出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/01/27 23:37:59」(JST)
| Conjunctivitis | |
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| Synonyms | pink eye, Madras eye |
| An eye with viral conjunctivitis | |
| Classification and external resources | |
| Specialty | Ophthalmology |
| ICD-10 | H10 |
| ICD-9-CM | 372.0 |
| DiseasesDB | 3067 |
| MedlinePlus | 001010 |
| eMedicine | emerg/110 |
| Patient UK | Conjunctivitis |
| MeSH | D003231 |
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[edit on Wikidata]
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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.[1] It makes the eye appear pink or reddish. There may also be pain, burning, scratchiness, or itchiness. The affected eye may have increased tears or be "stuck shut" in the morning. Swelling of the white part of the eye may also occur.[2] Itching of the eye is more common in cases due to allergies.[3] Conjunctivitis can affect one or both eyes.[2]
The most common infectious causes are viral followed by bacterial.[3] The viral infection may occur along with other symptoms of a common cold. Viral and bacterial cases are easily spread between people.[2] Allergies to pollen or animal hair is also a common cause.[3] Diagnosis is often based on signs and symptoms. Occasionally a sample of the discharge is sent for culture.[2]
Prevention is partly by handwashing. Treatment depends on the underlying cause.[2] In the majority of viral cases, there is no specific treatment.[3] Most cases due to a bacterial infection will also resolve without treatment; however, antibiotics can shorten the illness.[2][3] Those who wear contact lens and those with either gonorrhea or chlamydia as the cause should be treated. Allergic cases can be treated with antihistamine or mast cell inhibitor drops.[3]
About 3 to 6 million people get conjunctivitis each year in the United States.[2][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.[2][3] If there is visual loss, significant pain, sensitivity to light, signs of herpes, or a person is not improving after a week, further diagnosis and treatment may be required.[3] Conjunctivitis in a newborn, known as neonatal conjunctivitis, may also require specific treatment.[2]
Red eye, swelling of 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.
Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a common cold, and/or a sore throat. Its symptoms include excessive watering and itching. The infection usually begins with one eye, but may spread easily to the other.
Viral conjunctivitis shows a fine, diffuse pinkness of the conjunctiva, which is easily mistaken for the ciliary infection of iris (iritis), but there are usually corroborative signs on microscopy, particularly numerous lymphoid follicles on the tarsal conjunctiva, and sometimes a punctate keratitis.
Some other viruses that can infect the eye include Herpes simplex virus and Varicella zoster.[4]
Allergic conjunctivitis is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy.[5] Allergens differ among patients.
Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), swelling of the conjunctiva, itching, and increased lacrimation (production of tears). If this is combined with rhinitis, the condition is termed "allergic rhinoconjunctivitis". The symptoms are due to release of histamine and other active substances by mast cells, which stimulate dilation of blood vessels, irritate nerve endings, and increase secretion of tears.
Bacterial conjunctivitis causes the rapid onset of conjunctival redness, swelling of the eyelid, and mucopurulent discharge. Typically, symptoms develop first in one eye, but may spread to the other eye within 2–5 days. Bacterial conjunctivitis due to common pyogenic (pus-producing) bacteria causes marked grittiness/irritation and a stringy, opaque, greyish or yellowish mucopurulent 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 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.[citation needed] Common bacteria responsible for non-acute bacterial conjunctivitis are Staphylococci, Streptococci,[6] Haemophilus sp. Less commonly Chlamydia trachomatis is involved.[7]
Bacteria such as Chlamydia trachomatis or Moraxella can cause a non-exudative 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 are loosely adherent 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 C. diphtheriae. Corynebacterium diphtheriae causes membrane formation in conjunctiva of non-immunized children.[citation needed]
Chemical eye injury is due to either an acidic or alkali substance getting in the eye.[8] Alkalis are typically worse than acidic burns.[9] Mild burns will produce conjunctivitis, while more severe burns may cause the cornea to turn white.[9] Litmus paper is an easy way to rule out the diagnosis by verifying that the pH is within the normal range of 7.0—7.2.[8] Large volumes of irrigation is the treatment of choice and should continue until the pH is 6—8.[9] Local anaesthetic eye drops can be used to decrease the pain.[9]
Irritant or toxic conjunctivitis show primarily marked redness. If due to splash injury, it is often present in only 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.
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.[10] However, it is usually self-healing.[10]
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.
Conjunctivitis, when caused by an infection, is most commonly caused by a viral infection.[11] Bacterial infections, allergies, other irritants, and dryness are also common causes. Both bacterial and viral infections are contagious and passed from person to person, but can also spread through contaminated objects or water.
