string must be secure in the groove. Monofilament should be the correct color, and screw style, size and color must match the frame and each other. On drill mount frames, there should be no cracks around the drill holes, no tool marks on lenses, and no damaged or sharp edge screws. Screw style, size and color must match the frame and each other.

Paul Zito, President
Encore Optics LLC
South Windsor, Conn.

Q: What’s the best way to adjust an infant’s eyewear?

An infant’s Rx will typically be high-plus lenses. Frames must have comfort cable temples to wrap around the ear for security, since the infant will try to pull the glasses off. The cable should be long enough to encircle the ear lobe for proper grip. If the temple is too short the glasses may press into the face causing red marks or pressure at the bridge or ears. Since the bridge of an infants nose is not fully developed, the best-fitting frame in most cases is a plastic frame with a flat saddle bridge. This disperses the weight of the glasses evenly and allows the glasses to sit closer to the eyes. Nosepads on metal or plastic frames may break off or injure the infant. When adjusting, make sure the cable temples aren’t too tight. When the glasses are opened, the temples should be even and not skewed to one side. The temples when held to the side should also be angled somewhat even. If the right temple is angled too low the glasses will sit too high on the right side and conversely for the left side. Due to ears not being even, the temples should be adjusted to fit the individual with either pantoscopic or retroscopic tilt to balance the frame on the face. Polycarbonate or Trivex lenses are recommended, as they are the most impact-resistant.

Sam Odom, Director of Education and Marketing & Mark Schanbaum, National Sales Director
Legends 4.0, Optical Laboratory
Lewisville, Tex.

Q: What can a lab do to help an account sell-through frames that are languishing on the shelves?

We offer a practice management program that includes frame board management. For those ECPs on the program, we offer to exchange non-moving frames. We also send notices of frames being discontinued so accounts can take advantage of our exchange services. We encourage packaging of frame, lens and lens treatments, however making the packaged pricing more aggressive when the frame is a slow mover or discontinued is a good strategy. You can even give away frames at no charge with specified lens packages.

Dale Parmenteri, Vice President
Balester Optical Company
Wilkes-Barre, Pa.

Q: Should I insure my in-house lab? If so, what for (equipment catastrophe, equipment breakdown, loss of business, liability, etc.)?

Should you insure your in-house lab? Without a doubt, yes, and for all of the above! If you’re leasing equipment it’s likely that whoever leases you the equipment requires insurance as well. Many equipment manufacturers will train and/or certify users to help lower insurance costs and reduce the possibility of operator errors. Some real-life examples of what can happen in a lab and why you should be insured are: An electrical short makes a pump malfunction resulting in a flood that causes damage; someone operating a tint unit receives third-degree burns from the hot liquid. Anything can happen anytime, and you should be prepared. Also remember that whoever edges the lenses is responsible for making sure those lenses meet all industry standards. Polycarbonate and Trivex are safe lenses without a patient waiver if processed correctly; other lenses should have a waiver or patient acknowledgement form. To be effective, a waiver or form should be a standardized industry form, not practice-generated.

Keith Cross, Vice President
Northeast Lens Corp.
Newton Upper Falls, Mass.

Q: What steps should I take to help avoid clogging the edger pump? If the pump clogs, how do I clean it?

This is an easy fix. First and least expensive is to maintain the quality of the water in the edger reservoir. It should be changed at least twice a week to maintain a clean environment for the pump as well as the edger. Second, at a nominal cost, you could purchase a filtering system that will keep up the quality of the water for a longer period of time. These systems are available from many companies, like Practical Systems, Inc. for example. One note: You will have to change your filter cartridge from time to time, but it’s much easier and less messy than changing the edger bucket.

Joseph Seibert, Director of Operations
Three Rivers Optical
Pittsburgh, PA

Q: A majority of our patients are 50 to 90 years old. They want rimless frames but they’re often unintentionally rough on their glasses, plus several aren’t good candidates for PALs. How can we successfully get them into rimless?

Poly, a solution for higher-index and impact resistance, has some drawbacks. First, it’s tough to get good knife-edges on poly for high plus Rx’s. Second, some patients report light fringes and reflections. Third, drill holes can develop fractures, screws work loose or breakout, lenses can become loose in the frame, and fitting adjustments can be compromised.

John Miller, Vice President Sales
X-Cel Optical Company
(retired) Sauk Rapids, Minn.

Q: What’s the different between tensile strength and flexural strength in a lens, and why is it important?

A:	Tensile relates to a pulling action, for example, if your fingers are in a Chinese handcuff, you pull it to get the fingers apart, and it stretches but won’t let go. That’s tensile stress. Flexural relates to bending. Both tensile and flexural lens strength are tested using two different tests.

John Young, President
COLTS Laboratories
Clearwater, Fla.

Q: I have a new patient who got their last eyewear elsewhere. I can’t get the place to verify what lens material she’s wearing. How do I tell the difference between polycarbonate, Trivex, and high-index lenses?

You can tell the difference between poly and high-index by dropping the lens a few inches onto a table and listening to the sound. Poly has a sharper and more hollow sound than high-index. High-index has a flatter sound. It’s difficult to tell if a lens is poly or Trivex. If the patient is getting a smaller frame, you can rub a little acetone onto the edge of the lens. Acetone will damage poly but will not affect Trivex. Or, if you have a roughing wheel or hand-stone, you can shave a little off the lens edge. Poly will gum up where Trivex will shave off. We don’t recommend either of these methods because they will alter the original lens. If you aren’t very careful, these methods can make the lens unusable. It’s always best to try to find out the original order and see what was originally dispensed.

Glenn Hollingsworth, General Manager
Robertson Optical Laboratories, Inc.
Atlanta

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