Causes of Eye Infections
The causes of eye infections depend on the type of organism involved. Eye infections can be caused by bacteria, viruses, fungi, or parasites—each requiring different treatment and carrying varying risks.
Bacterial Infections
Bacteria are among the most common causes of eye infections. They may result from:
Staphylococcus aureus, commonly found on the skin
Streptococcus pneumoniae, often linked to respiratory infections
Pseudomonas aeruginosa, particularly in contact lens users
Bacterial conjunctivitis causes red, sticky eyes with yellow or green discharge. More serious infections like bacterial keratitis or endophthalmitis may follow trauma, surgery, or contact lens misuse.
Viral Infections
Viruses such as:
Adenoviruses – the most common cause of viral conjunctivitis (highly contagious)
Herpes simplex virus (HSV) – can infect the cornea and lead to recurrent keratitis
Varicella-zoster virus – causes shingles near the eye, which may affect the cornea or retina
Viral infections are often harder to treat than bacterial ones, as antibiotics have no effect. Antiviral medications or supportive care are usually required.
Fungal Infections
Fungal eye infections are less common but can be severe:
Fusarium or Aspergillus fungi may enter the eye after trauma with organic material
Common in tropical or agricultural areas
Often seen in people with compromised immunity or those using corticosteroid eye drops
These infections can be sight-threatening and require antifungal eye drops or systemic treatment.
Parasitic Infections
One of the most serious parasitic infections is caused by:
Acanthamoeba – found in water and soil, it can infect the cornea, especially in contact lens wearers who rinse lenses with tap water
These infections are rare but extremely painful and difficult to treat.
Risk Factors | Causes of Eye Infections
Poor hygiene
Use of contaminated eye makeup or lenses
Eye injury or surgery
Swimming in unclean water
Chronic illness or immunosuppression
Understanding the causes of eye infections helps doctors choose the correct treatment early and prevent vision loss.
[Next: Symptoms of Eye Infections →]
