The conjunctiva is a thin layer of cells, or membrane, between the inner surface of the eyelids and the whites of the eyes.
Inflammation causes tiny blood vessels, or capillaries, in the conjunctiva to become more prominent. This causes discomfort and a pink or red appearance that can last from a few days to several weeks.
Causes include irritation, allergy, and infection. This article will focus mainly on infective conjunctivitis.
Here are some key points about conjuncitivitis, or pink eye. More detail is in the main article.
- Pink eye can result from an allergy, an irriation, or an infection.
- A virus or a bacteria can cause an infection. Sometimes it is linked to a sexually transmitted infection (STI).
- Antibiotics are sometimes used, but they will not help if the cause is a virus.
- Symptoms normally last up to 2 weeks, but they can persist for longer.
- It is important to wash hands carefully and not to share personal items, such as towels, as this can spread the infection.
Inflammation can result from different kinds of bacteria or viruses.
Signs and symptoms may include the following:
- redness, because of irritation and widening of the tiny blood vessels in the conjunctiva
- a shiny, watery eye, as the tear glands become overactive
- a sticky or crusty coating on the eyelashes, especially on waking after a long sleep, because the infection produces mucus
- soreness and "grittiness," like sand in the eye
- swelling, due to inflammation or rubbing
The redness and soreness may affect one eye first, then spread to the other.
There may also be:
Swollen lymph nodes: The lymph node in front of the ear becomes swollen and slightly tender. It may feel like a button under the skin. The lymph node is part of the body's immune system, which fights infection.
A person should see a doctor if:
- the eye is very red and painful
- vision is affected
- the eye becomes very sensitive to light
These symptoms may indicate a more serious condition.
Newborns often develop pink eye. Symptoms include red, tender, and puffy eyelids. Urgent medical attention is needed to prevent complications and identify and treat any underlying conditions.
Nearly half of cases of infective conjunctivitis resolve without medical treatment within 2 weeks, and a doctor may suggest watching and waiting.
They may prescribe eye drops with decongestants or antihistamine to reduce the symptoms of swelling and irritation.
Antibiotics for infective conjunctivitis
Antibiotics will not help if the cause is viral, and even a bacterial infection may last up to a month with antibiotics. Some studies show that for 1 in 10 patients, antibiotics may help speed up recovery.
Treatment may include eyedrops containing antibiotics or an antihistamine.
However, antibiotics may be prescribed if symptoms are severe or have lasted more than 2 weeks. A doctor may give antibiotic eye drops just in case they will help.
The most commonly prescribed antibiotics for infective conjunctivitis are:
These are eye drops or ointment, administered straight onto the eye. Dosage depends on the type. Ointments may be easier to use than eye drops with an infant or young child.
Vision can become blurry shortly after using eye drops. Make sure you can see clearly before driving or operating machinery. If symptoms do not improve or there is pain or blurry vision you should return to your doctor.
A number of home remedies can help ease symptoms and possibly speed up recovery.
Contact lenses: Avoid using lenses until at least 24 hours after antibiotic treatment finishes, then throw away and replace the lenses, lens case, and solution
Artificial tear eye drops can be bought over the counter (OTC) or online to help relieve soreness and stickiness.
A wash cloth soaked in warm water can be used several times a day, to gently clean away any sticky substances. Do this gently, to avoid irritating the eyes. Use a clean washcloth for each eye.
Regular handwashing with warm water and soap will help prevent spreading the infection.
Warm compresses can soothe discomfort. Soak a clean, lint-free cloth in warm water, wring it out, then apply gently to the closed eye.
The following symptoms may indicate a more serious condition. They require immediate medical help:
- pain in the eye
- sensitivity to light, or photophobia
- loss of vision
- very intense redness
Usually, when the eyes look and feel normal again, the condition is no longer contagious.
Infection in the eye can be due to a virus or bacteria.
Viruses that cause conjunctivitis include adenoviruses and some types of herpes virus.
Bacterial causes include Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus species, and, less commonly, Chlamydia trachomatis.
Bacterial conjunctivitis is sometimes caused by a sexually transmitted infection (STI), such as Chlamydia. If symptoms do not disappear after a month, this may indicate an STI. Most other types of bacterial conjunctivitis will resolve more quickly with treatment.
