Lubricating Lens Focuses on Patient Comfort
Slow-release lubricating technology may promise patients continuous comfort throughout the day.
By Joachim Nick, Lynn Winterton, John Lally, & Bill Long
Many contact lens wearers report dryness and discomfort that often leads to reduced or discontinued contact lens wear. In the United States, an estimated 10 percent of contact lens wearers discontinue lens wear each year. Studies show that comfort is one of the principal barriers to patients successfully wearing contact lenses.
By replacing lenses more frequently, patients can avoid potential problems associated with deposits including reduced visual acuity, lens comfort and wettability. To address these issues, daily disposable lenses were introduced as a logical extension of frequent replacement lenses.
Both frequent replacement and daily disposable lenses are associated with reduced clinical problems, improved subjective performance and fewer unscheduled visits. Daily disposables offer advantages over frequent replacement lenses; they require no cleaning regimen and have higher rates of replacement compliance. Plus, patients wear fresh, clean lenses every day.
Despite the benefits of daily disposable lenses, some patients continue to report dryness and discomfort, especially at the end of the day.
Managing Symptoms of Dryness
There currently are a few strategies to manage symptoms of contact lens-related dryness and discomfort. However, these strategies have significant limitations.
Using solutions/rewetting drops or artificial tears is one common strategy to relieve dryness. Patients use these drops to mimic or supplement natural tears, and the artificial tears are able to temporarily ease discomfort due to dryness.
While drops and artificial tears are somewhat successful, it's been a challenge to develop a drop that provides comfort and relief of dryness symptoms throughout the wearing day. Because their time on the eye is short, frequent reinstillation of rewetting drops throughout the day is often necessary to provide effective comfort.
Additionally, a variety of strategies to enhance the wettability of the lens surface exist. Hydrogel lens wearers can soak their lenses in conditioning solutions to improve wettability and comfort on a temporary basis. Unfortunately, the effects wear off quickly.
Focus Dailies with AquaRelease
We believe Focus Dailies with AquaRelease (CIBA Vision) combines the benefits of a daily disposable lens with continuous lubrication. These are the first daily disposable contact lenses that contain a moisturizing agent designed for continuous release throughout the day. The slow release of polyvinyl alcohol (PVA) has been noted in original Focus Dailies, but in small concentrations.
Like the original Focus Dailies, the new lenses are made from nelfilcon A, which is a PVA-based material. Of the wide range of comfort drops and artificial tears available, a large number are based on PVA, which is known for its biocompatibility. Patients use artificial tears to relieve the dryness, gritty sensation and irritation associated with reduced or abnormal tear production. PVA is non-toxic, water soluble and moderately viscous at slightly elevated concentrations and molecular weights, which may contribute to better handling for the lens. The good surface spreading characteristics of PVA help prolong tear break-up time and relieve dryness symptoms.
Researchers believe that PVA works by decreasing the surface tension of the tears so that they spread more easily over the eye's surface and don't break into dry spots. It also has properties similar to the natural mucin produced by the conjunctiva, which soothes and lubricates the eye and enhances the stability of the tear film.
Focus Dailies with AquaRelease has five times the amount of PVA available for release as compared to the original Focus Dailies with the intent to provide further comfort enhancement. Through proprietary techniques, additional unbound PVA of a carefully selected molecular size and amount is incorporated into the nelfilcon A polymer matrix and slowly releases from the lens throughout the day. Research indicates that agents such as PVA interact with the tear film to stabilize the tears and have longer residence time in the eye. These effects may result in increased comfort and reduced dryness compared with the original nelfilcon A-based material.
As we mentioned, PVA is gradually released into the tear film throughout the day. Thus, the release of PVA, called AquaRelease is blink-activated. Pressure from each blink squeezes the lens, pumping minute amounts of PVA to the lens surface, distributing it over the surface and releasing small quantities into the tear film. Unlike the quick burst release that occurs with the instillation of drops, AquaRelease releases onto the lens in small quantities with every blink to help provide wettability and relief from dryness.
Clinical studies show that Focus Dailies with AquaRelease is a significant advance in the daily disposable market for end-of-day comfort.
In a randomized, masked, multicenter study, patients preferred the new Focus Dailies with AquaRelease over the original Focus Dailies lenses. This prospective, bilateral study included 395 patients who had at least two months' experience wearing the original Focus Dailies lenses. Half were switched to Focus Dailies with AquaRelease, half were dispensed original Focus Dailies lenses and all patients were asked to compare the study lenses to their habitual lenses after five to 10 days. Results showed statistically significant preference for the new lens.
This study also found that patients who wore the original Focus Dailies required no refitting with the new lens. A separate 133-patient, multicenter study confirmed these findings.
The practice of instilling soluble polymeric components in the form of a moisturizing agent has long served as a means of decreasing the discomfort experienced by many lens wearers. In the present case, we believe the use of the lens matrix as a delivery vehicle to bring about the controlled release of water-soluble PVA is a significant breakthrough in contact lens materials technology.
In Focus Dailies with AquaRelease, time-release moisturizing agent technology enhances the comfort of these single-use lenses. The continuous delivery of moisturizing agent may provide better relief than rewetting/comfort drops. Studies show that Focus Dailies with AquaRelease positively impact wearing comfort, an important factor for contact lens success.
Comfort enhancement seen with Focus Dailies with AquaRelease appears to be associated with modification of the anterior lens surface by releasing emergent PVA molecules from the lens matrix reservoir. In essence, the emerging PVA tendrils supply the lens surface and tears with a time-released moisturizing agent for comfortable contact lens wear and increased tear film stability throughout the day.
Joachim Nick is a senior clinical project manager at CIBA Vision, a Novartis company, Duluth, GA.
Lynn Winterton is a senior research fellow at CIBA Vision.
John Lally is the Global Head of Daily Wear R&D at CIBA Vision.
Bill Long is a project manager, Clinical Claims in North America Professional Services at CIBA Vision.
The authors thank Michelle Stephenson, Troutville, VA, for contributions to the preparation of this article.
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #122.