Ocular System


Conjunctivitis, also known as pink eye, is an inflammation of the conjunctiva characterized by dilatation of the conjunctival vessels, resulting in hyperemia and edema, typically with associated discharge

Conjunctivitis, also known as pink eye, is an inflammation of the conjunctiva characterized by dilatation of the conjunctival vessels, resulting in hyperemia and edema, typically with associated discharge

  • It is the most common presentation of eye redness in both primary care and the emergency department


Transparent, lubricating mucous membrane covering the outer surface of the eye. It is composed of two parts:
  • Bulbar conjunctiva: Covers the globe
  • Tarsal/palpebral conjunctiva: Lines the eyelid’s inner surface
Normal Conjunctival Anatomy
Normal Conjunctival Anatomy: The conjunctiva is a thin membrane covering the sclera (bulbar conjunctiva, labeled with purple) and the inside of the eyelids (palpebral conjunctiva, labeled with blue). | Azari, A. A., & Barney, N. P. (2013). Conjunctivitis: a systematic review of diagnosis and treatment. JAMA, 310(16), 1721–1729.


Conjunctivitis is the most prevalent etiology of eye redness and discharge. While there are many types of conjunctivitis, viral, allergic and bacterial are the three most common.

Viral conjunctivitis:

80% of acute cases of conjunctivitis are viral, the most common pathogen being Adenovirus.
  • Adenoviruses: M/C cause (65-90% cases)
  • Other common pathogens: Herpes simplex, Herpes zoster, and Enterovirus

Bacterial conjunctivitis:

More common in children than adults, and the pathogens responsible for bacterial conjunctivitis vary depending on the age group.
  • Adults: S. aureus, followed by S. pneumoniae and H. influenzae
  • Children: H. influenza, S. pneumoniae, and Moraxella catarrhalis
  • Neonates: N. gonorrhoeae
  • Other bacterial causes: C. trachomatis, and C. diphtheria.

Non-infectious conjunctivitis:

Allergens, toxins and local irritants are responsible for non-infectious conjunctivitis
  • Allergic conjunctivitis
  • Drug-, Chemical-, and Toxin-Induced Conjunctivitis
  • Systemic Diseases Associated With Conjunctivitis
Some systemic and dermatological conditions associated with conjunctivitis.
Some systemic and dermatological conditions associated with conjunctivitis. | Azari, A. A., & Arabi, A. (2020). Conjunctivitis: A Systematic Review. Journal of ophthalmic & vision research, 15(3), 372–395.


Irritation/infection of conjunctiva is due to the injection/dilation of the conjunctival vessels which results in the classic redness or hyperemia and edema of the conjunctiva. The entire conjunctiva is involved, and there is often discharge as well. The quality of discharge varies depending on the causative agent.

General symptoms:

  • Diffuse redness: Involves entire conjunctival surface, both bulbar and tarsal conjunctiva
  • Discharge from eye:
    • Bacterial conjunctivitis: Purulent discharge which reforms immediately after removal from the eye, or mucopurulent discharge which tends to be thicker and sticks to the eyelashes
    • Viral & allergic conjunctivitis: Watery discharge
  • Preauricular lymphadenopathy: Viral > allergic conjunctivitis
  • Ithing of eyes
  • Papillae (present in both noninfectious & infectious conjunctivitis): Small elevations usually under the superior tarsal conjunctival, with central vessels.
    • Often present in bacterial conjunctivitis, allergic conjunctivitis, and contact lens intolerance
    • Papillae in chronic allergic conjunctivitis can lead to a cobblestone appearance of the conjunctiva.
  • Follicles: Lymphocytic response presenting as small elevated yellow-white lesions found at the lower cul-de-sac (junction of the palpebral and bulbar conjunctiva)
    • Seen in chlamydial and adenoviral conjunctivitis.

