Keratitis (redirected from infectious keratitis)

Keratitis 

Definition

Keratitis is an inflammation of the cornea, the transparent membrane that covers the colored part of the eye (iris) and pupil of the eye.

Description

There are many types and causes of keratitis. Keratitis occurs in both children and adults. Organisms cannot generally invade an intact, healthy cornea. However, certain conditions can allow an infection to occur. For example, a scratch can leave the cornea open to infection. A very dry eye can also decrease the cornea's protective mechanisms.

Risk factors that increase the likelihood of developing this condition include:

Some common types of keratitis are listed below, however there are many other forms

Herpes simplex keratitis

A major cause of adult eye disease, herpes simplex keratitis may lead to:

This infection generally begins with inflammation of the membrane lining the eyelid (conjunctiva) and the portion of the eyeball that comes into contact with it. It usually occurs in one eye. Subsequent infections are characterized by a pattern of lesions that resemble the veins of a leaf. These infections are called dendritic keratitis and aid in the diagnosis.

Recurrences may be brought on by stress, fatigue, or ultraviolet light (UV) exposure (e.g., skiing or boating increase the exposure of the eye to sunlight; the sunlight reflects off of the surfaces). Repeated episodes of dendritic keratitis can cause sores, permanent scarring, and numbness of the cornea.

Recurrent dendritic keratitis is often followed by disciform keratitis. This condition is characterized by clouding and deep, disc-shaped swelling of the cornea and by inflammation of the iris.

It is very important not to use topical corticosteroids with herpes simplex keratitis as it can make it much worse, possibly leading to blindness.

Bacterial keratitis

People who have bacterial keratitis wake up with their eyelids stuck together. There can be pain, sensitivity to light, redness, tearing, and a decrease in vision. This condition, which is usually aggressive, can be caused by wearing soft contact lenses overnight. One study found that overnight wear can increase risk by 10-15 times more than if wearing daily wear contact lenses. Improper lens care is also a factor. Contaminated makeup can also contain bacteria.

Bacterial keratitis makes the cornea cloudy. It may also cause abscesses to develop in the stroma, which is located beneath the outer layer of the cornea.

Fungal keratitis

Usually a consequence of injuring the cornea in a farm-like setting or in a place where plant material is present, fungal keratitis often develops slowly. This condition:

Peripheral ulcerative keratitis

Peripheral ulcerative keratitis is also called marginal keratolysis or peripheral rheumatoid ulceration. This condition is often associated with active or chronic:

Superficial punctate keratitis

Often associated with the type of viruses that cause upper respiratory infection (adenoviruses), superficial punctate keratitis is characterized by destruction of pinpoint areas in the outer layer of the cornea (epithelium). One or both eyes may be affected.

Acanthamoeba keratitis

This pus-producing condition is very painful. It is a common source of infection in people who wear soft or rigid contact lenses. It can be found in tap water, soil, and swimming pools.

Photokeratitis

Photokeratitis or snowblindness is caused by excess exposure to UV light. This can occur with sunlight, suntanning lamps, or a welding arc. It is called snowblindness because the sunlight is reflected off of the snow. It therefore can occur in water sports as well, because of the reflection of light off of the water. It is very painful and may occur several hours after exposure. It may last one to two days.

Interstitial keratitis

Also called parenchymatous keratitis, interstitial keratitis is a chronic inflammation of tissue deep within the cornea. Interstitial keratitis is rare in the United States. Interstitial keratitis affects both eyes and usually occurs as a complication of congenital or acquired syphilis. In congenital syphilis it can occur between age two and puberty. It may also occur in people with tuberculosis, leprosy, or other diseases.

Causes and symptoms

In summary, keratitis can be caused by:

Symptoms of keratitis include, but are not limited to:

Diagnosis

A case history will be taken and the vision will be tested. Examination with a slit lamp, an instrument that's a microscope and focuses a beam of light on the eye is important for diagnosis. The cornea can be examined with fluorescein, a yellow dye which will highlight defects in the cornea. Deeper layers of the cornea can also be examined with the slit lamp. Infiltrates, hazy looking areas in the cornea, can be seen by the doctor and will aid in the diagnosis. Samples of infectious matter removed from the eye will be sent for laboratory analysis.

Treatment

Antibiotics, antifungals, and antiviral medication will be used to treat the appropriate organism. Broad spectrum antibiotics will be used immediately, but once the lab analysis determines the offending organism, the medication may be changed. Sometimes more than one medication is necessary. It depends upon the infection, but the patient should be clear on how often and how to use the medications.

A sterile, cotton-tipped applicator may be used to gently remove infected tissue and allow the eye to heal more rapidly. Laser surgery is sometimes performed to destroy unhealthy cells, and some severe infections require corneal transplants.

Antifungal, antibiotic, or antiviral eyedrops or ointments are usually prescribed to cure keratitis, but they should be used only by patients under a doctor's care. Inappropriate prescriptions or over-the-counter preparations can make symptoms more severe and cause tissue deterioration. Topical corticosteroids can cause great harm to the cornea in patient's with herpes simplex keratitis.

A patient with keratitis may wear a patch to protect the healing eye from bright light, foreign objects, the lid rubbing against the cornea, and other irritants. Sometimes a patch can make it worse, so again, the patient must discuss with the doctor whether or not a patch is necessary. The patient will probably return every day to the eye doctor to check on the progress.

