Eye Infections, Including
Bacterial, Fungal & Viral

By Marilyn Haddrill, with contributions and review by Brian Chou, OD

Eye infections occur when harmful microorganisms — bacteria, fungi and viruses — invade any part of the eyeball or surrounding area. This includes the clear, top layer of the eye (cornea) and the thin, moist membrane lining the outer eye and inner eyelids (conjunctiva).

More serious eye infections can penetrate the deeper, interior portions of the eye to create sight-threatening conditions such as endophthalmitis. With post-septal cellulitis, infection found in and around the soft tissue of the eyelids represents an emergency because the condition can spread if left untreated.

Anytime you suspect an eye infection, you should always visit your eye doctor for a diagnosis and treatment. Trying to self-diagnose your condition can delay effective treatment and potentially harm your sight.

What Symptoms Suggest an Eye Infection?

Your eye doctor needs to determine the type of eye infection you have in order to prescribe treatment.

Some conditions, such as eye allergies and dry eyes, can produce symptoms similar to eye infections. In cases like this, the correct treatment is very different than what you need for an eye infection. So it's important to determine if your symptoms have an infectious cause.

Eye infections can lead to redness, pain, discharge, watering and light sensitivity. Unlike allergies, which can cause both eyes to become itchy or watery, eye infections generally affect only one eye.

Your doctor may take a sample from the affected area of your eye for a culture to assess the exact type of infection you have, if any. This may help determine the most effective treatment, such as an antibiotic that selectively targets the type of bacteria causing the infection.

Causes & Types of Eye Infections

Examples of eye infections include:

• Pink eye or conjunctivitis. Pink eye is a layperson's description of a common, highly contagious eye infection that often is spread among children in day-care centers, classrooms and similar environments. Teachers and day-care workers also are at increased risk of pink eye when they work in close quarters with young children.
   
  Common infectious conjunctivitis types often have viral or bacterial origins. Infants also can acquire conjunctival eye infections (gonococcal and chlamydial conjunctivitis) during birth when a mother has a sexually transmitted disease.
• Other viral eye infections (viral keratitis). Besides common pink eye, other viral eye infections include ocular herpes, which occurs with exposure to the Herpes simplex virus.
• Fungal keratitis. This type of eye infection made worldwide news in 2006 when a contact lens solution now withdrawn from the market was linked to an outbreak among contact lens wearers. The outbreak was associated with Fusarium fungi, commonly found in organic matter. This and other fungi can invade the eye in other ways, such as through a penetrating injury caused by a tree branch.
• Acanthamoeba keratitis. Contact lens wearers are at increased risk of encountering parasites that invade and infect the eye. Acanthamoeba parasites are found in soil, outdoor water sources (lakes, streams and sea water), swimming pools, hot tubs and even in tap water. This is why contact lens wearers should observe certain safety tips, such as avoiding swimming while wearing contacts. If you do wear contact lenses when swimming or in a hot tub, make sure you remove and disinfect the lenses immediately afterward.
• 
  Endophthalmitis is a serious, severe form of eye infection and inflammation.
  Trachoma. While uncommon in the United States, an eye infection known as trachoma, related to Chlamydia trachomatis, is so widespread in certain under-developed regions that it is a leading cause of blindness. Flies can spread the infection in unsanitary environments. Reinfection is a common problem.
   
  Trachoma typically infects the inner eyelid, which begins to scar. Scarring then causes an "in-turning" of the eyelid, and eyelashes begin to brush against and destroy tissue on the cornea, with resulting permanent blindness. Good hygiene and availability of treatments such as oral antibiotics are essential to controlling trachoma.
• Endophthalmitis. When an eye infection penetrates the eye's interior, as with bacterial endophthalmitis, blindness could result without immediate treatment, often with potent antibiotics. This type of infection can occur with a penetrating eye injury or as a rare complication of eye surgery such as cataract surgery. Any time the eye's globe is penetrated and injured significantly, there is a 4 to 8 percent risk of endophthalmitis.*
   
  Mold that penetrates the eye's interior also can cause endophthalmitis, though rarely, with most cases reported in tropical regions.

An infection also can affect interior portions of upper and lower eyelids to create a stye or chalazion. When infection invades the eye's tear glands, inflammatory conditions such as dacryostenosis can result. Infection also can lead to inflammation and blockage of the eye's tear drainage (lacrimal) system and cause dacryocystitis.

Uveitis is inflammation of the eye's interior structures that can be due to parasites, fungi, bacteria or viruses.

Infection can be an underlying cause of a corneal ulcer, which resembles an abscess on the eye.

And in certain cases, sinus infections (sinusitis) cause symptoms such as eye pain and swelling around the eyes.

Eye Infection Treatments

Fortunately, most common bacterial eye infections clear up, particularly with prompt treatment such as prescription antibiotic eye drops or ointments.

Many common viral eye infections resolve on their own. In cases of severe viral eye infections, an antiviral eye drop may be prescribed. Some viral eye infections require careful administration of steroid eye drops to reduce related inflammation.

Depending on the underlying cause of your eye infection, your doctor also may prescribe antibiotics or antiviral medications that are taken orally.

Prevent eye infections by washing your hands before handling contact lenses.

How To Prevent Eye Infections

If you are near a person with a red eye, avoid contact around your own eye until you wash your hands first. You can minimize the likelihood of catching common bacterial or viral eye infections by using anti-infective sprays and cleansers liberally in public areas such as day-care centers and classrooms.

At home, if any family members have a red eye or a confirmed eye infection, keep their bedding and towels clean, and don't let them share these items with anyone else. Have them wash their hands often.

And in general, teach children to avoid touching their eyes without washing their hands first.

If you are a contact lens wearer, you should follow safety tips for good hygiene, such as hand washing before you handle your contacts. Also, be aware that sleeping while wearing contact lenses regularly, even with the newer "breathable" contact lenses FDA-approved for overnight wear, significantly increases your risk of eye infection.

Here are other safety tips that contact lens wearers can follow to help avoid eye infection:

• Make sure contact lenses and lens storage cases are cleaned and disinfected regularly, according to manufacturer's instructions.
• Replace contact lenses regularly, according to your eye doctor's directions.
• Don't place contact lenses in your mouth or use your saliva to wet them.
• Don't "top off" old solution in your contact lens case. Instead, discard old solution and replace it with fresh solution.
• Always rub contact lenses when you clean them, even if using a "no-rub" solution.

In June 2009, the FDA issued comprehensive guidelines to help reduce risks of eye infections among contact lens wearers.

These guidelines recommend that manufacturers include a discard date (not just a date of expiration) on contact lens cleaning and disinfecting products. Based on FDA concerns, discard any old, outdated products even if they have never been opened and used.

"Failure to use contact lenses and solution correctly can result in eye infections," the FDA advisory says. "Both bacterial and fungal infections can lead to serious consequences such as permanent loss of sight if left untreated."

Resources:

*Endophthalmitis after open globe injuries. American Journal of Ophthalmology. April 2009.

Endophthalmitis categories. Principles and Practice of Infectious Diseases, 6th ed. 2004.

Eye infections in the tropics. Cohen & Powderly: Infectious Diseases, 2nd ed. 2004.

Infections of the lacrimal system.Principles and Practice of Infectious Diseases, 6th ed. 2004.

Periorbital and orbital infections. Infectious Disease Clinics of North America. June 2007.

Polymerase chain reaction analysis of aqueous and vitreous specimens in the diagnosis of posterior segment infectious uveitis. American Journal of Ophthalmology. January 2009.

[Page updated October 2009]