Conjunctivitis
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Conjunctivitis is an inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), often due to infection. There are three common varieties of conjunctivitis, viral, allergic, and bacterial. Viral and bacterial conjunctivitis are contagious. Other causes of conjunctivitis include thermal and ultraviolet burns, chemicals, toxins, overuse of contact lenses, foreign bodies, vitamin deficiency, dry eye, dryness due to inadequate lid closure, exposure to chickens infected with Newcastle disease, epithelial dysplasia (pre-cancerous changes), and some conditions of unknown cause such as sarcoidosis.
Blepharoconjunctivitis is the combination of conjunctivitis with blepharitis.
Keratoconjunctivitis is the combination of conjunctivitis and keratitis.
An eye with Viral conjunctivitis
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Epidemiology
Viral conjunctivitis is due to spread by aerosol or contact of a variety of contagious viruses, including many that cause the 'common cold', so that it is often associated with upper respiratory tract symptoms. Clusters of cases have been due to transfer on ophthalmic instruments which make contact with the eye (eg, tonometers) and not adequately sterilised.
Allergic conjunctivitis occurs more frequently among those with allergic conditions, with the symptoms having a seasonal correlation. It can also be caused by allergies to substances such as cosmetics, perfume, protein deposits on contact lenses, or drugs. It usually affects both eyes, and is accompanied by swollen eyelids.
Bacterial conjunctivitis is most often caused by pyogenic bacteria such as Staphylococcus or Streptococcus from the patient's own skin or respiratory flora. Others are due to infection from the environment or from other people, usually by touch (especially in children), but occasionally via eye makeup or facial lotions.
Irritant, toxic, thermal and chemical conjunctivitis are associated with exposure to the specific agents, such as flame burns, irritant plant saps, irritant gases (eg, chlorine or hydrochloric acid ('pool acid') fumes), natural toxins (eg, ricin picked up by handling castor oil bean necklaces), or splash injury from an enormous variety of industrial chemicals, the most dangerous being strongly alkaline materials.
Xerophthalmia is a term that usually implies a destructive dryness of the conjunctival epithelium due to dietary vitamin A deficiency - a condition virtually forgotten in developed countries, but still causing much damage in developing countries. Other forms of dry eye are associated with ageing, poor lid closure, scarring from previous injury, or autoimmune diseases such as rheumatoid arthritis, and these can all cause chronic conjunctivitis.
Diagnosis
Symptoms
Redness, irritation and watering of the eyes are symptoms common to all forms of conjunctivitis. Itch is variable.
Acute allergic conjunctivitis is typically itchy, sometimes distressingly so, and the patient often complains of some lid swelling. Chronic allergy often causes just itch or irritation, and often much frustration because the absence of redness or discharge leads to accusations of hypochondria.
Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Its symptoms include watery discharge, variable itch, and the fact that the infection usually begins with one eye, but may spread easily to the fellow eye.
Bacterial conjunctivitis due to the common pyogenic bacteria causes marked grittiness/irritation and a stringy, opaque, grey or yellowish mucoid discharge (gowl or other regional names) that may cause the lids to stick together (mattering), especially after sleeping. However discharge is not essential to the diagnosis, contrary to popular belief. Many other bacteria (eg, Chlamydia, Moraxella) can cause a non-exudative but very persistent conjunctivitis without much redness. The gritty feeling is sometimes localised 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.
Irritant or toxic conjunctivitis is irritable or painful. Discharge and itch are usually absent. This is the only group in which severe pain may occur.
Signs
The patient should be examined in a well lit room. Injection (redness) of the conjunctiva on one or both eyes should be apparent, but may be quite mild. 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.
Allergic conjunctivitis shows pale watery swelling or oedema of the conjunctiva and sometimes the whole eyelid, often with a ropy, non-purulent mucoid discharge. There is variable redness.
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 biomicroscopy, particularly numerous lymphoid follicles on the tarsal conjunctiva, and sometimes a punctate keratitis.
Pyogenic bacterial conjunctivitis shows an opaque purulent discharge, a very red eye, and on biomicroscopy there are numerous white cells and desquamated epithelial cells seen in the 'tear gutter' along the lid margin. The tarsal conjunctiva is a velvety red and not particularly follicular. Non-pyogenic infections can show just mild injection and be difficult to diagnose. Scarring of the tarsal conjunctiva is occasionally seen in chronic infections, especially in trachoma.
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.
Differential diagnosis
Note that the symptoms and signs are relatively non-specific in conjunctivitis. Even after biomicrosopy, laboratory tests are often necessary if proof of aetiology is required.
Prominent itch and pale watery swelling (edema) of the conjunctiva or eyelids suggests allergy.
A purulent discharge strongly suggests bacterial cause, unless there is known exposure to toxins. Infection with Neiserria gonorrhea should be suspected if the discharge is particularly thick and copious.
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 biomicroscopy.
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 dry 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 carotico-cavernous fistula.
Investigations
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 & 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 (eg, sarcoidosis) or dysplasia are suspected.
Treatment
Conjunctivitis sometimes requires medical attention. The appropriate treatment depends on the cause of the problem. For the allergic type, cool compresses and artificial tears sometimes relieve discomfort in mild cases. In more severe cases, non-steroidal anti-inflammatory medications and antihistamines may be prescribed. Some patients with persistent allergic conjunctivitis may also require topical steroid drops. Bacterial conjunctivitis is usually treated with antibiotic eye drops or ointments that cover a broad range of bacteria.
There is no cure for viral conjunctivitis. However, the symptoms can be relieved with cool compresses and artificial tears. For the worst cases, topical steroid drops may be prescribed to reduce the discomfort from inflammation. Viral conjunctivitis usually resolves within 3 weeks.
Conjunctivitis due to burns, toxic and chemical require careful wash-out with saline, especially beneath the lids, and may require topical steroids. The more acute chemical injuries are medical emergencies, particularly alkali burns, which can lead to severe scarring, intraocular damage or even loss of the eye. Fortunately such injuries are uncommon, but the severity of the injury is often not recognised by the doctor or health worker initiating treatment.
External links
- Conjunctivitis article on KidsHealth.org (http://kidshealth.org/parent/infections/eye/conjunctivitis.html)
- Conjunctivitis article on StLukesEye.com (http://www.stlukeseye.com/Conditions/Conjunctivitis.asp) Warning: contains graphic, disturbing image
- Conjunctivitis article from the American Academy of Family Physicians (http://www.aafp.org/afp/980215ap/morrow.html) Warning: contains graphic, disturbing images
- eMedicine Health (http://www.emedicinehealth.com/articles/14613-1.asp)es:Conjuntivitis
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