Eye Infections: The 7 Most Common Types, Symptoms, and Causes - Spektrum Glasses

Eye Infections: The 7 Most Common Types, Symptoms, and Causes

An eye infection occurs when a harmful microorganism enters the eye area. The main causes are viruses and bacteria, but infections can also develop for other reasons. Infections most often affect the transparent, front part of the eye called the conjunctiva (i.e. the cornea and the covering of the eye), but all parts of the eye are susceptible to infection. There are many types of eye infections with different causes, which require different treatment approaches. If there is redness, itching, or pain in the eye, it is important to visit your eye doctor. It is important to start the treatment as soon as possible to avoid further complications, and treatment depends on the cause of the infection. Keep reading to find out about the most common eye infections and how to treat them.

Types and causes of eye infection

There are many types of eye infections, including conjunctivitis, eye herpes, bacterial keratitis, uveitis, trachoma, acanthamoeba keratitis, endophthalmitis, blepharitis, barley, corneal ulcer11, and orbital cellulitis.

1. Conjunctivitis

Conjunctivitis1 is the most common form of eye infection and is an inflammation of the conjunctiva, the transparent, smooth, shiny mucous membrane that connects the back surface of the eyelids and the eyeball. There are several types of conjunctivitis, and they are divided depending on their cause:

  • Infectious or viral conjunctivitis2 is the most common form of this infection and is transmitted by contact;
  • Allergic conjunctivitis12 is not contagious and is most often caused by pollen, animal hair, or cosmetics;
  • Bacterial conjunctivitis3 is caused by bacteria, and you will probably need proper therapy such as antibiotic eye drops to kill the bacteria.

Some of the symptoms of conjunctivitis include itching, red eye, burning of the eye, a sensation of a foreign body in the eye, and swollen eyelids. If you have bacterial conjunctivitis, excessive production of mucus and discharge from the eye is possible.

Conjunctivitis is treated depending on its type. Infectious or viral conjunctivitis is treated with cold compresses or artificial tear drops, during which it is important not to dry the eye.

Bacterial conjunctivitis is treated with antibiotics, while allergic conjunctivitis is treated with anti-allergy drugs (the choice of drugs depends on the type of allergy) and by avoiding allergens.

2. Keratitis

Keratitis4, or inflammation of the cornea, can be caused by infection or injury. Like conjunctivitis, there are several types of keratitis. Keratitis most often occurs as a result of an eye injury (e.g. stabbing with a sharp object). There is also bacterial keratitis, which often occurs due to failure to maintain the cleanliness of the lenses, whereby bacteria easily collect on the lens cases and the lenses themselves.

  • Viral keratitis5 most often occurs in combination with another disease such as a cold, flu, or chicken pox, and is related to reduced immunity. Vitamin A deficiency can also cause keratitis, as well as dry eye. The symptoms of keratitis and conjunctivitis are very similar at the beginning of an eye infection and include redness, the feeling of a foreign body being present in the eye, swelling, blurred vision, and discharge from the eye. In addition to the above symptoms, increased eye sensitivity to light and blurred vision are possible. Viral keratitis is treated with antiviral drops and tablets.
  • Bacterial keratitis6 is caused by bacteria and, in most cases, treated with antibiotics.

3. Endophthalmitis

Endophthalmitis7, or inflammation of the inside of the eyeball, is a type of eye infection that affects the fluid or tissue inside the eye itself. This infection is very dangerous for vision and, if not treated immediately, can cause blindness. Infection can occur in two ways: exogenously, which is more common and occurs after an eye injury, eye surgery, or eye injection, during which bacteria or fungi enter the eye; and endogenously, when the infection is transferred to the eye from another inflamed part of the body.

If you suffer from endophthalmitis, you will probably feel pain in the eyes, redness, and deterioration of vision, and your eyes will be more sensitive to light. Endophthalmitis is treated with antibiotics or antifungal drugs, but in some cases, emergency surgery is necessary to save your vision.


