Table 2.  Studies describing the annualised incidence of presumed microbial keratitis in silicone hydrogel contact lens wear, stratified by selection of controls (adapted from Stapleton et al⁷⁸).

Author (total cases)	Definition	Study design	Location	Incidence per 10 000 (95% CI). Daily wear	Incidence per 10 000 (95% CI). Extended wear
Denominator derived from random telephone survey of the community to identify penetrance of contact lens wearers
Stapleton11	Clinical diagnosis of microbial keratitis with either a positive corneal culture or infiltrate with overlying epithelial defect, with one or more of: lesion in the central cornea; anterior chamber response; pain	12-month prospective surveillance of practicing ophthalmologists and optometrists.	Australia	11.9 (10.0–14.6) 44 cases Vision loss 1.1 (0.9–1.4)	25.4 (21.2–31.5) 92 cases Vision loss 2.8 (2.3–3.5)
Prospective cohort study, 6245 participants using a silicone hydrogel lens on an extended wear schedule, 5561 wearer years of experience
Schein77	Presumed microbial keratitis based on presenting signs and symptoms and review by endpoint adjudication committee	12-month prospective cohort postmarket surveillance study	131 clinical practices widely distributed across North America	N/A	18.0 (8.5–33.1) 10 cases Vision loss 3.6 (0.4–12.9)
Denominator derived from fitting surveys, CL type and modality by matched controls
Morgan75	Prospective identification of corneal infiltrative events associated with CL wear. ‘Severe' keratitis defined as cases with clinical severity score >8/22. National fitting data applied to estimated hospital catchment population	12-month prospective study of patients presenting to hospital accident and emergency clinic	Royal Eye Hospital, Manchester, UK	0.0 (0.0–210.1) 0 cases	19.8 (6.7–58.0) 3 cases

Abbreviations: CI, confidence interval; CL, contact lens.