Medical term:

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:

poor contact lens care; overuse of contact lenses
illnesses or other factors that reduce the body's ability to overcome infection
cold sores, genital herpes, and other viral infections
crowded, dirty living conditions; poor hygiene
poor nutrition (especially a deficiency of Vitamin A, which is essential for normal vision)

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:

chronic inflammation of the cornea
development of tiny blood vessels in the eye
scarring
loss of vision
glaucoma

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:

usually affects people with weakened immune systems
often results in infection within the eyeball
may cause stromal abscesses

Peripheral ulcerative keratitis

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

rheumatoid arthritis
relapsing polychondritis (connective-tissue inflammation)
Wegener's granulomatosis, a rare condition characterized by kidney disease and development of nodules in the respiratory tract

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:

bacterial, viral, or fungal infections
dry eyes resulting from disorders of the eyelid or diminished ability to form tears
exposure to very bright light
foreign objects that injure or become lodged in the eye
sensitivity or allergic reactions to eye makeup, dust, pollen, pollution, or other irritants
vitamin A deficiency, which people with normal diets rarely develop

Symptoms of keratitis include, but are not limited to:

tearing
pain
sensitivity to light
inflammation of the eyelid
decrease in vision
redness

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:

glaucoma
permanent scarring
ulceration of the cornea
blindness

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.

keratitis

[ker″ah-ti´tis]

inflammation of the cornea. It 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 or by allergic reaction. Agents causing the inflammation can be introduced into the cornea during the removal of foreign bodies from the eye. All infections of the eye are potentially serious because opaque fibrous tissue or scar tissue may form on the cornea during the healing process and cause partial or total loss of vision. See also keratoconjunctivitis.

Causes. There are several kinds of keratitis. Dendritic keratitis is a viral form caused by the herpes simplex virus; it usually affects only one eye. Acute serpiginous keratitis is a bacterial form that may result from infection by pneumococci, streptococci, or staphylococci. Dendritic keratitis and certain other kinds may follow symptoms of upper respiratory tract infection, such as fever. Burns of the cornea, such as those produced by chemicals or ultraviolet rays, can also cause keratitis. In trachoma, a contagious disease of the conjunctiva, the eyes become inflamed, and small, gritty particles develop on the cornea. Herpetic keratitis may accompany herpes zoster. Interstitial keratitis is a type usually caused by congenital syphilis, appearing in children between ages 5 and 15; occasionally it may result from acquired syphilis. In rare cases it may result from tuberculosis or rheumatic infection in other parts of the body.

Symptoms. Symptoms vary somewhat among the different forms of keratitis, but pain, which may be severe, and photophobia (inability to tolerate light) are usual. There may also be considerable effusion of tears and a conjunctival discharge.

Treatment. Antibiotics are the usual treatment for keratitis caused by an infectious organism. Cortisone is used for other forms, but may be dangerous in some patients. Antiviral agents such as idoxuridine have been used to treat herpes simplex (dendritic) keratitis. In cases of syphilitic interstitial keratitis, the syphilis is treated. Congenital interstitial keratitis can be prevented if syphilis is detected early in pregnancy by means of blood tests and the mother is treated.

ker·a·ti·tis

(ker'ă-tī'tis),

Inflammation of the cornea.
See also: keratopathy.

[kerato- + G. -itis, inflammation]

keratitis

(kĕr′ə-tī′tĭs)

Inflammation of the cornea.

keratitis

Corneal inflammation, caused by nonspecific irritants or microorganisms.

keratitis

Ophthalmology Corneal inflammation, caused by nonspecific irritants, or microorganisms. See Interstitial keratitis.

ker·a·ti·tis

(ker'ă-tī'tis)

Inflammation of the cornea.
See also: keratopathy

[kerato- + G. -itis, inflammation]

keratitis

Inflammation of the outer lens of the eye (the CORNEA).

This implies a prior invasion of the cornea with blood vessels (vascularization). Keratitis commonly follows inadequately or incorrectly treated infections with cold sore (Herpes simplex) viruses and is also a feature of TRACHOMA and congenital SYPHILIS. There is pain, watering and acute sensitivity to light. Vision is severely affected if the centre of the cornea is involved. See also KERATOCONJUNCTIVITIS.