Although early detection and treatment can cure most forms of keratitis, the infection can cause:

Prevention

Children and adults who wear contact lenses should always use sterile lens-cleaning and disinfecting solutions. Tap water is not sterile and should not be used to clean contact lenses. It is important to go for follow-up checkups because small defects in the cornea can occur without the patient being aware of it. Do not overwear contact lenses. Remove them if the eyes become red or irritated. Replace contact lenses when scheduled to do so. Proteins and other things can deposit on the contacts, leading to an increased risk of infection. Rinse contact lens cases in hot water every night, if possible, and let them air dry. Replace contact lens cases every three months. Organisms have been cultured from contact lens cases.

Eating a well-balanced diet and wearing protective glasses when working or playing in potentially dangerous situations can reduce anyone's risk of developing keratitis. Protective goggles can even be worn mowing the lawn so that if twigs are tossed up they can't hurt the eye. Goggles or sunglasses with UV coatings can help protect against damage from UV light.

Resources

Organizations

American Academy of Ophthalmology. 655 Beach Street, P.O. Box 7424, San Francisco, CA 94120-7424. http://www.eyenet.org.

American Optometric Association. 243 North Lindbergh Blvd., St. Louis, MO 63141. (314) 991-4100. http://www.aoanet.org.

National Eye Institute. 2020 Vision Place, Bethesda, MD 20892-3655. (301) 496-5248. http://www.nei.nih.gov.

Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 331-2020. http://www.preventblindness.org.

Key terms

Abscess — A collection of pus.

Glaucoma — An eye disease characterized by an increase of pressure in the eye. Left untreated, blindness may result.

Infiltrate — A collection of cells not usually present in that area. In the cornea, infiltrates may be a collection of white blood cells.

Inflammation — A localized response to an injury. May include swelling, redness, and pain.

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keratitis /ker·a·ti·tis/ (ker?ah-ti´tis) inflammation of the cornea.

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keratitis bullo´sa  presence of blebs upon the cornea.

dendriform keratitis , dendritic keratitis herpetic keratitis which results in a branching ulceration of the cornea.

herpetic keratitis 

1. that, commonly with dendritic ulceration (dendriform or dendritic k.), due to infection with herpes simplex virus.

2. that occurring in herpes zoster ophthalmicus.

interstitial keratitis  chronic keratitis with deep deposits in the cornea, which becomes hazy.

lattice keratitis  bilateral hereditary corneal dystrophy with formation of interwoven filamentous lesions.

microbial keratitis  that resulting from bacterial or fungal infection of the cornea, usually associated with soft contact lens wear.

neuroparalytic keratitis  that due to injury to the trifacial nerve which prevents closing of the eyelids, marked by dryness and fissuring of the corneal epithelium.

phlyctenular keratitis  see under keratoconjunctivitis.

sclerosing keratitis  keratitis with scleritis.

trachomatous keratitis  pannus trachomatosus.

ulcerative keratitis  keratitis with ulceration of the corneal epithelium, frequently a result of bacterial invasion of the cornea.

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ker·a·ti·tis (kr-tts)

n. pl. ker·a·tit·i·des (-tt-dz)

Inflammation of the cornea.

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keratitis,

n any inflammation of the cornea.

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keratitis

inflammation of the cornea. Keratitis may be deep, when the infection causing it is carried in the blood or spreads to the cornea from other parts of the eye, or superficial, caused by bacterial or viral infection, trauma, or by allergic reaction. The clinical signs include pain, blepharospasm, ocular discharge, and when chronic, pigmentation.

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chronic superficial keratitis

a progressive cellular infiltration with vascularization and eventually pigmentation of the cornea that usually commences at the temporal (lateral) quadrant and advances towards the center. The whole cornea may become involved. It occurs in dogs, particularly German shepherd dogs. The cause is unknown, but exposure to ultraviolet light may be a factor. Cellular infiltrates suggest immune mechanisms are involved in the pathogenesis. Called also CSK, degenerative pannus, Uberreiter's syndrome.

eosinophilic keratitis

a superficial neovascularization and cellular infiltration of the cornea, beginning at the temporal limbus, in adult cats. Eosinophils and plasma cells are found in conjunctival or corneal scrapings and biopsies, and a peripheral eosinophilia is sometimes present. The cause is unknown, but it may be immune-mediated.

exposure keratitis

keratitis resulting from ineffective or incomplete closure of the eyelids with drying of the corneal tear film. Occurs in paralysis of the eyelids, brachycephalic dogs with prominent globes, and cats during ketamine anesthesia. See also lagophthalmos.

herpetic keratitis

herpesvirus infections of the cornea occur in feline and bovine rhinotracheitis infections, and are suspected in dogs. In cats there may be ulcerative keratitis with dendritic ulcers; in cattle conjunctivitis is more common than keratitis.

infectious keratitis

see thelazia, onchocerca, moraxellabovis.

interstitial keratitis

inflammation of the substantia propria, causing dense corneal clouding.

mycotic keratitis

see keratomycosis.

neurotrophic keratitis, neuroparalytic keratitis

a chronic keratopathy resulting from impairment of the sensory (trigeminal) innervation of the cornea.

keratitis nigrum

see corneal sequestrum.

keratitis sicca

see keratoconjunctivitis sicca.

superficial diffuse keratitis

see chronic superficial keratitis (above).

superficial pigmentary keratitis

a pigmentation of epithelium and superficial stroma of the cornea, resulting from chronic keratitis from a variety of causes. Seen most commonly in brachycephalic dogs in which the contributing factors are exposure keratitis, distichiasis, irritation from the nasal folds and sometimes keratoconjunctivitis sicca.

superficial punctate keratitis

a keratopathy with discrete opacities of the cornea, without ulceration. Can be caused by irritation.

ulcerative keratitis

see corneal ulcer.