Blepharitis8, or inflammation of the eyelids, can occur due to a bacterial infection, allergy, or blockage of the glands in the eyelids. Acute blepharitis affects the area around the eyelashes, while chronic blepharitis affects the inner side of the eyelid.

Symptoms of blepharitis are redness of the eye, itching, watery eyes, the feeling that something is in your eye, grease, and dandruff sticking on the eyelashes. Increased sensitivity to light is also possible. 

Blepharitis is an easily treatable eye infection and is most often treated at home by improving the hygiene of the area around the eyes. Of course, consultation with a doctor is recommended, but only severe cases of blepharitis require antibiotics or steroids.

5. Cellulitis

Cellulitis9 is a type of bacterial or fungal eye infection that can affect the eyes and the skin. There are two types of cellulitis, orbital and preseptal, and they differ in the area they affect. Orbital cellulitis affects the eye itself and the area around the eye, while preseptal cellulitis affects the eyelids. Symptoms of cellulitis may include swelling of the eyes, redness of the eyelids, double or blurred vision, and difficulty moving the eye. Cellulitis is often accompanied by a temperature and weakens the body.

Cellulitis can be diagnosed with an eye scan or a blood test, and requires antibiotic therapy. In more severe cases, it is necessary to remove the fluid from the infected area.

6. Uveitis

Uveitis10 is an inflammation of the middle layer of the eye or uvea that can damage vital eye tissue and even lead to permanent vision loss. There are four types of uveitis, depending on which part of the uvea is affected: anterior, middle, posterior, and the whole area. Uveitis can also be caused by a virus, bacteria, fungus, or parasite, and is associated with other diseases such as psoriasis, syphilis, AIDS, multiple sclerosis, and tuberculosis.

People with uveitis may experience redness around the eyes, sensitivity to light, blurred vision, and the sudden appearance of floating particles in their vision. Uveitis is diagnosed during an ophthalmological examination drawing on medical history, blood tests, and vision tests. It is treated with steroids in the form of drops, tablets, or injections.

7. Barley

Barley on the eye is a less common type of eye infection. Barley occurs during inflammation inside the eyelid, due to which a bump similar to a pimple appears. Barley most often occurs due to touching the eyes with dirty hands and generally poor eye hygiene.

Barley is not dangerous for vision, and complications are extremely rare, but barley is often painful and unpleasant and can be present for up to several months. In addition to the visible symptoms, inflamed bumps on the eyelid, barley can cause itching and swelling of the eyelid.

Barley can be treated in the comfort of your own home. One method of reducing barley is to put a warm compress on the eye for fifteen minutes, four times a day.

Corneal ulcer

A corneal ulcer is a localized infection of the cornea. It usually causes pain, redness, discharge from the eyes, and decreased visual acuity. Most corneal ulcers are caused by a bacterial infection that penetrates the cornea, often after an eye injury, trauma, or other damage.

People that wear contact lenses are particularly susceptible to this infection. Improper wearing of contact lenses can cause slight damage to the epithelium, allowing bacteria to penetrate the cornea. If you suspect you have a corneal ulcer, the most important step is to see an ophthalmologist immediately; otherwise, untreated ulcers can lead to a serious decrease in visual acuity.

Eye infections in children – conjunctivitis

One of the most common eye infections in children is conjunctivitis. The most common form is viral conjunctivitis, which often occurs with a cold or eye inflammation. It is characterized by a watery discharge. Bacterial conjunctivitis is not as common and is characterized by a sticky, purulent discharge (yellow or green), and severe redness of the eye.

Allergic conjunctivitis is caused by an allergic reaction. You should get medical help if an increasingly thick discharge appears, eye redness does not go away even after several days, or if the conjunctivitis (either bacterial or allergic) does not calm down after five days.

Final thoughts

Many types of eye infections are spread from person to person. If you have an eye infection or are around someone with an eye infection, such as a child, spouse, or co-worker, wash your hands thoroughly and often, avoid touching the eyes and face, do not share towels, pillows, or sheets with others, and if you are infected, do not wear contact lenses until the inflammation has passed. If you notice the presence of symptoms of eye inflammation, be sure to contact your doctor as soon as possible.

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