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Microbial Flora of Tears of Orthokeratology Patients, and Microbial Contamination of Contact Lenses and Contact Lens Accessories.

This Hong Kong study assessed 41 short-sighted overnight ortho-k corrective lens wearers aged between 8 and 36 through regular eye checks over a period of eight weeks to see whether wearing this type of lens only while sleeping was susceptible to a greater risk of infection than conventional daytime contact lenses. The results showed that those wearers who observed a consistently high standard of hygiene in lens cleaning and storage revealed no evidence of infection. Those whose lens cleaning and storage regime was inconsistent or not of a sufficiently high quality did reveal evidence of bacterial infection but this was resolved by improved lens hygiene. In particular, effective daily disinfecting of lenses after overnight wear using an appropriate lens cleaning solution and regular replacement of lens storage cases minimised the risk of any bacterial infection arising.

ABSTRACT: Purpose: The purpose of this study is to determine if there are changes in the ocular flora of overnight orthokeratology (ortho-k) patients, and the levels of contamination of their lenses and lens accessories, and to correlate compliance with levels of contamination.

METHOD: Normal ocular flora of 41 subjects was determined twice before commencing ortho-k lens wear by culture of the lower conjunctiva. Further specimens were collected on six follow-up visits after beginning lens wear, as were samples from their lenses, cases, and suction holders. A questionnaire on lens care was administered after the fifth visit.

RESULTS: Three subjects provided conjunctival samples yielding Staphylococcus aureus on one occasion before lens wear, one being positive for this organism after beginning lens wear. Of 38 subjects yielding no growth or only normal eye flora before use, 28 remained free of ocular pathogens after beginning lens wear. Only four subjects had positive cultures on more than one occasion after lens wear. There was no significant difference in isolation levels of pathogens with lens wear (p = 0.423) culture of 54% of subjects yielded no growth or normal flora only; lenses of 16 subjects yielded potential pathogens, including three subjects contaminated on more than one occasion. Lens isolates did not match the organisms transiently colonizing the eye. Lens case, the most frequently contaminated item, was associated with lens contamination (p < 0.001), the same organism being isolated from both items in 11 subjects. Lens suction holder was less frequently contaminated.Neither lens case nor suction holder contamination was associated with isolates from the eye. Reported good compliance correlated with lack of contamination in all but one subject. The most frequent breaches in the lens care protocol were failure to clean, disinfect, and replace the lens case.

CONCLUSION: Ocular flora was not altered by ortho-k lens wear over an extended period, and patients remained free of infection. Contaminants identified were generally of a transient nature.Most patients had significant contamination of at least one item, most frequently the lens case. Lens case isolates were significantly associated with those from the lens. The majority of patients reporting good compliance had low or no contamination of their lenses and accessories.(C) 2005 American Academy of Optometry

June 2005, Optometry and Vision Science BOOST, MAUREEN V. PhD, FIBMS; CHO, PAULINE PhD, FAAO

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