Keratitis is an inflammation of the cornea, the outermost part of the eye that covers the pupil and iris (the colored ring around the pupil). The most common causes of keratitis are infection and injury.
Bacterial, viral, parasitic and fungal infections can cause keratitis. An infectious keratitis can happen after an injury to the cornea. But an injury can inflame the cornea without a secondary infection occurring.
Viral keratitis occurs quite commonly and the types of viruses include:
- Adenovirus, which is one of the causes of upper respiratory infections.
- Herpes simplex type 1, the same virus that causes cold sores.
- Varicella zoster (also a herpes virus), which is associated with chickenpox and shingles.
Bacterial keratitis occurs less often than viral keratitis. Parasitic and fungal keratitis is rarely seen in developed countries.
Infectious keratitis usually begins by affecting the outer layer of the cornea, but it can go deeper into the cornea, increasing the risk of impaired vision.
Non-infectious keratitis is a feature of some autoimmune diseases, such as rheumatoid arthritis and Sjogren's syndrome.
Trauma to the front of the eye, as may occur with poorly fitting contact lenses, surgery on the cornea (including LASIK surgery), or any other injury to the cornea may lead to keratitis.
People who wear contact lenses are at increased risk for infectious keratitis. Lens wear should stop immediately if a person suspects that he or she is developing an eye infection.
Symptoms of keratitis include:
- Red eye
- Sensation of something, like sand, in the eye
- Sensitivity to light
- Watery eye
- Blurred vision
- Difficulty keeping the eyelids open
When caused by an injury or infection, such as herpes simplex virus, keratitis usually affects only one eye, but both eyes may be affected when keratitis is due to other causes.
Your health care professional will ask you about your symptoms, your vision, and your health in general. Your doctor, or an eye specialist, will use an instrument that magnifies the surface of the cornea to look for a tiny ulcer caused by viral infection. This ulcer when due to herpes simplex tends to send out star-like branches, and is best seen after a dye is used to stain the cornea temporarily. Herpes simplex infection of the cornea may be accompanied by infection of the eyelid. In this case, tiny, painful blisters resembling cold sores of the lips may appear on the eyelid.
Your doctor also may:
- Test your visual sharpness and clearness (visual acuity)
- Test of how well your pupil responds to light
- Examine your eye using a special instrument called a slit lamp
- Gently swab inside the eyelid to get a sample to send to the laboratory for culture.
Keratitis caused by a virus or bacterium tends to get better relatively quickly. Herpes keratitis and bacterial keratitis are treated with antiviral medication or antibiotics. Keratitis caused by other viruses usually gets better on their own within a few days.
If keratitis is related only to contact lenses, the duration tends to be brief.
Keratitis caused by autoimmune disease, some parasites or prior injury can be difficult to treat and may be long lasting (chronic). In these cases, permanent damage to the cornea with impaired vision may occur despite intense treatment.
The best way to prevent keratitis is to avoid eye injury by wearing sunglasses and appropriate eye gear as needed.
If you have a cold sore, do not put your fingers to your eyes, because that could spread the infection. If there is any suspicion that you have herpes simplex virus, steroid eye drops may be dangerous because they can make this infection worse.
Routine contact lens hygiene, a balanced diet and moisturizing eye drops may help prevent other causes of keratitis.
Treatment of keratitis depends upon the cause. If there is mild injury to the cornea, such as a scratched cornea, no specific treatment is necessary. An antibiotic ointment might be prescribed. This is done mostly for comfort.
If the keratitis is caused by herpes simplex or the herpes zoster virus that causes shingles, your doctor will prescribe antiviral eye drops or an antiviral oral medication or both. Bacterial keratitis needs to be treated with antibiotics. Depending on the severity of the infection, an oral antibiotic may be prescribed along with an antibiotic ointment or eye drops.
Artificial tears for lubrication usually are effective for keratitis related to ocular dryness. Keratitis caused by an autoimmune disease is often treated with topical corticosteroid eye drops. Also treating the underlying disease helps the keratitis heal with less chance of recurrence.
When To Call a Professional
The seriousness of keratitis varies widely, but you should call your doctor promptly if symptoms develop, especially if you have pain or your vision is impaired. Depending on how severe your symptoms are, your doctor may send you directly to an eye specialist who has special equipment for evaluating eye conditions.
The prognosis for most cases of keratitis is very favorable. With early treatment of keratitis caused by herpes simplex, shingles, or bacteria, most people will heal without loss of vision. Early treatment of parasitic and fungal keratitis also is essential. But even with appropriate treatment, the infection may persist. If vision is very impaired, your eye specialist may suggest corneal transplant.