A Healthier Oxygen Environment: Opportunities and Challenges for the Practitioner

Nicole Carnt - B. Optom (UNSW) Nicole Carnt graduated from the University of New South Wales in 1989 with a Bachelor of Optometry and spent 5 years in private practice in NSW before moving to the UK.  After qualifying for registration in the UK, she spent 4 years in private practice, working principally in the contact lens field.  Currently Nicole is a Research Optometrist at the Vision Cooperative Research Centre and the Institute for Eye Research, Sydney Australia.  Her principal areas of research are soft toric contact lens design and extended wear of soft lenses.

With the expansion of the silicone hydrogel market into daily wear, the number of silicone hydrogel lens types and lens care products available has expanded substantially. Much emphasis has been placed on the increased short and long term health benefits of increased oxygen both directed to the practitioner and marketed to the patient. It is vital that as practitioners we maintain control over prescribing and present a balanced view to patients on the risks associated with contact lens wear, the importance of hygiene and compliance to lens care regimes and continue to strive for best practice professional care.

While arguably increased oxygen afforded by silicone hydrogel lenses has significant physiological benefits,^{1, 5} the first epidemiological studies have indicated a similar risk for microbial keratitis for silicone hydrogel compared to hydrogel extended wear^{6, 7} (EW). While this may be affected by the demographics of the population, as may be the case with early adopters of other new modalities of vision correction,⁸ and one study indicated the severity of keratitis cases with silicone hydrogel EW is lower compared to hydrogel EW,⁹ patients should be counselled that EW still is associated with increased risk and EW for known risk takers should be avoided.

An increase risk of microbial keratitis has also been shown with occasional overnight use.¹⁰ With an average of 9% of patients in clinical studies sleeping in daily disposable lenses overnight¹¹ and industry estimates of up to 84% of patients napping in lenses, all patients should be advised of the risk of overnight wear.

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It has been shown that patients new to extended wear are more likely to experience an infection.¹⁰ It is important to ensure that subjects new to contact lens wear have an adequate period of daily wear before commencing EW to ensure they are familiar with the solution regime and are monitored closely in the initial stages of EW.

Poor hygiene and not washing hands, regardless of lens wearing modality, are factors that are in theory easily modified and can significantly reduce risk of infection.¹⁰ One study reported 74% of patients were non compliant with at least one aspect of lens care,¹² most of whom were unaware of their mistakes. Lens care regimes should aim to be simple, easy to follow, personalised and ritualised. They should be enforced verbally, frequently and consistently, and in written form wherever possible. The recent increase in the occurrence of Fusarium Keratitis, thought to be related to the instability of a new antimicrobial component of the solution used in the majority of cases, highlights the importance of compliance, with the majority of cases involving lapses in their lens care regime.¹³

Other modifiable risks associated with infection include use on holidays,¹⁴ swimming without goggles/disinfection,¹⁰ internet purchase,¹⁰ poor health¹⁰ and smoking.¹⁰ Contact Lens Acute Red Eye (CLARE) has also been associated with Upper Respiratory Tract Infection,¹⁵ another reason why not sleeping in lenses when sick is sound advice. Patients purchasing contact lenses online without having an eye exam or consulting their practitioner, risk filling an incorrect or outdated prescription and receiving poor fitting lenses. This may result in poor vision, or a lens-related complication.

While purchasing over the internet may be influenced by the type of personality likely to opt for this mode of purchase, it emphasises the importance of professional advice. Patients need to be counselled regarding the differences between different brands of lenses and the compatibility issues that may arise between certain lens materials and lens care systems. Patients also need to be aware that regular follow-up visits are still necessary. Recent information of the morbidity of microbial keratitis has shown that delay in appropriate treatment can lead to poorer outcomes,¹⁶ highlighting again the important role of the practitioner. While risk factors such as being male,⁷ of high socio economic status¹⁰ or young¹⁰ are not modifiable, they are part of the prescribing equation and should be kept in mind.

Solution related toxic staining, manifesting as diffuse punctate staining of the cornea and often asymptomatic, has recently been associated with an increased risk of inflammatory adverse events.¹⁷ As solution related toxic staining depends on the lens and solution combination, the same solution a patient has used successfully with a previous lens type, may not be suitable with other lens types. Solution related toxic staining may be asymptomatic and is more likely to be observed two to four hours after lens insertion.¹⁸ It may therefore be prudent to examine patients with fluorescein in this timeframe, and change the lens/ solution combination if signs of toxic staining are evident.

Corneal Staining

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Similarly it should be emphasised to patients to seek advice before changing lens care regimes and makes a good case for bundling lens care product with lenses to be sold as a unit. Lens care can be quite confusing with different brands with similar components but different formulations showing different effects, and with the marketing of lens care products with similar brand names, but different formulation. With the release of several lens care products designed specifically for silicone hydrogel use, more focus on lens care is welcomed and set to take place.

Upgrading patients to silicone hydrogels not only provides a healthier oxygen environment, it also provides an opportunity for practitioners to showcase their skills regarding patient care and management. It is vital that practitioners take a proactive approach.

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