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DESCRIPTION
If the cornea, the clear membrane covering the front of the eye overlying the iris (which is the colored part of the eye), is damaged, the eye becomes inflamed and vulnerable to infection that can result in ulceration (an open sore on the cornea). Damage may occur as a result of injury, a foreign body in the eye, or excessive or inappropriate wearing of contact lenses. The infections that can result in ulceration of the cornea may be caused by viruses, bacteria, or fungi.
OVERVIEW
A corneal ulcer, or ulcerative keratitis, is an inflammatory or more seriously, infective condition of the cornea involving disruption of its epithelial layer with involvement of the corneal stroma. It is a common condition in humans particularly in the tropics and the agrarian societies. In developing countries, corneal ulcer is frequently the cause of great morbidity as well as economic loss to the person and family. Children afflicted by Vitamin A deficiency are at high risk for corneal ulcer and may become blind in both eyes, which may persist lifelong, causing tremendous and avoidable loss to the person and the society.
CORNEAL HUMAN ANATOMY
The cornea is a transparent structure that is part of the outer layer of the eye. It refracts light and protects the contents of the eye. The corneal thickness ranges from 450 to 610 micrometers and on an average 550 µm. thick in Caucasian eyes. In Indian eyes, the average thickness is slightly less at 510 µm. The trigeminal nerve supplies the cornea via the long ciliary nerves. There are pain receptors in the outer layers and pressure receptors are deeper.
Transparency is achieved through a lack of blood vessels, pigmentation, and keratin, and through tight layered organization of the collagen fibers. The collagen fibers cross the full diameter of the cornea in a strictly parallel fashion and allow 99 percent of the light to pass through without scattering.
There are five layers in the human cornea, from outer to inner:
- Epithelium.
- Bowman's layer.
- Stroma.
- Descemet's membrane.
- Endothelium.
The outer layer is the epithelium, which is 25 to 40 µm micrometers and five to seven cell layers thick. The epithelium holds the tear film in place and also prevents water from invading the cornea and disrupting the collagen fibers. This prevents corneal edema, which gives it a cloudy appearance. It is also a barrier to infectious agents. The epithelium sticks to the basement membrane, which also separates the epithelium from the stroma. The corneal stroma comprises 90 percent of the thickness of the cornea. It contains the collagen fibers organized into lamellae. The lamellae are in sheets which separate easily. Posterior to the stroma is Descemet's membrane, which is a basement membrane for the corneal endothelium. The endothelium is a single cell layer that separates the cornea from the aqueous humor.
CORNEAL HEALING
An ulcer of the cornea heals by two methods: migration of surrounding epithelial cells followed by mitosis (dividing) of the cells, and introduction of blood vessels from the conjunctiva. Superficial small ulcers heal rapidly by the first method. However, larger or deeper ulcers often require the presence of blood vessels to supply inflammatory cells. White blood cells and fibroblasts produce granulation tissue and then scar tissue, effectively healing the cornea.
CAUSES
Corneal ulcers are a common human eye disease. They are caused by trauma, particularly with vegetable matter, as also chemical injury, contact lenses and infections. Other eye conditions can cause corneal ulcers, such as entropion, distichiae, corneal dystrophy, and keratoconjunctivitis sicca (dry eye).
Many micro-organisms cause infective corneal ulcer. Among them are bacteria, fungi, viruses, protozoa, and chlamydia.
- Bacterial keratitis is caused by Staphylococcus aureus, Streptococcus viridans, Escherichia coli, Enterococci, Pseudomonas, Nocardia and many other bacteria. Bacterial infections are common in people who wear contact lenses.
- Fungal keratitis causes deep and severe corneal ulcer. It is caused by Aspergillus sp., Fusarium sp., Candida sp., as also Rhizopus, Mucor, and other fungi. The typical feature of fungal keratitis is slow onset and gradual progression, where signs are much more than the symptoms. Small satellite lesions around the ulcer are a common feature of fungal keratitis and hypopyon is usually seen. Fungal infections may develop with improper care of contact lenses or the overuse of eyedrops that contain steroids.
- Viral keratitis causes corneal ulceration. It is caused most commonly by Herpes simplex (the virus that causes cold sores), Herpes Zoster (the varicella virus that causes chicken pox and shingles) and Adenoviruses. Also it can be caused by corona-viruses and many other viruses. Herpes virus cause a dendritic ulcer, which can be recur and relapse over the lifetime of an individual.
