The eyes are sensitive organs that can easily become irritated or affected by more serious conditions. Red eyes may have numerous causes, and be accompanied by other clinical signs and symptoms (such as pain and impaired vision).
Find out about what causes red eyes, good eye care habits, and in what situations you should consult your ophthalmologist.
What is red eye ?
Red eye happens when the conjunctiva (the inner surface of the eyelid and anterior surface of the eye, called the sclera) changes colour. This redness is most often caused by rupture of a blood vessel (haemorrhage), an inflammatory reaction, or dilation of a blood vessel in the eye, but it can also be the result of more complex pathologies.
Redness can affect one or both eyes. It has a different appearance depending on its cause: it can take the form of a single, localised red dot on the white of the eye, but equally can spread and cover the whole of the eye.
Causes of red eyes
The white of the eye can become red for a variety of reasons, such as external irritation, haemorrhage, inflammation or infection.
By examining the symptoms accompanying red eyes, for example pain or impaired visual acuity, a doctor or ophthalmologist will be able to make a precise diagnosis. He or she will then be able to assess the seriousness of the complaint and prescribe the appropriate treatment.
Eye irritation factors
There are many non-infectious causes of red eyes; most of the time they are environmental or physiological:
• Fatigue: in this case, red eyes may be accompanied by headaches and eyestrain. If the symptoms last longer than 24 hours, a doctor should be consulted so that more serious pathologies can be ruled out.
• Wearing contact lenses: red eyes most often occur when the correct hygiene measures are not taken (washing hands before and after touching contact lenses, disinfecting contact lenses with the appropriate product, leaving contact lenses in longer than the recommended period, cleaning contact lens holder and changing solution regularly). Redness can affect one or both eyes.
• Air pollution: when pollution is very dense, it causes eye irritation and redness. Tobacco smoke also causes these effects.
• Screen use (computer, mobile phone, tablet): excessive use can cause eyestrain and red eyes.
• Exposure to UV rays: if the eyes are not properly protected, UV rays can cause keratitis (corneal inflammation, most often due to infection). The same phenomenon can occur if chemical substances enter the eyes.
• Dry eyes: insufficient lachrymal secretion, termed “dry eye syndrome”.
• Consumption of alcohol or illegal substances.
In most cases, if eyes are red but not painful, the diagnosis will a priori not be serious. Red eyes due to these causes are therefore of little concern and will disappear by themselves after a few hours.
By contrast, if injury is caused by a foreign body entering the eye and damaging the eyeball, the consequences can be more serious. In this case, a bloodstain will appear on the eye and the sufferer will experience pain and impaired vision. An ophthalmologist must be consulted as a matter of urgency.
Red eyes caused by infection
In addition to irritation factors, there are several pathologies that can lead to red eyes. Depending on the specific case, they are accompanied by other eye symptoms such as pain, impaired vision, itchiness, etc. There are many such pathologies, so the list cannot be exhaustive.
If there is no visual impairment, the cause of red eyes may be conjunctivitis. This condition is often accompanied by eye discomfort and secretion which is transparent (viral or allergic conjunctivitis) or purulent (bacterial conjunctivitis). The infection may sometimes affect other parts of the eye and lead to a loss of visual acuity. If it is allergic conjunctivitis it will cause pruritus, i.e. itchiness, along with watery eyes and even swollen eyelids.
If eyes are bloodshot and painful and vision is impaired, this can also be due to infectious keratitis (infection of the cornea) or closed-angle glaucoma (increased pressure inside the eye). In this case, the sufferer may also experience headaches. It is therefore crucial to see an ophthalmologist, who will perform an examination and make the appropriate diagnosis.
Ocular rosacea (or rosacea) and seborrheic dermatitis also present symptoms of red eyes, swollen or inflamed eyelids (blepharitis) and dry eyes. In addition, the patient may feel a burning sensation or as if a foreign body were present in his or her eyes, in addition to redness that can sometimes become chronic.
Other lesions also exist that are associated with red eyes:
- Scleritis: inflammation of the sclera (the membrane forming the white of the eye), which causes painful red eyes but no visual impairment. The opinion of an ophthalmologist is often required here.
- Chalazion: inflammation of the Meibomian gland (a sebaceous gland located near the eyelids), which causes the eye to become bloodshot and painful.
- Uveitis: inflammation of the uvea (a membrane inside the eye), which causes eye pain and visual impairment, photophobia (sensitivity or intolerance to light) and ocular hypertension (increased pressure inside the eyes).
Lastly, subconjunctival hemorrhage underneath the conjunctiva (the inner surface of the eyelid) causes red eyes, but no visual impairment or pain. This bloodstain, which may sometimes spread out, may be linked to hypertension or diabetes.
How should you consult if you have red eyes?
Minor cases of irritation (caused by fatigue, screen use, smoke, sunlight, etc.) usually disappear by themselves. If the symptoms are not worrying, you can simply ask your pharmacist for advice. He or she will be able to suggest appropriate eye drops, preferably preservative-free ones. However, in the event of discomfort, persistent red eyes, or other symptoms (pain, itchiness, eyestrain, etc.), you should seek medical advice.
Sub-conjunctival bleeding without apparent external cause, allergic and viral conjunctivitis are usually treated by a general physician.
If the symptoms are severe and disabling, it is essential to consult an ophthalmologist or go to an ophthalmic emergency department so that a comprehensive eye examination can be performed. Moreover, if red eyes are accompanied by pain and impaired visual acuity, this may indicate a more serious eye condition. It is therefore essential to seek professional advice quickly.
Limiting the occurence of red eyes
Red eye treatment varies considerably and depends primarily on the diagnosis.
If the irritation is minor and caused by fatigue, air pollution or sunlight, you must rest your eyes. If redness occurs after wearing contact lenses for a prolonged period, simply swapping them for glasses will provide immediate relief.
Using artificial tears will also reduce discomfort. It’s available over the counter in the pharmacy. A few drops a day over a few days will help reduce eye redness.
Ophthalmic solutions containing trehalose and hyaluronic acid are also recommended for treatment of eye irritation, particularly dry eyes. These medical devices hydrate eyes more effectively and have a longer-lasting effect than ordinary eye drops. They come in the form of drops and should be applied several times a day.
If they do not have the desired effect, the pharmacist may suggest you a local treatment like eye drops or oinments.In more severe cases your ophthalmologist will made a clinical evaluation to diagnose and to treat your eye condition.Sometimes a stronger treatment is needed topical or orally (antihistamines, corticoid or no-corticoid anti-inflamatory, antibiotics… etc )
Red eye may also be a sign of a more severe disease that could require surgery.
Preventing red eyes ?
On a daily basis, preventive action may usefully be taken to limit eye irritation:
- Wash your hands before touching your eyes.
- Spend less time in front of screens.
- Try to adopt good sleeping habits.
- Wear sunglasses when you are exposed to bright sunlight (sea and mountain) and protective goggles when doing DIY.
- Clean your contact lenses properly and do not keep the same pair for too long.
- If a caustic substance enters your eyes, rinse them thoroughly with plenty of water.
- Use hypoallergenic makeup, and remove makeup each day.
- Have as few carpets and rugs as possible, and use anti-dust mite bedding and bedclothes.
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