Bacterial keratitis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at November 30, 2016
StartDiseasesBacterial keratitis

Bacterial keratitis is an infection of the eye that is characterized by inflammation. Though serious if left untreated, when symptoms are recognized early and treated by a doctor, prognosis is good and there is a low likelihood of losing one's vision.


Definition & Facts

Bacterial keratitis is an inflammation of the cornea of the eye caused by a bacterial infection. The swelling can cause pain and other complications if left untreated. Bacterial keratitis is less common than viral keratitis, though it is more common than parasitic keratitis or fungal keratitis. Since treatment of bacterial keratitis is relatively straightforward and effective, it is likely that patients who seek diagnosis from an eye doctor will recover without long-term complications such as vision loss.

Symptoms & Complaints

One who develops bacterial keratitis will likely notice redness in one or both eyes that may be accompanied by pain. The pain may first appear as mild, but it may also be severe and become so great that it prevents a patient from opening their eyelid.

Bacterial keratitis is also characterized by an excessive discharge from the eye. This is often in the form of tearing. Sensitivity to light is another sign that bacterial keratitis may be present.

As the condition progresses, an individual may notice that vision becomes blurred at times, or they may notice reduced visual acuity. Any time there is blurred or decreased vision, it is important to see a doctor as soon as possible in order to prevent, halt, or reverse vision loss.


Bacterial keratitis is caused by an infection from some form of bacteria. This bacteria enters the eye and can cause inflammation of the cornea or its covering, the epithelium. This can happen in a number of different ways.

First, if the eye is injured and the cornea is scratched or otherwise compromised, bacteria can find its way into the eye and cause bacterial keratitis. Even a small scratch breaks the barrier protection that the cornea offers to the eye.

Another potential source of infection is from contact lenses. The contact lenses or the carrying case that they are stored in can contain bacteria if not properly cared for. These bacteria can get into the eye, especially for contact lens wearers who keep their lenses in their eyes for too long, such that the corneal epithelium becomes damaged.

Finally, a bacterial keratitis infection can be acquired from water. The germs can enter the eyes from oceans, rivers, lakes, or hot tubs when one is swimming or bathing. Those people who have had any previous breakdown of the corneal epithelium, such as from wearing contact lenses for extended periods, may wind up suffering from bacterial keratitis.

Diagnosis & Tests

When a person goes to the eye doctor for diagnosis, she will begin with a medical history and a general eye examination to determine if bacterial keratitis is a possible cause of one's symptoms. The general exam will include observing the eye as well as tests for visual acuity.

While it may be uncomfortable to open the eyelid, it is important to do so to allow the doctor a chance to get a good idea of what is going on in the eye. The doctor is likely to examine the eye in order to assess the pupil’s reaction to light and its size. The doctor may also apply a stain to the surface of the eye to check for irregularities and ulcers of the eye.

A slit lamp examination may be completed. This tool provides intense light and magnification for the best view of the many structures of the eye. It can also help to pinpoint any irregularities and injuries. To help determine the type of bacterial infection, the doctor may take a sample of tears or some cells from the cornea to send for lab testing. This will help in determining the proper course of treatment for the particular infection of the eye.

Treatment & Therapy

Treatment of bacterial keratitis is generally pretty simple. For mild cases, the doctor will usually prescribe an antibiotic eye drop that will be applied directly in the eye several times per day. If the case is more severe, oral antibiotics may be required to treat the infection.

It will be necessary to refrain from wearing contact lenses while treatment is taking place. It may also be necessary to replace the contact lenses after treatment so that if the bacteria are in the lenses, it will not re-infect the patient.

Additionally, if there are any sores or tears in the cornea, care needs to be taken to assure that they heal properly. This may require other medications and an eye patch for a period until the healing is complete. If healing does not happen, it may be possible for some patients to have a corneal transplant. This is a riskier method of treatment that is not right for all patients.

Prevention & Prophylaxis

Since one of the biggest causes of bacterial keratitis is the improper use of contact lenses, it is important to follow all instructions when caring for them. Most importantly, it is important to wash hands well before handling contact lenses.

Another good tactic is to wash the contact lens case frequently as directed by the doctor and sterilize the lenses with the proper products. One should also consider wearing daily wear over extended wear lenses and ensure that they are taken out before going to sleep.

Besides taking care with contact lenses, one should take care to avoid eye injury by keeping foreign objects away from the eyes and wearing proper safety goggles when engaged in work or activities that present the risk of eye injury.