Just like any other part of the body, the cornea is also vulnerable to infection. In fact, the cornea is at higher risk for infection due to the fact it does not have its own blood supply that provides many of the body’s natural defenses against infection. Infections occur when a microorganism, a “germ or bug”, gains entry into the cornea and starts to multiply.
Corneal infections can be caused by bacteria, viruses or even less common organisms like fungi or amoebas. All of these organisms are common in our environment. For an infection to occur, the germ has to penetrate into the cornea. Fortunately, the cornea has some defense mechanisms to prevent this. Our natural defenses include:
Tears – Our own tears help wash away and dilute harmful organisms.
Defense Molecules – Our tears also have special molecules that fight infection. We also have specialized immune defenses against infection.
Surface Layer of the Cornea – The outermost layer of cells on the cornea, called the epithelium, provides a barrier that prevents organisms from entering the cornea.
Usually, our defenses protect us, however, many things can weaken our defenses and put us at higher risk of infection. The most common risk factors for infection include:
Contact Lenses –Contact lenses can irritate the surface of the eye and can cause the surface layer to break down. This occurs when patients are not fitted properly with contact lenses, they over wear them or do not replace them as prescribed, and they do not follow proper lens cleaning protocols. Never swim in contact lenses, use tap water or saliva to clean them, or wear cosmetic or Halloween contact lenses not prescribed by a doctor.
Trauma – Any scratch or injury can lead to infection
Chronic Eye Irritation – Anything that irritates the surface of the eye like in-turned eyelashes, dry eyes or lid inflammation can lead to infection.
If an organism breaks through all these defenses it can begin to grow in the tissues that make up the cornea. This can lead to a serious infection that can result in vision loss and needs immediate medical attention.
What Are the Signs & Symptoms of a Corneal Infection?
The most common symptoms include:
How Is a Corneal Infection Diagnosed?
A corneal infection can be diagnosed by an eye doctor through examination. Oftentimes, a white spot or ulcer may appear on the eye and identifying an infection is easy. Some infections may be more challenging to diagnose and obtaining a small sample from the cornea called a culture may be required.
A culture is sent to a laboratory to identify the organism that is causing the infection. This can be very helpful in determining the best course of treatment.
How Is a Corneal Infection Treated?
Corneal infection is usually treated with antibiotics in the form of eye drops. Depending on the severity of the infection, more than one type of antibiotic may be used and the drops may need to be administered very frequently both day and night. Some infections may be resistant to normal antibiotics. In these cases, antibiotic drops may need to be formulated by a special pharmacy to fight the infection. A corneal culture, or sample, may also be very helpful to identify the infection and help determine what type of antibiotic will be most effective for treatment. Most corneal infections can be eliminated with eye drops, however, some very severe infections can require the need for an injection of antibiotics into the eye or even a corneal transplant.
Corneal infections are vision-threatening conditions that can leave behind a corneal scar that may permanently decrease vision.