eMedicine Specialties > Emergency Medicine > Ophthalmology

Conjunctivitis: Differential Diagnoses & Workup

Author: Michael A Silverman, MD, Instructor of Emergency Medicine, The Johns Hopkins University School of Medicine; Chairman, Department of Emergency Medicine, Harbor Hospital
Coauthor(s): Edward Bessman, MD, Chairman, Department of Emergency Medicine, John Hopkins Bayview Medical Center; Assistant Professor, Department of Emergency Medicine, Johns Hopkins University
Contributor Information and Disclosures

Updated: Jun 1, 2009

Differential Diagnoses

Corneal Abrasion
Glaucoma, Acute Angle-Closure
Herpes Zoster
Herpes Zoster Ophthalmicus
Iritis and Uveitis
Scleritis

Other Problems to Be Considered

Episcleritis, an inflammatory condition of the episclera, usually is sectorial and self-limiting. The eye is often tender and mildly photophobic. Topical phenylephrine (Neo-Synephrine [2.5%]) can be used diagnostically; the conjunctival vessels blanch, but the episcleral vessels remain engorged in episcleritis as opposed to conjunctivitis, in which most vessels blanch.

Workup

Laboratory Studies

  • Conjunctivitis usually is diagnosed by history and physical examination. Lab tests typically are reserved for patients that do not improve in 48-72 hours despite treatment. Lab studies include the following:
    • Gram stain is considered the criterion standard for determining the bacterial cause of conjunctivitis. Simple conjunctivitis does not require a Gram stain. Eosinophils seen on Gram stain are indicative of allergic conjunctivitis but can be seen in parasitic causes.
    • Culture and sensitivity of conjunctival scrapings typically are not performed for simple conjunctivitis. Obtain cultures in all newborns, neonates, persons who are immunosuppressed, or when N gonorrhoeae is under consideration as the etiology. When performed, collect exudate from the lower conjunctival fornix with a calcium alginate swab moistened with saline. Sheep blood and mannitol agar plates routinely are used. Expect viral and chlamydial causes in culture-negative conjunctivitis.
    • Giemsa staining is performed to look for the inclusion bodies of Chlamydia versus a viral etiology in culture-negative conjunctivitis. This technique has a low yield, except in neonatal inclusion conjunctivitis. The presence of eosinophils is diagnostic of allergic conjunctivitis.
    • Immunofluorescent antibody testing of the conjunctival discharge can be performed to detect the immunoglobulin G (IgG) or immunoglobulin M (IgM) antibodies to Chlamydia. Consider chlamydial etiology when conjunctivitis persists beyond 14 days and in all sexually active individuals. A high index of suspicion is necessary in patients aged 15-50 years.

More on Conjunctivitis

Overview: Conjunctivitis
Differential Diagnoses & Workup: Conjunctivitis
Treatment & Medication: Conjunctivitis
Follow-up: Conjunctivitis
References
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References

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Further Reading

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Contributor Information and Disclosures

Author

Michael A Silverman, MD, Instructor of Emergency Medicine, The Johns Hopkins University School of Medicine; Chairman, Department of Emergency Medicine, Harbor Hospital
Michael A Silverman, MD is a member of the following medical societies: American College of Emergency Physicians, American College of Physician Executives, and American Medical Association
Disclosure: Nothing to disclose.

Coauthor(s)

Edward Bessman, MD, Chairman, Department of Emergency Medicine, John Hopkins Bayview Medical Center; Assistant Professor, Department of Emergency Medicine, Johns Hopkins University
Edward Bessman, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Medical Editor

William K Chiang, MD, Associate Professor, Department of Emergency Medicine, New York University School of Medicine; Chief of Service, Department of Emergency Medicine, Bellevue Hospital Center
William K Chiang, MD is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Medical Toxicology, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Douglas Lavenburg, MD, Clinical Professor, Department of Emergency Medicine, Christiana Care Health Systems
Douglas Lavenburg, MD is a member of the following medical societies: American Society of Cataract and Refractive Surgery
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Barry E Brenner, MD, PhD, FACEP, Professor of Emergency Medicine, Professor of Internal Medicine, Program Director, Emergency Medicine, University Hospitals, Case Medical Center
Barry E Brenner, MD, PhD, FACEP is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Chest Physicians, American College of Emergency Physicians, American College of Physicians, American Heart Association, American Thoracic Society, Arkansas Medical Society, New York Academy of Medicine, New York Academy of Sciences, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

 
 
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