ANTIMICROBIAL MANAGEMENT OF PRESUMED MICROBIAL KERATITIS - GUIDELINESFOR TREATMENT OF CENTRAL AND PERIPHERAL ULCERS

Aims-To determine the quantitative relation between the major risk fac tors for microbial keratitis of previous ocular surface disease and co ntact lens wear and central and peripheral infiltration, often associa ted with ulceration, in order to establish a rational chemotherapeutic management algorithm. Methods-Data from 55 patients were collected ov er a 10 month period. All cases of presumed microbial keratitis where corneal scrapes had been subjected to microbiological examination were included. Risk factor data and laboratory outcome were recorded. Anti microbial regimens used to treat each patient were documented. Results -57 episodes of presumed microbial keratitis were identified from 55 p atients, 24 male and 31 female. There were 30 central infiltrates and 27 peripheral infiltrates of which 28 were culture positive (73% of ce ntral infiltrates, 22% of peripheral infiltrates). 26 patients had wor n contact lenses of whom 12 had culture positive scrapes (9/14 for cen tral infiltrates, 3/12 for peripheral infiltrates). 31 patients had an ocular surface disease of whom five previous herpes simplex virus ker atitis patients developed secondary bacterial infection. Anterior cham ber activity and an infiltrate size greater than or equal to 4 mm(2) w ere more common with culture positive central infiltrates than periphe ral infiltrates (chi(2) test = 11.98, p<0.001). Conclusions-Predisposi ng factors for ''presumed'' microbial keratitis, either central or per ipheral, were: ocular surface disease (26/57 = 45.6%), contact lens we ar (26/57 = 45.6%), and previous trauma (5/57 = 8.8%). Larger ulcerati on (greater than or equal to 4 mm(2)) with inflammation was more often associated with positive culture results for central infiltration. No ne of these four variables (contact lens wear, ocular surface disease, ulcer size, anterior chamber activity) were of intrinsic value in pre dicting if a peripheral infiltrate would yield identifiable micro-orga nisms. Successful management of presumed microbial keratitis is aided by a logical approach to therapy, with the use of a defined algorithm of first and second line broad spectrum antimicrobials, for applicatio n at each stage of the investigative and treatment process considering central and peripheral infiltration separately.