Have you ever worked with a really tough contact lens patient, refined and dispensed the “perfect” fitting contact lens only to find out at follow-up that after very minimal wear time the lens becomes uncomfortable, vision blurs or fluctuates, the lens pops out, etc? After many visits and countless hours you may have thought you had it figured out but you weren’t finished yet. Lens coating technologies have helped in certain cases we’ve covered; many of us know these technologies exist but we do not know much about the technologies what gives them their properties.

What lies behind RGP coating technology?

The number one reason for contact lens dropout is poor comfort. Patients are motivated to have their visual needs addressed in contacts, but not by sacrificing comfort. Tangible Hydra-PEG coating developed to improve contact lens wettability, reduce tear film breakup and lens deposits, and improve lens lubricity.

The coating is 90% water polyethylene glycol-based polymer mixture which permanently binds to any contact lens material, creating a mucin-like hydrophilic shell at the surface, separating the lens from the ocular surface and tear film. By doing this, the lipid layer remains intact, reducing tear evaporation and stabilizing tear film thickness. An article written by Dr. Christine Sindt “Tangible Hydra-PEG: A Novel Custom Contact Lens Coating Technology Designed to improve Patient Comfort and Satisfaction” explains Tangible Hydra-PEG in all its glory; for those looking for more information it is a great read!

For us “process” geeks…

To be a contact lens fitting guru, know the intricacies of these “power tools”.

To covalently bind the Tangible Hydra-PEG polymers to a given lens, the outer lens surface must be activated. For lenses which are cast molded a functional chemical activator must be added to the lens monomer mix prior to molding. In the case of lathe-cut lenses the lens surface must be activated by getting exposed to a short plasma cycle. The lenses are then soaked in the Tangible Hydra-PEG polymers during the hydration step, or the polymers are added into the blister packs during the autoclave process. Regardless, the result is a lens enveloped in a layer of Tangible Hydra-PEG polymers allowing optimal surface wettability, improved tear film stability and deposit resistance, and better lubricity without modifying the existing lens material.

Who benefits the most?

The Tangible Hydra-PEG technology is of most benefit to patients with dry eye or contact lens-related discomfort, patients who tend to deposit moderate to heavy debris on lens surfaces, and scleral lens wearers who experience fogging.

Pacific University College of Optometry presented data at the 2015 Global Specialty Lens Symposium, showing clinically significant improvement in end-of-day comfort in 24 patients fitted with silicone hydrogel lenses treated with Tangible Hydra-PEG coating as compared to the same lenses without the coating. The same study used topographical data to establish an increased tear break up time in the treated lenses after eight hours of wear at zero, five, and ten seconds post-blink.

At the 2016 ARVO meeting, data was presented on Hydra-PEG treated lens and reduced lens deposits in three exiting GP wearers (moderate and severe depositors) after 4 weeks of wear, vs. plasma-treated lenses. (1)

For the patient

Patients should be made aware that once the lens is treated it becomes more slippery and the handling of the lens should be approached with more caution. This is a matter of adjustment and typically does not cause significant issue with contact lens insertion and removal, for both existing and new wearers.Daily contact lens care is necessary. Patients should be advised to use “compatible” lens cleaning solutions and to avoid harsh, alcohol-based solutions, as well as tap water.

To conclude

Tangible Hydra-PEG technology is something many of us rely on in daily practice to elevate the contact lens wear experience for many of our patients. We use it, we see results, and now we know how it works, how it is applied, and whom it benefits.