Corneal

If the cornea of your eye becomes damaged through disease, infection, or injury, the resulting scars can interfere with vision by blocking or distorting light as it enters the eye.

The cornea is the clear, protective outer layer of the eye. Along with the sclera (white of the eye), it serves as a barrier against dirt, germs, and other particles that can harm the eye's delicate components. The cornea is also capable of filtering out some amounts of the sun's ultraviolet light.

The cornea also plays a key role in vision. As light enters the eye, it is refracted, or bent, by the outside shape of the cornea. The curvature of this outer layer helps determine how well your eye can focus on objects close-up and far away.

There are three main layers of the cornea:

Epithelium. The most superficial layer of the cornea, the epithelium stops outside matter from entering the eye. This layer of the cornea also absorbs oxygen and nutrients from tears.
Stroma. The stroma is the middle and thickest layer of the cornea and is found behind the epithelium. It is made up mostly of water and proteins that give it an elastic but solid form.
Endothelium. The endothelium is a single layer of cells located between the stroma and the aqueous humor -- the clear fluid found in the front chamber of the eye. The endothelium works as a pump, expelling excess water back into the eye as it is absorbed into the stroma. Without this specialized function, the stroma would become waterlogged, creating a hazy and opaque cornea and reducing vision.

The term "corneal disease" refers to a variety of conditions that affect mainly the cornea. These include infections, degenerations, and many other disorders of the cornea that may arise mostly as a result of heredity.

What Are Symptoms of Cornea Problems?

With its ability for quick repair, the cornea usually heals after most minor injuries or infections. However, during the healing process a variety of symptoms may be experienced, including:

Pain
Blurred vision
Tearing
Redness
Extreme sensitivity to light

Although these symptoms may occur with many other types of eye problems, they may indicate a more serious problem or require special treatment. Therefore, if you experience any of these symptoms, seek care from an eye doctor.

What Conditions Can Damage the Cornea?

Keratitis

Keratitis is an inflammation of the cornea that sometimes occurs with infection after viruses, bacteria, or fungi enter the cornea. These microorganisms can enter the eye after superficial or deep injuries, causing infection, inflammation, and ulceration of the cornea. Though uncommon, this type of infection can also arise after injury from wearing contact lenses.

Symptoms of keratitis include: