Corneal Ulcer

Corneal Ulcer

Synonyms and Related Keywords

Bacterial keratitis, Fungal keratitis, Acanthamoeba keratitis, Herpes simplex keratitis, corneal infection, open sore on the cornea, contact lenses, contact lens wearers, ulcerative keratitis




What is corneal ulcer ?

A corneal ulcer is an erosion or open sore in the outer layer of the cornea the clear structure overlying the iris (which is the colored part of your eye). It is common associated with infection by a bacterium, virus, fungus, or parasite.The 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 & avoidable loss to the person and the society.



Corneal anatomy of the human

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 micrometres 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.

Most Commmon cause of corneal ulcers are caused by infections.

Corneal ulcers are most commonly caused by an infection with bacteria, viruses, fungi or amoebae. Other causes are abrasions (scratches) or foreign bodies, inadequate eyelid closure, severely dry eyes, severe allergic eye disease, and various inflammatory disorders.
Contact lens wear, especially soft contact lenses worn overnight, may cause a corneal ulcer. Herpes simplex keratitis is a serious viral infection. It may cause repeated attacks that are triggered by stress, exposure to sunlight, or any condition that impairs the immune system. Bacterial infections cause corneal ulcers and are common in people who wear contact lenses. Fungal keratitis can occur after a corneal injury involving plant material, or in immunosuppressed people. Acanthamoeba keratitis occurs in contact lens users, especially those who attempt to make their own homemade cleaning solutions.Fungal infections can cause corneal ulcers and may develop with improper care of contact lenses or the overuse of eyedrops that contain steroids.
Viral infections are also possible causes of corneal ulcers. Such viruses include the herpes simplex virus (the virus that causes cold sores) or the varicella virus (the virus that causes chickenpox and shingles).
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.
Risk factors are dry eyes, severe allergies, history of inflammatory disorders, contact lens wear, immunosuppression, trauma, and generalized infection.

Corneal Ulcer Symptoms

Eye pain
Impaired vision, Blurry vision
Eye redness( red eye)
White patch on the cornea
Sensitivity to light (photophobia)
Watery eyes, Tearing
Eye burning, itching and discharge
Feeling that something is in your eye
Pus or thick discharge draining from your eye
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 of Corneal ulcer

Because corneal ulcers are a serious problem, you should see your ophthalmologist (a medical doctor 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.
Visual acuity
Tear test
Slit-lamp examination
Pupillary reflex response
Keratometry (measurement of the cornea)
Scraping the ulcer for analysis or culture
Fluorescein stain of the cornea
Blood tests to check for inflammatory disorders may also be needed.
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 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.

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 oint 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.
So can conclude that how to treatment corneal ulcer
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 or ibuprofen.

Medical Treatment
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

Prognosis of corneal ulcer

Untreated, a corneal ulcer or infection can permanently damage the cornea. Untreated corneal ulcers may also perforate the eye (cause holes), resulting in spread of the infection inside, increasing the risk of permanent visual problems.

Possible Complications of corneal ulcer

Corneal scarring
Severe vision loss
Loss of the eye

Prevention of corneal ulcer

Prompt, early attention by an ophthalmologist for an eye infection may prevent the condition from worsening to the point of ulceration. Wash hands and pay rigorous attention to cleanliness while handling contact lenses, and avoid wearing contact lenses overnight.