“Red eye” is a general term used to describe red, irritated and bloodshot eyes. It also may refer to:
• Subconjunctival hemorrhage or broken blood vessel on the sclera
• Blepharitis or inflamed eyelids
• Stye or a red bump on the eyelid
• Special-effect contact lenses to create a “crazy” red-eye effect
• Red eyes in photos
Red eyes occur when the blood vessels on the surface of the eye expand.
The appearance of red eye ranges in severity from a bright red that completely covers the sclera to a few enlarged blood vessels that look like wiggly red or pink lines across the “white” of the eye.
Red eyes are usually caused by allergy, eye fatigue, over-wearing contact lenses or common eye infections such as pink eye (conjunctivitis).
However, redness of the eye sometimes can signal a more serious eye condition or disease, such as uveitis or glaucoma. If your red eye persists or worsens, always contact your eye doctor for proper diagnosis and treatment.
Common Causes of Red Eye
Conjunctivitis. Also called “pink eye,” conjunctivitis is one of the most common (and contagious) eye infections, particularly among school children.
It occurs when the conjunctiva — the thin, normally transparent membrane that covers the sclera and lines the eyelids — becomes infected.
When the conjunctiva is infected, the blood vessels within it become irritated and swell giving the eye a red or pink appearance. In fact, a reddish-pink eye is a telltale symptom of conjunctivitis.
There are different types of conjunctivitis — and therefore different ways to treat pink eye — so be sure to always visit your eye doctor for correct diagnosis.
Dry eyes. Dry eye syndrome occurs when your tear glands produce either an insufficient quantity or quality of tears to properly lubricate and nourish your eyes. Chronic dry eye can cause the surface of the eye to become inflamed and irritated, making your eyes look red.
While dry eye syndrome may not be curable, it can be managed. Treatment for dry eyes includes lubricating “artificial tears” eye drops and punctal plugs. Ask your eye care practitioner for the treatment options best for you.
Allergy. Red eyes often are referred to as “allergy eyes,” given that eye redness is a common indicator of an allergic reaction.
When your immune system reacts to a foreign substance, such as pollen, pet dander, dust or certain chemicals found in makeup or contact lens solutions, your body releases histamine as part of the inflammatory response that occurs to “fight off” the culprit allergens.
As a result, the histamine released causes blood vessels in your eyes to enlarge, making your eyes become red and watery.
Avoiding known allergens to which you are sensitive or taking medication advised by your doctor such as antihistamine eye drops can help keep dreaded hay fever and eye allergies at bay, especially during allergy seasons.
Contact lenses. One of the main culprits of red eye is over-wearing or not properly caring for your contact lenses, which can cause a build-up of irritating surface deposits and microbes on your eye.
Red eyes while wearing contacts could be a sign of a serious eye infection, such as keratitis or fungal eye infections. If your eyes become red while wearing contact lenses, remove your contacts immediately and visit your eye doctor.
Contact lenses also can worsen dry eye syndrome, as they typically reduce the amount of oxygen reaching your cornea and can restrict normal tear flow production, particularly with poorly fitting contacts.
You can minimize your risk of contact lens-induced red eye by keeping your lenses clean and disinfected, and replacing them according to your eye doctor’s directions. Your doctor also may advise you to try daily disposable lenses or a different type of contact lens material, such as gas permeable (GP) lenses.
Computer vision syndrome. Red, burning and tired eyes go hand-in-hand with staring at a computer screen for too long, which can cause computer vision syndrome. One reason is that you blink less when working at a computer, which dries out the surface of your eye.
Tips to reduce computer eye strain include taking frequent breaks while working at a computer, modifying your workstation and wearing specially designed computer glasses. Lubricating eye drops also will can help to keep your eyes moist and healthy — and red-free.
Eye injury. Trauma or injury to the eye, including cosmetic eyelid surgery, can result in red, bloodshot eyes, sometimes accompanied by a subconjunctival hemorrhage.
As an inflammatory response to injury, blood vessels in your eye dilate to allow more blood flow to the site of the injury for quicker healing. This dilation (and sometimes breakage) of blood vessels on the eye is what causes the redness.
Eye injuries can range from minor eye scratches (corneal abrasions) to deep puncture wounds and chemical burns. Whatever the source, always treat an eye injury as a medical emergency and see an eye doctor immediately.
PREVENTING RED EYES
✔ Don’t rub your eyes — irritants on your hands and fingers can cause even more redness and irritation. Plus, you could scratch your cornea doing so.
✔ Practice good hygiene when wearing contact lenses. Contacts and contact lens cases can act as a breeding ground for harmful bacteria, so it’s important to follow your eye doctor’s instructions about cleaning and replacing your contacts.
✔ Speak to your doctor about allergy medications to help keep allergies at bay.
