keratitis
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What is keratitis?
Keratitis is an inflammation of the cornea, the transparent, dome-like part of the eye in front of the iris and pupil. Infectious or non-infectious processes can cause it; non-infectious keratitis can predispose the cornea to secondary infections.
Causes of infectious keratitis include bacteria, viruses, fungi, and protozoans. Symptoms include pain, redness, light sensitivity, decreased vision, and discharge. Treatment requires identification of the causative organism via culturing for tailored antimicrobial therapy. Contact lens use raises the risk of serious infection.
Interstitial keratitis, deep corneal inflammation, can stem from congenital syphilis, tuberculosis, herpesvirus infection, or physical injury.
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What part of the eye does keratitis affect?
Keratitis is an inflammation of the cornea, which is the transparent, dome-shaped part of the eyeball that covers the iris and pupil. Keratitis can be caused by infectious or non-infectious agents. Symptoms can include pain, redness, light sensitivity, and decreased vision. In some instances, both the conjunctiva and the cornea become inflamed, a condition known as keratoconjunctivitis.
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What are common symptoms of keratitis?
Keratitis, or inflammation of the cornea, can stem from infectious or non-infectious causes. Symptoms of keratitis include redness, pain, decreased vision, light sensitivity, and discharge. A visible opacity may also appear within the cornea.
Infectious keratitis can be caused by bacteria, viruses, fungi, and protozoans. Non-infectious keratitis can result from dry eye, injury, or issues with eyelid closure.
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What can cause keratitis to develop?
Keratitis, or inflammation of the cornea, can stem from infectious or noninfectious causes, with noninfectious keratitis often leading to secondary infections.
Infectious causes include bacteria, viruses, fungi, and protozoans. Viral infections, especially herpesviruses, can cause dendritic ulcers. Bacterial infections usually follow a corneal injury. Fungal infections can also occur post-injury, particularly with corticosteroid use.
Noninfectious causes include excessive dryness from immune disorders or diseases affecting tear glands, such as Sjögren’s syndrome, or the inability to close the eyes completely. Chemical burns, especially from alkalis, can cause severe damage. Rosacea keratitis is linked to high levels of cathelicidin, an antimicrobial protein, while neuroparalytic keratitis results from interruption of sensory impulses, making the cornea more prone to injury and infection. Other causes include reactions to topical eye medications, toxin exposure, and allergic conditions.
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How do doctors diagnose and treat keratitis?
Keratitis is an inflammation of the cornea that can stem from infectious or non-infectious causes. Diagnosing the specific cause of keratitis is achieved through culturing the infected corneal tissue and discharge to identify the causative organism. Treatment is then tailored with appropriate antimicrobial therapy.
For interstitial keratitis, treatment aims to eliminate the underlying disease, such as syphilis or herpesvirus. In cases of excessive dryness, aggressive eye lubrication is the first step; if ineffective, closure of tear drainage holes or surgery to partially close the lids may be necessary. Chemical burns require immediate and copious irrigation with water to minimize damage.
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What are possible complications if keratitis is not treated properly?
If keratitis is not properly treated, several complications can arise, including the spread of blood vessels into the cornea and visual loss due to the cornea becoming opaque. Chemical burns, especially from acids and alkalis, are significant causes; alkali burns can cause severe, progressive damage, potentially "melting" the cornea if not quickly removed.
Additionally, neuroparalytic keratitis, resulting from interrupted sensory impulses, can lead to corneal ulceration, impaired vision, and potentially require enucleation (removal of the eye). In rosacea keratitis, severe pain and corneal scarring can impair vision.
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keratitis, inflammation of the cornea, the transparent domelike portion of the eyeball in front of the iris and pupil. There are several varieties of keratitis, which can be caused by either infectious or noninfectious processes. In many cases, however, changes in the cornea induced by noninfectious keratitis predispose it to secondary infections. Often there is inflammation of both the cornea and the conjunctiva, the mucous membrane that lines the inside of the eyelid and covers the white of the eye (the sclera). In this case, the condition is called keratoconjunctivitis.
Infectious causes of keratitis include bacteria, viruses, fungi, and protozoans. Symptoms vary but may include redness, pain, decreased vision, light sensitivity, discharge, or a frank opacity within the cornea. Treatment often requires culturing the infected corneal tissue and discharge in order to identify the causative organism so as to tailor antimicrobial therapy appropriately. The concurrent use of contact lenses increases the likelihood of serious infection in these cases and raises special considerations for the eye care specialist.
Interstitial keratitis, an inflammation deep in the cornea, may be caused by congenital syphilis, tuberculosis, herpesvirus infection, or even physical injury to the eye. Affected persons may note that their eyes are painful, tend to water, and are sensitive to light. Treatment is directed at eliminating the underlying disease. As with any keratitis, if corticosteroids are used in the course of treatment, close follow-up with an ophthalmologist is required, since certain conditions can worsen with these medications.
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In dendritic (branching) keratitis, or dendritic ulcer, the cornea is inflamed by infection with the herpes simplex (cold sore) virus or herpes zoster (shingles) virus. The lesions, as the name suggests, follow branching lines, along which minute blisters may form and break, leaving raw areas. The cornea may ultimately become insensitive, so the process may not be painful.
One type of noninfectious keratitis, called keratoconjunctivitis sicca, results from excessive dryness of the cornea. This condition is characterized by dryness and inflammation of the cornea and conjunctiva due to failure to secrete sufficient tears, which in turn can stem from immune disorders or diseases that infiltrate the lacrimal, or tear, gland. The condition is called Sjögren’s syndrome when the dry eye is associated with certain systemic disorders. In exposure keratitis the cornea may also become dry and inflamed when, because of protrusion of the eyeball or paralysis of the muscle that closes the lids, a person is unable to shut his eyes completely. Initial treatment employs aggressive eye lubrication; however, if this fails, closure of the eyelid puncta (tear drainage holes) or surgery to partially close the lids may be needed.
Keratitis can cause the spread of blood vessels onto and into the cornea and can cause visual loss by opacifying the cornea (making it cloudy). Keratitis from chemical burns, particularly burns from acids and alkalis, is a leading culprit. Early flooding of the eye with water, either slightly salted or straight from the tap, is standard procedure, since the extent of the damage depends in large part upon the length of time that the chemical remains in the eye. The most serious chemical burns are caused by alkali, which, if not quickly removed, can do severe and progressive damage to the point of “melting” the cornea.
Rosacea keratitis is a complication of acne rosacea, a disease in which the skin of the face is affected first by pronounced flushing and later by the formation of nodules and pustules. The keratitis may cause severe pain and corneal scarring with impairment of vision. Patients with rosacea keratitis have unusually high levels and abnormal forms of an antimicrobial protein called cathelicidin, which is synthesized by cells of the immune system, such as macrophages and neutrophils. Cathelicidin stimulates the production of inflammatory molecules that contribute to the symptoms and complications associated with rosacea.
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Neuroparalytic keratitis is inflammation of the cornea as a sequel to interruption of sensory impulses over the fifth (trigeminal) cranial nerve. The cornea’s loss of sensitivity leaves it much more subject to injury, exposure, and infection. This type of keratitis tends to lead to ulceration of the cornea and impairment of vision and may result in perforation of the eyeball, which could necessitate enucleation (removal of the eye). Treatment includes the intensive use of eye lubricants and may also include antibiotics if a secondary infection of the cornea is present.
Other possible causes of keratitis are numerous and include reactions to topical eye medications, toxin exposure, infection and inflammation of the eyelid margins (blepharitis), and various allergic conditions.