keratitis

Inflammation of the cornea. It can arise from various sources, the most common being: infection by bacteria, fungi or viruses, hypersensitivity to staphylococcal exotoxins, nutritional deficiencies, failure of the eyelids to cover the cornea, deficiencies in the precorneal tear film, contact lens wear (especially extended wear), mechanical, radiation or chemical trauma or interruption of the ophthalmic branch of the trigeminal nerve. It is usually characterized by a dullness and loss of transparency of the cornea due to infiltrates, neovascularization, oedema and is accompanied by ciliary injection. The discomfort varies from a foreign body sensation to severe pain, with lacrimation, photophobia, blepharospasm and an impairment of vision. If the condition is severe, ulcers and pus (hypopyon) will appear and the iris and ciliary body may become involved. It is important to identify the cause and the organism in order to treat the condition. Keratitis of bacterial origin is treated with antibiotic drugs. Keratitis of viral origin (e.g. herpes) is treated with antiviral agents and that of fungal origin with antifungal agents. See corneal infiltrates; keratomalacia; keratomycosis; keratopathy.
acanthamoeba keratitis A rare type of keratitis caused by the microorganism acanthamoeba, which invades the cornea. The symptoms begin with a foreign body sensation, which turns into pain, photophobia, tearing, blepharospasm and blurred vision. The signs are infiltrates that develop into a ring, and the cornea may eventually become opaque. Diagnosis of the disease is made by laboratory analysis of a corneal scraping. Contact lens wear has been found to be associated with this disease in about three-quarters of the cases, especially when the patient has used homemade or unpreserved saline. The other cases were due to contact with stagnant water or following an abraded cornea. The therapy is with repetitive doses of antiamoebic agents (e.g. biguanide) and an antibiotic (e.g. propamidine isethionate) or a combination of propamidine and neomycin. However, strict compliance with contact lens regimens and avoidance of exposure to dirty, stagnant water diminishes the risks of contracting the disease. See corneal infiltrates; disinfection; propamidine isethionate.
actinic keratitis See actinic keratoconjunctivitis.
acute epithelial keratitis See herpes zoster ophthalmicus.
acute stromal keratitis A complication of scleritis in which there are superficial and mid-stromal infiltrates in the limbal region. Lesions can also be noted in the central cornea and may develop vascularization and permanent opacification. In cases of scleritis that are limited (i.e. not diffuse), corneal changes are noted only in the bordering corneal region.
dendritic keratitis See herpes simplex keratitis.
disciform keratitis A deep localized keratitis involving the stroma, usually characterized by a disc-shaped grey area (Wessley ring) that may spread to the whole thickness of the cornea. It is due to a viral infection (e.g. herpes simplex virus) or to an immune reaction, or it may also occur as a sequel to trauma. It may heal without residue or may cause scarring and vascularization of the cornea. Treatment is with steroid and antiviral agents. See central corneal clouding; keratic precipitates; Wessley ring.
epithelial keratitis See punctate epithelial keratitis.
exposure keratitis See exposure keratopathy.
filamentary keratitis Keratitis characterized by the presence of fine epithelial filaments. It can occur as a result of herpes, thyroid dysfunction, corneal abrasions, keratoconjunctivitis sicca, etc.
fungal keratitis A keratitis caused by a fungus, such as Fusarium, Aspergillus, or Candida albicans. The condition may develop after eye injury (e.g. fingernail or contact lens scratch, tree branch), especially in agricultural areas. However, it has become more common since the use of corticosteroids. It may also occur in eyes suffering from corneal disease, after keratoplasty, diabetes or extended-wear contact lenses. It is characterized by greyish-white, rough ulcers with indistinct and feathery edges with filaments infiltrating into the stroma (filamentary keratitis). There is ciliary and conjunctival injection and it may be accompanied by ring abscesses and, in severe cases, hypopyon. The ulcers have oval or round outlines with a plaque-like surface and the cornea is fully oedematous. Differential diagnosis is facilitated by corneal scraping or biopsy of the ulcer. Management consists mainly of antifungal agents. Syn. mycotic keratitis. See keratomycosis.
herpetic keratitis Keratitis caused by either herpes simplex or herpes zoster viruses. See herpesvirus; herpes simplex keratitis.
herpes simplex keratitis An inflammation of the cornea, which occurs occasionally as a result of a blepharoconjunctivitis caused by the herpes simplex virus (usually type 1). The disease begins with skin vesicles typically spread over the lids, conjunctiva and periorbital area. Symptoms include irritation, photophobia, tearing, reduced corneal sensation and blurred vision if the central cornea is involved. The characteristic sign is a dendritic ulcer, which enlarges progressively resulting in a configuration referred to as a geographical ulcer. Treatment is with an antiviral agent (e.g. aciclovir) or debridement of the epithelium if unresponsive to antiviral agents. Syn. dendritic ulcer. See herpesvirus; disciform keratitis; interstitial keratitis; punctate epithelial keratitis; ulcerative keratitis.
