Rely on ocular, systemic signs for differential diagnosis of viral vs. bacterial infections

When making a differential diagnosis between bacterial and viral infections, practitioners are able to glean information from several ocular and systemic findings.

“When a patient walks into your office with an eye infection, you first start to categorize the symptoms,” said Robert Abel Jr., MD, a practitioner based in Wilmington, Del. “You ask yourself, ‘Is there lid involvement? Does the patient have dry eye? Is there an allergic history? Is the involvement acute?’”

The practitioner can also be guided in this diagnosis by the fact that viral infections occur much more frequently than do bacterial infections, Dr. Abel said.

“There are probably 20 viral infections compared to one bacterial infection in an adult population,” he said. “People who you see with bacterial infections tend to be elderly people who are sequestered in nursing homes, alcoholics with poor nutrition and immunocompromised people.”

Viral vs. bacterial conjunctivitis

Many practitioners agree that viral conjunctivitis occurs with substantially greater frequency in adults than does bacterial conjunctivitis.

“Part of the reason for that is that immunity is much better against bacteria,” Dr. Abel said. “Viruses keep changing, and, therefore, you don’t get develop resistance to them very quickly.”

According to William D. Townsend, OD, who is in private practice in Canyon, Texas, the contagious nature of viruses also factors into this disparity. “Viruses are very contagious – just one virus in the eye can cause an infection,” he said. “On the other hand, you usually must have a large quantity, i.e. colony of bacteria to really cause an infection.”

Paul C. Ajamian, OD, center director of Omni Eye Services of Atlanta, said he regularly sees bacterial infections secondary to other conditions.

“I see tons of chronic bacterial conjunctivitis secondary to staph lid disease,” he said. “I see occasional adenoviral conjunctivitis and very rarely acute bacterial conjunctivitis.”

Systemic findings for diagnosis

According to Dr. Abel, a viral conjunctivitis might be accompanied by a variety of systemic findings. “You might see cold symptoms, a runny nose, a low-grade fever, aches and pains,” he said. “These symptoms would go along with a viral infection.”

According to Christopher Quinn, OD, a practitioner based in Iselin, N.J., a viral conjunctivitis would also affect the respiratory system. “It is far more common in patients who have viral conditions to have that conjunctivitis preceded by or concurrent with an upper respiratory infection,” he said. “That is a helpful factor that differentiates the two.”

Dr. Townsend said that he does not rely heavily upon systemic findings, except in a few types of infections. “With chlamydial infections, which are usually sexually transmitted, patients might end up with urethritis or, in women, pelvic inflammatory disease,” he said. “Or with people who have pharyngeal conjunctival fever, there might also be a sore throat or a bit of a cough.”

In the case of a bacterial infection, the systemic findings might be more localized, Dr. Abel said. “Often, with a bacterial infection, the findings might be more around the eye and might include puffiness of the lids or lacrimal tract infection,” he said. “So it is more localized, except in cases like strep Hemophilus and Neisseria gonorrhoeae, which can be systemic.”

Ocular findings

Several ocular manifestations are also quite useful to practitioners in making the differential diagnosis between viral and bacterial infections. “I look at corneal involvement, the quality of discharge and conjunctival reaction, meaning papules or follicles or nonspecific redness of the conjunctiva,” Dr. Abel said. “Certain diseases can give you follicles, which are more likely to be viral.”

Dr. Townsend said some of the ocular symptoms for bacterial and viral infections are similar in type. “People with bacterial and viral infections both will complain about a gritty sensation, as if there were sand in their eyes,” he said. “But certain telltale signs are good for differentiating.”

Burning is one of these signs, Dr. Townsend said. “Viral infections tend to make the tear film very unstable,” he said, “so these people will complain that their eyes burn a lot.”

Photosensitivity is also a distinguishing factor, Dr. Townsend said. “Patients with bacterial conjunctivitis have very little sensitivity to light, whereas people with viral infections tend to get both conjunctivitis and keratitis, so they will complain of sensitivity to light,” he said. “Now, if there is a bacterial ulcer or bacterial keratitis, those people will definitely complain of severe photophobia.”

Generally speaking, however, Dr. Townsend said patients with recent-onset burning, red eyes tend to fall into the viral category. The question of whether the infection is monocular or binocular is also a factor, he added.

“A good question is, ‘Is it one eye or both eyes?’” he said. “Viral conjunctivitis in the vast majority of cases spreads from one eye to the other, always with the second eye less involved.”

