Eye Redness (Red Eye)

We have selected the following expert medical opinion based on its clarity, reliability and accuracy. Credit: Sourced from the MSD Manual, Consumer Version; authored by Dr Christopher J. Brady (see below). Please refer to your own medical practitioner for a final perspective, assessment or evaluation.

Overview

Eye redness refers to a red appearance of the normally white part of the eye. The eye looks red or bloodshot because blood vessels on the surface of the eye widen (dilate), bringing extra blood into the eye. Pinkeye typically refers to eye redness caused by a specific viral infection.


Blood vessels can dilate as a result of:

• Infection
• Allergy
• Inflammation caused by something other than an infection
• Elevated pressure inside the eye, typically caused by sudden, closed-angle glaucoma, in which fluid pressure increases in the front chamber of the eye

Several parts of the eye may be affected, most commonly the conjunctiva (the thin membrane that lines the eyelid and covers the front of the eye), but also the iris (the coloured part of the eye), the sclera (the tough white fibre layer covering the eye), and the episclera (the connective tissue layer between the sclera and the conjunctiva).

An Inside Look at the Eye

Rarely is eye redness the only eye symptom. People may have tearing, itching, the feeling that a foreign object is in the eye (foreign body sensation), sensitivity to light, pain, or even changes in vision. Sometimes people have symptoms that affect other areas of the body, such as a runny nose or cough, or nausea and vomiting.

Causes

Many disorders can cause eye redness. Some are emergencies, but others are mild and go away without treatment. The degree of redness does not indicate the seriousness of the disorder. The presence of eye pain or vision problems is more likely to suggest a serious cause.

The most common causes of eye redness are:

• Inflammation of the conjunctiva caused by an infection (infectious conjunctivitis, or pinkeye)
• Inflammation of the conjunctiva caused by an allergic reaction (allergic conjunctivitis)
• Scratches of the cornea (the clear layer in front of the iris and pupil) and foreign objects in the eye are also common causes of eye redness. In these cases, however, the person is more likely to consider the problem to be an eye injury, eye pain, or both. Corneal scratches may be caused by contact lenses or by foreign objects or tiny particles trapped under the eyelid. Occasionally, very dry air can cause some eye redness and irritation.

Serious causes of eye redness are much less common. They include corneal ulcers, herpes simplex keratitis (herpes infection in the cornea), herpes zoster ophthalmicus (shingles in or around the eye), acute closed-angle glaucoma, and scleritis (a deep, painful inflammation of the sclera).

Evaluation

Not every case of eye redness requires evaluation by a doctor. The following information can help people decide when to see a doctor and to know what to expect during an evaluation. In most cases, people with eye redness can be evaluated by a general health care practitioner rather than an ophthalmologist (a medical doctor who specializes in the evaluation and treatment—surgical and nonsurgical—of eye disorders).

Warning signs

In people with eye redness, certain symptoms and characteristics are cause for concern.

They include:

• Sudden, severe pain and vomiting
• Rash on the face, particularly around the eyes or on the tip of the nose
• Decreased sharpness of vision (visual acuity)
• An open sore on the cornea

When to see a doctor

Deep eye pain should be distinguished from irritation. People who have warning signs, particularly deep pain or a change in vision, should see a doctor right away. If no warning signs are present, it is safe to wait a couple of days or so, but people may want to see a doctor sooner so that they can start treatment quickly.

What the doctor does

Doctors first ask questions about the person's symptoms and medical history and then do a physical examination. What they find during the history and physical examination often suggests a cause of eye redness and the tests that may need to be done (see Table: Some Causes and Features of Eye Redness).

Doctors ask:

• How long redness has been present
• Whether redness has occurred before
• Whether there is pain or itching
• Whether there is discharge or the eyes are tearing
• Whether there is a change in vision
• Whether there has been an eye injury
• Whether the person wears contact lenses and whether they have been overused
• Whether the person has been exposed to substances (such as dust or eye drops) that could irritate the eyes
• Whether there are other symptoms (such as headache, halos around lights, runny nose, cough, or sore throat)
• Whether the person has allergies

Pain together with nausea or vomiting or halos around lights is a potentially serious combination of symptoms. These symptoms often occur in acute closed-angle glaucoma. Pain and sensitivity to light may indicate a disorder of the cornea, such as a scratch or a foreign object. An absence of pain and sensitivity to light may indicate a disorder of the conjunctiva.

During the physical examination, doctors examine the head and neck for signs of disorders that may cause eye redness, such as runny nose and cough that may indicate an upper respiratory infection or allergy or a rash that may indicate shingles (herpes zoster infection).

The eye examination is the most important part of the physical examination. Doctors check the person's eye and the area around the eye for injuries or swelling. They check the person's vision (with glasses or contacts if the person wears them), pupil size and response to a light, and eye movement.

Doctors use a slit lamp (an instrument that enables a doctor to examine the eye under high magnification) to examine the eye. Doctors put a drop of anaesthetic and then a drop of fluorescein stain in the eye to diagnose corneal disorders. While the eye is anesthetized, pressure inside the eye (intraocular pressure) is often measured (called tonometry).

