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Tuesday / May 24.
HomemicontactEvidence Backs Anecdotes

Evidence Backs Anecdotes

One thing I’ve long espoused is the fact that wherever possible we should be fitting daily disposable lenses to enhance outcomes and reduce possible complications.

It’s been a while since I covered interesting abstracts and journal articles in micontact. One of the reasons has been that there are so many articles, features and news items in mivision that expertly cover many of the issues that are currently de rigueur. Things like dry eye, scleral lenses, OrthoK and myopia control are but some examples and I’ve felt that there’s no point in duplication.

I was recently pleased to see a few ‘hot off the press’ papers that reinforce some of the things I’m passionate about. These papers provide a fresh perspective and will help steer clinical practice. One of these papers, published ahead of print in Optometry and Vision Science, included respected researchers from our very own shores, which added impact.

The paper Preinflammatory Signs in Established Reusable and Disposable Contact Lens Wearers1 by Chao, Stapleton, Willcox et al, discusses the significance of higher tear inflammatory cytokine concentrations and greater conjunctival metaplasia in reusable contact lens (CL) wearers and the association with CL discomfort. They mention that daily disposables (DD) are used to improve CL comfort but that their effect on ocular inflammatory response has not been fully investigated. The study aimed to compare “concentrations of tear cytokines and conjunctival cell morphology in healthy habitual DD and reusable soft CLs”. They concluded that, “higher ocular inflammatory responses, as indicated by higher tear cytokine concentrations and higher conjunctival epithelial metaplasia, were found in reusable CL wearers than in DD CL wearers”.

60 per cent of the suspected counterfeit lenses… were contaminated

They suggest the balance of proinflammatory and anti-inflammatory cytokines may be helpful in assessing the inflammatory status of the eye.

The study reinforces the improved results that experienced clinicians who promote daily disposables have anecdotally observed. It seems however, that some practitioners are unadventurous and unconvinced and rely on the evidence base before embarking on a specific mode of practice. This evidence will help convince them and their patients, of the undoubted benefits of daily disposable wear and switch more wearers to this superior modality.

Check out the more detailed abstract at the link in the references that follow.

Peroxide Rocks

Where daily disposables are not an option, I have, for well over two decades, promoted the use of hydrogen peroxide disinfection systems over multipurpose chemical disinfection systems. All too often, clinicians have seen and reported on the benefits of reduced symptoms and better outcomes arising from the use of peroxide systems, especially in sensitive and allergic patients. Peroxide systems have been relatively static in terms of evolution. It was, therefore, of interest to note that researchers in another Optometry and Vision Science paper published ahead of print, Fibrous Catalyst-Enhanced Acanthamoeba Disinfection by Hydrogen Peroxide2, discussed research that identifies a potential next-generation, one-step H2O2 system, built around a case-based peroxide catalyst.

In the paper, they agreed that H2O2 disinfection systems are problem solvers but note that “antimicrobial efficacy can be limited because of the rapid neutralisation of the peroxide from the catalytic component of the systems”; an argument often cited by critics of H2O2 disinfection. They therefore investigated whether adding “an iron-containing catalyst bound to a non-functional propylene:polyacryonitrile fabric matrix could enhance the antimicrobial efficacy” of one-step H2O2 systems. They used B+L PeroxiClear and AOSept Plus – based on 3 per cent H2O2 with platinum neutralising discs – as the test systems. “These were tested with and without the presence of the catalyst fabric using acanthamoeba cysts as the challenge organism. After six hours’ disinfection, the number of viable cysts was determined. In other studies, the experiments were also conducted with biofilm formed by Stenotrophomonas maltophilia and Elizabethkingia meningoseptica bacteria”. They reported; “Both control systems gave approximately 1-log10 kill of Acanthamoeba cysts compared with 3.0-log10 kill in the presence of the catalyst (P < .001). In the biofilm studies, no viable bacteria were recovered following disinfection in the presence of the catalyst compared with ≥3.0-log10 kill when it was omitted.”

They also showed “no loss in enhanced biocidal efficacy of the material. The catalytic fabric was also shown to not retard or increase the rate of H2O2 neutralization”.

In conclusion they believe that incorporating the catalyst into the case of one-step H2O2 disinfection systems could improve antimicrobial efficacy and provide a greater margin of safety for contact lens users.

It would be great to see commercialisation of an evolutionary modification of well-proven and established H2O2 disinfection systems, with even better efficacy – and therefore improved safety – that would help silence critics of such systems.

Online Ammo

A final item that recently came to my attention detailed investigations by the U.S. Food & Drug Administration’s (FDA’s) Forensic Chemistry Centre.3 Published in the Journal of Forensic Sciences, the results show that online purchases of “unapproved, counterfeit and decorative contact lenses tested positive for the kinds of microbial contamination frequently found in hospital waste water or spoiled food”.

That’s scary stuff!

Pseudomonas aeruginosa and Bacillus cereus were just some of the microorganisms identified in the examination of more than 300 contact lenses obtained without a prescription from “sources such as import seizures, novelty stores, tattoo parlours, flea markets and internet marketplaces…60 per cent of the suspected counterfeit lenses and 27 per cent of the authentic non-corrective contact lenses obtained directly from manufacturers without a prescription were contaminated”.

This reportedly compares to only 3 per cent contamination of authentic, prescribed CLs. They also identified other microbes commonly associated with serious eye infections and vision loss, such as microbial keratitis and bacterial endophthalmitis. This backs up other studies, like Fiona Stapelton’s 2008 paper that showed a four times increased risk of microbial keratitis in patients who purchased contact lenses online.

This frightening information needs to be widely disseminated to the general online contact lens buying public. It will also help practitioners convince patients to always purchase their lenses from reputable sources – to a valid prescription, following regular aftercare – ideally through their practices. This should help improve safety and reduce the unacceptable, increased risk of sight threatening microbial keratitis that’s especially linked to serious infections, particularly in wearers of costume and novelty cosmetic lenses worn for things like parties, Halloween and the like.

Fortunately social media is helping spread the word with some nasty stories of disfigured eyes and vision loss arising from the reckless supply of lenses to an uninformed and unsuspecting public.

References
1. www.ncbi.nlm.nih.gov/pubmed/28858005
2. www.ncbi.nlm.nih.gov/pubmed/28902008
3. www.aoa.org/news/clinical-eye-care/counterfeit-contact-lens-infections-study?platform=hootsuite

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