Experts Advise Caution in Abandoning Hydrogel Lenses
BY PETER BERGENSKE, OD, MS, FAAO, S. BARRY EIDEN, OD, FAAO, GREGG RUSSELL, OD, FAAO, & ART EPSTEIN, OD, FAAO
In the marketing frenzy around extended wear materials, momentum may have carried enthusiasm for silicone hydrogels too far. While oxygen certainly provides benefits to the cornea for extended wear, we're concerned about the risk of contact lens dropouts resulting from prescribing silicone hydrogel lenses in the wrong situations. Following are our thoughts on why comfort still matters, and why current silicone hydrogels while certainly a step forward leave room for improvement.
Peter Bergenske, OD, MS, FAAO: I think we may have forgotten that comfort is still one of the principal elements of successful contact lens wear. Many factors influence comfort: Lens design, fit, surface quality and physiological impact.
End-of-day comfort typically declines with most materials. For some patients, higher oxygen transmission has an impact on end-of-day comfort. We know it reduces corneal swelling and redness. But when is it enough, even for the most demanding daily wear patient? It's probably a lower level than what we have with current silicone hydrogel lenses. We had pure silicone lenses at one time. They provided virtually 100 percent oxygen transmissibility. Yet, they were so uncomfortable that patients outright refused them, and they didn't last long in the market.
I recently conducted a clinical trial to compare the performance and comfort outcomes in 40 subjects for daily wear of two lenses silicone hydrogel O2Optix (CIBA Vision) and the more conventional Proclear (CooperVision). In the majority of cases, subjects rated the Proclear lens at least as comfortable as, if not more comfortable than, the O2Optix lens; in fact, close to one-third of patients felt notably less comfortable in the silicone hydrogel lens than in the HEMA lens. Clinically, we weren't able to detect significant differences, with the exception of better limbal redness scores with O2Optix. Other than that, the lower Dk Proclear lens performed at least as well as, if not better than, the silicone hydrogel material in this daily wear scenario. In a forced choice, the majority of patients preferred Proclear.
Admittedly, Proclear isn't a typical HEMA lens. It has properties that most other conventional soft lenses don't: Strong dehydration resistance and the highest Dk/t of any non-silicone hydrogel lens. Nevertheless, I was quite surprised by these results. I expected the new lens technology to outperform the older, but it didn't.
We have a journey ahead of us before silicone hydrogel lenses become the daily wear answer for all patients. We've gained physiological benefits with these new materials, but we've lost some ground with comfort. In fact, a healthy percentage of my silicone hydrogel new fits return and request their old lenses again. I think we all get so caught up with high oxygen discussion, we forget that patients want a lens they can put in the eye and forget it's there.
S. Barry Eiden, OD, FAAO: Silicone hydrogel lenses have a significant place in my practice. But I find that in certain cases they don't result in optimal comfort or vision. I rely on a wide variety of lenses to keep my patients happy. It's important to integrate new materials into our armamentarium, but no one lens will be the best match for every patient.
I strive to meet the triad of safety, comfort and vision success for each contact lens patient. I don't always choose a silicone hydrogel lens. Most soft lenses on the market have long histories of safety, especially for daily wear. Patients must be able to wear their lenses for as long as they want. This is a huge consideration we all know that comfort is a major reason for contact lens dropouts.
There's a promising new horizon with new lens materials, including silicone hydrogel, but we have some way to go before we reach the "ultimate contact lens material." I use a wide variety of lens materials and I encourage practitioners to keep an open mind when prescribing lenses. Each patient is different. Our role is to take the time to match patients to the right material, design and regimen every time.
Gregg Russell, OD, FAAO: I believe that silicone hydrogel lenses have a place in improving lens wearing experiences, especially for extended wear. However, I've not yet been able to accurately predict which patients will have comfort and visual performance issues with these materials.
In my experience, the majority of patients who become disappointed with their vision do so because of dry eye issues. I ask my patients to compare "end-of-the-day" and "beginning-of-the-day" vision. For individuals who note a difference and begin to describe issues such as visual variability when reading books or computer screens, night driving concerns or increasing eye redness and lens discomfort over the day, I dedicate my efforts towards resolving dry eye concerns. Clearly, material selection will matter.
Silicone hydrogel lenses are beneficial in extended wear. But uncomfortable lenses for daily wear just for the sake of higher oxygen? I can't say this is always a fair trade and I'm concerned we might be doing our patients a disservice. While I think that oxygen transmission plays a role in comfort, we can debate how much we need for daily wear. If a lens has great oxygen transmission, but isn't comfortable, then patients won't wear it.
One alternative is the Proclear Compatibles lens. The material performs differently from traditional hydrogels. Specifically, it holds water much better than other designs and is less likely to dehydrate. It's comfortable for patients, easy to fit and provides great visual stability even in patients who have marginal tear film.
I believe the tear film compatibility to dehydration ratio is just as important as oxygen for daily wear. Analyze each patient individually to assess material compatibility, tear film production and visual performance, and prescribe accordingly.
Art Epstein, OD, FAAO: Some of the most important factors for contact lens selection include wettability, lubricity, resistance to contamination, oxygen transmission and modulus. The relative importance of these factors changes for extended wear vs. daily wear. For extended wear, I think we all agree that high oxygen permeability is necessary to avoid hypoxia. But is oxygen so critical if patients aren't sleeping in their lenses?
Remember that since 1971, daily wear has proven highly successful for patients around the world. We don't encounter significant corneal compromise or hypoxia. In fact, most patients do just fine in conventional soft contact lens materials. Oxygen is good, but we must weigh permeability in the context of all other factors.
Silicone hydrogel lenses are still in their infancy, and some still fall short on the comfort scale. Approximately 25 percent of patients for whom I prescribe silicone hydrogel lenses come back and ask for their old hydrogel lenses. We still haven't reached the point where we can prescribe silicone hydrogel lenses for every patient. We can provide all the oxygen in the world, but if the lens isn't comfortable, more oxygen won't help.
A healthy contact lens practice has a mix of patients who wear a variety of lenses: Toric lenses, multifocals, continuous wear and daily wear. Patient loyalty comes from a belief that you'll go to extremes to meet their needs. Success demands a patient-focused attitude. To do that, you must rely on a range of lens materials. The simple truth is that far more options are available to meet patient needs in conventional hydrogels than are currently available in silicone hydrogel materials.
No one material will solve every challenge. Many interesting silicone hydrogel products are available on the market now, but they're not a magic bullet. Material advances will continue as new designs and new generations appear on the market. Until then, practitioners should continue to use a wide variety of materials to meet each patient's individual vision needs.
Dr. Bergenske, a past chair of the American Academy of Optometry's Section on Cornea and Contact Lenses, is a clinical assistant professor and director of the Contact Lens Institute at Pacific University College of Optometry.
Dr. Eiden is president of a private group practice specializing in primary eye care, contact lenses and refractive surgery.
Dr. Russell is in practice at the Marietta Eye Clinic. His clinical research interests are in dry eye, aberration control, presbyopia and contact lens design.
Dr. Epstein is a senior partner of North Shore Contact Lens & Vision Consultants, PC, and is director of the Contact Lens Service, North Shore University Hospital, NYU School of Medicine.