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Eyes prefer plasma-coated contacts.

Eyes prefer plasma-coated contacts

More comfortable contact lenses and more biocompatiblesurgical implants are just two of the envisioned applications for a new plasma-polymerization treatment developed at the University of Missouri's Materials Research Center in Rolla. According to Hirotsugu Yasuda, a developer of the process, not only does an ultrathin (30-nanometer-thick) coating of methane-plasma polymer make "hard' contact lenses more durable, scratch resistant and comfortable, but such coatings could also rescue prospects for silicone rubber as a preferred material for extended-wear lenses. And his preliminary animal studies indicate that this coating, when applied to the polymeric materials used as replacement veins and arteries, reduces their tendency to spawn blood clots.

Yasuda's process involves ionizing methane gas in a 70| to100|C vacuum chamber. This generates a methane plasma and its polymer--a three-dimensional "network' of amorphous (noncrystalline) carbon containing hydrogen atoms--that coats out to form an ultrathin surface.

In one test, five people were asked to temporarily surrendertheir "hard' contacts while Yasuda coated one lens in each pair. It wasn't long before these people began complaining to their eye doctor that one of their contacts was bothering them; invariably it turned out to be the untreated lens, the one they had previously worn without complaint. These limited data suggest, Yasuda says, that the coating will make any lens considerably more comfortable.

But their big application may be for the extended-wearmarket. Here silicone rubber has shown promise, Yasuda notes, because it has better oxygen permeability than any other polymer, good mechanical strength, excellent optical clarity and a physical softness the eyes appreciate. Unfortunately, he adds, it sticks to anything it touches and contributes to the eyes drying out. Yasuda found that by coating the surfaces of these lenses with the new methane plasma, he was able to eliminate both problems.
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Title Annotation:contact lenses
Author:Raloff, Janet
Publication:Science News
Date:Apr 18, 1987
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