ask the labs
Getting Crazy
by Karlen McLean, ABOC, NCLC
CRAZY AR
Q I've heard that if cleaned incorrectly or exposed to solvents, polycarbonate lenses can crack or craze. What exactly should I tell my patients to steer clear of solvent-wise, and what should I recommend they clean their poly lenses with?
A Poly exposed to even a small amount of acetone will cause the exposed edges of the poly lenses to have cracks. This will not occur on the surface of the lens, as the poly substrate is protected by a hardcoat. So the edge of the lenses can have many cracks, and sometimes these cracks can run very far into the lens. It is best to steer clear of using acetone on poly.
Rubbing alcohol used with caution can work for cleaning poly. However, it would not be a good idea to expose the lens to alcohol for extended time.
— Bill Markham, AR technical manager, Essilor of America
ANIMAL EYES
Q "Because of photochromic situations as mentioned in the July Ask the Labs on 'Paranormal Photochromics,' how can I ensure upfront that I won't deliver color-inconsistent photochromic lenses?
A Not all photochromic technology is the same. It's important to know what brand of photochromic lenses you're requesting.
Bull's-eye or racooning photochromics occur when the lens is darkest where it's thickest, depending on the Rx. Bull's-eye can occur with high-plus photochromic lenses (darker in the center) and racooning with high-minus photochromic lenses (darker around the edges) in lenses using in-mass technology.
| Back to School Q Can you recommend a good book on solving today's eyeglass wearing problems? —Anthony Ribaldo, George Westinghouse School, New York A Our industry does not have one magic book with all the answers to fitting, dispensing, and troubleshooting eyewear. The best advice we can give is to develop a relationship with a reputable full-service optical lab. Today's successful labs devote a great deal of time to training ECPs and problem-solving. Two books we recommend: The Indispensable Dispensing Guide resource manual available from the Optical Laboratories Association and Systems for Ophthalmic Dispensing by Brooks and Borish. You also might find additional resources from national and state professional organizations.—Jeff Szymanski, sales manager, Toledo Optical Laboratory, Toledo, Ohioe |
If bull's-eye or racooning occurs, regrinding the lens with the same technology may not solve the problem. Typically, surface photochromic technologies can help avoid bull's-eye or racooning effects.
—James Schafer, manager customer service and technical sales, Transitions Optical, Florida
If you have a question you'd like to have answered in Ask the Labs, send it to Karlen McLean. E-mail: mcleank@lwwvisioncare.com. Fax: 215-643-1705. An archive of past Ask the Labs columns can be found on the Eyecare Business Website at www.eyecarebusiness.com.
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