While conjunctivitis may not be why we went into emergency medicine, it is a common complaint that we will see on a weekly, if not daily, basis.  There are many aspects of conjunctivitis to consider when seeing a patient, and not all is solved by a prescription for antibiotic drops.  In this post we will start off by reviewing the anatomy of the conjunctiva and then discuss the three major types of conjunctivitis: Bacterial, Viral, and Allergic.


Figure 1. Conjunctiva Anatomy. Courtesy of Wikimedia commons (7).

As we remember from medical school, the anatomy of the eye is complicated.  To keep it simple, we'll stick to the conjunctiva.  The conjunctiva is a thin, translucent membrane that lines the anterior part of the sclera and the inside of the eyelids.  It is separated into three parts.  The portion overlying the sclera is termed the bulbar (ocular) conjunctiva, the part lining the eyelids is the palpebral (tarsal) conjunctiva, and the junction where they connect is termed the fornix.  Take a look at the image to help orient yourself.  

Conjunctivitis is inflammation of the conjunctiva.  This is separated into infectious and non-infectious causes.  Virtually all types of conjunctivitis will have redness, discharge, and some type of irritation.  However, this is very non-specific.  For example, itching, which classically is a hallmark of allergic conjunctivitis, in one study was found in 58% of patients with culture proven bacterial conjunctivitis.  

Below, we will separately outline each type of conjunctivitis.

Bacterial Conjunctivitis

Presentation and Etiology:

Figure 2. Gonorrhea Conjunctivitis.  Courtesy of Cogan Collection, NEI/NIH (8).

Figure 3. Chlamydia Conjunctivitis.  Courtesy of Wikimedia Commons (9).

  • Classically characterized by acute onset of purulent discharge, erythema, edema, chemosis, and mattering of eyelids.
    • Hyperacute variant: severe copious purulent discharge, eye pain, vision changes.  Consider gonorrhea/chalmydia in these patients.
  • Common organisms include S. Aureus, S. Pneumonia, and H. Influenza.
    • Consider gonorrhea/chlamydia in sexually active patients, especially those with GU symptoms.


  • 60% of cases of bacterial conjunctivitis are self-limiting within 1-2 weeks.  Antibiotic treatment has been shown to reduce duration of disease but no difference in outcome.
  • Antibiotics recommended for cases of purulent/mucopurulent conjunctivitis, suspected cases of gonorrhea/chlamydia, and for contact lens wearers.
  • Compresses can be used to help with discomfort.
  • See treatment table at the bottom of the post for specific regimens.  No study has shown superiority of any specific regimen, choice will depend on cost and local practice pattern.  For contact lens wearers, be sure to cover for pseudomonas with a fluoroquinolone.  

Viral Conjunctivitis


Figure 4. Adenovirus Conjunctivitis. Courtesy of Cogan Collection, NEI/NIH (10).

Presentation and Etiology:

  • Classically a thin, watery discharge, mild burning/irritation.
  • 65-90% of cases caused by adenovirus.
    • Pharyngoconjunctival fever: fever, pharyngitis, bilateral conjunctivitis, periauricular node enlargement.
    • Epidemic keratoconjunctivitis: watery discharge, chemosis, ipsilateral lymphadenopathy, foreign body sensation.


  • Cold compresses, artificial tears for comfort
  • Hand washing to limit spread


Herpes Simplex:

  • Typically unilateral, thin/watery discharge, vesicular eyelid/oral lesions.
  • Treat with topical and oral antivirals (see treatment table).

Figure 5. HSV Conjunctivitis. Courtesy of Cogan Collection, NEI/NIH (11).

Figure 6. HSV Vesicles. Courtesy of Wikimedia Commons (12).

Herpes Zoster:

Figure 7. Herpes Zoster. Courtesy of Wikimedia Commons (13).

Figure 7. Herpes Zoster. Courtesy of Wikimedia Commons (13).

  • Occurs due to reactivation of the herpes zoster virus in the ophthalmic division of the trigeminal nerve.
  • Risk factors include aging, poor nutrition, immunocompromised state
  • Involves eyelids (46%) or conjunctiva (41%), but can also lead to corneal complications and uveitis.  Typically in a dermatomal pattern. 
  • Patients will have vesicles and pain in this distribution.  They also will have typical conjunctivitis symptoms if there is conjunctival involvement.
  • If suspected eye involvement or Hutchinson sign (skin lesions at the tip of the nose), refer to ophthalmology as there is a risk of blindness.
  • Treatment consists of oral antivirals (see treatment table). 

Allergic Conjunctivitis

Presentation and Etiology:

Figure 8. Allergic Conjunctivitis.  Courtesy of Wikimedia Commons (14).

  • Type I IgE mediated hypersensitivity reaction precipitated by allergens
    • Allergens include: dust, pollens, animal dander, mites, mold
  • Patients have bilateral itching, conjunctival injection, watery discharge, edema


  • Eliminate the allergen.
  • Topical tear substitutes to lubricate and wash out allergen.
  • Antihistamine drops can help itching/redness (see treatment table).
  • Do no prescribe topical steroids unless in consultation with an ophthalmologist

Treatment Table

Table 1. Conjunctivitis Treatment Regimens.

While the three types of conjunctivitis described here are the most common, it is important to not overlook some other process that could be manifesting itself as conjunctivitis (autoimmune disease, SJS, carotid-cavernous fistula).


  1. Viruses cause the vast majority of infectious conjunctivitis and 60% of bacterial conjunctivitis is self limiting.  Reserve antibiotic therapy for cases of chlamydia/gonorrhea and severe purulent/mucopurulent conjunctivitis.
  2. If vesicles are present, suspect herpes, which needs antiviral therapy and possible ophthalmology consultation.
  3. Always consider other disease processes that could be manifesting themselves as conjunctivitis (autoimmune disease, SJS, carotid-cavernous fistula).


  1. Høvding, G. (2008), Acute bacterial conjunctivitis. Acta Ophthalmologica, 86: 5–17. doi:10.1111/j.1600-0420.2007.01006.x
  2. Amir A. Azari, Neal P. Barney. ConjunctivitisA Systematic Review of Diagnosis and Treatment. JAMA.2013;310(16):1721–1730. doi:10.1001/jama.2013.280318
  3. American Academy of Ophthalmology Cornea/External Disease Panel. Preferred Practice Pattern Guidelines.  Conjunctivitis.  San Francisco, CA: American Academy of Ophthalmology; 2013.  Available at:
  4. Knoop, Kevin J. “Viral Conjunctivitis.” The Atlas of Emergency Medicine, McGraw-Hill Medical, 2016, pp. 33–34.
  5. Knoop, Kevin J. “Bacterial Conjunctivitis.” The Atlas of Emergency Medicine, McGraw-Hill Medical, 2016, pp. 32–32.
  6. Knoop, Kevin J. “Allergic Conjunctivitis.” The Atlas of Emergency Medicine, McGraw-Hill Medical, 2016, pp. 35–35.

Authored and Posted by Timothy G Murphy, MD