Debra Lynn Dadd

Eyeglass lens material

QUESTION:

Hi Debra,

I've read many of your answers to questions about the safety of plastics, a hot topic these days.

I think the material used often for eyeglass lenses is either polycarbonate or high index plastic.

In addition, teflon or other based coatings are used for scratch proofing, anti-reflective coating, or UV coating. Frames are often made of plastic or have some sort of coating on them.

What are your thoughts on the safety of such materials sitting so close to one's face all day?

Do you wear glasses personally? And, if so, what kinds of materials have you used for yourself?

Thanks.

POSTED BY LISA :: AZ USA :: 04/29/2008 12:04 AM


DEBRA'S ANSWER:

Yes, a lot of plastics are used for eyeglasses.

The thing to remember about polycarbonate is that the concern is not outgassing, but leaching into food and water from contact. Since our skin does not contact the eyeglass lens, I don't believe there is a problem with toxicity during use.

I do wear eyeglasses. Just reading glasses I buy at the drug store. I buy the type with metal frames, not plastic. At the moment I am wearing a pair with metal sides and frameless lenses. Sometimes the metal sides make my skin break out in a rash, but others don't. Seems to depend on the brand and quality of the metal.

Plastic eyeglass frames, though, are not particularly toxic. Look for frames made from zyl (zylonite, or cellulose acetate). It is actually a plant-based plastic that is made from wood pulp and has been in use for decades.

Other frames are made from propionate, a nylon-based plastic that is hypoallergenic and nontoxic.

Debra :-)


COMMENTS:

Thank you! Great info. I think I know why your skin might break out from certain metal eye glass frames. I have heard that the nickel content is to blame. An optometrist I spoke with said to buy frames without nickel content.

COMMENT FROM DEBRA: That sounds right to me.

POSTED BY LISA :: AZ USA :: 05/06/2008 11:28 AM


I need glass for reading. The plastic of the frames and lens does annoy me (I am chemically sensitive). I had metal ones for a while which felt better on my skin but the lenses still irritate my eyes. I hope to find glass lenses but plastic or metal frames is a toss-up for me.

POSTED BY LAURA :: MAINE USA :: 05/06/2008 11:46 AM


Glen's Optiques in Dallas, TX makes heat-tempered glass lenses with no chemicals. 214-321-6753 Best-- Dorothy

POSTED BY DOROTHY :: MA USA :: 05/15/2008 12:56 PM


Just be sure you don't wear metal farmed glasses at the computer...the metal becomes an antenna...

POSTED BY AIMEE :: WASHINGTON USA :: 05/15/2008 11:56 PM


Debra, this question arises from your helpful comments about polycarbonate eyeglass lenses, which you noted should not be a problem because the lenses don't contact the skin. I wonder, however, about contact lenses, which sit directly on the eyes. Do contact lenses (and perhaps contact-lens solutions) expose us to toxic plastic chemicals that we should avoid? Thanks very much.

COMMENT FROM DEBRA: Found this at http://ask.yahoo.com/20020716.html
In the 1960s, the first contact lenses that became commonly available were made of poly(methyl methacrylate) (PMMA). PMMA is used in Plexiglas and Lucite and for things like aquariums and hockey rink barriers. It's even found in latex paints. PMMA lenses are hard, rigid, and not very comfortable. These lenses don't allow oxygen to pass directly to the cornea, which can be detrimental to the eye. Hard lenses are not very popular anymore.

In 1971, the first soft contact lenses were introduced commercially in the United States. These were also made of a polymer, but this time it was a polyacrylamide, which contains nitrogen. This polymer dissolves in water, and it's similar to polymers used to make acrylic fibers for fabric. Crosslinked polyacrylamide actually absorbs water, so it's a good material for contact lenses. Anywhere from 38% to 79% of a soft contact lens is water, and the water keeps the lens soft and flexible. Over 75% of contact lens wearers in the U.S. use soft lenses.

In 1979, the first rigid gas-permeable lenses (also known as RGPs) hit the market. These lenses combine PMMA with silicone and fluoropolymers so oxygen can pass directly through the lens to the eye. This makes the lens more comfortable for the wearer. Plus, the rigidity of RGPs can make vision crisper, and RGPs are better suited to correcting astigmatism and bifocal needs.
It seems to me that the the soft lenses made from soft plastics may outgass plastic and the eye would easily absorb them, however, I am speculating by saying this. But silicone and fluoropolymers (read Teflon)?

And here's a whole post from this very blog about contact lens solution: Q&A: Contact Lens Solution


POSTED BY DC :: UTAH USA :: 05/19/2008 9:29 PM


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