SILICONE HYDROGEL CARE

Comparing Lens Care Systems for Silicone Hydrogel Contact Lenses

This study compared subjective preferences for a peroxide-based system and several multipurpose systems for silicone hydrogel daily wear.

By Chris Amos, MSc, BSc

Chris Amos joined CIBA Vision in 1994, with principle activities in lens care research and product development, after eight years of specialist contact lens practice at Emory University's School of Medicine in Atlanta, GA. He graduated in Optometry from the City University in London, England.

CIBA Vision introduced Clear Care into the U.S. market in 2001 when one-bottle multipurpose solutions had grown to hold the largest share of the market for lens care products and there was some skepticism over the future need for peroxide-based systems. Even though Clear Care is a one-bottle system, preservative-based multipurpose solutions were perceived as less complex to use and adequate for care of frequent replacement lenses. Practitioners have tended to regard Clear Care and other hydrogen peroxide-based care systems as niche products reserved for patients who have heavy deposits, allergies, sensitivities to other preservatives and/or marked contact lensrelated dryness.

Clear Care addresses the ease of use issues associated with previousgeneration disc-based peroxide systems in which patients needed to purchase the disc separately and place it in the lens cup and a separate cleaning solution was required. Clear Care comes with its own lens case that incorporates the neutralizing disc on the stem of the lens holder. The solution contains a specific low-foaming surfactant to eliminate the need for a separate cleaning agent, which is the same idea behind multipurpose preservative-based solutions.

Clear Care demonstrates favorable performance on conventional and frequent replacement hydrogel lenses. Results from 103 subjects in two trials against ReNu MultiPlus (Bausch & Lomb), a leading multipurpose solution, were significantly in favor of Clear Care. Not only did Clear Care perform better with regard to symptoms and clinical signs, subjective ratings steadily increased in favor of Clear Care over time. The final three-month visit revealed statistically significant results for application comfort, overall comfort, cleanness and symptoms of dryness for both 1-to-10 scores and preferences (all p≤0.003). For overall preference, 51 subjects preferred Clear Care, nine the multipurpose solution and 43 had no preference (p<0.0001).

Favorable results from a later large multi-center clinical trial further demonstrated the comfort provided by Clear Care.

With the growing popularity of silicone hydrogel lenses, we have reason to revisit questions concerning the performance and compatibility of lens care products with these lens materials. More than onethird of the soft daily wear fits during 2006 across the United States and in five other countries were with silicone hydrogel lenses. The Andrasko staining grid has reported negligible levels of corneal staining after two hours of wear with several silicone hydrogel lenses presoaked with Clear Care, whereas it reports wide variations of corneal staining with silicone hydrogel lenses presoaked with preservative-based multipurpose solutions. Other studies confirm that this result with Clear Care remains the case over the period of time a lens is worn before replacement.

There's no evidence associating solution-related staining with serious clinical events such as microbial keratitis, and this type of staining is often asymptomatic. Discomfort and dryness, however, remain the leading causes of contact lens dropout. The issue of solution compatibility has become more important as evidence mounts that lens care solutions can have an influence on the day-to-day wearing experience and long-term success of silicone hydrogel lens daily wear.

We recently conducted a large clinical trial to determine how well Clear Care performs compared to the leading multipurpose solutions when dispensed with several types of silicone hydrogel lenses.

Trial Design

The clinical trial was a one-month, prospective, crossover, randomized, investigator-masked trial with several important features:

Figure 1.

• With 193 subjects, the study was large enough to be able to detect statistically significant differences based on standard deviation data from previous studies.

• We excluded current hydrogen peroxide users so as to eliminate possible bias in favor of Clear Care.

• Inclusion criteria required that subjects currently wear O₂Optix (CIBA Vision), PureVision (B&L), Acuvue Advance (Vistakon) and Acuvue Oasys (Vistakon) silicone hydrogel lenses on a daily wear basis (minimum two weeks experience). Subjects wore a new pair of their habitual lenses in the trial, and the randomization was stratified for equal numbers of subjects in each of the combinations to meet the requirements of the statistical analysis plan.

• Investigators evaluated subjects at follow-up visits within four hours of lens application to standardize the time of observance for corneal staining.

• Subjects were masked to the sponsor and randomized into several treatment groups; subjects received one of four multipurpose solutions — ReNu MultiPlus Multi-Purpose Solution, Opti-Free Replenish MPDS (Alcon), Opti-Free Express MPDS Alcon) and Complete MoisturePlus Multi-Purpose Solution (Advanced Medical Optics) — and then crossed over to Clear Care or vice versa for twoweek exposure periods for both solutions.

Methods

We enrolled only subjects who had "healthy eyes" with no significant slit lamp findings and who were correctable to at least 20/40 distance visual acuity in each eye with contact lenses. Qualified subjects were dispensed new lenses and asked to follow the manufacturer's instructions for each lens care product, which was minimally a five-second rinse for each side of the lens and overnight soaking (minimum four to six hours), without pre-application rinse. If the investigator recommended extra cleaning or if some subjects habitually did so, those subjects were permitted to rub their lenses with the lens care product according to the directions in the manufacturer's instructions, except for Clear Care subjects whom we supplied with Softwear Saline (CIBA).

