Conjunctivitis


Conjunctivitis, also known as pink eye, is inflammation of the conjunctiva, the thin and clear layer that covers the white surface of the eye and the inner eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may occur. The affected eye may have increased tears or be stuck shut in the morning. Swelling of the sclera may also occur. Itching is more common in cases that are due to allergies. Conjunctivitis can affect one or both eyes.
The most common infectious causes in adults are viral, whereas in children bacterial causes predominate. The viral infection may occur along with other symptoms of a common cold. Both viral and bacterial cases are easily spread among people. Allergies to pollen or animal hair are also a common cause. Diagnosis is often based on signs and symptoms. Occasionally a sample of the discharge is sent for culture.
Prevention is partly by handwashing. Treatment depends on the underlying cause. In the majority of viral cases, there is no specific treatment. Most cases that are due to a bacterial infection also resolve without treatment; however antibiotics can shorten the illness. People who wear contact lenses and those whose infection is caused by gonorrhea or chlamydia should be treated. Allergic cases can be treated with antihistamines or mast cell inhibitor drops.
Between three and six million people get acute conjunctivitis each year in the United States. Typically they get better in one or two weeks. If visual loss, significant pain, sensitivity to light or signs of herpes occur, or if symptoms do not improve after a week, further diagnosis and treatment may be required. Conjunctivitis in a newborn, known as neonatal conjunctivitis, may also require specific treatment.

Signs and symptoms

, 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 should be normal.
Conjunctivitis is identified by inflammation of the conjunctiva, manifested by irritation and redness. Examination using a slit lamp may improve diagnostic accuracy. Examination of the palpebral conjunctiva, which overlies the inner aspects of the eyelids, is usually more diagnostic than examination of the bulbal conjunctiva, which overlies the sclera.

Viral

Approximately 80% of cases of conjunctivitis in adults and less than 20% in children are due to viruses, with 65% to 90% of these cases being attributed to adenoviruses.
Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, or a sore throat. Other associated signs may include pre-auricular lymph node swelling and contact with another person with a red eye. Eye pain may be present if the cornea is also involved. Its symptoms include excessive watering and itching. The discharge in viral conjunctivitis is usually watery. 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 may be mistaken for iritis, but corroborative signs on microscopy, particularly numerous lymphoid follicles on the tarsal conjunctiva, and sometimes a punctate keratitis are seen.

Allergic

is inflammation of the conjunctiva due to allergy. 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, swelling of the conjunctiva, itching, and increased production of tears.

Bacterial

Bacteria are responsible for approximately 70% of conjunctivitis in children and less than 20% of cases in adults. Common bacteria responsible for bacterial conjunctivitis are Staphylococcus including Staph aureus, Streptococcus such as strep pneumoniae, Haemophilus species and Moraxella catarrhalis. Less commonly, Chlamydia spp. and Niesseria species may be the cause. Infection with Escherichia coli may also cause conjunctivitis, particularly in the neonatal subtype ophthalmia neonatorum. Bacterial conjunctivitis usually causes a 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.
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 the conjunctiva of unimmunized children.

Chemical

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

Biomarkers

Omics technologies have been used to identify biomarkers that inform on the emergence and progression of conjunctivitis. For example, in chronic inflammatory cicatrizing conjunctivitis, active oxylipins, lysophospholipids, fatty acids, and endocannabinoids alterations, from which potential biomarkers linked to inflammatory processes were identified.

Other

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

Causes

Viruses are the most common cause of infectious conjunctivitis. 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 surrounding skin, from the nasopharynx, from infected eye drops or contact lenses, from the genitals, or from the bloodstream. Infection by human adenovirus accounts for 65% to 90% of cases of viral conjunctivitis.

Viral

are the most common cause of viral conjunctivitis. Herpetic keratoconjunctivitis, caused by herpes simplex viruses, can be serious and requires treatment with aciclovir. Acute hemorrhagic conjunctivitis is a highly contagious disease caused by one of two enteroviruses, enterovirus 70 and coxsackievirus A24. These were first identified in an outbreak in Ghana in 1969 and have spread worldwide since then, causing several epidemics.

Bacterial

The most common causes of acute bacterial conjunctivitis are Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae. Though very rare, hyperacute cases are usually caused by Neisseria gonorrhoeae or Neisseria meningitidis. Chronic cases of bacterial conjunctivitis are those lasting longer than 3 weeks and are typically caused by S. aureus, Moraxella lacunata, or Gram-negative enteric flora.

Allergic

Conjunctivitis may also be caused by allergens such as pollen, perfumes, cosmetics, smoke, dust mites, Balsam of Peru, or eye drops. The most frequent cause of conjunctivitis is allergic conjunctivitis, and it affects 15% to 40% of the population. Allergic conjunctivitis accounts for 15% of eye related primary care consultations; most including seasonal exposures in the spring and summer or perpetual conditions.

Other

Cultures are not often taken or needed, as most cases resolve either with time or typical antibiotics. If bacterial conjunctivitis is suspected, but no response to topical antibiotics is seen, swabs for bacterial culture should be taken and tested. Viral culture may be appropriate in epidemic case clusters.
A patch test is used to identify the causative allergen in allergic conjunctivitis.
Although conjunctival scrapes for cytology can be useful in detecting chlamydial and fungal infections, allergies, and dysplasia, they are rarely done because of the cost and the general dearth of laboratory staff experienced in handling ocular specimens. Conjunctival incisional biopsy is occasionally done when granulomatous diseases or dysplasia are suspected.