Viruses, bacteria, fungi and parasites can infect the eye. Typically, one eye is initially infected, with the spread to the other eye in some cases. Eye infections, also known as conjunctivitis, cause local irritation and symptoms of varying intensity. Eye infection symptoms are often similar among the differing causes. Your eye doctor can examine the eye and perhaps perform tests to determine the cause and appropriate treatment.
Redness and Photophobia
All types of eye infections cause redness or hyperemia of the whites of the eyes and the insides of the eyelids. The redness reflects irritation of these surfaces by the infecting agent. Light sensitivity (photophobia) frequently accompanies eye irritation. Bacterial infections of the eye typically cause more intense redness than viral eye infections, notes the Merck Manual for Healthcare Professionals. Bacterial eye infections often cause small areas of bleeding in the whites of the eyes called petechial hemorrhages.
Eye Pain
Certain types of eye infections cause eye pain. Ocular herpes infections caused by the herpes simplex virus are typically associated with exquisite pain in the affected eye, notes the University of Illinois at Chicago Department of Ophthalmology and Visual Sciences. According to the National Eye Institute, approximately 400,000 Americans have had ocular herpes, and an estimated 50,000 new and recurrent cases occur each year.
Itching
Itching is a frequent symptom of eye infections, the Mayo Clinic says. This symptom is also common with eye allergies. A clue that the cause may be an infection and not allergies is the fact that one eye is usually involved with infections, whereas both eyes are typically equally affected with allergies.
Eye Discharge and Tearing
Eye infections usually cause tearing and possibly discharge from the eye. Irritation of the lining of the inner eyelids and surface of the eye precipitates tearing or eye watering. Some types of eye infections also cause discharge from the infected eye. Bacterial eye infections typically cause a thick, yellowish green discharge from the eye. The discharge builds up in the eyelashes and dries, causing crusting upon awakening, says the Merck Manual for Healthcare Professionals. Some viral eye infections can also cause crusting, although it's usually less intense than with bacterial eye infections.
Scratchiness
Irritation of the inner lining of the eyelids and eye surface due to infection often leads to a sensation of scratchiness or grittiness in the affected eye, according to the Mayo Clinic. People frequently are convinced something is in the infected eye.
Blurry Vision
Some types of eye infections may cause blurry vision due to lesions on the cornea, the clear area in front of the colored part of the eye. Fungal eye infections typically cause this symptom, the National Eye Institute says. Contact lens wearers may be particularly susceptible to fungal eye infections. The Centers for Disease Control and Prevention says scrupulous hand washing before handling contact lenses can help prevent fungal eye infections, which may threaten vision.
