Contact Lens Case Hygiene

Lens case contamination is common and can compromise lens disinfection routines. An important step in reducing rates of contamination is the development of uniform lens case hygiene recommendations across contact lens products and by practitioners.

It is estimated that there are 125 million contact lens wearers in the world.⁵ For those who wear contact lenses weekly, monthly or yearly, the disposable lenses require the use of disinfecting solutions and lens storage cases.

Contact lens storage cases facilitate the disinfecting process of the lenses after removal from the eyes. However, studies have shown that contamination of lens storage cases remains common, occurring in 30 to 80 per cent of cases.^6-9 Lens cases have also been shown to be the most frequently^6,10 and heavily¹¹ contaminated of all lens care accessories, including the disinfecting solution and contact lens. In addition, the lens case provides an environment favourable for static biofilm growth.¹² The formation of biofilm may compromise routine contact lens disinfection, as the micro-organisms may be resistant to anti-microbial agents.¹³

Lens cases have also been shown to be the most frequently and heavily contaminated of all lens care accessories, including the disinfecting solution and contact lens

Lens Case Contamination

A study completed in April last year, where lens cases were collected from lens wearers in various states in Australia, has found that microbial contamination is present in approximately 60 per cent of lens storage cases with up to 105 organisms per case well.⁹ The use period of lens cases collected ranged from less than a month to two years.

The most common micro-organisms found from lens storage cases were coagulase-negative staphylococci, Bacillus spp. and fungi. Of concern is that Gram-negative bacteria, potentially virulent pathogens (e.g. Pseudomonas aeruginosa, Serratia marcescens) were also recovered from lens cases.

Among the contaminated cases, more than half had multiple bacterial species, with a maximum of seven different strains recovered in one lens case. This is a major concern as other studies have shown that the co-existence of multiple strains promotes the growth of Acanthamoeba.

There are many reasons lens case contamination is so high. They include:

1. Poor hygiene

It is believed that non-compliant hygiene behaviour contributes to high contamination rates in lens storage cases, although contamination has been reported in association with good compliance.^14,15

2. Biofilm formation

Factors other than hygiene compliance issues, such as biofilm formation¹³ and inherent microbial resistance¹⁶, may be associated with persistent microbial contamination of contact lens storage cases. One study has shown that current multipurpose disinfecting solutions may not be effective against the biofilm forms of bacteria.¹⁷ Thus; cleaning steps additional to the use of these solutions should be included routinely in lens case hygiene practices.

3. Limited lens case hygiene guidelines

Current lens case recommendations are inconsistent amongst various sources (industry, FDA and optometrists).¹⁸ The cleaning instructions are often lacking in detail, compromising lens wearer compliance. At the same time, it is difficult to identify the reasons for non-compliant patient behaviour. Possible explanations might include: intentional non-compliance by patients; lens wearers following outdated instructions; eye care practitioners failing to provide lens wearers with adequate lens hygiene instructions in the first place; and lens wearers being confused by different recommendations provided by manufacturers.

New CL Case Hygiene Guidelines

It is a challenge for eye care practitioners to deliver detailed and uniform instructions given the limited evidence-based findings on the effectiveness of lens case guidelines.

The Asia Pacific Contact Lens Care Summit held in Singapore in 2007, took the initiative, recommending that the industry and practitioners restore the emphasis on proper lens care and develop better guidelines to help eye care professionals educate their patients on the importance of proper contact lens care to avoid eye infections.¹⁹

In view of the current situation, a team from the Brien Holden Vision Institute and the School of Optometry and Vision Science at the University of New South Wales has undertaken multiple approaches involving in vitro and clinical investigations to determine the best microbe elimination procedures for contact lens cases.

Recommendations for non-contamination of CL cases include:

1. Frequent replacement of lens cases

The FDA recommends lens cases be replaced every three to six months, and our study supports such a recommendation with results showing that the level of lens case contamination was significantly lower in cases that were replaced more frequently.⁹

2. Air-drying lens cases

Recapping the lids after use should be discouraged. Air-drying the lens case – particularly face-down – will minimise air-borne contamination.²⁰

This ongoing project is expected to release its new lens case guidelines in the coming year.

Yvonne Wu, B.Optom, Gradcert (OcularTher), is a PhD candidate at the Brien Holden Vision Institute and School of Optometry and Vision Science, University of New South Wales (UNSW).

References

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15. Wilson LA, Sawant AD, Simmons RB, Ahearn DG. Microbial contamination of contact lens storage cases and solutions. Am J Ophthalmol 1990; 110: 193-198.

16. Lakkis C, Fleiszig SMJ. Resistance of Pseudomonas aeruginosa Isolates to Hydrogel Contact Lens Disinfection Correlates with Cytotoxic Activity. J Clin Microbiol 2001; 39: 1477-1486.

17. Szczotka-Flynn LB, Imamura Y, Chandra J, Yu C, Mukherjee PK, Pearlman E, Ghannoum MA. Increased resistance of contact lens-related bacterial biofilms to antimicrobial activity of soft contact lens care solutions. Cornea 2009; 28: 918-926.

18. Wu Y, Carnt N, Willcox M, Stapleton F. Contact lens and lens storage case cleaning instructions: whose advice should we follow? Eye Contact Lens 2010; 36: 68-72.

19. Sweeney D, Holden B, Evans K, Ng V, Cho P. Best practice contact lens care: a review of the Asia Pacific Contact Lens Care Summit. Clin Exp Optom 2009; 92: 78-89.

20. Wu Y, Zhu H, Willcox MD, F S. Effects of lens case drying position and location on contamination levels. Optom Vis Sci 2010; 87: in press.