If pain develops in the affected eye (particularly if it is shut at this time) when a light is shined in the unaffected eye, the problem may be anterior uveitis or a corneal disorder. The use of an anaesthetic makes the examination easier, and the person's response to the anaesthetic may be a clue to the diagnosis. Anaesthetic eye drops do not relieve pain that is caused by glaucoma, uveitis, or scleritis.

Some Causes and Features of Eye Redness 

Allergic or seasonal conjunctivitis

• Inflammation of the conjunctiva—the membrane that lines the eyelid and covers the front of the eye
• Affecting both eyes
• An itching or scratching sensation and tearing
• In people with known allergies or other features of allergies (such as a runny nose that recurs during certain seasons)
• Sometimes in people who use eye drops (particularly neomycin)

Chemical (irritant) conjunctivitis

• An itching or scratching sensation and tearing
• Exposure to potential irritants (such as dust, smoke, ammonia, or chlorine)
• Episcleritis (inflammation of the tissue between the sclera—the white of the eye—and the overlying conjunctiva)
• Affecting only one eye
• A spot of redness on the white of the eye
• Mild irritation of the eye

Infectious conjunctivitis (pinkeye)

• An itching or scratching sensation, tearing, and sensitivity to light
• Sometimes a discharge from the eye and eyelid swelling
• Sometimes swollen lymph nodes in front of the ears

Subconjunctival haemorrhage (bleeding under the conjunctiva)

• Affecting only one eye
• A red patch or large area of redness (that looks like blood or ketchup)
• No tearing, irritation, itching, change in vision, pain, or discharge from the eye
• Sometimes in people who have had an eye injury, sneezed violently, or tried to exhale without letting air escape, as may occur during a bowel movement or while lifting a heavy weight (called the Valsalva manoeuvre)
• Often in people known to use drugs that help prevent blood from clotting (such as aspirin or warfarin)

Contact lens keratitis

• Inflammation of the cornea—the clear layer in front of the iris and pupil—caused by wearing contact lenses for long periods of time
• Usually affecting both eyes
• Eye ache and a feeling of grittiness in the eye
• Eye redness, tearing, and sensitivity to light
• In people who wear contact lenses for long periods of time

Corneal scratch (abrasion) / A foreign object (body)

• Symptoms that begin after an eye injury, which may not be noticed in infants and young children
• Pain in the affected eye when blinking and a foreign body sensation
• Eye redness, tearing, and usually sensitivity to light

Corneal ulcer

• Often a greyish patch on the cornea that later becomes an open, painful sore
• Eye ache and a foreign body sensation
• Eye redness, tearing, and sensitivity to light
• Sometimes in people who have had an eye injury or who have slept with their contact lenses in

Herpes simplex keratitis (infection of the cornea caused by the herpes simplex virus)

• Usually affecting only one eye
• Early: Symptoms that begin after an episode of conjunctivitis
• Blisters on the eyelid, sometimes with crusting
• Late or recurring: Eye redness and watering, eye pain, impaired vision, and sensitivity to light

Shingles (Herpes zoster ophthalmicus)

• Affects the face and eye, caused by the chicken pox (varicella-zoster) virus
• Usually affecting only one eye
• Early: A rash with blisters and/or crusts on one side of the face, around the eye, on the forehead, and sometimes on the tip of the nose
• Late: Eye redness, tearing, usually sensitivity to light, and eyelid swelling

Glaucoma (closed-angle)

• Severe eye ache and redness
• Headache, nausea, vomiting, and pain with exposure to light
• Disturbances in vision such as halos seen around lights and/or decreased vision

Anterior uveitis

• Inflammation of the anterior chamber—the fluid-filled space between the iris and cornea
• Eye ache and sensitivity to light
• Eye redness (particularly around the cornea)
• Blurring or loss of vision
• Often in people who have an autoimmune disorder or who recently had an eye injury

Scleritis (inflammation of the white of the eye called the sclera)

• Very severe pain, often described as boring, and sensitivity to light
• Watering of the eyes
• Red or violet patches on the white of the eye
• Often in people who have an autoimmune disorder

Tests and special investigations

Testing is usually unnecessary

If doctors suspect a viral infection (herpes simplex virus or varicella-zoster virus), they may take samples of discharge or blister fluid to send to the laboratory. The sample is placed in a culture medium (a substance that allows bacteria or viruses to grow). Samples for culture may also be taken when the person has a corneal ulcer, so doctors can give antibiotics that are most likely to be effective. Gonioscopy (use of a special lens to examine the drainage channels in the eye) is done in people with glaucoma. Sometimes people with uveitis are tested for autoimmune disorders, especially if there is no obvious cause (such as an injury) for the uveitis.

People with scleritis are usually referred to an ophthalmologist who often does additional tests.

Treatment

Treatment of the cause

The cause is treated: Eye redness itself does not require treatment. It usually clears up on its own as the cause resolves (for example, a few days for infectious conjunctivitis or a couple of weeks for subconjunctival haemorrhage). Cool washcloths or artificial tears can be applied if any itching is particularly bothersome. Eye drops that aim to eliminate redness (available over-the-counter) are not recommended.

KEY POINTS

• Usually, eye redness is caused by conjunctivitis.
• Pain, a rash around the eye or nose, and changes in vision suggest a potentially serious cause.

About the author

Dr Christopher J. Brady

MD

Assistant Professor of Ophthalmology, Wilmer Eye Institute, Retina Division, Johns Hopkins University School of Medicine

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