Eyes – Infections (conjunctivitis)

Conjunctivitis (commonly called "pink eye" or "Madras eye") is an acute inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), most commonly due to an allergic reaction or an infection (usually viral, but sometimes bacterial). While this article relates generally to humans, animals such as canines (dogs) and cattle can experience this condition.

Signs and symptoms

Redness (hyperaemia), irritation (chemosis) and watering (epiphora) of the eyes are symptoms common to all forms of conjunctivitis.

Allergic conjunctivitis

Allergic conjunctivitis is typically itchy, sometimes distressingly so, and often involves some eye swelling. Chronic allergy often causes just itching or irritation.

Allergic conjunctivitis shows pale watery swelling or edema of the conjunctiva and sometimes the whole eyelid, often with a ropy, non-purulent mucoid discharge. There is variable redness.

Viral conjunctivitis

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

Viral conjunctivitis, commonly known as "pink eye", shows a fine diffuse pinkness of the conjunctiva which is easily mistaken for the 'ciliary injection' of iritis, but there are usually corroborative signs on bio microscopy, particularly numerous lymphoid follicles on the tarsal conjunctiva, and sometimes a punctate keratitis.

Bacterial conjunctivitis

Bacterial conjunctivitis due to the common pyogenic (pus-producing) bacteria causes marked grittiness/irritation and a stringy, opaque, grey or yellowish mucopurulent discharge (mucus, gowl, goop, gunk, eye crust, or other regional names, officially known as 'gound') that may cause the lids to stick together (matting), especially after sleeping. Another symptom that could be caused by bacterial conjunctivitis is severe crusting of the infected eye and the surrounding skin. However discharge is not essential to the diagnosis, contrary to popular belief. Bacteria such as Chlamydia trachomatis or Moraxella can cause a non-exudative but persistent conjunctivitis without much redness. The gritty and/or scratchy feeling is sometimes localized enough for patients to insist they must have a foreign body in the eye. The more acute pyogenic infections can be painful. Like viral conjunctivitis, it usually affects only one eye but may spread easily to the other eye. However, it is dormant in the eye for three days before the patient shows signs of symptoms.

Pyogenic bacterial conjunctivitis shows an opaque purulent discharge, a very red eye, and on bio microscopy there are numerous white cells and desquamated epithelial cells seen in the tear duct along the lid margin. The tarsal conjunctiva is a velvety red and not particularly follicular. Non-pyogenic infections can show just mild infection and be difficult to diagnose. Scarring of the tarsal conjunctiva is occasionally seen in chronic infections, especially in trachoma.

Chemical conjunctivitis

Irritant or toxic conjunctivitis is irritable or painful when the infected eye is pointed far down or far up. Discharge and itch are usually absent. This is the only group in which severe pain may occur.

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

Other

Inclusion conjunctivitis of the newborn (ICN) is a conjunctivitis that may be caused by the bacteria Chlamydia trachomatis, and may lead to acute, purulent conjunctivitis. However, it is usually self-healing.

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 have any confidence in the diagnosis. Examination of the tarsal conjunctiva is usually more diagnostic than the bulbar conjunctiva.

Causes

Conjunctivitis is most commonly caused by viral infection, often adenovirus, but bacterial infections, allergies, other irritants and dryness are also common etiologies for its occurrence, eg particles of faeces. Both bacterial and viral infections are contagious, but usually don't require treatment. A rare exception is Herpetic keratoconjunctivitis, which requires treatment antiviral aciclovir. Commonly, conjunctival infections are passed from person-to-person due to lack of hygiene measures.

Differential diagnosis

Conjunctivitis symptoms and signs are relatively non-specific. Even after bio microscopy, laboratory tests are often necessary if proof of etiology is needed.

A purulent discharge (a whitish-yellow, yellow or yellow-brown substance more commonly known as pus) strongly suggests bacterial cause from fecal matter, unless there is known exposure to toxins. Pink eye can also be caused by bacteria from faeces, pet hair, or by smoke or other fumes. Infection with Neisseria gonorrhoeae should be suspected if the discharge is particularly thick and copious.

Itching (rubbing eyes) is the hallmark symptom of allergic conjunctivitis. Other symptoms include past history of eczema, or asthma.

A diffuse, less "injected" conjunctivitis (looking pink rather than red) suggests a viral cause, especially if numerous follicles are present on the lower tarsal conjunctiva on bio microscopy.

Scarring of the tarsal conjunctiva suggests trachoma, especially if seen in endemic areas, if the scarring is linear (von Arlt's line), or if there is also corneal vascularisation.

Clinical tests for lagophthalmos, dry eye (Schirmer test) and unstable tear film may help distinguish the various types of pink eye.

Other symptoms including pain, blurring of vision and photophobia should not be prominent in conjunctivitis. Fluctuating blurring is common, due to tearing and mucoid discharge. Mild photophobia is common. However, if any of these symptoms are prominent, it is important to exclude other diseases such as glaucoma, uveitis, keratitis and even meningitis or caroticocavernous fistula.

Many people who have conjunctivitis have trouble opening their eyes in the morning because of the dried mucus on their eyelids. There is often excess mucus over the eye after sleeping for an extended period.

Diagnosis

These are done infrequently because most cases of conjunctivitis are treated empirically and (eventually) successfully, but often only after running the gamut of the common possibilities.

Swabs for bacterial culture are necessary if the history and signs suggest bacterial conjunctivitis, but there is no response to topical antibiotics. Research studies indicate that many bacteria implicated in low-grade conjunctivitis are not detected by the usual culture methods of medical microbiology labs, so negative results are common. Viral culture may be appropriate in epidemic case clusters. Conjunctival scrapes for cytology can be useful in detecting chlamydial and fungal infections, allergy and dysplasia, but are rarely done because of the cost and the general lack of laboratory staff experienced in handling ocular specimens. Conjunctival incisional biopsy is occasionally done when granulomatous diseases (e.g., sarcoidosis) or dysplasia are suspected.

Management

Conjunctivitis resolves, in 65% of cases, within 2 – 5 days.

Allergic

For the allergic type, cool water poured over the face with the head inclined downward constricts capillaries, and artificial tears sometimes relieve discomfort in mild cases. In more severe cases, non-steroidal anti-inflammatory medications and antihistamines may be prescribed. Persistent allergic conjunctivitis may also require topical steroid drops.

Bacterial

Bacterial conjunctivitis usually resolves without treatment. Antibiotics eye drops or ointment are thus only needed if no improvement is observed after 3 days. Even though antibiotics speed recovery time ( from 4.6 days to 3.3 days) no serious effects were noted either with or without treatment.

Viral

Although there is no specific treatment for viral conjunctivitis, symptomatic relief may be achieved with cold compresses and artificial tears. People are often advised to avoid touching their eyes or sharing towels and washcloths.

Chemical

Conjunctivitis due to chemicals is treated via irrigation with Ringer's lactate or saline solution. Chemical injuries (particularly alkali burns) are medical emergencies as they can lead to severe scarring, and intraocular damage.