What GP lens material do you recommend?
(A list of materials is available on this website.)
“It’s important not to get too caught up with the large number of materials that are presently available. Utilize the laboratory consultant for this decision. They know how to match material with design and patient. I often recommend high Dk lens materials, erring on the side of oxygen to avoid corneal hypoxia. They also hold up better under stressful situations — such as ultrathin and toric designs — than previous-generation high Dk lens materials. You don’t see 3 & 9 o’clock staining as much with these materials, due to the quality of manufacturing with better-wetting high Dk materials and ultrathin designs resulting in less inferior decentration.” (Keith Parker, Advanced Vision Technologies)
“We use several different materials, and we will recommend a specific material for a given design and patient. As with the GP Lens Institute, we have all of the materials and their respective properties on our website.” (George Mera, Tru-Form Optics)
“There is a wide array of GP materials available today that will provide the best product for patients’ needs. High Dk materials provide the most oxygen to the cornea; low specific gravity materials are useful in combating thick lens designs; high specific gravity materials aid in reducing high-riding lenses due to excessive upper lid attachment; and more rigid materials reduce lens flexure. The material of choice will depend on the needs of the patients and the design of choice.” (Ann Shackelford, ABB-Concise)
“There are a few factors that determine what GP lens material I choose, depending on the kind of lens and what the patient’s needs are. For multifocals I recommend Paragon HDS or Boston XO because they are durable and work well with the optics. The Boston ES is one I recommend for its durability and good wetting angle.” (Kelsey Roberts, Valley Contax)
Plasma treatment of GP lenses: What is it, and what are the benefits?
“Plasma treatment is a process wherein a finished lens is bombarded with high-energy radio waves in an oxygen-rich environment. Exotic oxygen radicals strike the surface of the lens, dislodging hydrocarbons such as oils that may have been picked up in the manufacturing process. Additionally, the molecules on the surface of the lens are rearranged such that carbon migrates away from the surface while oxygen and nitrogen migrate toward the surface. As a result of plasma treatment, the surface of a lens will become ionized, increasing its ability to attract liquids. These actions combine to make the lens surface more wettable, which in turn can improve the comfort of the lens and reduce fogging problems.” (Kurtis Brown, Menicon)
“Plasma treatment ensures that the lens surface will be pristine and exhibit excellent initial wettability. Although now laboratories use water-soluble compounds, not solvent-based — greatly reducing the possibility of residue-induced poor initial wettability — plasma treatment ensures a very wettable lens surface.” (Keith Parker, Advanced Vision Technologies)
“Plasma treatment is a process where the lens is bombarded with ions in a vacuum. This decreases the lens hydration time by reducing the wetting angle of the lens. The plasma greatly increases patient initial comfort and allows the lens to wet well right out of the gate.” (Kelsey Roberts, Valley Contax)
“Plasma treatment is sometimes referred to as a coating, but to be clear, plasma treatment is not a coating put on the lens. It is a process in which the lens is subjected to high-frequency radio waves in an ionized gas chamber. This process reacts with any manufacturing contaminants on the lens, freeing them from the surface of the lens. This process also allows for maximum wettability, which will result in improved initial lens comfort.” (Susan Faul, Paragon Vision Sciences)
What causes plasma treatment to become ineffective?
“Plasma treatment affects only a very thin layer of the lens, measurable on a nanometer scale. Many common lens cleaning practices involve abrasive components that can wear away this thin layer of affected plastic. Lens care products that contain an abrasive component should not be used with plasma treatment. In-office ‘clean and polish’ services that involve cleaning a lens with abrasive contact lens polish should never be performed on a plasma-treated lens. Proteins and lipids that accumulate on lens surfaces can just as effectively be removed chemically with lens care products for that purpose.” (Kurtis Brown, Menicon)
“Plasma treatment can be impacted by in-office cleaning with a solvent-based extra-strength cleaner, use of an abrasive cleaner, or in-office polishing. This wears off the surface hydrophilic area and thus exposes the unaffected hydrophobic silicone beneath.” (David Rusch, Firestone Optics)
“If the thin layer of rearranged molecules is worn off, the lens surface returns to the original wetting angle of that material. This is not a problem if the material has a good wetting angle. We have found that cleaners with gritty properties removes the treatment.” (Al Vaske, Lens Dynamics Corporation)