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What Causes Red Eyes?

Author : Dr Deepak Garg
Causes and precautions for red eyes

Having a red eye is something most of us would have experienced at some point or the other. The cause of red eye often depends on what other symptoms are present. Associated Red Eye symptoms can include itching, watering, stickiness, discharge, difficulty in looking at a bright light, pain, and blurring of vision. And so also, red eye causes can range from very harmless, to those that require urgent treatment.

Dry Eyes

Dryness in the eyes is one of the most common eye conditions we see these days. We see several patients who come in because their eyes are feeling heavy and tired, or because they have itching and watering from their eyes and very often red eyes. Individuals may also experience light sensitivity, blurry vision, and eye strain.

The reason screen time causes dry eyes is reduced blink rate. We tend to stare at the screen. Dry eyes can also be seasonal and associated with allergic Conjunctivitis. Other associated conditions that may cause dry eyes are,

  1. Meibomian Gland disease or MGD is an eyelid disorder where the oil glands don’t secrete the right amount of oil on the surface of the eye. This is probably the most common cause of dry eyes.
  2. Lack of sleep – There is a lot of buzz about blue light-blocking glasses which may help with sleep. While they don’t do any harm one must keep in mind that their benefits may vary for different people.
  3. Old age
  4. Cigarette smoke
  5. Autoimmune conditions like Sjogren’s Syndrome
  6. Immediately after eye surgery, one can get dryness which may last for a few weeks to a few months
  7. Dryness can also get aggravated after a dip in the swimming pool

The treatment for dry eyes is using lubricating eye drops or artificial tears. These drops can be used 3-4 times a day. There are a few drops available in the market and the doctor would choose one depending on the severity of the disease. Most patients with dryness have a mild disease but in some the dryness becomes severe. Rarely this dryness can lead to severe gritty sensation and also corneal ulcers which may lead to permanent damage to the cornea

In addition to this, those working on screens for long hours need to remember to blink often, take frequent breaks and follow the 20-20-20 rule: look away from the screen every 20 minutes, for 20 seconds and focus on something 20ft away.

Sometimes this condition is also referred to as Dry eye syndrome, where we get dry eyes, redness, itching, fatigue, and heaviness in the eyes. Computer vision syndrome is also how this can be referred to.

Infective Conjunctivitis

Don’t look at me! I have conjunctivitis and you might get it too!! So goes the age-old myth, and surprisingly many people believe it till date. But, that’s all it is – a myth.

Infective conjunctivitis is one of the commonest causes of red eyes and is a common eye infection. It can cause redness, irritation, and itching of the eyes, sticky discharge, difficulty in looking at a bright light, and swelling of the eyelids. Knowing about how conjunctivitis spreads can help us take appropriate precautions. It is extremely contagious but DOES NOT spread by looking at the person’s eyes. It spreads through contact, and hence it is very important to not touch or rub the eyes. Every time the infected eye is touched, one must wash the hands with soap. This is the best way to prevent it from spreading to others. Dark glasses can be worn, as they also offer some comfort, but in no way do they prevent the spread.

Infective conjunctivitis can be caused by any type of organism but more commonly we see viral infections or viral conjunctivitis. Less commonly we also see bacterial conjunctivitis. Recently we have been seeing more infective conjunctivitis because of Covid infections.

The treatment is by antibiotic drops. Many patients purchase over-the-counter drops which might contain steroids, However, steroid eye drops should never be used in an infection. Atleast not initially. It can lead to corneal ulceration and even loss of sight. Thus, it is strongly advised to take only prescription medication for this type of infection and not self-medicate.

Allergic Conjunctivitis

Conjunctivitis can also be allergic, in which case eyes are generally very itchy and watery. Patients complain of a gritty feeling or a foreign body sensation. This condition is very common in children and keeps occurring every so often. Sometimes it reduces with eye drops and comes back a week after stopping the drops and some other times it won’t come back for a year.

Eye Allergy can be a seasonal allergy but we do have patients where allergy lasts for years and in severe cases, they also have to be on these drops for that long. 

