Q. Glass Lenses/Nylon Suspension Mountings
Our patient has requested that we put glass lenses in his rimless corded frame. We edge in our office and want to know if this is safe and legal.

-Linda Sabittini

A.
There is nothing illegal about dispensing grooved glass lenses. However, the OLA has consistently advised against using glass lenses in drilled or groove mounted frames since an early Tech Topics on this subject in May, 1993.

A glass lens that has been edged, drilled or grooved, and properly tempered will probably pass the FDA impact test (note also that essentially all glass lenses are required to be individually impact tested after tempering).

However, when in use, the edge of the lens is unprotected. Simply placing the lenses carelessly on a rough surface or dropping them on a hard surface can produce small chips or microcracks that will significantly reduce the impact strength of the lens. Even if the lenses do not break, the patient may be dissatisfied with the appearance of the eyewear due to edge chipping.

The same concern is present in all glass lenses, whether crown glass, photochromic glass or high index glass.

Previous Technical Director George Chase suggested that if a prescriber/dispenser insists on drilled or grooved glass lenses, a warning label be provided. The text of the warning label states: To Prescriber/Disp-enser: The glass lenses in this rimless mounting were made according to your work order. Instruct your patient to take care to avoid damaging the edge. Should the exposed edge of the lens become damaged, have it replaced immediately. Edge damage reduces the original impact resistance of the lenses. Plastic lenses are strongly recommended for such mountings."

Additionally, it would be important for the prescriber/dispenser to conform to the Duty to Warn program to document that more impact resistant lens options were discussed.

-Dan Torgersen, technical director, Optical Laboratories Association

Q. Poly to the Rescue
 
I am a scientist who uses a ultraviolet transilluminator to view the fluorescence of molecules like ethidium-stained DNA. I have polycarbonate glasses that were ordered with UV protection. Am I protected against 302nm light?

A.
Yes. You are protected at 100 percent, up to 360nm.

-John Young, Colts Laboratories

A.
Manufacturer applied anti-fog coatings are your easiest solution. The simple way to test this before you buy a face shield is to breathe on it and check the lens. But since you already have a face shield, your best solution is to purchase a daily use anti-fog product at a local optical or sporting goods store. The effectiveness of daily use anti-fog lasts from one to three days depending on temperature, your activity, and your body temperature. One caution to be aware of is that some polycarbonate hard coated lenses contain a silicone residue. Silicone will not accept an anti-fog application. Unfortunately, the only way to find out if there is a silicone residue is to apply the anti-fog and see what happens. These lenses, however, represent a small portion of the market.

-Brij Singh, vice president, R&D, Nanofilm, Ltd EB

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