Lens care can have a considerable impact on patients’ contact lens-wearing experience and overall satisfaction with their vision correction. Hydrogen peroxide (H₂O₂) lens care systems have a long history of safe and efficacious disinfection, and they have evolved in important ways since their first introduction.¹ Given these facts, how compelling is the case for H₂O₂ to be the first choice that practitioners prescribe to their reusable lens wearers?

Although less commonly recommended than multipurpose solutions (MPSs) are, H₂O₂ use has increased in recent years and now accounts for about 25% of lens care recommendations made by U.S. practitioners.² Still, the relatively low usage of H₂O₂ care systems in comparison to MPSs suggests that, in general, practitioners may have concerns about recommending H₂O₂ to patients or may perceive MPSs to offer better convenience, safety, or efficacy. An examination of the current scientific and clinical evidence, however, reveals that H₂O₂ lens care provides several important advantages versus MPS and, therefore, presents an opportunity for practitioners to improve their patients’ lens-wearing experience.

EASE OF USE AND COMPLIANCE

In the early two-step H₂O₂ systems, users disinfected their lenses by soaking them in 3% H₂O₂ and then neutralizing the solution by manually adding a neutralizing agent. One of the benefits of these two-step systems was the prolonged exposure of the lenses to the full-strength H₂O₂ solution prior to adding the neutralizing agent.¹ The one-step systems in use today simplify lens care for patients by combining effective disinfection and neutralization into a single step, either through the inclusion of a platinum neutralizing disc in the lens case assembly or through use of a time-release neutralizing tablet.¹

Despite perceptions that MPS systems are easier for patients to use, noncompliance remains a common problem.^3-5 One-step H₂O₂ systems have features that promote ease of use; in addition to combining disinfection and neutralization into a single step, a rub step is not needed prior to disinfection, and visible bubbling helps prevent solution reuse (“topping off”).⁴ Studies show that compared to MPSs, H₂O₂ use significantly improves overall patient compliance with directions for use as well as specific compliant behaviors (including using fresh solution for every disinfection cycle and replacing the lens case within three months), the likelihood of following their practitioner’s lens care brand recommendation, and frequency of office visits for eye examinations.^4,5

Consistent with H₂O₂’s ease of use, a 2017 U.S. Food and Drug Administration (FDA) Joint Panel Report documented a total of only 370 Medical Device Reports related to H₂O₂ lens care misuse over a period from 2006 to 2016, a time frame covering several million H₂O₂ lens care uses,⁶ thus making such incidents very uncommon.

The Joint Panel Report, as well as clinical case report findings, indicates that symptoms of exposure to non-neutralized H₂O₂ are transient and that patients typically recover without the need for medical intervention.^6,7 Further, there is currently no evidence to suggest any risk of permanent ocular damage or loss of vision after exposure to non- or incompletely neutralized 3% H₂O₂. Because exposure can cause serious acute discomfort, however, practitioners should ensure that patients fully understand H₂O₂ lens care directions for use as well as the importance of consulting with their practitioner if such exposure should occur.

SOLUTION INTERACTIONS WITH THE LENS AND THE OCULAR SURFACE

The interactions between a lens care solution and the lenses as well as the ocular surface are important considerations when making any lens care recommendation. The biocides used in MPSs also act as preservatives, and some of these biocides (particularly biguanides) can present challenges in this respect due to their potential for uptake and release by lenses. Avoiding uptake and release of MPS biocides is desirable because uptake can deplete levels in the remaining solution and therefore reduce disinfection efficacy,⁸ while subsequent release of certain biocides onto the eye can lead to symptoms of ocular discomfort.⁹ H₂O₂ does not present the same challenge. As a result of its small size, H₂O₂ can be taken up by lenses in large quantities (hence the stinging sensation if a non-neutralized lens is applied); but, after neutralization, there is little-to-no H₂O₂ present on or in the lens, and any residual concentration can be rapidly metabolized by the eye’s natural antioxidant defenses.¹⁰ This relative absence of complex interactions between H₂O₂ and both the lenses and the ocular surface helps avoid concerns regarding uptake and release.

DISINFECTION EFFICACY

H₂O₂ has a mechanism of disinfection that is fundamentally different from that of MPSs. H₂O₂ disinfects lenses by producing free radicals that act as oxidizing agents and destroy microorganism cell membranes and essential cell components. In contrast, biocides used in many of today’s MPS options interact electrostatically with microorganism cell membranes to cause leakage of intracellular components.¹¹ Different biocides are typically effective against different microorganisms, and many MPS options include a combination of two or more biocides.