Infective conjunctivitis is extremely contagious and can easily be passed on to another person.
Causes in newborns
Pink eye in newborns can be due to infection, irritation, or a blocked tear duct. The cause can be hard to determine, because each type produces similar symptoms.
Sometimes bacteria or a virus is passed on from the mother during delivery, even if she does not have symptoms. The bacteria or virus may be related to an STI.
The virus that causes oral and genital herpes can also be transmitted at birth and appear as conjunctivitis.
In some cases, pink eye occurs as a reaction eyedrops given at birth, to prevent infection. In this case the symptoms will normally pass after 24 to 36 hours.
Other causes of red eyes
Reddened eyes can also be a symptom of:
Blepharitis: This is a common inflammation of the eyelids that causes redness, irritation, and itching. There will also be dandruff-like scales on the eyelashes. Blepharitis is not contagious.
Acute glaucoma: This is a rare form of glaucoma, in which pressure builds up in the eye. Symptoms can appear quickly and include pain, red eyes, and vision loss, which may become permanent without treatment.
Keratitis: The cornea becomes inflamed and possibly ulcerated. If scarring of the cornea occurs, this can lead to permanent loss of vision. The cornea is the transparent part at the front of the eye.
Iritis: The iris becomes inflamed. Untreated iritis can cause the iris to become stuck to the front surface of the lens, preventing fluid draining from the pupil. This can eventually lead to permanent eye damage. The iris is the colored part of the eye, the part that controls the amount of light that enters into the eye.
There are three different types of conjunctivitis, depending on the cause.
Chemical or irritant conjunctivitis: If something irritates the eye, it can become inflamed and sore. The irritant could be an eyelash that is misdirected into the eye, or chlorine after a swimming in a pool.
Allergic conjunctivitis: This happens when an allergen comes into contact with the eye, such as dust mites, pollen, or animal fur. An allergen makes the body's immune system overreact, causing irritation and inflammation.
Infective conjunctivitis: A bacteria or virus causes an infection, making the eyes red or pink and watery. There can be sticky coating on the eyelashes and mucus in the eyes.
A doctor can diagnose conjunctivitis by looking at the signs and symptoms and asking some questions. Treatment for irritant and allergic conjunctivitis is different from that for an infection.
Some cases of infective conjunctivitis resolve within a a few days to 2 weeks without treatment, but some may take up to a month. For bacterial conjunctivitis, antibiotics can shorten recovery time and reduce the spread of infection to others.
If symptoms persist for 2 weeks or more, the person should return to see their doctor, who will reassess the diagnosis and adjust the treatment.
The doctor may take a swab from the infected eye, for testing in a lab. Knowing what type of bacteria is causing the infection will enable them to prescribe an appropriate treatment. However, most doctors do not do this test.
The risk of catching or passing on infective conjunctivitis can be reduced by:
- not touching or rubbing the eyes
- washing the hands frequently with soap and warm water, or use hand sanitizer
- always removing contact lenses at night, and following instructions about lens hygiene
- keeping eyeglasses clean
- not sharing personal items such as towels and pillows, make up and contact lenses with other people
- using goggles in a swimming pool, and not swimming if you have an infection
After the infection has gone, it is a good idea to throw away any contact lens solution and eye make up.
The risk of irritant and allergic conjuncitivitis can be reduced by avoiding potential or known irritants and allergens.
This includes making sure rooms are well ventilated, air conditioning units are cleaned and maintained, and avoiding smoky atmospheres.
The risk of complications from infective conjunctivitis cause by bacteria or a virus is small. However, if pink eye is a symptom of an underlying condition, such as an STI, complications are possible.
Newborns have a higher risk of complications. Neonatal infective conjunctivitis can be severe and progress rapidly. In very severe cases, it may affect vision.
In rare cases, other types of bacterial conjunctivitis may also cause complications for a newborn.
- Meningitis: A potentially fatal illness in which the meninges, a layer of cells that covers the brain and spinal cord, becomes infected.
- Cellulitis: A bacterial infection of the deepers layers of skin and the fat and soft tissues that are under the skin.
- Septicemia, or blood poisoning: Bacteria enter the bloodstream and attack the tissues in the body.
However, most infants make a full recovery from infective conjunctivitis with no complications.