Dr. Ajamian also relies on certain ocular symptoms in making his diagnosis. “A preauricular node points to viral, along with a follicular response,” he said. “Bacterial, of course, involves mucous discharge, crusting in the morning and matter on the lids.”

Dr. Quinn added that he has not always found the quality of discharge to be an effective indicator for diagnosis. “Traditionally, people have looked at discharge as something important in differentiating bacterial infections from other causes of infections,” he said. “However, my experience has been that it is a poor indicator, and it has relatively poor ability to differentiate the two.

“Corneal infiltrates strongly suggest that the etiology of a red eye is viral,” added Dr. Townsend.

Tx for adenoviral conjunctivitis

For an adenoviral infection, treatment may depend upon a variety of factors, including the stage at which the virus is caught and the degree of pain. “If it is caught within the first 48 hours, I like 5% povidone iodine,” Dr. Abel said. “If it has been longer, I tend to go with an antibiotic/steroid combination. I would tend to use TobraDex (tobramycin dexamethasone, Alcon) due to the limited allergy with tobramycin.”

Dr. Townsend said he makes his decision based upon the acuteness of the infection. “It depends on how bad it is – at the very worst, you will start to get something called pseudomembranes forming on the surface of the eyelid,” he said. “These have to be removed. When you get to that point, you use a steroid.”

In the case of a patient with a basic adenoviral infection without complications, Dr. Townsend would recommend nonsteroidals such as Acular (ketorolac tromethamine, Allergan) or Voltaren (diclofenac sodium 0.1%, Novartis Pharmaceuticals).

“I generally try to avoid steroids because some patients literally get ‘hooked’ on them. If possible, I like to get them through the first few days of real discomfort with nonsteroidals,” he said. “I find that patients with a straight adenoviral infection without complications benefit from nonsteroidals because they are anti-inflammatories, but people don’t get hooked on them.”

Dr. Ajamian described his varied treatment approach to viral conjunctivitis. “I use lots of lubricants and often will use a mild steroid/antibiotic combination drop for comfort, especially when they have pseudomembranes or corneal infiltrates. I have not used Betadine (povidone-iodine, Purdue Frederick) treatment, and I don’t know anyone who has.”

Dr. Abel said he has had a great degree of success with Betadine swabs early in the infection. “I haven’t found the Betadine washes to be that helpful after 48 hours,” he said. “We use a lot of palliative treatment such as compresses.”

Proper hygiene is also important to stop the spread of viral conjunctivitis, practitioners agree. “You want to inform the family of how contagious the virus is,” Dr. Townsend said. “You also want to quarantine the area where a person does his or her hygiene. It really does spread through families.”

Dr. Abel added: “You want to segregate the patient’s towels and other belongings from those of the rest of the family.”

“Among eye practitioners, fluoroquinolones have become standard therapy for acute bacterial infections. Pediatricians and family doctors tend to use a lot of Polytrim (trimethoprim sulfate and polymyxin B sulfate, Allergan) and gentamicin,” added Dr. Ajamian.

In addition to the clues provided by ocular and systemic findings, optometrists may also rely upon laboratory techniques for the differential diagnosis. “There are routine Giemsa stains that can look at the cell types, which will distinguish allergy, polymorphonuclear cells and lymphocytes,” Dr. Abel said. “If you had that available, you could tell very quickly.”

Dr. Townsend pointed out that viral cultures may not always be the most practical option. “Viral cultures take a long time and are expensive,” he said.

Dr. Abel said although both viral and bacterial infections are serious, bacterial infections need to be followed more closely. “The issue of therapy is that viral therapy can be casual, it can be non-specific and the condition will go away. Also, most people will not get opacities,” he said. “Bacterial disease cannot be ignored and needs to be intensely treated, or it will get worse.”

For Your Information:

• Robert Abel Jr., MD, can be reached at 3501 Silverside Road, Wilmington, DE 19810; (302) 477-3937; fax: (302) 477-2650.
• William D. Townsend, OD, is a consultant at the VAMC in Amarillo, Texas, and an adjunct professor at University of Houston College of Optometry. He can be reached at 1801 4th Avenue, Canyon, TX 79015; (806) 655-7748; fax: (806) 655-2871.
• Paul C. Ajamian, OD, can be reached at Omni Eye Services of Atlanta, 5505 Peachtree Dunwoody Road, Atlanta, GA 30342; (404) 257-0814; fax: (404) 256-5445.
• Christopher Quinn, OD, can be reached at 485 Rt. 1, Iselin, NJ 08830; (732) 750-0400; fax: (732) 750-1507.