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Title: Conjunctivitis
Authors: Trey Winter, 1st Year Medical Student, University of Utah; Mike Murri, MD, University of Utah Moran Eye Center
Photographer: James Gilman, CRA, FOPS


Figure 1: External photograph demonstrating allergic conjunctivitis. Note the injected conjunctival vessels and associate nodules at the limbus.


Figure 2: A case of vernal conjunctivitis showing the typical elevated, gelatinous conjunctival nodules at the limbus.


Figure 3: A case of chronic, untreated chlamydial conjunctivitis with significant scarring found on the undersurface of the upper eyelid, or the palpebral conjunctiva. There is significant scarring which is quite specific to this entity but typically only in cases with delayed treatment, most often seen in the developing world.


Figure 4: An everted upper eyelid demonstrating giant papillary conjunctivitis.


Conjunctivitis is the inflammation of the conjunctiva. The conjunctiva is the mucous membrane that lines the inner eyelid and covers the sclera up to the cornea. The conjunctiva can be divided into two anatomical can also be divided into two areas: the bulbar conjunctiva, which covers the actual eye; and the palpebral conjunctiva, which extends onto the undersurface of the eyelids. The “red eye” or “pink eye” appearance of the conjunctiva is secondary to inflammation which can be caused by hyperemia (increased blood flow) and increased diameter of conjunctival blood vessels which causes edema. Inflammation can also cause an acute generalized hyperplasia or lymphocyte aggregation in the lymphoid layer of the conjunctiva.

Conjunctivitis is divided into two broad categories: infectious and non-infections. Infectious conjunctivitis can be subclassified as bacterial or viral. Non-infectious conjunctivitis can be subclassified as allergic or non-allergic.

All types of conjunctivitis typically present with reddening of the conjunctiva. Additionally, inflammation and epiphora (watery eye) are common presentation signs. Conjunctivitis does not typically impair vision and pupils should still be reactive to light.

Infectious Conjunctivitis


Viral conjunctivitis is often accompanied by signs of a viral infection in the upper respiratory tract. Viral conjunctivitis is extremely contagious and is spread by contact with secretions from those infected, fomites contaminated with the virus, or from public areas such as swimming pools. Adenovirus is the most common viral infectious agent. Other viral agents causing conjunctivitis include Herpes Simplex Virus 1 and enteroviruses.

Viral infectious conjunctivitis typically presents with upper respiratory tract symptoms such as a runny nose or sore throat. Lymph nodes are often enlarged on the same side of the affected eye upon physical exam. The eye is usually excessively watery accompanied by irritation and pruritis. Patients may complain of a sandy or gritty feeling in the infected eye, and the appearance of the eye is usually diffusely pink. Viral infections of the conjunctiva usually begin unilaterally, but often will spread through contact to eventually infect both eyes. The symptoms can last a few weeks and don’t respond to antibiotic eye drops.


Bacterial conjunctivitis is commonly caused by Staphylococcus aureus, Streptococcus pneumonia, Haemophilus influenza, and Moraxella catarrhalis. These organisms can spread from the nasal and sinus mucosa or from another affected individual. Adult bacterial conjunctivitis is typically caused by Staphylococcus aureus while children commonly contract the other three pathogens listed above. An extreme case of acute bacterial conjunctivitis caused by the sexually transmitted Neisseria gonorrhoeae can lead to blindness through rapid spread to the corneal surface and typically occurs very rapidly. It is transmitted from genitals to the hands and finally to the eyes. Chlamydia trachoma presents in a similar manner to Neisseria but the development is slow and insidious (see Image 3).

Unlike viral conjunctivitis, bacterial conjunctivitis presents with a sticky, purulent discharge. This discharge can be yellow, white or green in color. Patients with conjunctivitis of all types can present with a crusted, closed eye in the morning from discharge, however with bacterial conjunctivitis, thick purulent discharge will persist throughout the day. In addition, patients with bacterial conjunctivitis often do not experience pruritis. Like viral conjunctivitis, bacterial conjunctivitis initially presents unilaterally, eventually spreading to the other eye.

Other infectious causes

Other less-common causes of conjunctivitis beyond scope of this article but that can be considered are fungal, parasitic, and rickettsial pathogens.

Non-Infectious Conjunctivitis


Allergic conjunctivitis is a type-1 hypersensitivity reaction caused by airborne or other allergens. The allergens cause the degranulation of mast cells and release of histamine and other factors causing swelling and redness of the conjunctiva. This swelling can present on the palpebral conjunctiva as a cobblestone appearance with central blood vessels (papillae, see Image 4 for a dramatic case).

