While some corneal infections result in only a mildly irritated eye, depending on the underlying cause and its location on the cornea, a corneal infection has the potential to severely impact eye health, causing permanent damage to your sight. A corneal infection can be caused by bacterial or viral infections, or be due to a fungus or microscopic parasite. In some unfortunate cases, an eye may be infected by more than one pathogen simultaneously.
The cornea is the front surface of the eye and must remain clear and transparent in order for light to pass through to reach the retina at the back of the eye and provide vision. Any disruption to this tissue, such as damage and scarring from corneal infections, can physically impede the passage of light into the eye, resulting in blurred vision. The cornea is also the most sensitive part of the eye, with a speck of dust being able to cause a great deal of discomfort.
Causes of Corneal Infection
A corneal infection is often referred to as keratitis, which translates to inflammation of the cornea. Although not all keratitis cases are necessarily active infections, all corneal infections involve inflammation at some point in their development.
Most corneal infections are caused by bacteria, usually staphylococcus aureus or pseudomonas aeruginosa. Bacterial keratitis, in particular pseudomonas infections, can be aggressive and a significant threat to eye health, and so should be addressed promptly by an eyecare practitioner endorsed to prescribe antibiotic medications.
Risk factors for the development of a bacterial keratitis include contact lens wear, in particular when poor contact lens hygiene is practised, such as overnight wear or wearing a lens for longer than the recommended disposal schedule. Other underlying causes of compromised eye health can also predispose a person to bacterial keratitis, such as being immunocompromised or an eye injury.
Symptoms of bacterial corneal infections include mild pain, redness, and a mucous or pus discharge from the eye. You may also be able to see a round whitish opacity on the cornea, which is an ulcer caused by the infection. If this ulcer is large and central, or if there is significant discharge, you will also experience some effect to your vision.
You may have heard of the herpes virus and adenoviruses in a context outside of eye health. However, these two viruses are in fact most commonly responsible for viral infections of the eye. Herpes simplex keratitis is caused by the type 1 herpes simplex strain of virus, the same strain responsible for causing cold sores around the mouth. It is also possible to get shingles in the eye in a condition known as herpes zoster ophthalmicus, caused by the varicella zoster virus of the herpes family. Once infected by a herpes virus, the virus remains in the body for life, typically lying dormant unless reactivated. Reactivation of the virus causes recurrent infection and inflammation, which can cause significant damage to the corneal tissues if not adequately managed.
Adenoviruses are a group of viruses often behind the common cold, causing characteristic symptoms such as fever, cough, and sore throat. Adenoviral infections of the eye are highly contagious and can be spread through droplets of bodily fluids left on surfaces, including tears.
Viral infections of the cornea typically present as a red, sore, watery eye with blurry vision. Patients also often report light sensitivity and in the case of adenoviral infections, may feel a burning or itching sensation in the affected eye. Viral keratitis is usually only on one side, though due to the contagious nature of the adenovirus, may transfer to the other eye in a matter of days if proper hygiene isn’t observed. Cases of herpes keratitis often have a history of cold sores or may have an active shingles infection along the scalp and face. Patients with an adenoviral infection may report having had a recent cold or flu or having been in contact with someone else with a cold or eye infection. Both a herpes and adenoviral infection of the cornea have the potential to cause scarring of the cornea, especially if recurrent.
Fungal keratitis is often more difficult to diagnose due to the slow nature of its development and the fact that symptoms typically present only days after the original infection. Many fungal eye infections also cause very little pain or irritation, which can further delay diagnosis and treatment, resulting in severe consequences for eye health and vision.
Contact lens wear is again a risk factor for fungal keratitis, as is an immunocompromised state. It is not uncommon for a fungal corneal infection to be caused by some sort of vegetative trauma to the eye, such as a scratch to the cornea by a branch or a leaf or dirt flicking into the eye.
Parasitic keratitis is usually caused by a ubiquitous protozoan found in air, soil, and water, known as acanthamoeba. Acanthamoeba keratitis is uncommon, which is fortunate as the characteristic symptom of this infection is pain disproportionate to the appearance of the eye. Other symptoms include redness, watery discharge, and light sensitivity; however, these are typically mild in comparison to the pain reported. Acanthamoeba eye infections are an ocular emergency and must be treated promptly with potent antimicrobial eye drops to prevent permanent blindness.
Any suspect corneal infection should be seen immediately by an eyecare practitioner for proper diagnosis and management. Call us at (03) 9070 5753 today.