These allergies can be because of dust which is the most common irritant causing eye allergies. Others are pollen or some other environmental irritant or even pet dander. Eye Allergies can also occur as a contact lens complication.  

This type of conjunctivitis requires treatment with anti-inflammatory drops or anti-allergic eye drops. 

This is differentiated from infective conjunctivitis by the following factors

  1. There is no real eyelid swelling in the allergic conjunctivitis
  2. The severity of redness is usually more in infective conjunctivitis
  3. The discomfort is usually much more in infective conjunctivitis than in allergic conjunctivitis
  4. Allergic conjunctivitis is usually in both eyes while infective can be in one or both eyes
  5. There is usually associated subconjunctival haemorrhage with infective conjunctivitis. This is not seen with allergic conjunctivitis
  6. There may or may not be a history of meeting someone else who had conjunctivitis for the infective kind.

Corneal Infections

The cornea is the outermost, transparent layer of the eye. A Corneal infection can occur after prolonged contact lens wear, injury to the eyes, severely dry eyes, or following conjunctivitis. It can be an extremely painful condition, causing the eye to become red and watery, and the patient will experience a lot of difficulty in looking at light – photophobia. It is also accompanied by diminished vision. 

Corneal infections can range from mild to severe. Severe infections are called corneal ulcers and if not treated in time can lead to corneal scarring and blinding.  

A corneal infection has to be treated as soon as possible with the appropriate antibiotic or antifungal drops. Sometimes we have to scrape the corneal ulcer to find out the causative organism. In severe infections, a corneal transplant may also be needed to save the eye. If the infection has spread significantly then sometimes your eye doctor may have to remove the entire eye to prevent the spread of the infection. This surgery is called evisceration.  


Uveitis refers to inflammation inside the eye. There are many different causes. At times uveitis is an isolated inflammation in the eye, and other times it can occur due to inflammation elsewhere in the body, which also affects the eye. Sometimes uveitis can lead to uveitic glaucoma which is raised eye pressure and if severe the raised eye pressure as explained later in the article can itself lead to red eyes and pain.

It presents with pain in the eye, and photophobia – difficulty in looking at bright light. The vision can also be blurred in some cases.

Uveitis needs to be treated with steroid drops, something which is not used for conjunctival or corneal infections. Hence it’s essential to reach the correct diagnosis before starting treatment. These steroid drops are tapered over a few weeks. To reduce the pain associated with this condition some dilating drops are also used. These drops relax the internal eye muscles and reduce the pain to a great extent.

Acute Glaucoma

There are 2 types of glaucoma, open-angle glaucoma, and angle-closure glaucoma. Acute angle closure glaucoma or acute glaucoma presents with sudden onset eye pain, a red eye, and a drop in visual acuity or blurred vision. It represents an ophthalmic emergency, as the eye pressure can shoot up to 50 mmHg (normal being in the range of 10-21 mm Hg). What happens here is the fluid circulation in the eye stops and causes a rise in the pressure. If the pressure is not brought down right away, it can permanently damage the optic nerve, and result in loss of vision. The severe pain is associated with vomiting which occurs with increased pressure.

Treatment involves topical medications or glaucoma eye drops along with systemic medications to reduce pressure. Sometimes intravenous mannitol is administered which helps in the immediate lowering of eye pressure.

Eye Injury

Any sort of mechanical or chemical injury to the eye can present with eye redness and pain. An injury to the eye requires immediate evaluation. If a harmful chemical has entered the eye, it has to be washed out as soon as possible. The eye wash is done by a doctor in the clinic. After that, the patient is put on eye drops and monitored frequently to look for complications.

If a mechanical injury has occurred, it could be mild or severe. A minor injury may get better with just eye drops or an eye patch. Severe injuries may need eye drops for a longer duration and sometimes even surgery. Of course, the most important is the initial assessment which includes checking how severe the injury is, and accordingly deciding if treatment will be by eye drops or by surgery.  