- Protozoa infection like Acanthamoeba keratitis is characterized by severe pain and is associated with contact lens users swimming in pools.
- Chlamydia trachomatis can also contribute to development of corneal ulcer.
Tiny tears to the corneal surface may become infected and lead to corneal ulcers. These tears can come from direct trauma by scratches or metallic or glass particles striking the cornea. Such injuries damage the corneal surface and make it easier for bacteria to invade and cause a corneal ulcer.
Disorders that cause dry eyes can leave your eye without the germ-fighting protection of tears and cause ulcers.
Disorders that affect the eyelid and prevent your eye from closing completely, such as Bell's palsy, can dry your cornea and make it more vulnerable to ulcers.
Any condition which causes loss of sensation of the corneal surface may increase the risk of corneal ulceration.
Chemical burns or other caustic (damaging) solution splashes can injure the cornea and lead to corneal ulceration.
People who wear contact lenses are at an increased risk of corneal ulcers. The risk of corneal ulcerations increases tenfold when using extended-wear soft contact lenses. Extended-wear contact lenses refer to those contact lenses that are worn for several days without removing them at night. Contact lenses may damage your cornea in many ways:
- Scratches on the edge of your contact lens can scrape the cornea's surface and make it more vulnerable to bacterial infections.
- Similarly, tiny particles of dirt trapped underneath the contact lens can scratch the cornea.
- Bacteria may be on the improperly cleaned lens and get trapped on the undersurface of the lens. If your lenses are left in your eyes for long periods of time, these bacteria can multiply and cause damage to the cornea.
- Wearing lenses for extended periods of time can also block oxygen to the cornea, making it more susceptible to infections.
SUPERFICIAL & DEEP CORNEAL ULCERS
Superficial ulcers involve a loss of part of the epithelium. Deep ulcers extend into or through the stroma and can result in severe scarring and corneal perforation. Descemetoceles occur when the ulcer extends through the stroma. This type of ulcer is especially dangerous and can rapidly result in corneal perforation, if not treated in time.
The location of the ulcer depends somewhat on the cause. Central ulcers are typically caused by trauma, dry eye, or exposure from facial nerve paralysis or exophthalmos. Entropion, severe dry eye and distichiasis (inturning of eye lashes) may cause ulceration of the peripheral cornea. Immune-mediated eye disease can cause ulcers at the border of the cornea and sclera. These include Rheumatoid arthritis, rosacea, systemic sclerosis which lead to a special type of corneal ulcer called Mooren's ulcer. It has a circumferential crater like depression of the cornea, just inside the limbus, usually with an overhanging edge.
SYMPTOMS
Corneal ulcers are extremely painful due to nerve exposure, and can cause tearing, squinting, and vision loss of the eye. There may also be signs of anterior uveitis, such as miosis (small pupil), aqueous flare (protein in the aqueous humour), and redness of the eye. An axon reflex may be responsible for uveitis formation - stimulation of pain receptors in the cornea results in release inflammatory mediators such as prostaglandins, histamine, and acetylcholine.
- Red eye.
- Pain in the eye.
- Feeling that something is in your eye.
- Tearing.
- Pus or thick discharge draining from your eye.
- Blurry vision.
- Pain when looking at bright lights.
- Swollen eyelids.
- A white or gray round spot on the cornea that is visible with the naked eye, if the ulcer is large.
DIAGNOSIS & TREATMENT
EXAMS & TESTS
GENERAL DIAGNOSIS OVERVIEW
Because corneal ulcers are a serious problem, you should see your ophthalmologist (a medical health care provider who specializes in eye care and surgery).
Your ophthalmologist will be able to detect if you have an ulcer by using a special eye microscope, known as a slit lamp. To make the ulcer easier to see, he or she will put a drop containing the dye fluorescein into your eye.
If your ophthalmologist thinks that an infection is responsible for the ulcer, he or she may then get samples of the ulcer to send to the laboratory for identification.
