Cultures are not usually done, but are indicated for patients with the following: Clinically suspected gonococcal or chlamydial conjunctivitis Severe symptoms Immunocompromise A vulnerable eye (eg, after a corneal transplant, in exophthalmos due to Graves disease) Ineffective initial therapy Halos Halos around light may result from cataracts; conditions that result in corneal edema, such as acute angle-closure glaucoma or disorders that cause bullous keratopathy; corneal haziness; mucus on the cornea; or drugs, such as digoxin or chloroquine.