Laboratory studies in acute conjunctivitis.

In 84% of 700 consecutive cases of untreated acute conjunctivitis subjected to conjunctival cultures and scrapings, a presumptive etiologic diagnosis could be made based on standard microbiologic and cytologic criteria. Of these 583 cases, 264 were bacterial, 245 were viral, 51 were allergic, and 17 were chlamydial. In 75% of the cases, clinical impressions were consistent with laboratory findings. On the basis of these results, laboratory workup is recommended in (1) follicular conjunctivitis to differentiate viral from chlamydial processes, (2) purulent conjunctivitis to identify pathogens and decide on appropriate antimicrobial therapy based on sensitivity data, and (3) those cases in which the clinical picture is not sufficiently distinctive to suggest an etiologic diagnosis.