The Most Common Eye Infections

Eye infections usually cause discomfort such as itching, irritation, redness, and pain. However, you must know what type of microorganism causes them in order to treat them properly.
The Most Common Eye Infections

Last update: 04 October, 2021

Symptoms such as redness, eye irritation, itching, and pain are often caused by common eye infections. These can be due to various pathogens, such as viruses, bacteria, or fungi. Most cases evolve favorably but some complicate.

How can you recognize them? What are the treatments? Resolving these questions is crucial in order to intervene in a timely manner. For this reason, we’d like to tell you about the most relevant aspects of every one of these types of infections.

About the eye and visual health

The eye is an organ that detects light and converts it into electrochemical impulses. These travel through neurons in the optic nerve. As you can imagine, this biological tool is essential for conceiving the three-dimensional space in which we find ourselves and responding accordingly.

Sight is the most valued sense, and hearing is the second one, according to some empirical data. There’s no solid evidence to support this though. However, the symptomatology of a condition that weakens or impedes the functioning of the ocular apparatus is quite noticeable and annoying.

What causes ocular discomfort?

There are several eye conditions, most of them associated with vision loss, such as myopia, astigmatism, cataracts, etcetera. These are caused by internal morphological faults, which may include a bad curvature or opacity of the crystalline lens.

Infections have an exogenous origin, however. That is, they’re caused by microscopic germs such as bacteria, viruses, and even fungi. The eyes can become good breeding grounds for pathogens due to the moisture of the surrounding tissue.

A tired woman.
It’s important to learn to differentiate between eye diseases and infections. The latter can be caused by viruses, bacteria, or fungi.

The most common eye infections

There are many and it’s necessary to establish their cause in order to choose an appropriate treatment even though they may have similar symptoms. Here are the main ones.


This is one of the most common eye conditions, as it has different origins and a general clinical condition that includes infection or inflammation of the conjunctival mucous membrane.

According to the Centers for Disease Control and Prevention (CDC), conjunctivitis is generally caused by these two types of microorganisms:

  • Bacterial conjunctivitis is due to Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenza, among others. It can spread easily, especially in unhygienic environments where several people share toiletries. However, it’s more common in children than in adults, usually from December to April. The main characteristic is oozing pus from the eye.
  • Viral conjunctivitis can be due to several different agents, such as adenoviruses. Its main characteristic is severe eye irritation that begins in one eye and quickly spreads to the other one. It’s also quite contagious.

There are other possible causes of conjunctivitis, such as allergies, chemical exposure, foreign bodies in the eye, and contact lens wear. These are often one-time episodes of irritation and aren’t contagious.

Antibiotics are useful for bacterial infections but corticosteroid eye drops are the treatment of choice for viral and allergic conjunctivitis. In any case, the choice between one option and the other belongs to the attending physician or ophthalmology specialist.


These are the second most common eye infections. Furthermore, people often mistake this condition for a parasite within the eye. In reality, it’s usually the accidental work of staphylococcus bacteria.

Styes are due to a bacterial proliferation that forms a small abscess in the sebaceous glands surrounding various areas of the eyelid.

The general symptoms of this infection include the following:

  • A red bump on the eyelid
  • Pain and swelling of the eyelid
  • Excessive tearing

Most styes disappear on their own but antibiotics or even local surgery may be necessary to drain the pus from the affected area on rare occasions. The attending professional will determine it.

As always, proper hygiene is the best type of prevention when it comes to bacterial diseases. Thus, not touching the eyes without washing your hands is essential in order to avoid this type of condition.

An eye with conjunctivitis.
The characteristic symptom of styes is a bulging of the eyelid. It may improve on its own but sometimes requires treatment.


This infection is the result of a fungal infection of the ocular cornea. This condition isn’t that common in people who aren’t in contact with the rural environment and, therefore, occurs mainly in farmers, gardeners, and construction workers.

Keratomycosis can be due to the kind of trauma that allows contact of the eye with contaminated plant surfaces, alterations of the tear film, or the use of dirty contact lenses in poor condition.

The signs of this condition are:

  • Photophobia
  • Ocular pain
  • The sensation of having a foreign element in the eye
  • Ulceration with concentric lines

Keratomycosis requires diagnosis by direct culture or PCR because one can easily mistake it for either of the bacterial conditions mentioned above. Thus, the nature of the infectious agent requires treatment that includes the use of antifungals and even surgery, in severe cases.

Other common eye infections

The eye infections discussed above are the most common but there are others to consider when it comes to the presence of symptoms. Of course, a physician or ophthalmologist must make the final diagnosis.

  • The cause of blepharitis may be bacteria. The main symptom is the inflammation of the eyelids due to an obstruction of the sebaceous glands. Treatment may include corticosteroid drops or ointments and antibiotics.
  • Endophthalmitis is either fungal or bacterial and may cause pain, pus, and sensitivity to light, among others. Antibiotics, antifungals, or other treatments may be necessary depending on the cause.
  • Uveitis may result from a viral infection or eye injury. It doesn’t usually cause long-term problems, but can lead to vision loss if not treated properly. Furthermore, treatment varies depending on the cause and includes the use of sunglasses, eye drops, and eye injections, among others.

Things to keep in mind about common eye infections

As we mentioned above, various pathogens can affect the eyes and cause symptoms such as redness, swelling, and excessive tearing. Thus, we must take precautionary and hygienic measures before touching our eyes.

Finally, consult a doctor or ophthalmologist if you have any symptoms of infection. The professional will determine an appropriate treatment according to the cause after making the pertinent tests.

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