Contact lens hygiene

Showering and sleeping while wearing contact lenses the most important risk factors for microbial keratitis

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Poor hygienic practices like showering and sleeping while wearing contact lenses can increase the risk of microbial keratitis by up to seven-fold, according to a study led by Professor Parwez Hossain PhD, FRCOphth, FRCS (Ed), FHEA, recently published online in the in the British Medical Journal-Ophthalmology. The case-control study involved 37 contact lens wearers with microbial keratitis and 41 control contact lens wearers without infection attending University Hospital Southampton Eye Casualty between October 2015 and December 2015. Participants underwent face-to-face interviews to identify lens wear practices, including lens type, hours of wear, personal hygiene and sleeping and showering in lenses. This is the first study of its kind to identify and grade the different personal hygiene practices, using face-to-face interviews with a validated approach on contact lens wearers who present to hospital and have clinically proven contact lens infection, Dr Hossain told EuroTimes. In a univariate analysis, the greatest risk factor the study’s authors identified was showering in contact lenses (p=0.03), with showering daily in lenses compared with never, increasing the risk of microbial keratitis by over seven times (p=0.002). Other risk factors included sleeping in lenses (p=0.026), and being aged 25-to-39 years (p=0.010) and 40-to-54 years (p=0.056). Showering while wearing contact lenses has the potential to introduce pathogens like acanthamoeba into the contact lens-cornea interface, the authors said. Sleeping while wearing contact lenses can impair oxygen diffusion on the corneal surface. Studies have shown that corneal hypoxia when a contact lens is present can lead to increased binding of pseudomonas bacteria, the most common cause of microbial keratitis. Non-compliance with annual after-care appointments did not appear to be a risk factor for microbial keratitis. Compliance in attending annual follow-up appointments was high among both the case group (83.7%) and the control group (78%). However, nearly half of both the case group and the control group said they had not been informed or were not sure if they had been informed of the risks of infections when first prescribed contact lenses. The study’s authors noted that despite advances in contact lens technology, the incidence of contact lens microbial keratitis has remained consistent at around four per 10, 000 daily contact lens wearers per annum. Previous research suggest that two-thirds of complications observed in contact lens wearers are attributable to poor hygiene practices. “Focusing attention on improving education of infection and retention of information may help improve compliance with lens wear practices, which may help reduce incidence of CLMK and associated sight loss,” they concluded. The full article is available at http://bmjophth.bmj.com/cgi/content/full/bmjophth-2020-000476. Parwez Hossain: P.N.Hossain@soton.ac.uk