MEDICAL DIAGNOSIS PROCEDURE
Diagnosis is done by direct observation under magnified view of slit lamp revealing the ulcer on the cornea. The use of fluorescein stain, which is taken up by exposed corneal stroma and appears green, helps in defining the margins of the corneal ulcer, and can reveal additional details of the surrounding epithelium. Herpes simplex ulcers show a typical dendritic pattern of staining. Rose-Bengal dye is also used for supra-vital staining purposes, but it may be very irritating to the eyes. In descemetoceles, the Descemet's membrane will bulge forward and after staining will appear as a dark circle with a green boundary, because it does not absorb the stain. Doing a corneal scraping and examining under the microscope with stains like Gram's and KOH (potassium hydroxide) preparation may reveal the bacteria and fungi respectively. Microbiological culture tests may be necessary to isolate the causative organisms for some cases. Other tests that may be necessary include a Schirmer's test for keratoconjunctivitis sicca and an analysis of facial nerve function for facial nerve paralysis.
GENERAL MEDICAL TREATMENT OVERVIEW
Your ophthalmologist will remove your contact lenses if you are wearing them.
Your ophthalmologist will generally not place a patch over your eye if he or she suspects that you have a bacterial infection. Patching creates a warm dark environment that allows bacterial growth.
Hospitalization may be required if the ulcer is severe.
GENERAL MEDICATIONS OVERVIEW
Because infection is a common occurrence in corneal ulcers, your ophthalmologist will prescribe antibiotic eyedrops. If the infection appears very large, you may need to use these drops as often as one drop an hour.
Oral pain medications will be prescribed to control the pain. Pain can also be controlled with special eyedrops that keep your pupil dilated.
MEDICAL TREATMENT
Proper diagnosis is essential for optimal treatment. Bacterial corneal ulcer require intensive fortified antibiotic therapy to treat the infection. Fungal corneal ulcers require intensive application of topical anti-fungal agents. Viral corneal ulceration caused by herpes virus may antivirals like topical acyclovir ointment instilled at least five times a day. Alongside, supportive therapy like pain medications are given, including topical cycloplegics like atropine or homatropine to dilate the pupil and thereby stop spasms of the ciliary muscle. Superficial ulcers may heal in less than a week. Deep ulcers and descemetoceles may require conjunctival grafts or conjunctival flaps, soft contact lenses, or corneal transplant. Proper nutrition, including protein intake and Vitamin C are usually advised. In cases of Keratomalacia, where the corneal ulceration is due to a deficiency of Vitamin A, supplementation of the Vitamin A by oral or intramuscular route is given. Drugs that are usually contraindicated in corneal ulcer are topical corticosteroids and anesthetics - these should not be used on any type of corneal ulcer because they prevent healing, may lead to superinfection with fungi and other bacteria and will often make the condition much worse.
REFRACTORY CORNEAL ULCERS
(Recurrent Corneal Erosion)
Refractory corneal ulcers are superficial ulcers that heal poorly and tend to recur. They are also known as indolent ulcers or Boxer ulcers. They are believed to be caused by a defect in the basement membrane and a lack of hemidesmosomal attachments. They are recognized by undermined epithelium that surrounds the ulcer and easily peels back. Refractory corneal ulcers are most commonly seen in diabetics and often occur in the other eye later. They are similar to Cogan's cystic dystrophy.
MEDICAL TREATMENT
Topical fortified antibiotics are used at hourly intervals to treat infectious corneal ulcers. Cycloplegic eye drops are applied to give rest to the eye. Pain medications are given as needed. Loose epithelium and ulcer base can be scraped off and sent for culture sensitivity studies to find out the pathogenic organism. This helps in choosing appropriate antibiotics. Complete healing takes anywhere from about few weeks to few months.
Refractory corneal ulcers can take a long time to heal, sometimes months. In case of progressive or non-healing ulcers, surgical intervention by an Ophthalmologist with corneal transplantation may be required to save the eye. In all corneal ulcers it is important to rule out predisposing factors like Diabetes Mellitus and Immunodeficiency.
MELTING ULCERS
Melting ulcers are a type of corneal ulcer involving progressive loss of stroma in a dissolving fashion. This is most commonly seen in Pseudomonas infection, but it can be caused by other types of bacteria or fungi. These infectious agents produce proteases and collagenases which break down the corneal stroma. Complete loss of the stroma can occur within 24 hours.
MEDICAL TREATMENT
Treatment includes antibiotics and collagenase inhibitors such as acetylcysteine. Surgery in the form of corneal transplantation (penetrating keratoplasty) is usually necessary to save the eye.
