Eye hospitals continue to report a significant cause of red-eye presentation associated with contact lens wear. This begs the questions: why is this, what are we doing wrong and is there anything we can do about it? It is not only bad for the individual concerned but also bad for the contact lens industry/profession and for overstretched hospital eye departments.
Numerous studies show storage case biofilm contamination is likely to be a significant cause of complications1,2,3,4,5 and that daily disposable lenses pose a significantly lower risk of serious visual loss than re-usable lenses.6 Worryingly it also may well be that the disinfecting solutions we rely upon are not as effective as we think particularly against some strains of Pseudomonas7 which Acanthamoebae feed upon.
Logically one would anyway expect a lower risk of complications with daily disposable (DD) rather than re-usable lenses (REL) as there is (i) no maintenance requirement (ii) no storage case contamination possibility and (iii) no potential chemical or preservative sensitivity issue.
Simon Kilvington’s presentation at last year’s BCLA conference (S Kilvington. Bacteria Biofilms Provide Protection From Disinfection By Multipurpose Contact Lens Care Solutions. BCLA Conference, Birmingham, 2014) showed yet again how nasty storage cases can be; even ones that look clean may not be as disclosing agents reveal biofilms invisible to the naked eye.
If lack of compliance can be minimised through ECPs making a much greater effort to repeat both verbal and written instruction at first fitting and annual reviews, from the above there is a strong case to be made that as a professional duty of care ECPs should always fit daily lenses in preference to re-usable lenses if the prescription permits largely because one of the risks, the storage case, has been removed.
However, there is one possible cause of complications even with DD lenses which may have been overlooked and that is back-surface contamination either from fingers or eye-lashes. Simon Kilvington’s same BCLA presentation showed little difference in microbial growth on agar plate hand imprints before and after careful hand washing, demonstrating how hand washing has remarkably little effect upon the microbial bioburden. However, many manufacturers and ECPs continue to advise patients to remove lenses from the blister pack by placing the finger into the back of the lens thereby trapping the transferred microbial bioburden between the lens and cornea, and the smallest epithelial compromise may well explain many of the cases seen at eye departments.
We therefore promote a ‘tap-and-tip’ method for accessing lenses whereby the lens is loosened by tapping the blister pack before tipping and pouring the lens into the palm of the hand thereby avoiding any possibility of back surface finger contamination. I declare no proprietary interest, but the Menicon flat pack lenses are designed to address this problem, so the Japanese seem to agree!
Mike Killpartrick
Bath
References
1 Larkin DF, Kilvington S, Easty DL. Contamination of contact lens storage cases by Acanthamoeba and bacteria. Brit J Ophthalmol 1990; 74:133–135.
2 Wilson ,L A.,Sawant,A.D., and Ahearn, D.G., Comparative efficacies of soft contact lens disinfectant solutions against microbial films in lens cases Arch Ophthalmol 1991, 109 1155 -1157
3 Kilvington S, Powell CH, Lam A, Lonnen J. Antimicrobial efficacy of multi-purpose contact lens disinfectant solutions following evaporation. Contact lens & anterior eye: The Journal of the British Contact Lens Association 2011;34:183-7
4 Fiona Stapleton, Katie Edwards, Lisa Keay, Thomas Naduvilath, John K G Dart, Garry Brian, Brien Holden Risk-factors-for-moderate-and-severe-microbial-keratitis-in-daily-wear-contact-lens-users Ophthalmology 2012 Aug 21;119(8):1516-21
5 Kilvington S, Shovlin J, Nikolic M. Identification and susceptability to multipurpose disinfectant solutions of bacteria isolated from contact lens storage cases of patients with corneal infiltrative events. Cont Lens Anterior Eye 2013 (epub ahead of print) doi: 10.1016/j.clae.2013.02.001
6 Dart JK1, Radford CF, Minassian D, Verma S, Stapleton F. Risk factors for microbial keratitis with contemporary contact lenses: a case-control study. Ophthalmology. 2008 Oct;115(10):1647-54.
7 Craig Winstanley presentation at Society for General Microbiology Annual Conference Liverpool April 2014.