Pursuing Comfort in a Multi-Purpose Solution
By Peter Donshik, MD; Rebecca Madden, OD; and Peter A. Simmons, PhD,
Researchers test the comfort benefits of adding an artificial tear lubricant to a multi-purpose solution.
Patients are often frustrated by diminished comfort while wearing their contact lenses. One potential source for these complaints is the care product(s) they use to maintain their lenses. Patients are more likely to attribute their discomfort to the lenses themselves or the external environment.
The majority of contact lens patients in the United States use a multi-purpose cleaning, rinsing, disinfecting and storing solution to care for their lenses. Independent market research on multi-purpose solutions has determined that patients want a lens care product that will moisturize, protect, keep their eyes comfortable while wearing their lenses and reduce or eliminate the dry, irritative symptoms that they often experience at the end of the day.
Figure 1. Structure of Hydroxypropyl methylcellulose (HPMC).
Symptoms of Discomfort
As eyecare practitioners, we are aware that patients may develop ocular discomfort or drying after a long period of contact lens wear. This may be the result of the physiological effects of aging or environmental effects such as computer use. Often these patients are baby boomers who are reaching middle age and facing the increasing demands of family and career obligations. Their dry eye symptoms may require them to remove and reinsert their lenses during the day or apply rewetting drops to rehydrate their lenses. A care product that provides all-day moisturizing comfort and dryness relief could better meet their needs.
The introduction of hydrogel contact lenses in the 1970s brought with it a desire for an alternative to heat disinfection of these lenses. Over the years, in addition to antimicrobial disinfection efficacy, lens care product development has sought to address the adverse physiological responses from ocular exposure to active ingredients in the care solution.
Historically, manufacturers have generally improved comfort by developing less irritating disinfectants or decreasing the amount of potentially irritating disinfecting agents in the lens care product. While this trend is limited by the amount of active agent required to maintain sufficient microbial kill, care systems have continuously improved. Today's multi-purpose solutions cause fewer adverse ocular events while maintaining acceptable disinfection efficacy.
Focus on Comfort
With effective multi-purpose solution disinfectant formulation, the door has opened to shift the focus in lens care product development to the relief of symptoms while maintaining optimum ocular physiology and excellent microbial kill. This involves adding components to enhance the lens wear experience, particularly in regard to comfort.
Allergan first introduced a lubricating agent, hydroxypropyl methylcellulose (HPMC), in their multi-purpose solution Complete Comfort Plus in 1997. HPMC was chosen to enhance comfort for contact lens wearers by virtue of its safety profile, its physical properties that make it an excellent lubricant and its chemical compatibility with other multi-purpose solution components. HPMC, a polymer derived from plant polysaccharide cellulose (Figure 1), has been used for over 50 years in a variety of products, including foods, cosmetics and pharmaceuticals. The FDA considers HPMC to be Generally Recognized As Safe (GRAS) and lists it as one of the 13 compounds useful for relieving the irritation and symptoms associated with dry eye.
Benefits of HPMC
HPMC possesses properties that make it an ideal candidate for a contact lens/ocular lubricant. Its viscosity has been emphasized in the development of ophthalmic lubricating agents. Adding HPMC to the Complete formula produced a predictable increase in its viscosity in comparison with other multi-purpose solutions (Figure 2). Today it is recognized that HPMC's additional properties as a humectant, surfactant, emulsifier and lubricant also contribute to enhancing lens wear comfort. Its large molecular weight and lack of charge allows HPMC to treat the hydrogel lens surface without becoming absorbed into the lens matrix.
Figure 2. Viscosity of multi-purpose solutions. Viscosity as measured in centipoise is indicated for Complete Comfort Plus with HPMC, Complete without HPMC and other current multi-purpose solutions.
Complete vs. Complete Comfort Plus
HPMC was initially added to Complete without any other alterations to the solution formulation. Therefore, clinical studies comparing Complete with HPMC to Complete without HPMC directly measure the effect of its addition to the formulation. One such study evaluated 147 subjects wearing both conventional and two-week replacement hydrogel lenses who regularly used multi-purpose solutions. These subjects were exposed to either original Complete (without HPMC) or Complete Comfort Plus (with HPMC) in a crossover design. All subjects used both solutions, were masked and randomized for sequence of solution use, and were evaluated for their responses to each solution alone and in comparison with the other. This study evaluated the acceptability of each of the two solutions in terms of subjective comfort and preference. An independent consumer product evaluation firm conducted the preference segment of the clinical evaluation. Key questions related to lens wearing comfort are given in Table 1.
