Approach Considerations
Generally, a diagnosis of viral conjunctivitis is made on the clinical features alone. Signs of acute viral conjunctivitis include inferior palpebral conjunctival follicles, tender palpable preauricular lymph node, watery discharge, red and edematous eyelids, pinpoint subconjunctival hemorrhages, punctuate keratopathy, and membrane/pseudomembrane. Intraepithelial microcysts may be an early corneal finding, which, when present, can be helpful in the diagnosis. Subepithelial corneal infiltrates may develop 1-2 weeks after the onset of the conjunctivitis. HSV infection may demonstrate the classic corneal dendrites. Extensive multiple dendrites may suggest immunocompromise (eg, due to long-term topical steroid therapy, systemic immunosuppressive medications, HIV infection).
Conventional laboratory culture identification can be expensive and time-consuming but may be helpful in certain circumstances. [6, 7, 8, 9]
Culture, Smear, and Stain
Specimens should be obtained for culture and smear if inflammation is severe, in chronic or recurrent infections, with atypical conjunctival reactions, and with failure to respond to treatment.
Giemsa staining of conjunctival scrapings may aid in characterizing the inflammatory response. Polymorphonuclear cells are prevalent in bacterial infections, whereas mononuclear cells and lymphocytes are seen with viruses.
Viral Isolation
Viral isolation methods may be helpful in the diagnosis of acute follicular conjunctivitis, but they are not indicated in chronic conjunctivitis.
Direct immunofluorescence monoclonal antibody staining and enzyme-linked immunosorbent assay (ELISA) are rapid and widely available detection techniques.
Alternative methods include the use of immunoperoxidase, electron microscopy, and polymerase chain reaction (PCR) assay. These tests usually are performed only in the context of a research program.
Serologic tests are available but generally require 2 serum samples at least 2 weeks apart, which can delay treatment decisions. The ready availability of the point-of-service Adenoplus test (RPS Diagnostics) precludes many of the traditional diagnostics owing to its relatively low cost, rapidity, patient tolerability, and accuracy.
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Viral conjunctivitis. Image courtesy of Wikimedia Commons.
