It can be caused by inflammation of any structure of the eye
In severe cases, it may threaten sight or be a sign of an underlying disorder
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What is red eye?
A red eye is usually a short-lived, harmless problem. However, there are times when it may threaten your sight or may be a sign of a severe underlying disorder.
What can cause a red eye?
A red eye may be caused by inflammation of any structure from the front to the back of the eye so we will consider these structures from front to back. This is not a complete list of all the causes of a red eye, but includes important information about the more common and severe conditions.
Conditions affecting the eyelids
Infections
Infection of the eyelids, called blepharitis is a common, chronic infection of the meibomian glands (glands on the edge of the eyelids) or the eyelash follicles caused by a bacterial infection. It often affects both eyes. Oils from the meibomian glands are changed into acid-like compounds which irritate the eye and cause it to turn red.
There is usually history of discomfort or “dry-eye” symptoms. There is also crusting of the eyelids on waking in both eyes. The symptoms may move between the eyes and be of varying severity. The condition can last weeks or months.
There is no loss of vision. Irregularity of the edges of the eyelid may be visible. The treatment includes eyelid cleansing with baby shampoo or a commercial preparation, or oral and topical antibiotics. Recurrences are common.
Styes
A stye, also called an acute chalazion, is a red mass on the eyelid and may cause a red eye. It may respond to oral antibiotics and warm compresses. However, opening up the stye and draining the pus is the most effective treatment for acutely inflamed and chronic lesions. Less severe styes will go away on their own without treatment.
Redness in the white of the eye (the conjunctiva)
One of the most common causes of a sudden red eye is a subconjunctival haemorrhage. This is caused by bleeding under the white part of the eye (conjunctiva) and not by inflammation. It is seldom anything to worry about. It usually occurs spontaneously or occasionally by trauma.
Conjunctivitis
Conjunctivitis may be allergic or infective. It is a common condition, which affects both eyes. There is an associated watery or mucous discharge and there is no loss of vision or significant pain.
Allergic conjunctivitis
Allergic conjunctivitis may occur in someone with a history of hayfever, eczema or asthma. It may be seasonal or can be associated with a facial cream or other cosmetics or soaps used on the face or head.
Isolation of the cause of the allergy is difficult but careful history taking and elimination of a new cosmetic or shampoo may be helpful. Treatment with antihistamine eyedrops is usually effective. Steroid eyedrops are effective but may also cause loss of vision so you should be seen regularly by an ophthalmologist if you are using this treatment.
Infective conjunctivitis
Infective conjunctivitis is usually viral but may be bacterial. Viral conjunctivitis is often caused by a close relative of the ‘flu virus and is therefore often accompanied by ‘flu-like symptoms. It is highly contagious and usually occurs in epidemics.
The symptoms and signs are very similar to allergic conjunctivitis except that there may be swelling of the lymph glands and it may be associated with ‘flu-like symptoms.
The illness is brief and treatment is aimed at the relief of symptoms. Topical over the counter astringent preparations and lubricants may offer some relief, and once again steroids are effective but risky. Young children need special attention for infective conjunctivitis as there may be severe consequences.
Pterygium
A pterygium can cause a localised area of redness and is caused by sun and dust exposure. These are common in South Africa.
It starts as a small grey opacity on the nose side of the eye, which then grows over the cornea (the clear part of the front of the eye). A pterygium goes through active, inflamed phases and quiet phases over months to years as it slowly grows onto the cornea. Lubricants and sunglasses provide relief of symptoms, but removal by surgery is the only cure. Recurrences are fairly common.
Scleritis
Scleritis presents with an extremely painful, single red eye. The redness may be localised or it may be more diffuse. There may be mild to severe visual loss in the affected eye. Scleritis may be associated with an underlying disorder such as rheumatoid arthritis. This means that patients with scleritis should be referred for investigation for an underlying disorder.
Conditions affecting the cornea
The cornea is very well supplied with pain receptors, as anyone who has ever stuck a finger in their eye knows. Therefore any disruption of the membrane over the cornea (the corneal epithelium) causes exposure of these nerve endings and severe pain.
Arc eye
Arc eye is an extremely painful condition caused by arc welding without an appropriate visor. Multiple small burns to the cornea caused by the intense light from the welding torch cause the pain. The pain settles when the cornea has healed, usually within 24 hours.
Foreign bodies
Foreign bodies on the cornea are also extremely uncomfortable. Angle grinding without protective eyewear is a common cause in workmen. The foreign body is removed with a sterile hypodermic needle after the eye has been anaesthetised with eye drops.
Corneal ulcers
Corneal ulcers cause a painful, red eye, and the vision is mildly to severely affected. Herpes viruses cause a recurring, typical, branching type of ulcer which is difficult to notice in the early phase. Permanent loss of best vision can occur as a result of scarring. Bacterial and fungal ulcers are even more sight threatening and must be referred to an ophthalmologist as soon as possible. Amoebic ulcers are subtle but very painful ulcers usually occurring in soft contact lens wearers. Sterile peripheral corneal ulcers may be associated with underlying disorders such as rheumatoid arthritis.
Conditions affecting the iris
Iritis
Inflammation of the iris, the coloured part of the eye, is called iritis. Iritis may be associated with an underlying disorder such as sarcoid or tuberculosis. One or both eyes may be affected and may have minimal to moderate pain, decreased vision or light sensitivity. The condition may be recurrent and may result in glaucoma, cataracts and other complications.
Acute glaucoma
Glaucoma is usually a painless condition associated with loss of vision in the late stages. However, acute angle closure glaucoma is a different condition. It is sudden, painful and is potentially sight-threatening.
The pressure in the eye increases and the patient experiences severe eye pain and a headache. Vision is decreased and nausea and vomiting are common.
The eye is red, the cornea is cloudy and the eye is hard to the touch. The pressure inside the eye (intra-ocular pressure) must be reduced urgently with medication. To prevent a recurrence, both eyes need small holes made in the iris with a laser to allow the fluid inside the eye to escape and prevent further build-up of pressure.
How is red eye diagnosed?
An accurate diagnosis may be difficult without the diagnostic equipment commonly used by ophthalmologists (eye specialists).
Most importantly, there are symptoms and signs which, if present, should prompt you to seek an eye specialist’s opinion. Special investigations such as blood tests may also be necessary before treatment is started.
When to see a specialist
Symptoms and signs which need an ophthalmologist’s opinion include:
Decreased vision
Pain (i.e. severe pain that keeps you awake at night, not just discomfort)
One red eye only
Failure to improve within a few days
The more of these features that are present, the earlier you should see an ophthalmologist.
Reviewed by Dr L.C. Boezaart, M.B.Ch.B, M.Prax.Med, M.Med (Ophth).
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