His caution is grounded in years of studying the behavior and treatment of microorganisms in the eye. O'Brien uses delicate, purpose-built tools to sample eye tissues and their surroundings for the bacteria, viruses, fungi or other parasites that cause a variety of diseases such as blepharitis, conjunctivitis, keratitis and endophthalmitis. Often, a biopsy is necessary to examine deeper vitreous or retinal tissues. Pinpointing the proper pathogen is often trickier than for other organs, O'Brien says, because such small numbers may be involved. Also, since many bacteria and other microbes are exquisitely attuned to eye tissues, O'Brien often must use more varied or obscure types of culturing media than general pathology labs.
Molecular probes can give a quick ID on such viruses as herpes or adenovirus.
O'Brien quickly tailors treatment to the identified agent. Corneal infections usually subside with topical antibiotic eye drops. For intraocular infections, direct injection into the eye works best, and if the infection's sight-threatening, surgical removal of infected tissue may be necessary to buy time for the antibiotics before vital tissue's destroyed. And you don't have a lot of it. Hopkins' Ocular Microbiology Laboratory at Wilmer is one of only two or three in the country.