Keratitis is an inflammation of the cornea — the clear, dome-shaped tissue on the front of your eye that covers the pupil and iris. Keratitis may or may not be associated with an infection. Noninfectious keratitis can be caused by a relatively minor injury, such as from wearing your contact lenses too long or getting a foreign body in the eye. Infectious keratitis can be caused by bacteria, viruses, fungi and parasites.

If you have eye redness or other symptoms of keratitis, make an appointment to see an eye specialist. With prompt attention, mild to moderate cases of keratitis can usually be effectively treated without loss of vision. If left untreated, or if an infection is severe, keratitis can lead to serious complications that may permanently damage your vision.

Symptoms of keratitis include:

• Eye redness
• Eye pain
• Excess tears or other discharge from your eye
• Difficulty opening your eyelid because of pain or irritation
• Blurred vision
• Decreased vision
• Sensitivity to light, called photophobia
• A feeling that something is in your eye

When to see a doctor

If you notice any of the symptoms of keratitis, make an appointment to see an eye specialist right away. Delays in diagnosis and treatment of keratitis can lead to serious complications, including blindness.

Causes of keratitis include:

• Injury. If any object scratches or injures the surface of your cornea, noninfectious keratitis may result. In addition, an injury may allow microorganisms to gain access to the damaged cornea, causing infectious keratitis.
• Bacteria, fungi or parasites. These organisms may live on the surface of a contact lens or contact lens carrying case. The cornea may become contaminated when the lens is in your eye, resulting in infectious keratitis. Poor contact lens hygiene or contact lens overwear can cause both noninfectious and infectious keratitis.
• Viruses. The herpes viruses — herpes simplex and herpes zoster — may cause keratitis.
• Bacteria. Staphylococcus, streptococcus and pseudomonas are common bacteria involved in keratitis.
• Contaminated water. Bacteria, fungi and parasites in water — particularly in oceans, rivers, lakes and hot tubs — can enter your eyes when you're swimming and result in keratitis. However, even if you're exposed to these organisms, a healthy cornea is unlikely to become infected unless there has been some previous breakdown of the corneal surface — for example, from wearing a contact lens too long.

Factors that may increase your risk of keratitis include:

• Contact lenses. Wearing contact lenses — especially sleeping in the lenses —increases your risk of both infectious and noninfectious keratitis. The risk typically stems from wearing them longer than recommended, improper disinfection or wearing contact lenses while swimming.

  Keratitis is more common in people who use extended-wear contacts, or wear contacts continuously, than in those who use daily wear contacts and take them out at night.

• Reduced immunity. If your immune system is weakened due to disease or medications, you're at higher risk of developing keratitis.
• Corticosteroids. Use of corticosteroid eye drops to treat an eye disorder can increase your risk of developing infectious keratitis or make existing keratitis worse.
• Eye injury. If one of your corneas has been damaged from an injury in the past, you may be more vulnerable to developing keratitis.

Potential complications of keratitis include:

• Chronic corneal inflammation and scarring
• Chronic or recurrent viral infections of your cornea
• Open sores on your cornea, called corneal ulcers
• Temporary or permanent reduction in your vision
• Blindness

Caring for your contact lenses

If you wear contact lenses, proper use, cleaning and disinfecting can help prevent keratitis. Follow these tips:

• Choose daily wear contacts and take them out before going to sleep.
• Wash, rinse and dry your hands thoroughly before handling your contacts.
• Follow your eye care provider's recommendations for taking care of your lenses.
• Use only sterile products that are made specifically for contact lens care, and use lens care products made for the type of lenses you wear.
• Replace your contact lenses as recommended.
• Replace your contact lens case every 3 to 6 months.
• Discard the solution in the contact lens case each time you disinfect your lenses. Don't "top off" the old solution that's already in the case.
• Don't wear contact lenses when you go swimming.

Preventing viral outbreaks

Some forms of viral keratitis can't be completely eliminated. But the following steps may control viral keratitis occurrences:

• If you have a cold sore or a herpes blister, avoid touching your eyes, your eyelids and the skin around your eyes unless you've thoroughly washed your hands.
• Only use eye drops that have been prescribed by an eye doctor.
• Washing your hands frequently can reduce viral outbreaks.