✔ Take a break from looking at the computer screen and follow the 20-20-20 rule: look away from your computer every 20 minutes and gaze at a distant object 20 feet away for at least 20 seconds.
✔ Schedule an eye exam to rule out a more sinister cause of red eyes such as eye disease or a sight-threatening infection.
✔ Don’t over-use “whitening” eye drops — they can make your eyes redder over time!
Other Causes of Red Eyes
Corneal ulcer. Infections of the cornea, including a corneal ulcer, are potentially sight-threatening and should be treated as an emergency. In addition to red eyes, corneal ulcer symptoms almost always include eye pain, reduced vision and eye discharge. A corneal ulcer typically is caused by an untreated eye infection or trauma to the eye.
Ocular herpes. Also called eye herpes, this is a recurrent viral infection caused by the type 1 herpes simplex virus — the same virus that causes common cold sores.
Signs and symptoms of ocular herpes include eye redness, swollen eyes, eye pain, watery discharge and light sensitivity.
Herpes of the eye can cause scarring of the cornea if left untreated, and in some cases may require a cornea transplant to restore vision.
Uveitis. An inflammation of the middle layer of the eye (uvea), uveitis typically is characterized by red eyes, light sensitivity and visual disturbances such as floaters and blurry vision.
Uveitis has many known causes; the most common are eye infections, eye injury or trauma, or a systemic autoimmune disorder. But in many cases, the underlying cause of uveitis is unknown.
If not treated early enough, uveitis can result in a detached retina, cataracts and high ocular pressure, all of which can lead to permanent loss of vision.
Glaucoma. In most cases, glaucoma is gradual and asymptomatic when it first develops. But a sudden onset of painful, bright-red eyes accompanied by halos around lights, vision loss and nausea may signal acute angle-closure glaucoma.
Acute angle-closure glaucoma is a sight-threatening condition that warrants urgent medical attention. The spike in intraocular pressure (the internal pressure in your eyes) can cause permanent vision loss within a matter of hours if it is not reduced.
Whitening eye drops. Eye drops marketed for red eyes contain vasoconstrictors, which are chemicals that shrink the blood vessels on the surface of your eye to reduce redness.
Ironically, whitening eye drops can cause more harm than good over the long term. Many people who regularly use eye drops formulated to “get the red out” build up a resistance to their whitening effects and need to use more and more drops to achieve the same results. Also, chronic use of eye whitening drops can actually cause the redness to worsen after the drops wear off — a condition called rebound hyperemia.
Cold and flu. Bloodshot and puffy eyes, along with a runny nose, are common symptoms of a cold or flu. Red eyes in this instance typically are caused by a sinus infection or blocked sinuses, especially when accompanied with sneezing and coughing.
Pregnancy. Hormonal changes during pregnancy can affect your eyes in many ways. Your eyes may become red and bloodshot, as well as dry, itchy and sensitive to light.
Pregnancy also can alter the shape of your cornea and you may develop an intolerance to contact lenses or even experience blurry vision. These problems, including eye redness, usually are temporary and resolve completely within weeks or months after childbirth.
Smoking. The dangers of cigarette smoking to your heart and lungs and other diseases associated with smoking are well-known, but did you know smoking harms your eyes, too?
In addition to significantly increasing the risk of age-related macular degeneration (AMD), cataracts and uveitis, tobacco smoke is a toxic eye irritant that also can cause dry, red and itchy eyes.
Smoking marijuana also causes red, bloodshot eyes. THC, the main psychoactive ingredient in marijuana, causes significant dilation of blood vessels on the eye, producing eye redness that can last several hours or even longer.
Excessive alcohol consumption also can cause eye redness. Alcohol reduces oxygen to your red blood cells, causing blood vessels to clump together and resulting in a ruddy complexion and red, bloodshot eyes.
Environment and workplace hazards. Extremely dry air, dust, smoke and excessive sun exposure are known eye irritants that can cause red eyes, among other symptoms.
Corneal scratches caused by windblown particles such as sand and wood filings or flying bits of metal and glass can cause a serious eye injury.
Always wear protective eyewear such as safety glasses when you’re at risk of foreign objects striking your eye, whether it be at work, playing sports or performing chores around the house such as mowing the lawn.
Lack of sleep. The appearance of your eyes is a dead giveaway when you’re tired. Puffy eyes and dark circles are tell-tale signs you haven’t had enough sleep. And remember: rubbing sleepy eyes will only aggravate eye redness!
Swimming. Chlorine and other pool sanitizers — as well as bacteria found naturally in any type of water, including oceans, lakes and rivers — can wreak havoc on swimmers’ eyes. If you are prone to red eyes, use swim goggles before taking a dip to avoid irritated, bloodshot eyes after swimming.
Also, never swim with contact lenses. Doing so puts you at significant risk of contracting a sight-threatening eye infection such as Acanthamoeba keratitis.