New perspectives on CL-associated keratitis

Professor Nathan Efron and Dr Philip Morgan explain the clinical implications of their widely publicised recent work into the incidence of keratitis among contact lens wearers

Dramatic changes have taken place in the contact lens market over the past decade and two innovations in particular have had a strong impact on prescribing trends. These are the introduction of daily disposable contact lenses in the mid-1990s and the launch of silicone hydrogel lenses around 2000. These lens types currently represent about 34 per cent and 19 per cent of lens fits in the UK, respectively.¹

It might be expected that these new products will be associated with lower levels of ocular complications, as well as providing greater levels of comfort and convenience for contact lens wearers. For example, daily disposable lenses could reduce the risk of problems² because they obviate the need for lens maintenance and avoid long-term surface spoilation. Silicone hydrogel lenses should minimise clinical problems relating to corneal hypoxia because of their greater capacity to transmit atmospheric oxygen to the ocular surface.³ Despite these significant advances, there have still been case reports of severe keratitis with daily disposable lenses⁴ and silicone hydrogel lenses.⁵

Keratitis is an inflammation of the cornea characterised by leukocytic migration into the inflammatory focus. Clinical features can include a combination of the following signs and symptoms: pain, photophobia, mucopurulent discharge, corneal infiltrates, epithelial staining, limbal and conjunctival redness, anterior chamber flare and hypopyon. It has long been recognised that the safety of various forms of contact lens wear are best described by determining the incidence of keratitis among lens wearers.

To fully appreciate this problem from the perspective of the patient, it is necessary to consider the 'clinical journey' experienced in cases of contact lens associated keratitis. Virtually all patients who develop symptomatic forms of this condition, regardless of severity, will cease lens wear and visit their contact lens practitioner or a hospital emergency department. They will be distressed and inconvenienced. To only consider severe or 'microbial' keratitis, and to ignore the less severe or so-called 'sterile' keratitis - as has been the practice in the past⁶ - is a false distinction for the reasons outlined above. In view of this, we have adopted a new approach to this problem by surveying both non-severe and severe forms of hospital-presenting cases of contact lens-associated keratitis.