Investigation of the Microbiome of the Cornea in Microbial Keratitis

Design: Prospective observational diagnostic study and methods-comparison. Aims: The overall aim of the project is to better define the pathogenic microorganisms in patients with microbial keratitis (MK) through a better understanding of the corneal and ocular surface microbiome in health and disease. This will be achieved through the following objectives: 1. Using NGS, analyse the corneal microbiome of the affected and unaffected eye of patients with and without MK and compare with simultaneous results from CDC and MTPCR. 2. Determine the microbiological spectrum of the cornea, ocular surface and contiguous structures, in patients with MK, healthy controls, contact lens wearers and eye drop users. Outcome measures: 1. A comparison of isolation rates and identified bacteria obtained from CDC, MTPCR and NGS processing of MK corneal samples will be made. 2. Microorganisms identified in the eyes with MK will be compared to the fellow eye and other control groups and subtractive bioinformatics methodology applied to identify the most likely pathogenic organisms compared to those seen in the healthy corneal and ocular surface microbiome. 3. Comparisons of the relative abundance of microorganisms obtained from MK corneal samples over the participant's follow-up visits will be used to evaluate longitudinal changes in the corneal and ocular surface microbiome during treatment and resolution of MK. 4. A direct comparison between the relative abundance of microorganisms isolated from participants cornea, conjunctiva, eyelids and nose (contiguous structures) will be made to identify any possible endogenous sources of infection for MK. Population Eligibility: * All patients aged 18 years and over presenting with unilateral clinically suspected MK to St. Paul's Eye Unit, The Royal Liverpool University Hospital. * Patients with keratoconus undergoing cross-linking, subjects with no history of MK, subjects with no history of MK who are contact lens wearers and subjects wit