Article Date: 11/1/2006

contact lens materials
Plasma Treatment for GP Contact Lenses

BY JEFF SCHAFER, OD, MS

Most contact lens fitters have experienced the frustration of designing a perfect fitting GP lens only to have the lens not wet at the initial dispense to the patient. This is a common result if residue from the manufacturing process remains on the lens surfaces or if the lens surfaces come into contact with essential oils or soap from fingers during the verification process.

A non-wetting GP lens will lead to blurry or fluctuating vision, as well as a reduction in initial comfort. We're then forced to re-clean the lens with lab solvents and hope for improvement. Two major GP material manufacturers have unveiled a remedy for this age-old problem.

Recently, Paragon Vision Sciences and Bausch & Lomb received FDA clearance to allow authorized GP manufacturers to plasma treat their GP lens materials. Menicon Z lenses are routinely manufactured with plasma treatment. Plasma surface treatment systems were designed for various applications, including cleaning organic and inorganic contamination from a variety of substrates such as metal, ceramic, glass and silicon. A secondary outcome is to improve lubricity, wettability and bond strength of materials.

This technology has been used with medical devices (including GP lenses), circuit boards and electronics. GP contact lens plasma treatment is specifically intended to prepare the surfaces of a newly manufactured contact lens to maximize initial wettability and potentially improve patient comfort.

How It Works

The plasma treatment process involves treating the material surfaces with cold plasma gas in a reaction chamber. Plasma is matter consisting of electrons, positive ions and neutrons in a highly energized state. Plasmas can etch a surface, deposit a film, add or modify chemical structures or alter surfaces to control water characteristics. Cold plasmas do not adversely affect the bulk properties of polymers because the effect is localized to the surface.

GP contact lens treatment effectively removes all remaining residues from the manufacturing process and results in a remarkably clean lens surface. The most favorable outcome is dramatic reduction in wetting angle measurements. It's this reduction that results in improved on-eye wettability, which translates into the potential for increased patient comfort.

Initial Benefits   

Offering plasma-treated lenses in your practice will likely improve your patients' first impression with their new lenses. A wettable surface may result in less lens awareness, crisp vision and an easier adaptation for new GP wearers. To maximize the benefits of a plasma-treated lens, it's recommended that the lens is shipped wet, and the lens should be handled minimally before dispensing to the patient.

The effect is likely to last several weeks, but will diminish over time as patients wear and handle their lenses. Because of this, I'm hesitant to recommend plasma treatment to solve dry eye or chronic discomfort symptoms. Patients will initially notice the benefits of this treatment, but you should de-emphasize long-term effects when educating patients.

What It Costs

The cost of this service will likely vary for each manufacturer. Labs must invest in reasonably expensive equipment and some may choose to offer plasma treatment on an a la carte basis, passing on the cost to you by charging a nominal fee of a few dollars for each treated lens. Others may choose to treat every lens they manufacture and invoke a small increase in lens prices across the board to cover their costs.

Dr. Schafer is a clinical assistant professor and chief of the contact lens service at The Ohio State University College of Optometry.



Contact Lens Spectrum, Issue: November 2006