4 Types of Conjunctivitis (Red Eye) Explained

Conjunctivitis is the inflammation of the thin layer covering the front of the eye. It is the most common cause of the Red eye.

It affects all age groups and is usually treatable with specific eye drops. Some types affect one eye while others affect both eyes.

Conjunctiva’s main function is to protect and keep the eye moist. Conjunctiva is a transparent layer that contains blood vessels that are too small to be visible under normal circumstances but become prominent when it is inflamed.


The main symptom of conjunctivitis is redness of the eye commonly called Pink eye. It is accompanied by pain which feels like there is sand in the eye.

The pain is worse when looking at bright objects. Other symptoms depend on the cause of Conjunctivitis; there may be Itching, excessive tears or purulent discharge. Headache is also common, although other causes of headache needs to be excluded.

Causes and Classification

Conjunctivitis is classified into 4 main types according to cause:

  1. Infectious conjunctivitis: subdivided into Viral and bacterial conjunctivitis.
  2. Allergic conjunctivitis
  3. Chemical Conjunctivitis
  4. Traumatic conjunctivitis

Infectious conjunctivitis

Infection of the conjunctiva is the most common cause of a “pink” eye. The infection may be bacterial or viral. It is important to know the difference between the two since the treatment is not the same.

Read the main differences below:

Bacterial Conjunctivitis

Red eye with Purulent discharge seen in bacterial conjunctivitis
Purulent discharge covering eye

Bacterial conjunctivitis is more serious than viral conjunctivitis. It is usually caused a bacterial infection on one eye initially, but may spread to the second eye. The spread to another eye occurs if you touch the infected eye and then touch another eye without washing hands.

Common Bacteria that are known to cause conjunctivitis are:

  • Staphylococcus aureus
  • Streptococcus pneumonia
  • Moraxella Catarrhalis
  • Neisseria Gonorrhoeae in new-borns causes a potentially blinding conjunctivitis called Ophthalmia Neonatorum
  • Chlamydia infection has also been identified to cause Conjunctivitis, which is usually chronic

The main sign of bacterial conjunctivitis is purulent discharge of the affected eye, redness and pain. There is no need to take swab and identify specific types of bacteria that has infected the patient through M,C&S as most of them are treated with the same types of antibiotics. It should only be done if the treatment has failed.

Treatment of conjunctivitis caused by bacteria is Chloramphenicol eye ointment applied twice a day on the affected eye for 7 to 10 days. This is an antibiotic that has a broad spectrum of activity, meaning that it kills many kinds of bacteria without the need for additional tests.

Chloramphenicol eye ointment
Chloramphenicol eye ointment

Other antibiotics that can be used include moxifloxacin 0.5% eye drops 3 times a day for 7 to 10 days.

Viral Conjunctivitis

Viral Conjunctivitis is a less severe form of infection that is caused by virus infection in the eye. It is very infectious but is also self-limiting.

Many viruses are known to cause pink eye, the most common is Adenovirus. This virus causes mild symptoms also causes common cold symptoms like fever and sore throat.

red eye from viral conjunctivitis
viral conjunctivitis

The main feature here is that there is no purulent discharge. Symptoms of viral conjunctivitis are pain which feels like there is sand in the eye; redness and increased sensitivity to wind and sunlight.

Treatment is usually given to reduce pain and redness, not specifically to kill the virus. Oxymetazoline 0.025% eye drops together with oral Pain medication is enough for viral conjunctivitis.

To Prevent Spread of infection:

  • Avoid touching non-infected eye after touching the infected eye
  • Avoid swimming in pools
  • Avoid sharing towels as viruses are very infectious
  • Use hand sanitizer or wash hands after touching eyes or nasal secretions

Allergic conjunctivitis

Allergic conjunctivitis is caused by allergy usually to pollen or dust in people who are also having other allergies.

It is common in people who have Asthma, Atopic Dermatitis and Seasonal Rhinitis/Sinusitis. Here the eyes are both affected similarly.

The main symptoms are itching of the eyes and brownish discoloration. There is usually no pain. Excessive tears is common.

It is treated with Topical (eye drops) anti-Histamines like Olopatadine, Ketotifen and Cetirizine.

Antihistamines like Cetirizine can also be taken as by mouth to treat Allergic conjunctivitis and other allergies.

Chemical and Traumatic conjunctivitis

As the names suggest, chemical conjunctivitis is caused by exposure to chemical that causes irritation while traumatic conjunctivitis is induced by trauma.

Chemicals that can cause conjunctivitis can be household items like sanitizers, cleaning chemicals and even shampoo. Exposure can also occur at the workplace with more corrosive substances like acids, strong bases or paint.

Trauma can result from any injury that involves the eye. It can either be blunt trauma or trauma by a sharp object which scratches the conjunctiva.

Treatment for both types has a similar approach:

The first step is to thoroughly wash the eye with clean fresh water at home or irrigation can be done in health facility with Normal Saline. This should be done for a minimum of 5 minutes. At home washing the whole face is the best way to irrigate the eye. Wash the face for 5 to 10 minutes with clean fresh, water cold or warm.

The second part is treatment with eye drops that reduce inflammation if there is redness. Corticosteroids and artificial tears are helpful. They should be combined with Naproxen or Ibuprofen orally for pain relief.

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