TABLE 1: Key Comfort Index Questions Used in Consumer Preference Study
1. Which of the two multi-purpose contact lens solutions that you tried do you prefer overall?
2. Thinking about how the two products felt in your hand, which of the two products you tried do you prefer?
3. Thinking about how the two products felt in your eyes, which of the two products you tried do you prefer?
4. Which of the two products you tried do you prefer in terms of comfort in your eyes?
5. Which of the two products you tried do you prefer in terms of the amount of time it takes for your lenses to settle on your eyes?
6. Which of the two products you tried do you prefer in terms of keeping your contact lenses moist/wet in your eyes?
7. Which of the two products you tried do you prefer in terms of keeping your contact lenses lubricated in your eyes?
8. Which of the two products you tried do you prefer in terms of being soothing to your eyes?
Some 98.6 percent (145/147) of subjects completed the two phases using each solution. The overall incidence rate of clinically significant subjective symptoms of discomfort was low with both solutions (6.8 percent for Complete and 0.68 percent for Complete Comfort Plus [Table 2]). Complete Comfort Plus had significantly (p=0.001) fewer symptoms that were considered to be related to the multi-purpose solution itself.
TABLE 2:Comparison of Incidence of Symptoms from Clinical Study (n=147)
|Symptom||Complete Comfort Plus with HPMC||Complete without HPMC|
|All Causes, Any Severity||19 (12.93%)||25(17.01%)|
|All Causes, Clinically Significant||1 (0.68%)||10 (6.80%)|
|Blurry Vision||8 (5.44%)||9 (6.12%)|
|Dry Eye Feeling||9 (6.12%)||17 (11.56%)|
|Increased Lens Awareness||8 (5.44%)||15 (10.20%)|
Of the 132 subjects who completed questionnaires comparing the two different solutions for acceptability and comfort, a significantly greater percentage of subjects preferred Complete Comfort Plus over Complete in terms of eight key variables (Figure 3). Of further positive note, the incidence of slit lamp findings was low and comparable for both solutions, indicating that the addition of HPMC to Complete did not adversely affect the ocular safety profile.
Figure 3. Patient preference scores for eight comfort indices (n=132). Comparison between Complete Comfort Plus with HPMC and Complete without HPMC. In all cases, the addition of HPMC produced a significant improvement in patient comfort.
In the development of Complete Comfort Plus, it was expected that HPMC would favorably influence initial lens comfort as well as lens cleaning and handling. Longer-term benefits were not anticipated in lens wear comfort given that topically applied drops containing HPMC are rapidly diluted by tears and subsequently achieve a relatively short ocular contact time, providing only temporary relief of symptoms.
The clinical study results were surprising, therefore, in the statistically significant reduction of symptoms overall and in the preference data favoring the solution with HPMC for "keeping your contact lenses moist/wet in your eyes" and "keeping your contact lenses lubricated in your eyes." Use of HPMC in Complete Comfort Plus differs from topical use in two fundamental aspects: 1) a small volume of post-lens tear film under hydrogel lenses may act as a reservoir for tears and/or lubricants; and 2) lens-HPMC association occurs during the soak in the lens case (Table 3). These findings show that the benefits of HPMC are not necessarily limited to initial comfort but may also benefit the patient throughout the day.
TABLE 3 HPMC in Eye Drops HPMC in Complete Comfort Plus
|HPMC in Eye Drops||HPMC in Complete Comfort Plus|
|Duration of exposure||Brief; subject to rapid dilution in tear fluid||Four hours to overnight; free from dilution by tears|
|Presence in post-lens tear film||Limited by short ocular contact time and low tear exchange behind lens||Established by creation of a post lens tear reservoir|
|Interaction with lens||Primarily front surface||Both front and back surfaces|
Since its introduction into the market in Europe and the United States in 1997, Complete Comfort Plus has demonstrated worldwide success in meeting patient demands for a multi-purpose solution. Its comfort-enhancing properties due to the addition of HPMC offer to patients high levels of sustained comfort with their contact lenses.
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Dr. Donshik, current clinical professor and Chief of the Division of Ophthalmology at the University of Connecticut Health Center and past president of the Joint Commission on Allied Health Personnel in Ophthalmology (JCAHPO), practices in Bloomfield, CT.
Dr. Madden is a research optometrist and manager of lens care clinical research for Allergan.
Dr. Simmons has served on the faculty of the Southern California College of Optometry and has conducted numerous clinical research studies in the areas of tear physiology and contact lens care. He currently conducts research for Allergan.