Bacterial conjunctivitis:

  • Redness and foreign body sensation
  • Morning matting of the eyes
  • White-yellow purulent or mucopurulent discharge
  • Conjunctival papillae
  • Infrequently preauricular lymphadenopathy
Characteristic Appearance of Bacterial and Viral Conjunctivitis
Characteristic Appearance of Bacterial and Viral Conjunctivitis: A, Bacterial conjunctivitis characterized by mucopurulent discharge and conjunctival hyperemia. B, Severe purulent discharge seen in hyperacute bacterial conjunctivitis secondary to gonorrhea. C, Intensely hyperemic response with thin, watery discharge characteristic of viral conjunctivitis. | Images © 2013 American Academy of Ophthalmology | Azari, A. A., & Barney, N. P. (2013). Conjunctivitis: a systematic review of diagnosis and treatment. JAMA, 310(16), 1721–1729.

Viral conjunctivitis:

  • Itching and tearing symptoms
  • History of recent upper respiratory tract infection
  • Watery discharge
  • Inferior palpebral conjunctival follicles
  • Tender preauricular lymphadenopathy
Case photographs of adenoviral conjunctivitis
Case photographs of adenoviral conjunctivitis. (A) gross examination of acute adenoviral conjunctivitis; (B) bilateral AdenoPlus-positive EKC; (C) high magnification of the conjunctiva of positive EKC. | Photos provided by Scott Hauswirth and Elizabeth Yeu. The patients have given permission for publication of these photos. | EKC, epidemic keratoconjunctivitis. | Yeu, E., & Hauswirth, S. (2020). A Review of the Differential Diagnosis of Acute Infectious Conjunctivitis: Implications for Treatment and Management. Clinical ophthalmology (Auckland, N.Z.), 14, 805–813.

Allergic conjunctivitis:

  • Itching/burning symptoms
  • History of allergies/atopy
  • Watery discharge
  • Edematous eyelids
  • Conjunctival papillae
  • No preauricular lymphadenopathy


History and physical examination are, of course, essential in the diagnosis of conjunctivitis, and in determining the cause and therefore treatment of the condition.

Ocular history includes the timing of onset, prodromal symptoms, unilateral or bilateral eye involvement, associated symptoms, previous treatment and response, past episodes, type of discharge, the presence of pain, itching, eyelid characteristics, periorbital involvement, vision changes, photophobia, and corneal opacity.

Suggested Algorithm for Clinical Approach to Suspected Acute Conjunctivitis
Suggested Algorithm for Clinical Approach to Suspected Acute Conjunctivitis | Azari, A. A., & Barney, N. P. (2013). Conjunctivitis: a systematic review of diagnosis and treatment. JAMA, 310(16), 1721–1729.

Eyelid cultures and cytology:

Obtaining conjunctival cultures is generally reserved for cases of suspected infectious neonatal conjunctivitis, recurrent conjunctivitis, conjunctivitis recalcitrant to therapy, conjunctivitis presenting with severe purulent discharge, and cases suspicious for gonococcal or chlamydial infection.
Gram –ve rods (Pseudomonas) and white cells | Photo: Melville Matheson | Wood M. (1999). Conjunctivitis: diagnosis and management. Community eye health, 12(30), 19–20.

Rapid antigen testing:

For adenoviruses and can be used to confirm suspected viral causes of conjunctivitis to prevent unnecessary antibiotic use.

Differential diagnosis:

There are many emergent and non-emergent causes of eye redness. When considering a diagnosis of conjunctivitis, it is essential to rule out the emergent causes of vision loss. Some signs and symptoms that point to diagnosis other than conjunctivitis include localized redness, redness that does not include the entire conjunctiva, ciliary flush, elevated intraocular pressure, vision loss, moderate to severe pain, hypopyon, hyphema, pupil asymmetry, decreased pupil response, and trouble opening the eye or keeping the eye open.
  • Generalised redness (involve entire bulbar conjunctiva but spare tarsal conjunctiva): Keratitis, iritis, and angle closure glaucoma

Emergent sight-threatening complications:

All patients with hypopyon, hyphema, suspected iritis, keratitis, scleritis, corneal ulcer or corneal foreign body should be evaluated by an ophthalmologist within 12-24 hours of presentation, while patients with suspected angle-closure glaucoma should see the ophthalmologist as soon as possible.
  • Glaucoma: Semi-dilated pupil, corneal opacity, ciliary flush, and elevated intraocular pressure
  • Anterior uveitis (iritis): Pain, blurred vision, photophobia, ciliary flush, and hypopyon
  • Hypopyon (white or whitish-yellow collection of inflammatory cells in the anterior chamber): Associated with iritis, infectious keratitis or corneal ulcer
  • Corneal involvement (ulcer, abrasion or foreign body): Foreign body sensation and trouble opening the eye or keeping the eye open.
  • Foreign body and orbital trauma: Hyphema (collection of blood in anterior chamber)
  • Scleritis: Severe pain radiating to face and is worse in the morning and/or at night, associated with photophobia, pain with extraocular movement, tenderness to palpation and scleral edema

Non-emergent causes of eye redness:

  • Localized redness: Foreign body, pterygium or episcleritis
  • Foreign body sensation, itching or burning (similar to allergic conjunctivitis)
    • Blepharitis: Crusting of the eyelids and marked erythema and edema of the eyelid margins
    • Contact overuse
    • Dry eyes: Lack of blinking
  • Subconjunctival hemorrhage: Due to bleeding of conjunctival vessels and appears as blood in the subconjunctival space rather than the typical injection or vessel dilation seen in conjunctivitis


Treatment of both viral and bacterial conjunctivitis should include patient education to decrease the rate of transmission.

Bacterial conjunctivitis:

Initial treatment for acute, non-severe bacterial conjunctivitis varies depending on the antimicrobial agent, but generally is administered to the affected eye from every two to every 6 hours for 5 to 7 days. Antibiotic options are available as liquid solutions and topical ointments. While ointments typically last longer than drops, they tend to interfere with vision.
  • Liquid suspension/solutions: Polymyxin b/trimethoprim, ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin, gatifloxacin or azithromycin
  • Ointment: Bacitracin, erythromycin or ciprofloxacin
  • Specific cases:
    • Contact lens wearers: Fluoroquinolones (empiric coverage for Pseudomonas)
    • Gonococcal conjunctivitis: Ceftriaxone 1gm IM (recommended to treat for concurrent chlamydial infection with 1gm azithromycin PO)

Viral conjunctivitis:

Topical corticosteroids are not recommended for cases of bacterial or viral conjunctivitis, except for herpes zoster, as they can prolong the disease or potentiate the infection, resulting in complications including corneal damage and blindness. Patients should have a follow-up with ophthalmologists within 2 to 5 days to monitor for complications.
  • Adenoviruses (symptomatic relief): Cold compresses and artificial tears
  • Herpes simplex keratitis (antiviral therapy):
    • Trifluridine (1% drops every 2 hours or 8-9x daily, 10-14 days)
    • Topical ganciclovir (0.15% gel 1 drop 5x daily until epithelial heals and then 3x daily for 1 week)
    • Oral acyclovir (400mg PO 5 times a day for 7 to 10 days): Limit epithelial toxicity
  • Herpes zoster conjunctivitis (combination of oral antivirals and topical steroids):
    • Oral acyclovir (800mg 5x daily, 7-10 days)
    • Oral famciclovir (500mg 3x daily, 7-10 days)
    • Oral valacyclovir (1g 3x daily, 7-10 days)

Allergic conjunctivitis:

Treatment for allergic conjunctivitis consists of allergen avoidance, artificial tears, cold compresses, and a wide range of topical agents.
  • Topical agents: Topical antihistamines alone or in combination with vasoconstrictors, topical mast cell inhibitors and topical glucocorticoids for refractory symptoms
  • Oral antihistamines can also be used in moderate to severe cases of allergic conjunctivitis.


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