Diagnosing keratitis typically involves the following:

• Eye exam. Although it may be uncomfortable to open your eyes for the exam, it's important to have your eye care provider examine your eyes.
• Penlight exam. Your eye doctor may examine your eye using a penlight, to check your pupil's reaction, size and other factors. A stain may be applied to the surface of your eye. Used with the light, this stain makes it easier to see damage to the surface of the cornea.
• Slit-lamp exam. Your eye care provider will examine your eyes with a special instrument called a slit lamp. It provides a bright source of light and magnification to detect the character and extent of keratitis, as well as the effect it may have on other structures of the eye.
• Laboratory analysis. Your eye care provider may take a sample of tears or some cells from your cornea for laboratory analysis to determine the cause of keratitis and to help develop a treatment plan for you.

Noninfectious keratitis

Treatment of noninfectious keratitis varies depending on the severity. For example, with mild discomfort from a corneal scratch, artificial tear drops may be the only treatment. However, if keratitis is causing significant tearing and pain, topical eye medications may be necessary.

Infectious keratitis

Treatment of infectious keratitis varies, depending on the cause of the infection.

• Bacterial keratitis. Antibiotic eye drops are the primary treatment for bacterial keratitis. Depending on the severity of the infection, drop frequency can range from around four times a day to every 30 minutes, even during the night. Sometimes oral antibiotics are used as a supplement.
• Fungal keratitis. Keratitis caused by fungi typically requires antifungal eye drops and oral antifungal medication.
• Viral keratitis. If a virus is causing the infection, antiviral eye drops and oral antiviral medications may be effective. Other viruses need only supportive care such as artificial tear drops.
• Acanthamoeba keratitis. Keratitis caused by the parasite acanthamoeba can be difficult to treat. Antiparasitic eye drops are used, but some acanthamoeba infections are resistant to medication and can require treatment for several months. Severe cases of acanthamoeba keratitis may require a cornea transplant.

If keratitis doesn't respond to medication, or if it causes permanent damage to the cornea that significantly impairs your vision, your eye care provider may recommend a cornea transplant.

You may start by seeing or calling your health care provider if you have eye-related symptoms that worry you. Depending on the type and severity of your symptoms, your provider may refer you to an eye specialist, called an ophthalmologist.

What you can do

• Be aware of any pre-appointment restrictions when you make the appointment. Ask if there's anything you need to do in advance, such as stop wearing contact lenses or stop using eye drops.
• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Make a list of all medications, including vitamins and supplements that you're taking.
• Write down questions to ask during your appointment.

Your time is limited, so preparing a list of questions can help you make the most of your appointment. For keratitis, some basic questions to ask include:

• What is likely causing my symptoms?
• What are other possible causes for my symptoms?
• What kinds of tests do I need?
• What is the best course of action?
• What are the alternatives to the approach you're suggesting?
• I have other health conditions. How can I best manage them together?
• Are there any restrictions that I need to follow?
• Should I see a specialist? Is there a generic alternative to the medicine you're prescribing?
• Are there any brochures or other printed material that I can take with me? What websites do you recommend?
• What will determine whether I need to be seen for a follow-up visit?

In addition to the questions you've prepared, don't hesitate to ask other questions anytime you don't understand something.

What to expect from your doctor

Your provider is likely to ask you a number of questions, including:

• When did you begin experiencing symptoms?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Has your eye been injured recently?
• Have you been swimming or been in a hot tub recently?
• Do your symptoms affect one eye or both eyes?
• Do you use contact lenses?
• Do you sleep in your contact lenses?
• How do you clean your contact lenses?
• How often do you replace your contact lens storage case?
• Have you had a similar problem in the past?
• Are you using eye drops now or have you used any recently?
• How is your general health?
• Have you ever had a sexually transmitted infection?
• Are you taking prescription medications or supplements?
• Have you recently changed the type of cosmetics that you are using?