We know that at the front of our eye there is a clear layer of tissue which is called cornea. It is like a window that lets light enter the eye. Tears defend the cornea against fungi, bacteria and viruses. The corneal ulcer is an open sore which is forming on the cornea. Corneal ulcer is usually caused by an infection. Also the small injuries to the eye or the erosion that is caused by wearing contact lenses too long can lead to infections. 
Corneal ulcer symptoms
If you have infection, you can notice signs of it before you are aware that you have corneal ulcer. Here are some symptoms of an infection:
- Sensitivity to light
- Red or pink eye
- Burning or stinging sensation in the eye
- Pus – like discharge from the eye
- Watery eye
- Itchy eye
Here are some signs and symptoms of corneal ulcer:
- Feeling like something is in your eye (foreign body sensation)
- Sensitivity to light
- Pus or eye discharge
- Swollen eyelids
- White spots on your cornea
- Blurred vision
- Excessive tearing
- Sore eye
- Eye inflammation
All of the above mentioned symptoms of corneal ulcer are severe and they should be treated immediately to prevent the blindness . The corneal ulcer itself looks like a white or gray area or spot on the usually transparent cornea. There are some corneal ulcers which are too small to be seen without magnification, but you feel the symptoms of corneal ulcers. If you have some of the above mentioned symptoms of corneal ulcers, then you should visit your doctor as soon as possible.
Corneal ulcer causes
It is known fact that the most common cause for corneal ulcers is the infection. Here are some types of infections which cause corneal ulcers:
- Fungal keratitis: This is a type of fungal infection which is developing after an injury to the cornea that is involving a plant material or plant. This fungal infection can develop in people who have weakened immune system. 
- Herpes simplex keratitis: This is a viral infection which is causing repeated flare – ups of lesions or sores in the eye. There are many different things which can trigger flare – ups, including prolonged exposure to sunlight, stress or anything that can weaken the immune system. 
- Acanthamoeba keratitis: This type of infection is most often happening in people who are wearing contact lenses. This is an amoebic infection and there are rare cases when it can lead to blindness. 
Other causes: Also there can be other causes for corneal ulcer such as
- Vitamin A deficiency 
- Tiny tears to the cornea can also lead to corneal ulcers. These tears can come from direct traumas in which are included scratches and particles such as small pieces of steel, glass or sand. These types of injuries damage the cornea and they make it easier for bacteria to invade and to cause a serious ulcer.
- Wearing unsterilized contact lenses 
- Also there are some disorders which are affecting the eyelid and they can prevent the eye from closing completely such as the Bell’s palsy. This condition can dry your cornea which is making it more vulnerable to ulcers.
- Inflammatory disorders
- Also the chemical burns or other damaging (caustic) solution splashes can injure the cornea. 
- Eye injury
- There are some disorders which cause dry eye. These disorders can leave the eye without the germ – fighting protection of tears which can lead to corneal ulcers. 
Also those people who wear disposable contact lenses for an extended period (including overnight) or people who wear expired contact lenses, have an increased risk of developing corneal ulcer . If there are scratches on the edge of your contact lenses, then they can scrape the surface of the cornea and it can make your cornea more open to bacterial infections. Also the tiny particles of dirt which are trapped underneath the contact lenses can scratch the cornea. Also there can be bacteria on your lenses or in your cleaning solutions and it gets trapped on the undersurface of your lenses. If you left your lenses for a long period, then the bacteria can multiply and it can cause damage to the cornea.
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