Allergic conjunctivitis presents similarly to viral conjunctivitis with a few key differences. Like viral conjunctivitis, allergic conjunctivitis presents with injection (redness), a watery discharge, and itching. A key distinguishing factor is that allergic conjunctivitis more commonly presents bilaterally and often has more lid irritation. The itching in allergic conjunctivitis is constant and not accompanied by the additional description of sandy or gritty. Patients may develop elevated conjunctival nodules at the limbus with chronic, allergic conjunctivitis (see Images 1 and 2).  A history of asthma, exczema, or specific allergies or hay fever are key factors in suspecting allergic conjunctivitis, as well as new pets, makeup, eye drops, creams or lotions.


Non-allergic conjunctivitis it classically caused by a chemical or physical problem. Chemicals splashed in the eye may cause mucus formation and redness, but will typically resolve within 24 hours. The two common factors relating to physical problems are dryness or a foreign body. The most common foreign body-induced non-allergic conjunctivitis are contacts. A reaction to contacts is most commonly seen in those who have poor contact-lens hygiene (sleeping in contacts, extended use of contacts, improper storage, etc.).

Non-allergic conjunctivitis has a variable presentation depending on the cause. Discharge is more commonly mucus as opposed to pus. Most of these cases resolve after around 24 hours or after removal of the foreign body.


Conjunctivitis does not regularly cause complications with the exception of the sexually transmitted bacterial infections. Complications are more common in those that are immunocompromised.

Complications from conjunctivitis (in order of most common to least common) include: keratitis (infection of the cornea), cellulitis, otitis media, genital coinfection, bacteremia and meningitis.

Differential Diagnosis

The differential diagnosis for conjunctivitis is broad and includes many conditions causing a red eye. Conditions include, but are not limited to: keratitis, angle-closure glaucoma, iritis, corneal abrasion, subconjunctival hemorrhage, pinguecula, blepharitis and poor contact lenses fit.


It is important to make an accurate diagnosis of conjunctivitis and to educate patients on the etiology of their disease. Many patients with conjunctivitis will assume that there is a bacterial cause and desire antibiotics. It is important to take a detailed history and perform a physical exam including signs of upper respiratory infection and lymph node examination. Diagnosis can be made based on the presentations detailed above. On physical examination of conjunctivitis, the red reflex and visual acuity should be intact. Presentation of visual problems in addition to the physical findings indicate another condition.

Typically, cultures are not required for diagnosis. Information in the history and on physical examination can assist in diagnosis of the type of conjunctivitis. Persistent cases that do not respond to treatment may necessitate a bacterial and fungal culture. Rapid adenovirus tests exist that can be used to definitively diagnose an adenoviral conjunctivitis, but this is usually unnecessary.

Physical examination is especially important in patients who use contact lenses, as the reddening of the eye can be caused by poorly fitting contacts or poor contact lens hygiene. Removal of the contacts for a period may reveal if contacts are the cause of the injection.


Conjunctivitis is usually self-limiting and treatment reduces symptoms, but does not speed duration of the illness. For bacterial conjunctivitis, antibacterial eye drops are not always necessary but may be prescribed to decrease the severity of the infection. In areas with high risk of contagion such as schools and daycare centers, patients must often be treated for 24 hours before they can return. In these cases a topical antibiotic that is inexpensive and nontoxic may be given. The treatment of bacterial conjunctivitis is erythromycin ointment or trimethoprim-polymixin eye drops.

Viral conjunctivitis can be treated with antihistamines or lubricating agents to provide relief of the symptoms and inflammation. Notably these do not actually treat the viral root cause. The same treatment is administered for patients with non-allergic conjunctivitis.

Allergic conjunctivitis can be treated with antihistamines, artificial tears, and if known, avoiding the agents that cause the allergic reaction. A patch test can be performed for patients with severe allergies. In all cases of conjunctivitis, patients should be advised to avoid contact lens use, refrain from rubbing the eyes, and wash hands frequently.


Azari, AA; Barney, NP (23 October 2013). “Conjunctivitis: a systematic review of diagnosis and treatment”. JAMA. 310 (16): 1721–9.

Fitch CP, Rapoza PA, Owens S, et al. Epidemiology and diagnosis of acute conjunctivitis at an inner-city hospital. Ophthalmology 1989; 96:1215.

Friedlaender MH. A review of the causes and treatment of bacterial and allergic conjunctivitis. Clinical Therapy 1995; 17:800.

Gigliotti F, Williams WT, Hayden FG, et al. Etiology of acute conjunctivitis in children. Journal of Pediatric Medicine 1981; 98:531.

Wan WL, Farkas GC, May WN, Robin JB. The clinical characteristics and course of adult gonococcal conjunctivitis. American Journal of Ophthalmology 1986; 102:575.

Weiss A, Brinser JH, Nazar-Stewart V. Acute conjunctivitis in childhood. Journal of Pediatric Medicine 1993; 122:10.

Faculty Approval by: Griffin Jardine, MD

Identifier: Moran_CORE_26899

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