Eye infections arise when pathogenic microorganisms – bacteria, fungi or viruses – invade any part of the eyeball or the surrounding area.
Areas that can be affected by eye infections include the front surface of the eye (the cornea), the thin, moist membrane that lines the outer eye, and the inner eyelids (the conjunctiva).
There are many different types of eye infections, and it is crucial in each individual case to identify the particular type of eye infection in order to assess the proper treatment.
Eye infections, if left untreated, can damage structures in the eye leading to low vision and, in the most severe cases, blindness.
Even if the eye is protected by the continuous flow of tears which contains antibacterial molecules and enzymes such as lactoferrin, the infection and inflammation, once they arise, may not resolve spontaneously and in these cases require immediate management.
Symptoms of eye infections can include:
- Red eyes
- ache
- excessive tearing or dry eyes
- sensitivity to light
- swelling in or around the eyes
- burning
- blurry vision
Bacterial conjunctivitis
Bacterial conjunctivitis is a common, highly contagious eye infection that often spreads among children in kindergartens, classrooms, and similar settings. Teachers are also more prone to conjunctivitis because they work closely with young children.
The most common types of infectious conjunctivitis are viral or bacterial in origin. Normally, bacterial conjunctivitis is a self-limiting benign disease, which can be resolved in a matter of days through the topical application (directly into the eye) of antibiotics.
Together with the viral and allergic variant, bacterial conjunctivitis represents one of the most common eye disorders; precisely, it is an infection that affects the conjunctiva, the thin protective film that covers the inner eyelid and the eyeball. Although it is rather easy to eradicate, bacterial conjunctivitis should not be underestimated: it is in fact important to always carry out all the necessary tests to ascertain that the infection has an actual bacterial origin and does not mask a systemic pathology.
Bacterial conjunctivitis is an extremely common infection: this type of eye infection appears to account for roughly half of all types of acute conjunctivitis.
In adults, bacterial inflammation of the conjunctiva is most often caused by Staphylococcus spp., Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis.
In children, however, bacterial conjunctivitis is mainly caused by H. influenzae, S. pneumoniae and M. catarrhalis.
Some patients are more exposed to bacterial infections in general and infectious conjunctivitis in particular. All forms of conjunctivitis show common symptoms, such as:
- hyperemia (redness of the eyes)
- abnormal tearing
- photophobia
- swollen eyelids
Precisely because of the non-specific nature of the symptoms, it is often difficult to immediately identify the precise type of conjunctivitis.
Nonetheless, some symptoms are unique and characteristic of a conjunctival infection; therefore, from a meticulous analysis of the clinical picture, we can drive ourselves towards a precise variant of conjunctivitis. Specifically, bacterial conjunctivitis can be recognized by observing the tear secretion: the typically infectious conjunctival secretion is abundant and purulent, and takes on a yellowish, sometimes greenish hue. Collecting in the conjunctival sac and partially overflowing, this secretion causes the typical "glue" effect on the eyelids, which struggle to open.
Unlike allergic conjunctivitis, the bacterial form does not show intense itching and lachrymation is not particularly abundant.
It is definitely important to distinguish bacterial conjunctivitis from diseases that involve similar symptoms, such as:
- uveitis
- glaucoma
- keratitis
- eye trauma
- episcleritis (inflammation of the superficial layers of the sclera of the eye),
- viral conjunctivitis
- allergic conjunctivitis
- dry eye syndrome
- cancer (sebaceous carcinoma of the eye).
Bacterial keratitis
Infectious keratitis is a process affecting the cornea. Although it can ideally affect anyone, infectious keratitis occurs more often in severely immunocompromised (eg, HIV-infected) and debilitated patients.
Keratitis are always symptomatic: in fact, most of the time the observable signs and the symptoms perceived at the ocular level manifest themselves in a rather evident way.
In most cases, keratitis begins with severe eye pain with fast onset, together with intolerance to light (photophobia), hyperemia (red eyes) and profuse lacrimation. Alongside these symptoms, the patient suffering from keratitis often complains of an alteration of vision (blurred vision) and the perception of a foreign body inside the eye.
Sometimes, keratitis can cause such pain that the patient cannot even open their eyes.
Keratitis of bacterial origin are very common; a bacterial infection of the cornea is often linked to incorrect use of contact lenses and their poor hygiene and maintenance; even the habit of wearing contact lenses during the night's rest can promote a keratitis. Other causes that can favor the onset of a bacterial form are corneal abrasions and eye make-up that may have been contaminated by bacteria. The bacterial agents most frequently involved are Staphylococcus aureus and Pseudomonas aeruginosa (especially in contact lens wearers).
Endophthalmitis
Endophthalmitis is a kind of infection that can occurs after a penetrating injury to the eye or as a fortunately uncommon complication of eye surgery such as cataract surgery. Each time the globe is penetrated and significantly injured, there is a 4-8% risk of endophthalmitis.