Detecting Infection
Here are some tips to help you recognize the signs and symptoms of infectious irritation.

How do you differentiate between infectious and noninfectious ocular conditions? Severe infections are relatively easy to identify, but pinpointing the cause of less acute red eye may be more difficult. Here are some basic guidelines that can help you make an accurate diagnosis.

Consider all the possibilities. Don't immediately dismiss the likelihood of infection. "Corneal ulcers are rare compared with infiltrates," says Randall K. Thomas, O.D., M.P.H., F.A.A.O. "I've seen only three contact lens-induced ulcers during my 24 years in practice. We have to understand the big picture, as well as assess the epidemiology before choosing a course of treatment."

Evaluate the anterior chamber. "I look at the anterior chamber reaction and the degree of conjunctival injection," says Jimmy D. Bartlett, O.D., F.A.A.O. "If I see cells in the anterior chamber and 2+ to 3+ conjunctival injection, the patient probably has an infectious ulcer." Ron Melton, O.D., F.A.A.O., adds, "If conjunctival injection is diffuse instead of confined to a specific sector, you know the patient has a more significant problem."

Assess the tear film. Walter S. Ramsey, O.D., F.A.A.O., checks the tear meniscus for signs of infection. "If I see cells in the tear film, I become concerned about the possibility of bacterial infection," he says.

Monitor visual changes. "Infectious keratitis often is accompanied by decreased visual acuity," says Paul M. Karpecki, O.D., F.A.A.O. "We don't expect lesions in the mid-peripheral cornea to affect vision, but stromal edema surrounding the infiltrate can significantly reduce visual acuity."

Examine corneal infiltrates. Dr. Thomas uses high magnification with a narrow slit beam in a dark room to document the distribution of infiltrates on the cornea. "Almost every red eye we encounter in our practices is inflammatory in nature -- we very rarely see red eyes caused by infectious processes," he says. "If corneal infiltrates are diffuse, the problem is purely inflammatory. However, multiple infiltrates concentrated in a single inflamed area could portend the development of an infectious ulcer."

Solve the dilemma

When you suspect infection or risk of infection, you're likely to choose combination steroid and antibiotic drugs over concurrent therapy with separate agents. However, the decision may not be as clear as you'd like.

"Sometimes we're faced with a diagnostic dilemma," Dr. Bartlett says. "Is a small amount of ocular discharge secondary to allergy or a sign of early bacterial infection or viral conjunctivitis? If we're not sure, we'll use a combination drug to address both possibilities."

Dr. Melton also welcomes combination drugs for treating indeterminate conjunctivitis. "We diagnose red eye as nonspecific conjunctivitis when we can't definitively identify bacterial or adenoviral conjunctivitis," he says. "Most red eyes are inflammatory in nature, but it's often impossible to know what created the inflammation. Combination steroids and anti-infectives work well on the nonspecific conjunctivitis we see so often."