SURGERY
If the ulcer cannot be controlled with medications or if it threatens to perforate the cornea, you may require an emergency surgical procedure known as corneal transplant.
FOLLOW-UP & AT HOME CARE
If you do not need hospitalization, your ophthalmologist will prescribe eyedrops and pain medications for you to take regularly at home. You will need to follow up with your ophthalmologist daily until your ophthalmologist tells you differently.
You should contact your ophthalmologist immediately if you experience symptoms such as worsening vision, pain, discharge, or fever.
HOLISTIC RECOMMENDATIONS & NUTRITION
CORNEAL ULCER TREATMENT - SELF-CARE AT HOME
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.
Take over-the-counter pain medications, such as acetaminophen (Tylenol) or ibuprofen (Motrin).
NUTRITIONAL SUPPLEMENTS
Unless otherwise specified, the dosages recommended here are for adults. For a child between the ages of 12 and 17, reduce the dose to 3/4 the recommended amount. For a child between 6 and 12 years of age, use 1/2 the recommended dosage, and for a child under the age of 6, use 1/4 the recommended amount.
PREVENTION
Seek medical attention from your ophthalmologist immediately for any eye symptoms. Even seemingly minor injuries to your cornea can lead to an ulcer and have devastating consequences, including blindness or loss of the eye.
Wear eye protection when exposed to small particles that can enter your eye.
If you have dry eyes or if your eyelids do not close completely, use artificial teardrops to keep your eyes lubricated.
If you wear contact lenses, be extremely careful about the way you clean and wear your lenses.
Always wash your hands before handling the lenses. Never use saliva to lubricate your lenses because your mouth contains bacteria that can harm your cornea.
Remove your lenses from your eyes every evening and carefully clean them. Never use tap water to clean the lenses.
Never sleep with your contact lenses in your eyes.
Store the lenses in disinfecting solutions overnight.
Remove your lenses whenever your eyes are irritated and leave them out until your eyes feel better.
Regularly clean your contact lens case.
EXPECTED OUTCOME
A corneal ulcer is a true emergency. Without treatment, the ulcer can spread to the rest of your eyeball, and you can become partially or completely blind in a very short period of time. Your cornea may also perforate, or you could develop scarring, cataracts, or glaucoma.
With the proper treatment, corneal ulcers should improve within two to three weeks.
If scars from previous corneal ulcers impair vision, a corneal transplant may be needed to restore normal vision.
RECOMMENDATIONS
If you suspect that a corneal ulcer may be developing, consult a health care provider immediately.
HELPFUL RELATED LINKS & RESOURCES
American Academy of Ophthalmology
655 Beach Street
Box 7424
San Francisco, CA 94120
(415) 561-8500
www.aao.org
Medem Medical Library: Eye Health
TYPES OF EYE PROBLEMS & DISORDERS
Maintaining Healthy Eyes
NOTIFY YOUR MIDWIFE OR HEALTH CARE PROVIDER IF...
You or a family member are having problems with vision and/or you suspect an infection. Call your health care provider immediately if you experience severe eye pain or a sudden change in your vision, such as loss of vision or double vision, feeling that something is in your eye, obvious discharge draining from your eye, or if you have a history of scratches to the eye or exposure to chemicals (always follow lab safety precautions when handling any kind of chemical or biohazardous materials) or flying particles (an example is a welder or metal grinder getting metal shards in the eye, or a wood worker getting bits of wood splinters in the eye... always wear protective eye wear when doing any kind of work in which your eyes can be damaged).
You have any increase of symptoms. You may need frequent changes in your eyeglass prescription. If you have blurred or double vision that develops slowly; are having a problem seeing because of daytime glare or have difficulty driving at night because of glare from headlights, you need to see your health care provider.
You have any unexpected or unusual symptoms. There may be underlying health issues that need to be addressed.
Are having vision problems that are affecting your ability to perform daily activities.
Call your child's health care provider if your baby does not look directly at or respond readily to faces or large, colorful objects by age 2 to 3 months or if your child scowls, squints, or shields his or her eyes more than expected when in sunlight, or light seems to hurt your child's eyes.
You and your family members should have your eyesight checked regularly by your health care provider to rule out any problems and to receive a prescription for contacts or eyeglasses, if they are needed. Preserve you vision... it is very important.
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