The symptoms of ocular allergies, infections, and Dry Eye can be similar — burning, tearing, and redness. Itching is usually a symptom of allergies, and not usually of infections. Because both allergies and infections can be present at the same time, it important to see a doctor, particularly if symptoms persist, for a definitive diagnosis.
Infections are usually indicated by crusting in the lashes, on the skin around the eyes, and on the lids. Discharge, debris in the eye lashes, and redness or burning on the lid margins and conjunctiva, may also indicate infection. Eye pain, foreign body sensation, photophobia, and impared vision can all be signs of infection.
Infections should not go untreated because they can lead to permanent damage and blindness. See your doctor immediately if you suspect you have an eye infection.
Sometimes cultures are taken in the areas of the suspected infection. The areas are swabbed with sterile cotton swabs that are dipped into a growing medium in petri dishes. The cultures may be observed in the office for a day, and, if positive, sent to a lab for further testing. Some offices send all cultures to labs.
Lab tests can determine the strain of bacteria present, and the antibiotic most effective in killing the bacteria.
Because the incidence of antibiotic resistant bacteria is on the rise, running tests to determine the strain of bacteria and effective antibiotics is more common, although this may also be more costly to the patient.
Reference
Bacterial Conjunctivitis
Yeung KK
Medscape Drugs and Diseases>Bacterial Conjunctivitis
Retrieved October 5, 2015 from Medscape http://emedicine.medscape.com/article/1191730-overview