Ask the Labs
By Joseph L. Bruneni

PROGRESSIVE READERS

Q We're looking for over-the-counter reading glasses that have progressive lenses in them (bottom corrected for presbyopia, top without correction). Is such a thing available in polycarbonate? Can you help us find some?

A Hilco looked at such a product years ago but did not see it as a big opportunity. We did not add it to our reader collection. I have not seen any company that carries a progressive lens in a reader. I do believe that Franel has one, a reader (in a full frame) with a plano/bifocal lens. I believe the lenses are acrylic.

--Bob Woyton, Director, Sales Operations, Hilco

POLY AND PREGNANCY

Q I have a pregnant optician who works in a shop working with edging various lens materials. You stated in May that gases and fumes from poly may irritate eyes, skin, respiratory tract, etc. How safe is this for a pregnant woman?

A Polycarbonate dust is more of an irritant and to the best of our knowledge is NOT toxic or carcinogenic. Medically, polycarbonate dust is considered less hazardous than common household and cosmetic dusts and powders. While polycarbonate dust is NOT listed by OSHA as hazardous or toxic, exposure limits have been published that regards it as a nuisance or irritant only. My recommendation would be to assure proper ventilation if such dust is a concern.

--Denny DeCourcy, Vision-Ease Lens

Editor's note: Perhaps the best way to relieve the young lady's concern would be to provide her a copy of the Material Safety Data Sheet (MSDA) provided by the manufacturer of the polycarbonate lens that is being edged.

CORRECTING AN AR BOO-BOO

Q When a lab makes a mistake on one lens of a pair after both lenses have been AR coated, is it permissible to redo only that one lens? I have noticed a slight color difference between lenses when both are not AR coated at the same time. Do you feel that as a point of quality that labs should always redo both lenses when AR coating is involved?

--Debra Collins, The Optical Shop, Silver Spring, Md.

A One of the most closely controlled factors in an AR coating facility is maintaining a consistent residual color in the coatings. All AR coatings reveal some faint residual color. The particular color is not important and has no effect on the patient's vision. Coating labs go to great lengths to make sure that lenses received from them today have identical color to what they produce next month (or next year). In spite of this tight control, most coating labs prefer to ensure there is no color match problem by stripping the good lens and coating it along with the replacement lens to ensure an exact color match.

COLOR ME ISOCHROMATIC

Q We have a patient who is a pilot. He was told by his flight surgeon that he should wear isochromatic sunglass lenses. He was told any eyewear location would have them. We've never heard of them. Can you explain what they are and where we could find them?

A The Dictionary of Ophthalmic Optics, published by the National Academy of Opticianry, defines isochromatic as: Possessing the same color throughout. James Bailey, OD, PhD, a color scientist on the faculty of Southern California College of Optometry reports that he's never seen the term applied to ophthalmic lenses. We suspect the flight surgeon wants lenses that transmit all colors equally without distorting color relationships (such as blue-blocking lenses can do). Gray lenses have been the preferred choice by the Air Force because of their even color transmission. A gray sunglass lens should make everyone happy.

If you have a question you'd like to have answered in Ask the Labs, send it to Joseph L. Bruneni. Fax: 310-533-8165. Phone: 310-533-4975. E-mail: joe@bruneni.com. Or mail questions to: Vision Consultants, 2908 Oregon Court, #I-2, Torrance, CA 90503. An archive of past Ask the Labs columns can be found on the Eyecare Business Website at www.eyecarebiz.com.