The most common cause of viral conjunctivitis is adenoviruses (see: Adenoviral keratoconjunctivitis).[12] Herpetic keratoconjunctivitis (caused by herpes simplex viruses) can be serious and requires treatment with acyclovir. 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.[13]
The most common causes of acute bacterial conjunctivitis are Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae.[12] Though very rare, hyperacute cases are usually caused by Neisseria gonorrhoeae or N. meningitidis. Chronic cases of bacterial conjunctivitis are those lasting longer than 3 weeks, and are typically caused by Staphylococcus aureus, Moraxella lacunata, or gram-negative enteric flora.
Conjunctivitis may also be caused by allergens such as pollen, perfumes, cosmetics, smoke,[14] dust mites, Balsam of Peru,[15] and eye drops.[16]
Conjunctivitis is part of the triad of reactive arthritis, which is thought to be caused by autoimmune cross-reactivity following certain bacterial infections. Reactive arthritis is highly associated with HLA-B27. Conjunctivitis is associated with the autoimmune disease relapsing polychondritis.[17][18]
Cultures are not often taken or needed as most cases resolve either with time or typical antibiotics. Swabs for bacterial culture are necessary if the history and signs suggest bacterial conjunctivitis but there is no response to topical antibiotics. Viral culture may be appropriate in epidemic case clusters.
A patch test is used to identify the causative allergen in the case where conjunctivitis is caused by allergy.[19]
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.
Classification can be either by cause or by extent of the inflamed area.
Blepharoconjunctivitis is the dual combination of conjunctivitis with blepharitis (inflammation of the eyelids).
Keratoconjunctivitis is the combination of conjunctivitis and keratitis (corneal inflammation).
There are more serious conditions that can present with a red eye such as infectious keratitis, angle-closure glaucoma, or iritis. These conditions require the urgent attention of an ophthalmologist. Signs of such conditions include decreased vision, significantly increased sensitivity to light, inability to keep eye open, a pupil that does not respond to light, or a severe headache with nausea.[20] 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 consider other diseases such as glaucoma, uveitis, keratitis and even meningitis or carotico-cavernous fistula.
A more comprehensive differential diagnosis for the red or painful eye includes:[20]
The best effective prevention is hygiene and not rubbing the eyes by infected hands. Vaccination against adenovirus, haemophilus influenzae, pneumococcus, and neisseria meningitidis is also effective.[citation needed]
Povidone-iodine eye solution has been found to prevent conjunctivitis following birth.[21] As it is less expensive it is being more commonly used for this purpose globally.[21]
Conjunctivitis resolves in 65% of cases without treatment, within two to five days. The prescription of antibiotics is not necessary in most cases.[22]
Viral conjunctivitis usually resolves on its own and does not require any specific treatment.[11] Antihistamines (e.g., diphenhydramine) or mast cell stabilizers (e.g., cromolyn) may be used to help with the symptoms.[11] Povidone iodine has been suggested as a treatment, but as of 2008 evidence to support it was poor.[23]
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, nonsteroidal anti-inflammatory medications and antihistamines may be prescribed. Persistent allergic conjunctivitis may also require topical steroid drops.
Bacterial conjunctivitis usually resolves without treatment.[11] Topical antibiotics may be needed only if no improvement is observed after three days.[24] In people who received no antibiotics, recovery was in 4.8 days, with immediate antibiotics it was 3.3 days, and with delayed antibiotics 3.9 days. No serious effects were noted either with or without treatment.[25] As they do speed healing in bacterial conjunctivitis, their use is also reasonable.[26]
In those who wear contact lenses, are immunocompromised, have disease which is thought to be due to chlamydia or gonorrhea, have a fair bit of pain, or who have lots of discharge, antibiotics are recommended.[11] Gonorrhea or chlamydia infections require both oral and topical antibiotics.[11]
When appropriate, the choice of antibiotic varies, differing based on the cause (if known) or the likely cause of the conjunctivitis. Fluoroquinolones, sodium sulfacetamide, or trimethoprim/polymyxin may be used, typically for 7–10 days.[12] Cases of meningococcal conjunctivitis can also be treated with systemic penicillin, as long as the strain is sensitive to penicillin.
When investigated as a treatment, Povidone-iodine ophthalmic solution has also been observed to have some effectiveness against bacterial and chlamydial conjunctivitis, with a possible role suggested in locations where topical antibiotics are unavailable or costly.[27]
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. People with chemically induced conjunctivitis should not touch their eyes, regardless of whether or not their hands are clean, as they run the risk of spreading the condition to another eye.
Conjunctivitis is the most common eye disease.[28]
A former superintendent of the Regional Institute of Ophthalmology in the city of Madras (the present-day Chennai) in India, Kirk Patrick, was the first to have found the adenovirus that caused conjunctivitis, leading to the name "Madras eye" for the disease.[29]
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| リンク元 | 「結膜充血」「conjunctival injection」 |
| 関連記事 | 「conjunctival」「hyperemia」 |