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Microbial keratitis in orthokeratology: the Australian experience

iGO SUMMARY: This Australian study summarises the findings of a major survey carried out amongst members of the Orthokeratology Society of Australia (OSA) who average over seven years of experience in fitting overnight ortho-k corrective contact lenses for short-sighted patients. The survey focused on identifying any cases of serious bacterial infection which could represent a possible safety issue for the Overnight Vision Correction (OVC) treatment and from the population of over 500 OVC lens wearers, nine cases of serious bacterial infection were reported of which seven were confirmed as resulting directly from the wearer following an ineffective lens cleaning and storage regime. (The other two cases were not supported by additional information on possible cause.)

BACKGROUND: This study was conducted to investigate the demographics of orthokeratology (OK) practice in Australia, to uncover any previously undocumented cases of serious adverse responses in OK, including microbial keratitis (MK), and to review the demographics of MK in OK in Australia.

METHODS: A questionnaire was sent to the 62 members of the Orthokeratology Society of Australia (OSA). Questions related to aspects of their OK practice, demographics of their OK patient base and any adverse responses to OK lens wear that they had encountered.

RESULTS: Thirty-three questionnaires (53 per cent) were returned. OSA members have been fitting OK lenses for a median of 7.5 years. OK patients were predominantly female, Caucasian, aged between 15 and 39 years and wearing lenses in an overnight modality. In addition to two cases reported previously, the survey uncovered seven further cases of MK in OK patients over an eight-year period. The infecting organism was Pseudomonas aeruginosa in four cases, Acanthamoeba spp. in two cases and unknown in three cases. There was no loss of visual acuity in seven cases. One case resulted in vision of counting fingers at one metre and another case resolved with 6/12 visual acuity. Non-compliance with instructions on lens care and after-care was reported in seven of nine cases of MK.

CONCLUSION: Overall, OSA members who responded to the survey have many years of experience in OK. The typical Australian OK patient is in young adulthood, female and Caucasian. A total of nine cases of presumed MK associated with OK have been reported in Australia over an eight-year period and seven of these were new cases uncovered by this survey. Our analysis suggests that the demographics of MK cases in OK reflect the demographics of the OK lens-wearing population.

May 2007 Clinical and Experimental Optometry, Kathleen G Watt BOptom, Gavin C Boneham PhD, Helen A Swarbrick PhD, School of Optometry and Vision Science, University of New South Wales, Sydney, Australia  

For full article : PubMed

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