Incidence of ulcers with conventional anddisposable daily wear soft contact lenses

Corneal ulcers induced by contact lens wear constitute the most serious and worrying adverse effect associated with thisform of ametropic correction. Risks have been shown to be higher for SCL than RGP and for EW than DW. Also in the UK, regardless of the modality of wear, disposable contact lenses have been reported to be associated with a much greater relative risk of ulcerative keratitis than conventional contact lenses. The UK studies, however, are case-control studies from referral centres that may not be representative of primary care contact lens practice, where the bulk of contact lens fitting is carried out. The current investigation was therefore a historical cohort study carried out in four UK contact lens practices representative of the UK mode of practice and geographic distribution. The study reviewed 647 conventional daily SCL wearers with a mean wearing time of 1.97 years and 780 disposable daily SCL wearers with a mean length of wear of 1.45 years. The results obtained lead to the following conclusions: the annualised corneal ulcer incidence rates were 1.10% for conventional daily wear soft contact lenses and 0.88% for Acuvue disposable contact lenses worn on a daily wear basis. The annualised incidence rates for corneal ulcers that might have been microbial in origin were 0.39% for conventional DW and 0.18% for disposable DW. With conventional DW, none of the ulcers encountered were central; four were paracentral and the remaining 10 were peripheral. The clinical picture observed suggests that the majority of the ulcers were not of a microbial origin, but self-limiting ‘sterile’ peripheral ulcers of yet unknown aetiology. By not differentiating ulcers by type/origin, other researchers may have substantially overestimated the true risk of contact lens related microbial keratitis. The results of this study seem to support the findings of similar studies carried out in other European countries, whereby DW with disposable contact lenses carries a similar or lower risk of keratitis than conventional DW.