Factors Influencing the Morbidity of Contact Lens Related Microbial Keratitis

Abstract

Abstract: : Purpose: To examine factors influencing the severity of contact lens (CL) related microbial keratitis (MK) managed in hospitals and private clinics Methods: Cases of CL related MK in 15–64 year olds, wearing CLs for the correction of simple refractive error were detected through surveillance of ophthalmic practitioners in Australia and New Zealand. Clinicians provided information on treatment and patients were interviewed by telephone where possible at least one month after the event. Morbidity was assessed in terms of direct and indirect costs, days before symptoms resolved (up to 28 days) and percentage of cases with 2 or more lines of vision loss. The effect of pathogen, CL modality (DW/EW), CL material (low/high Dk) and delay in CL removal or seeking consultation were examined. Results: The mean age was 37±13 years (mean±SD) and 59% were female (n=139). One third (60%) delayed CL removal by >4 hours and 67% delayed >24 hours before seeking medical advice. Medical visits and hospital bed days were used to calculate the direct costs [$799(1810)], indirect costs included days off work for patients [2(5)] and their carers [1(2)] combining to $553(1671), patients were symptomatic for 7(9) days of the first month [median(IQR)] and >2 lines of vision loss was documented in 7.3% of cases. Culture proven cases appeared to be more costly to treat (p<0.2) and had longer duration of symptoms (14±10 vs 6±5 days, p=0.02). 50% of cases were in DW (25% high Dk, 38% occasional overnight wear) and the remainder EW (95% high Dk). DW cases had longer duration of symptoms (11±9 vs 7±7 days, p=0.02) and rate of visual loss was higher but this did not reach statistical significance (6/52 vs 1/43, p=0.12). There was no difference in costs (p>0.4). Delay in seeking consultation was associated with longer duration of symptoms (11±9 vs 7±5 days, p=0.04) but no difference in cost or rate of vision loss. Multivariate analysis will more fully explore these relationships. Conclusions: Both positive identification of a microbial pathogen and CL modality/material are determinants of morbidity. However modifiable factors such as delays in treatment appear to have some influence on disease outcome. Cost analysis and symptom duration are useful measures of morbidity for a condition, which ranges widely in severity but is rarely associated with vision loss.

Keywords: contact lens • keratitis • microbial pathogenesis: clinical studies