Infectious conjunctivitis is most commonly viral conjunctivitis Viral Conjunctivitis Viral conjunctivitis is a highly contagious acute conjunctival infection usually caused by an adenovirus. Symptoms include irritation, photophobia, and watery discharge. Diagnosis is clinical... read more 
or bacterial conjunctivitis Acute Bacterial Conjunctivitis Acute conjunctivitis can be caused by numerous bacteria. Symptoms are hyperemia, lacrimation, irritation, and discharge. Diagnosis is clinical. Treatment is with topical antibiotics, augmented... read more 
and is contagious. Rarely, mixed or unidentifiable pathogens are present. Numerous allergens can cause allergic conjunctivitis Allergic Conjunctivitis Allergic conjunctivitis is an acute, intermittent, or chronic conjunctival inflammation usually caused by airborne allergens. Symptoms include itching, lacrimation, discharge, and conjunctival... read more 
. Nonallergic conjunctival irritation can result from foreign bodies; wind, dust, smoke, fumes, chemical vapors, and other types of air pollution; and intense ultraviolet light of electric arcs, sunlamps, and reflection from snow.
Conjunctivitis is typically acute, but both infectious and allergic conditions can be chronic. Additional conditions that cause chronic conjunctivitis include ectropion Ectropion Entropion is inversion of an eyelid. Ectropion is eversion of the lower eyelid. This photo shows entropion, inversion of the eyelid that most commonly affects the lower eyelids of older adults... read more 
, entropion Entropion Entropion is inversion of an eyelid. Ectropion is eversion of the lower eyelid. This photo shows entropion, inversion of the eyelid that most commonly affects the lower eyelids of older adults... read more , blepharitis Blepharitis Blepharitis is inflammation of the eyelid margins that may be acute or chronic. Symptoms and signs include itching and burning of the eyelid margins with redness and edema. Diagnosis is by history... read more 
, and chronic dacryocystitis Dacryocystitis Dacryocystitis is infection of the lacrimal sac that sometimes leads to abscess formation. The usual cause is a staphyloccocal or streptococcal species, typically as a consequence of nasolacrimal... read more 
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Symptoms and Signs of Conjunctivitis
Any source of inflammation can cause lacrimation or discharge and diffuse conjunctival vascular dilation. Discharge may cause the eyes to crust overnight. Thick discharge may blur vision, but once discharge is cleared, visual acuity should be unaffected.
Itching and watery discharge predominate in allergic conjunctivitis. Chemosis and papillary hyperplasia also suggest allergic conjunctivitis Allergic Conjunctivitis Allergic conjunctivitis is an acute, intermittent, or chronic conjunctival inflammation usually caused by airborne allergens. Symptoms include itching, lacrimation, discharge, and conjunctival... read more . Irritation or foreign body sensation, photophobia, and discharge suggest infectious viral conjunctivitis Viral Conjunctivitis Viral conjunctivitis is a highly contagious acute conjunctival infection usually caused by an adenovirus. Symptoms include irritation, photophobia, and watery discharge. Diagnosis is clinical... read more ; purulent discharge suggests bacterial conjunctivitis Acute Bacterial Conjunctivitis Acute conjunctivitis can be caused by numerous bacteria. Symptoms are hyperemia, lacrimation, irritation, and discharge. Diagnosis is clinical. Treatment is with topical antibiotics, augmented... read more . Severe eye pain suggests scleritis Scleritis Scleritis is a severe, destructive, vision-threatening inflammation involving the deep episclera and sclera. Symptoms are moderate to marked pain, hyperemia of the globe, lacrimation, and photophobia... read more 
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Diagnosis of Conjunctivitis
Clinical evaluation
Sometimes culture
Usually, diagnosis of conjunctivitis is made by history and examination (see table Differentiating Features in Acute Conjunctivitis Differentiating Features in Acute Conjunctivitis 
), usually including slit-lamp examination with fluorescein staining of the cornea and, if glaucoma Overview of Glaucoma Glaucomas are a group of eye disorders characterized by progressive optic nerve damage in which an important part is a relative increase in intraocular pressure (IOP) that can lead to irreversible... read more is suspected, measurement of intraocular pressure. In order to prevent transmitting infection to other patients and to staff, meticulous disinfection of equipment that touches the eye is particularly important after examination of patients who could have conjunctivitis.
Other disorders can cause a red eye Red Eye Red eye refers to a red appearance of the opened eye, reflecting dilation of the superficial ocular vessels. Dilation of superficial ocular vessels can result from Infection Allergy Inflammation... read more . Deep pain in the affected eye when a light is shone in the unaffected eye (true photophobia) does not occur in uncomplicated conjunctivitis and suggests a disorder of the cornea or anterior uvea. Circumcorneal conjunctival hyperemia (sometimes described as ciliary flush) is caused by dilated, fine, straight, deep vessels that radiate out 1 to 3 mm from the limbus, without significant hyperemia of the bulbar and tarsal conjunctivae. Ciliary flush occurs with uveitis Overview of Uveitis Uveitis is defined as inflammation of the uveal tract—the iris, ciliary body, and choroid. However, the retina and fluid within the anterior chamber and vitreous are often involved as well.... read more 
, acute glaucoma Overview of Glaucoma Glaucomas are a group of eye disorders characterized by progressive optic nerve damage in which an important part is a relative increase in intraocular pressure (IOP) that can lead to irreversible... read more , and some types of keratitis (see Corneal Disorders Introduction to Corneal Disorders Symptoms that suggest corneal involvement (eg, rather than simple conjunctivitis) include unilateral involvement, pain (foreign body sensation and ache—not just a gritty sensation), particularly... read more ) but not with uncomplicated conjunctivitis.
The cause of conjunctivitis is suggested by clinical findings. However, cultures are indicated for patients with severe symptoms, immunocompromise, a vulnerable eye (eg, after a corneal transplant, in exophthalmos due to Graves disease), or poor response to initial therapy.
Clinical differentiation between viral and bacterial infectious conjunctivitis is not highly accurate. However, if the history and examination strongly suggest viral conjunctivitis, withholding antibiotics initially is appropriate. Antibiotics can be prescribed later if the clinical picture changes or if symptoms persist.
Treatment of Conjunctivitis
Prevention of spread
Treatment of symptoms
Most infectious conjunctivitis is highly contagious and spreads by droplets, fomites, and hand-to-eye inoculation. To avoid transmitting infection, physicians must
Use hand sanitizer or wash their hands properly (fully lather hands, scrub hands for at least 20 seconds, rinse well, and turn off the water using a paper towel)
Disinfect equipment after examining patients
Patients should do the following:
Use hand sanitizer and/or wash their hands thoroughly after touching their eyes or nasal secretions
Avoid touching the noninfected eye after touching the infected eye
Avoid sharing towels or pillows
Avoid swimming in pools
Eyes should be kept free of discharge and should not be patched. Small children with conjunctivitis should be kept home from school to avoid spreading the infection. Cool washcloths applied to the eyes may help relieve local burning and itching. Antimicrobials are used for certain infections.
Key Points
Conjunctivitis typically results from infection, allergy, or irritation.
Infectious conjunctivitis is usually highly contagious.
Typical findings are redness (without ciliary flush) and discharge, without significant pain or loss of vision.
Diagnosis is usually clinical.
Treatment includes measures to prevent spread and treatment of the cause (sometimes antimicrobials).
