In a recent letter to the editor of Clinical & Experimental Ophthalmology, Dr. Stephanie Watson et al reported a ‘cluster’ of four microbial keratitis cases in the months of late 2013, all associated with orthokeratology patients, and in each case the patient was a young Asian male. One was identified as acanthamoeba and will require grafting to restore vision.
Moorfields Eye Hospital London recently reported a spike in acanthamoeba presentations compared to an earlier high incidence rate in the ‘90s; with 80 cases in just over 12mths. Four eyes have been lost, one in a 12-year old boy.
How these infections arose is yet to be studied fully, however in the case of the orthokeratology acanthamoeba patient, the patient’s parent admitted to storing the lenses in tap water, presumably to save expenses, but indicating a lack of education at time of prescribing the lenses.
The warning for contact lens wearers, and in the case of young orthokeratology wearers, and their parents as well, is for hygiene such as hand washing, compliance with solution instructions given by the practitioner, no topping up storage solutions, and most importantly avoidance of tap water exposure for rinsing or storage. Swimming and showering when wearing contact lenses is to be avoided although the direct link to infections under those conditions has not been established.
It should be noted that the Boston Advance Cleaner instruction sheet advises patients to rinse the cleaner off with tap water. US FDA has considered this matter without resolution for an alternative. Saline solution is the most obvious alternative choice. Many practitioners advocate hydrogen peroxide use instead of RGP specific solutions for stronger disinfection action.
The lesson is long term vigilance over contact lens wearers’ compliance, reminders at aftercare visits, with particular attention to the young children (and their parents) in the orthokeratology cohort who we believe may benefit so much with reduction in myopia progression.
Acanthamoeba will be discussed at the forthcoming Orthokeratology Society of Oceania Meeting, from 17-19 October at the Sheraton Hotel on the Gold Coast.
Ian G Sim (B.Optom) is an optometrist at the Royal Perth Hospital Eye Clinic and Past National President of the CCLSA. He has a special interest in contact lens practice and recently presented a case study of acanthomoeba in orthokeratology at the third Chinese Orthokeratology Meeting in Shanghai.