For the slit lamp evaluation, investigators used a #12 yellow Wratten filter to enhance the staining appearance and defined solution-related corneal staining as staining in three or more peripheral quadrants.

Statistical Analysis

We analyzed test and control data using a repeated measures model that took solution pairing and lens sequencing into account. The preference and agree/disagree questionnaire was analyzed via exact binomial testing for subjects who expressed a preference. We performed consistency testing among the four lens groups or solutions, and if we observed any significant differences we analyzed each individual group separately. Because of the careful stratification and consistency testing across the materials and solutions, it was possible to evaluate the comparison of Clear Care to the multipurpose solutions as a group with a single p-value of <0.05 representing statistical significance.

Figure 2. Answers to "How much do you agree/disagree?" for Clear Care (neutral equals neither agree nor disagree).

Clinical Trial Results

Of the 193 subjects enrolled, 187 subjects completed and six discontinued for nonproduct-related reasons (lost to follow up [4], wearing old lenses [1] and viral conjunctivitis [1]). One subject was four days early for the one-month visit; we excluded exit questionnaire data for that subject, which brought the total subject count for the subjective ratings to 186.

There were no reports of accidental introduction of un-neutralized peroxide into the eye.

Mean solution-related corneal staining, conjunctival staining and palpebral redness were statistically significantly lower with Clear Care compared to the other multipurpose solutions (Table 1).

Clear Care had statistically significantly higher mean scores for 1-to-10 point scale subjective ratings (1=extremely bad and 10=best possible) for cleanness (p=0.002) and clarity of vision (p=0.019).

Subjects regarded Clear Care more highly at statistically significant levels against the other solutions for the vast majority of the exit questionnaire preference questions. Figure 1 displays preferences based on the question "How would you rate Clear Care compared to the other solution you used during the study?"

Note in Figure 1 that end-of-day (EOD) dryness comparing Clear Care with the multipurpose solutions was not consistent across all lens materials. Clear Care was statistically superior for EOD dryness against all multipurpose solutions with Acuvue Advance (p=0.034) and O₂Optix (p=0.011) lenses, while there was no significant difference for Acuvue Oasys and PureVision lenses in this category.

Figure 3.

Figure 2 shows agree/disagree responses to the following statements:

• After using Clear Care, I can't feel that I'm wearing my lenses.

• Clear Care cleans my lenses better than the other solution I used during the study.

• Clear Care is easy to use.

• Overall, Clear Care is superior to the other solution I used during the study.

Figure 3 shows overall preferences. We asked the subjects to compare Clear Care to the other solution they used in the study and to consider:

• Their overall preference.

• Which solution provided a natural "no lens" feel.

Discussion

Our results indicate excellent performance of Clear Care across the silicone hydrogel materials particularly with regard to comfort and providing a no-lens feel. As is the case with HEMA lenses, practitioners need not be concerned about solution compatibility when using Clear Care with silicone hydrogel lenses.

In addition, our subjects found that Clear Care was easy to use, contrary to the belief held by some practitioners. In this trial we received no reports of accidental introduction of un-neutralized peroxide into the eye. Similar results have been reported in the past (two incidents out of 4,346 uses) and in recent trials (two incidents out of 6,600 uses). Thus, accidental introduction of peroxide into the eye is a rare event and we believe is overstated as a reason for not choosing peroxide over multipurpose solutions.

On the other hand, "topping-off" is a major compliance weakness of multipurpose solutions that is not uncommon and should be of concern.

Consumer acceptance of Clear Care is high, in fact often enthusiastic. Independent consumer organization Information Resources Inc. reports good retention rates with Clear Care — typically 65 percent to 70 percent, compared to 40 percent to 50 percent rates with leading brand polyhexamethyl biguanide (PHMB) and polyquaternium-1 (Polyquad) based multipurpose products. Also, 97 percent of consumers who currently use Clear Care reported that they will purchase the brand again.

For today's contact lens wearers, the ocular stresses of modern day living such as long commutes, hours of computer use, air conditioning etc., alter blink habits and tax the complex tear film physical chemistry to its limits. Lens material advances may not solely address discomfort, dryness and poor vision, and lens care products can affect the state of the lens surface and pre-lens tear film, which is particularly relevant in daily wear.

In the trials reported here it appears that lens care does impact comfort in a measurable way. However, because generic products now account for more than 25 percent of the U.S. volume of lens care products, it appears that many contact lens wearers are unaware of these comfort and performance differences. Practitioners now need to decide whether greater scrutiny of lens care products and interactions with lens materials is something worth discussing more seriously with their patients.

The scientific data presented here makes a compelling case that practitioners should consider Clear Care as the lens care system of choice for many more contact lens wearers, particularly for those who wear silicone hydrogel lenses and for those who experience comfort issues. CLS

To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #145.