Subconjunctival Hemorrhage

This refers to bleeding under the conjunctiva. It is quite frightening, as it occurs suddenly, gives a bright red appearance to the eye, and lasts for days. But it doesn’t cause any other symptoms, is generally harmless and tends to resolve on its own in 7-10 days. This occurs because of the rupture of a blood vessel on or under the conjunctiva.  

Most of the time this occurs without any known reason but this is known to occur in those who have high blood pressure or certain bleeding disorders.

If this happens a few times frequently then certain blood tests are ordered to rule out systemic conditions that can cause this.

There is no active treatment for this condition. It usually takes 7-10 days to go away completely. The red area usually increases while the intensity of the redness decreases as time passes by until it completely disappears.

Eye Infection

Internal eye infections can cause eye redness. This is not very common but a very serious condition. These infections are called endophthalmitis. The most common cause of endophthalmitis is post-cataract surgery. This is the most dreaded complication of cataract surgery. But sometimes these infections can occur without any known causative factor.

If not treated as an emergency this can lead to impaired vision and this poor vision may be for almost the rest of your life.

Treatment options include giving eye injections and starting eye drops. These eye drops can be antibiotics or antifungal agents depending on the type of infection. Sometimes your eye doctor may perform surgery to reduce the infective load and also test which organism is causing the infection.

Orbital Infections

Orbital infections are usually not very common. In the new covid world that we live in, orbital infections have become increasingly more common.  

Normally these are bacterial infections but post covid we are seeing fungal infections. The organism is Mucormycosis and is also known as the black fungus.  

These orbital infections have the potential to spread to the brain via the orbital apex or the back of the orbit. This is the part from where the optic nerve which originates in the brain comes to the eye.  

This is being seen for a few reasons.

  1. Low immunity secondary to increased steroid administration to reduce covid related respiratory inflammation
  2. High blood sugar because of these steroids or otherwise uncontrolled diabetes.
  3. Contaminated oxygen tubings and masks.

Symptoms include headaches, dull eye ache, red eyes, blurry vision, and fever amongst others. Poor vision is also a common symptom.

Treatment for these types of infections is very aggressive. Patients need to be admitted and started on systemic medications and are closely monitored. In the case of fungal infection, the treatment is very aggressive and may involve the removal of the eye and tissues surrounding the eyeball also known as exenteration.

The following video is of Dr. Akshay Nair, our oculoplastic specialist who talks about mucormycosis.

Precautions for red eyes

  1. Unless very mild make an appointment with an ophthalmologist
  2. Do not use steroids as the first eye drops which pharmacists may give you over the counter
  3. As the first drop without an ophthalmologist’s opinion, an antibiotic would be the best choice.
  4. If you are a contact lens wearer do not wear your contact lenses and discard the old lenses
  5. Don’t keep touching or rubbing your eyes

When should red eyes be treated by an Ophthalmologist

All red eyes should be seen by an ophthalmologist.

Yes, there are conditions which are harmless or mild or not vision-threatening. At the same time, however, there can be serious eye conditions and it’s important that treatment is started early. Treatment options also vary greatly depending on the cause of red eyes. Antibiotics, steroids and lubricants are some of the drops that may be needed.

Here are some conditions when you should be seen by an ophthalmologist

  • Eyes are painful
  • Vision is blurry
  • Eyes become extra sensitive to light – Photophobia
  • Symptoms have continued for a week or more, or are getting worse
  • The eye is producing a lot of pus or mucus/discharge
  • A fever or aches are also present with the eye discomfort

Bottom line is to go see an ophthalmologist as it’s always better to be safe than sorry.


The take-home message is this – If you have a red eye that is accompanied by eye pain, consult your eye doctor immediately. It could be due to corneal infection, eye inflammation, or a rise in eye pressure, all of which require urgent management, and can be sight-threatening.

On the other hand, a red eye without pain, but associated with itching, burning, or discharge is generally less serious, and not as much cause for worry.

Understanding the different symptoms and their causes will help us to stay calm and not panic, especially in today’s times, as we find ourselves in the middle of a pandemic, and there is so much fear everywhere around us.

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