Corneal ulcer: Description, Causes and Risk Factors:
Alternative Name: Ulcerative keratitis, eyesore.
Corneal ulcer is a condition in which the epithelium of the eye is disrupted. It may arise from injury, infection, intrinsic abnormalities of the cornea and neighboring structures, and rarely due to autoimmune processes.
Corneal ulcers are most commonly caused by an infection with bacteria, viruses, fungi. Other causes are abrasions or foreign bodies, inadequate eyelid closure, severe dry eyes, severe allergic eye disease, contact lens wearers and various other inflammatory disorders.
The most common cause of corneal ulcers is germs, but most of them cannot invade a healthy cornea with adequate tears and a functioning eyelid. They gain access because injury has impaired these defense mechanisms. A direct injury from a foreign object inoculates germs directly through the outer layer of the cornea, just as it does to the skin.
- Infection alone rarely causes Corneal ulcer. One exception is herpes simplex virus infection which may cause dendritic or geographic ulceration. Bacterial, fungal or amoebic agents are not normally able to invade an intact cornea and usually only do so in the presence of damaged epithelium. This may arise for example from a traumatic abrasion or a minor degree of epithelial abnormality as when an amoebic infection arises in a contact lens wearer.
- The most common viruses to damage the cornea are adenoviruses and herpes viruses. Viral and fungal infections are often caused by improper use of topical corticosteroids. If topical corticosteroids are used in a patient with herpes simplex keratitis, the ulcer can get much worse and blindness could result.
- Other injuries include excessive exposure to ultraviolet radiation of a wavelength of approximately 290 nM (nanometer) and include snow blindness, welder's arc burns and exposure to sun lamps and UVC (germicidal) lamps.
- Improper use of contact lenses has become a common cause of corneal injury that sometimes lead to corneal ulcer.
- Eyelid or tear function failure is the other way to make the eye vulnerable to infection. Tears and the eyelid together wash the eye and prevent foreign material from settling in. Tears contain enzymes and other substances to help protect against infection. Certain diseases dry up tear production, leaving the cornea dry and defenseless and make vulnerable to corneal infection and ulcer.
- Marginal corneal ulcers, which occur mainly in the elderly, are due to an immune reaction to staphylococcal protein. As the name suggests they occur mainly around the corneal margin.
Inflammation of the corneal stroma: Inflammation of the corneal stroma from any cause, e.g. herpetic keratitis, may damage the overlying epithelium and result in frank ulceration.
- Chemical injury: Chemical injuries of varying degrees of severity are also a common cause of Corneal ulcer, and a wide variety of substances have a direct toxic effect on the cells of the corneal epithelium. Chemical ulcers are frequently slow to heal.
- Dystrophic changes: Dystrophic changes of various kinds may result in corneal epithelial damage and ulceration. Inherited corneal dystrophies which may be complicated by ulceration include anterior membrane dystrophy, Reis-Buckler's dystrophy, granular, and lattice dystrophies. Corneal epithelium previously involved in ulceration may fail to adhere to the underlying stroma and such dystrophic epithelium is prone to recurrent ulceration.
- Stem cell insufficiency: Some eye disorders are associated with a deficiency of the cells which normally replenish the corneal epithelium. This stem cell deficiency may cause recurrent and intractable ulceration.
- Epitheliopathy: The normal process whereby these limbal stem cells develop and differentiate into corneal epithelial tissue may be disrupted by a number of factors. These include tear film disturbance and consequent altered nutrition and oxygenation. Tear film disruption may also be caused by recurrent trauma, e.g. due to entropion (inverted eyelashes) or contact lens wear.
- Denervation: The anaesthetic cornea is especially prone to ulceration, e.g. in trigeminal nerve injury. This may be due to the absence of neuropeptides, which are normally supplied by the neural tissue and appear to have a role in maintaining the corneal epithelium.
- Miscellaneous causes: Other, rarer causes of Corneal ulcer include chronic serpiginous ulcer, an autoimmune condition which occurs mainly in elderly subjects.
Corneal ulcers are extremely painful due to nerve exposure, and can cause tearing, squinting, and vision loss of the eye.
- Inflammation and redness in the conjunctiva of the eye and in the anterior chamber of the eye.
- Blurry vision.
- Feeling that something is in your eye.
- Pus or thick discharge draining from your eye.
- White or gray round spot on the cornea could be visible with the naked eye if the ulcer is large.
The doctor will take a case history to try to determine the cause of the ulcer. This may include improper use of contact lenses; injury, such as a scratch from a twig; or severe dry eye. An instrument called a slit lamp will be used to examine the cornea. The slit lamp is a microscope with a light source that magnifies the cornea, allowing the extent of the ulcer to be seen. Fluorescein, a yellow dye, may be used to illuminate further detail. If a germ is responsible for the ulcer, identification may require scraping samples directly from the cornea, conjunctiva, and lids, and sending them to the laboratory for further examination.
Tests: The patient should be checked for his blood glucose level or history of diabetes.
If you wear contact lenses, remove them immediately.
- Apply cool compresses to the affected eye.
- Do not touch or rub your eye with your fingers.
- Limit spread of infection by washing your hands often and drying them with a clean towel.
Specific Treatment:Treatment of corneal ulcers and infections depends upon the cause, and should be treated as soon as possible to prevent further injury to the cornea. Broad antibiotic coverage is started and then more specific antibiotic, antiviral, or antifungal eye drops are prescribed (as soon as the type of ulcer has been identified). Severe ulcers may need to be treated with corneal transplantation.
Corneal transplantation (keratoplasty) is the most successful of all tissue transplants with an overall success rate greater than 90%. The success rate mostly depends on the cause of the corneal opacity.
Disclaimer: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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