Available MPS and H₂O₂ systems meet International Organization for Standardization (ISO) criteria for lens disinfection against planktonic (free-floating) bacteria and fungi;^12,13 however, current evidence also indicates that H₂O₂ can provide important efficacy advantages over MPSs. While current ISO standards do not require testing against biofilms, this form of microbial growth tends to be more resistant to host defenses and to certain disinfectants.¹⁴ Lens care efficacy against biofilms is therefore important, and studies have shown greater efficacy against bacterial and fungal biofilms with H₂O₂ than with several MPSs.^13,15 Similarly, ISO standards do not require testing against Acanthamoeba, a well-known cause of rare but often severe infections. Laboratory studies have shown greater efficacy against Acanthamoeba trophozoites and cysts with H₂O₂ versus with MPSs,^16,17 suggesting an opportunity to help lens wearers reduce their Acanthamoeba infection risk. Importantly, there are also laboratory data showing efficacy against Acanthamoeba with some MPSs as well as with a povidone iodine disinfection system.^12,18,19 In line with laboratory findings regarding H₂O₂’s efficacy against Acanthamoeba, case-control analysis of data from an Acanthamoeba keratitis (AK) outbreak showed little to no association between AK and H₂O₂ lens care use.²⁰

OCULAR SURFACE HEALTH

Normal physiological processes regularly expose the ocular surface to oxidative threats. Early studies showed that the intact corneal epithelium is relatively impermeable to physiological levels of H₂O₂²¹ and that antioxidant enzymes at the ocular surface can rapidly metabolize low levels of H₂O₂.¹⁰ Furthermore, with available H₂O₂ lens care systems, residual H₂O₂ levels after neutralization are 5ppm to 60ppm, a range well below human detection thresholds (which exceed 100ppm).²²

Cell collection and confocal microscopy experiments provide cellular evidence for the ocular surface benefits of H₂O₂, revealing lower levels of corneal epithelial cell shedding among users of H₂O₂ in comparison to polyhexamethylene biguanide (PHMB)-containing MPSs.²³ Clinically, a retrospective study of different lens/lens care combinations reported better general performance (based on analysis of comfort measures and adverse events) with H₂O₂ versus MPSs,²⁴ and a study of symptomatic patients indicated that switching from biguanide-containing MPS to an H₂O₂ system resulted in significant improvements in lid papillae and in the frequency and intensity of associated symptoms.²⁵ Clinical studies also suggest a low risk of corneal infiltrative events among H₂O₂ users.²⁶

LENS-WEARING COMFORT

The Tear Film and Ocular Surface Society’s International Workshop on Contact Lens Discomfort noted that lens care choice can affect lens-wearing comfort, either reducing it as a result of uptake and release of solution components by the lens or enhancing it through adsorption of comfort additives onto the lens.²⁷ An important fundamental difference between H₂O₂ and MPSs is that H₂O₂ systems do not contain the MPS biocides that also serve as preservatives.¹ This aspect of H₂O₂ systems can help wearers avoid potential discomfort related to preservative sensitivity. In addition, as with some MPS products, H₂O₂ lens care systems can include surfactants and comfort-enhancing ingredients to help improve patients’ lens-wearing experience.

Comparative studies examining comfort-related outcomes have identified advantages related to H₂O₂ system use, including greater lens wettability,²⁸ longer comfortable lens wear per day,²⁹ and greater comfort on lens application²⁴ versus MPS. Still, findings on subjective comfort outcomes are not unequivocal, with evidence also suggesting no significant differences between H₂O₂ and MPS use with respect to comfort and dryness ratings,²⁹ end-of-day comfort,²⁴ comfortable wear time,³⁰ and Contact Lens User Experience (CLUE) scores.³⁰ While further investigation of comfort outcomes may be warranted, particularly as additional H₂O₂ and MPS lens care options become available, the current evidence suggests that H₂O₂ lens care can help users avoid potential comfort issues related to certain MPS biocides.

SUMMARY

Taken together, the scientific and clinical evidence provides support for H₂O₂ as an easy-to-use, efficacious lens care option with a wide range of benefits for today’s reusable lens wearers (Table 1). Given its ease of use, H₂O₂ use can help simplify lens care and provide an enhanced lens-wearing experience for new lens wearers from the start. H₂O₂ can also be a promising option for experienced lens wearers, including, for example, patients who have a history of noncompliance with MPSs, of ocular surface issues, or of preservative sensitivity. While providing important benefits for patients who wear soft contact lenses, H₂O₂ can also offer unique advantages for GP lens wearers. Scleral lens wear, for example, can limit tear exchange, making it important to limit exposure of the ocular surface to potentially irritating preservatives, such as the biocides used in MPSs. Similarly, GP lenses are replaced relatively infrequently, making effective disinfection especially important throughout the wear cycle. Still, there are patients for whom MPS is the preferable option, including part-time lens wearers (H₂O₂ should not be used to store lenses for more than seven days) and frequent travelers (to facilitate safe storage during travel).

Given that H₂O₂ provides an opportunity to support successful lens wear and help improve patient outcomes, there is compelling evidence to suggest that practitioners should consider making H₂O₂ their first-line contact lens care recommendation for many reusable lens wearers (Table 2). This recommendation is based on current evidence, and ongoing evaluation of the benefits of different lens care systems as new products and data become available will continue to be critical to supporting best patient outcomes. CLS

Acknowledgements: Editorial and administrative support were provided by BioScience Communications through funding provided by Alcon. This article is a revised summary of Nichols JJ, Chalmers RL, Dumbleton K, et al. The Case for Using Hydrogen Peroxide Contact Lens Care Solutions: A Review. Eye Contact Lens. 2019 Mar;45:69-82. The authors acknowledge Jason J. Nichols, OD, MPH, PhD; Robin L. Chalmers, OD; Kathy Dumbleton, PhD, MCOptom; Mohinder M. Merchea, OD, PhD, MBA; and Loretta Szczotka-Flynn, OD, PhD, for their work on the original article.

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