Conjunctivitis

Classification	D ICD-10: H10; ICD-9-CM: 372.0; MeSH: D003231; DiseasesDB: 3067;
External resources	MedlinePlus: 001010; eMedicine: emerg/110; Patient UK: Conjunctivitis;

Conjunctivitis
Other names	Pink eye
	An eye with viral conjunctivitis
Specialty	Ophthalmology
Symptoms	Reddish eye, scratchiness[1]
Duration	Viral conjunctivitis: up to two weeks[2]
Causes	Viral, bacterial, allergies[3]
Diagnostic method	Based on symptoms, microbial culture[1]
Prevention	Handwashing[1]
Treatment	Based on underlying cause[3]
Frequency	3–6 million per year (US)[1][3]

Conjunctivitis, also known as pink eye, is inflammation of the outermost layer of the white part of the eye and the inner surface of the eyelid.[4] It makes the eye appear pink or reddish.[1] Pain, burning, scratchiness, or itchiness may occur.[1] The affected eye may have increased tears or be "stuck shut" in the morning.[1] Swelling of the white part of the eye may also occur.[1] Itching is more common in cases due to allergies.[3] Conjunctivitis can affect one or both eyes.[1]

The most common infectious causes are viral followed by bacterial.[3] The viral infection may occur along with other symptoms of a common cold.[1] Both viral and bacterial cases are easily spread between people.[1] Allergies to pollen or animal hair are also a common cause.[3] Diagnosis is often based on signs and symptoms.[1] Occasionally, a sample of the discharge is sent for culture.[1]

Prevention is partly by handwashing.[1] Treatment depends on the underlying cause.[1] In the majority of viral cases, there is no specific treatment.[3] Most cases due to a bacterial infection also resolve without treatment; however, antibiotics can shorten the illness.[1][3] People who wear contact lenses and those whose infection is caused by gonorrhea or chlamydia should be treated.[3] Allergic cases can be treated with antihistamines or mast cell inhibitor drops.[3]

About 3 to 6 million people get conjunctivitis each year in the United States.[1][3] In adults, viral causes are more common, while in children, bacterial causes are more common.[3] Typically, people get better in one or two weeks.[1][3] If visual loss, significant pain, sensitivity to light, signs of herpes, or if symptoms do not improve after a week, further diagnosis and treatment may be required.[3] Conjunctivitis in a newborn, known as neonatal conjunctivitis, may also require specific treatment.[1]

Signs and symptoms

Red eye, swelling of the conjunctiva, and watering of the eyes are symptoms common to all forms of conjunctivitis. However, the pupils should be normally reactive, and the visual acuity normal.

Conjunctivitis is identified by irritation and redness of the conjunctiva. Except in obvious pyogenic or toxic/chemical conjunctivitis, a slit lamp (biomicroscope) is needed to confirm the diagnosis. Examination of the eyelid conjunctiva is usually more diagnostic than examination of the scleral conjunctiva.

Viral

Viral conjunctivitis

Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Its symptoms include excessive watering and itching. The infection usually begins in one eye but may spread easily to the other eye.

Viral conjunctivitis manifests as a fine, diffuse pinkness of the conjunctiva, which is easily mistaken for a ciliary infection of the iris (iritis), but corroborative signs on microscopy, particularly numerous lymphoid follicles on the tarsal conjunctiva, and sometimes a punctate keratitis are seen.

Allergic

An eye with allergic conjunctivitis showing conjunctival edema

Allergic conjunctivitis is inflammation of the conjunctiva due to allergy.[5] The specific allergens may differ among patients. Symptoms result from the release of histamine and other active substances by mast cells, and consist of redness (mainly due to vasodilation of the peripheral small blood vessels), swelling of the conjunctiva, itching, and increased production of tears.

Bacterial

An eye with bacterial conjunctivitis

Bacterial conjunctivitis causes the rapid onset of conjunctival redness, swelling of the eyelid, and a sticky discharge. Typically, symptoms develop first in one eye, but may spread to the other eye within 2–5 days. Conjunctivitis due to common pus-producing bacteria causes marked grittiness or irritation and a stringy, opaque, greyish or yellowish discharge that may cause the lids to stick together, especially after sleep. Severe crusting of the infected eye and the surrounding skin may also occur. The gritty or scratchy feeling is sometimes localized enough that patients may insist that they have a foreign body in the eye.

Common bacteria responsible for nonacute bacterial conjunctivitis are Staphylococcus, Streptococcus,[6] and Haemophilus species. Less commonly, Chlamydia spp. may be the cause.[7]

Typical membranous conjunctivitis

Bacteria such as Chlamydia trachomatis or Moraxella spp. can cause a nonexudative but persistent conjunctivitis without much redness. Bacterial conjunctivitis may cause the production of membranes or pseudomembranes that cover the conjunctiva. Pseudomembranes consist of a combination of inflammatory cells and exudates and adhere loosely to the conjunctiva, while true membranes are more tightly adherent and cannot be easily peeled away. Cases of bacterial conjunctivitis that involve the production of membranes or pseudomembranes are associated with Neisseria gonorrhoeae, β-hemolytic streptococci, and Corynebacterium diphtheriae. C. diphtheriae causes membrane formation in conjunctiva of unimmunized children.[8]

Chemical

Chemical eye injury may result when an acidic or alkaline substance gets in the eye.[9] Alkali burns are typically worse than acidic burns.[10] Mild burns produce conjunctivitis, while more severe burns may cause the cornea to turn white.[10] Litmus paper may be used to test for chemical causes.[9] When a chemical cause has been confirmed, the eye or eyes should be flushed until the pH is in the range 6–8.[10] Anaesthetic eye drops can be used to decrease the pain.[10]

Irritant or toxic conjunctivitis is primarily marked by redness. If due to a chemical splash, it is often present in only the lower conjunctival sac. With some chemicals, above all with caustic alkalis such as sodium hydroxide, necrosis of the conjunctiva marked by a deceptively white eye due to vascular closure may occur, followed by sloughing off of the dead epithelium. A slit lamp examination is likely to show evidence of anterior uveitis.

Other

An eye with chlamydial conjunctivitis

Inclusion conjunctivitis of the newborn is a conjunctivitis that may be caused by the bacterium Chlamydia trachomatis, and may lead to acute, purulent conjunctivitis.[11] However, it is usually self-healing.[11]

Causes

Infective conjunctivitis is most commonly caused by a virus.[3] Bacterial infections, allergies, other irritants, and dryness are also common causes. Both bacterial and viral infections are contagious, passing from person to person or spread through contaminated objects or water. Contact with contaminated fingers is a common cause of conjunctivitis. Bacteria may also reach the conjunctiva from the edges of the eyelids and the surrounding skin, from the nasopharynx, from infected eye drops or contact lenses, from the genitals or the bloodstream.[12] Infection by human adenovirus accounts for 65% to 90% of cases of viral conjunctivitis.[13]