hypopyon keratitis Purulent keratitis with ulcer resulting in the presence of pus in the anterior chamber, which gravitates to the bottom. The ulcer is a dirty grey colour and the conjunctiva is also inflamed. The usual cause of the infection is the pneumococcus which gives rise to a corneal ulcer (often called serpiginous ulcer because of its tendency to creep forward in the cornea). See hypopyon; ulcerative keratitis; corneal ulcer.
interstitial keratitis Keratitis involving the stroma. It is characterized by deep vascularization of the cornea and is often associated with iridocyclitis. Formerly, the most common cause was congenital syphilis (syphilitic keratitis). However, nowadays it is usually the result of a herpes simplex infection, or it may be part of a syndrome (Cogan's) or other systemic diseases (e.g. leprosy, tuberculosis). Management involves cycloplegics, topical antiviral agents and in severe cases corticosteroids. Syn. stromal interstitial keratitis. See Wessley ring; Hutchinson's sign.
lagophthalmic keratitis See exposure keratopathy.
marginal keratitis A condition characterized by subepithelial peripheral corneal infiltrates which may spread circumferentially and are separated from the limbus by a clear zone, which may eventually become invaded by blood vessels. It is a hypersensitivity response to staphylococcal exotoxins. There is discomfort, pain, redness and photophobia. Treatment is with topical steroids.
microbial keratitis, contact lens induced A keratitis caused by a microorganism such as a bacteria (e.g. Pseudomonas aeruginosa, Serratia marcescens), amoeba (e.g. Acanthamoeba), or less commonly a virus or fungus. The incidence of the condition is relatively low. It has been estimated to be 2 to 5 individuals with daily wear of soft lenses and 10 to 20 with extended wear of soft lenses per 10 000 per year. High oxygen permeability leads to less infection. Signs and symptoms include pain, infiltrates, redness, lacrimation, photophobia, corneal oedema, reduced vision, discharge, swollen lids and aqueous flare. The condition may have been precipitated by non-compliance, poor hygiene, dirty lens case, etc. Management includes cessation of lens wear and drug therapy.
mucous plaque keratitis See herpes zoster ophthalmicus.
mycotic keratitis See fungal keratitis.
non-ulcerative keratitis See contact lens acute red eye.
neuroparalytic keratitis Keratitis caused by a failure of blinking or infrequent or incomplete blinking causing inadequate spread of tears. See exposure keratopathy.
neurotrophic keratitis See neurotrophic keratopathy.
peripheral ulcerative keratitis A severe form of keratitis most often associated with a systemic disease, the most common being rheumatoid arthritis, Wegener's granulomatosis, lupus erythematosus and polyarteritis nodosa. It is characterized by pain, usually redness and peripheral ulceration with corneal thinning. Treatment is urgent and directed towards the primary cause. See Mooren's ulcer.
phlyctenular keratitis See phlyctenular keratoconjunctivitis.
punctate epithelial keratitis (PEK) An inflammation of the cornea characterized by either multiple, small, superficial, punctate lesions or minute, flat, epithelial dots resulting from bacterial infection (e.g. chlamydial, staphylococcal), vitamin B₂ deficiency, virus infection (e.g. herpes) and also from exposure to ultraviolet light, injury to the eye with aerosol products or contact lens solutions. The condition is usually associated with conjunctivitis. Treatment depends on the causative agent (e.g. antiviral agents will be used to suppress symptoms in herpes simplex keratitis). Syn. superficial punctate keratitis (SPK), although this term is more often used to describe a PEK of viral origin. See adult inclusion conjunctivitis; Thygeson' superficial punctate keratitis.
rosacea keratitis Keratitis associated with acne rosacea of the face. It is characterized by marginal vascularization at the limbus. The vessels extend into the cornea surrounded by a zone of grey infiltration. The infiltrates and vascularization are in the cornea proper and not raised above the surface (unlike phlyctens). There is little tendency to ulcerate. It is usually associated with an inflammation of the conjunctiva (keratoconjunctivitis). Treatment involves topical steroid drops as well as systemic antibiotic therapy. See acne rosacea; phlyctenular keratoconjunctivitis.
keratitis sicca See keratoconjunctivitis sicca.
superficial punctate keratitis See punctate epithelial keratitis.
stromal keratitis; syphilitic keratitis See interstitial keratitis.
Thygeson's superficial punctate keratitis A rare type of punctate epithelial keratitis. It is characterized by circular or oval, greyish-white epithelial lesions commonly located centrally and slightly elevated with a cluster of granular dots. The lesions show punctate staining with fluorescein. The cause is unknown, although a virus is suspected. It gives rise to mild irritation, photophobia and slight blurring of vision. Treatment includes artificial tears, corticosteroids (but this may induce recurrence) and therapeutic soft contact lenses. Untreated, it may subside within a few years.
ulcerative keratitis Any keratitis in which there is an ulcer of the cornea. The cause may be bacterial or viral infection, trauma or contact lens wear (particularly extended wear). The ulcer is a dirty grey coloured area on the cornea, the eye is red, the pain can be severe, there is photophobia, lacrimation, and vision may be affected. Immediate treatment is necessary: if due to contact lenses, cessation of wear and topical antibiotics will be used. See herpes simplex keratitis; corneal ulcer.
ultraviolet keratitis See actinic keratoconjunctivitis.

ker·a·ti·tis

(ker'ă-tī'tis)

Inflammation of the cornea.

[kerato- + G. -itis, inflammation]

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