The cornea is the clear, protective outer layer of the eye.
Along with the sclera (white of the eye), the cornea 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. If the cornea becomes
damaged through disease, infection, or injury, the resulting scars
or discoloration can interfere with vision by blocking or
distorting light as it enters the eye.
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 also absorbs oxygen and nutrients from tears.
- Stroma: The stroma is the largest 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 and rear chambers of the eye. The
endothelium works as a pump, expelling excess water as it is
absorbed into the stroma. Without this specialized function, the
stroma could become waterlogged and hazy and opaque in appearance,
also 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 that may arise mostly as a
result of heredity.
What are the symptoms of corneal conditions?
With its ability for quick repair, the cornea usually heals after
most injury or disease. However, when there is deep injury to the
cornea, the healing process may be prolonged, possibly resulting in
a variety of symptoms, including:
- Pain
- Blurred vision
- Tearing
- Redness
- Extreme sensitivity to light
- Corneal scarring
If you experience any of these symptoms, seek care from an eye
doctor. They may indicate a more serious problem or require special
treatment.
What conditions can damage the cornea?
Keratitis
This is an inflammation of the cornea that sometimes occurs with
infection after bacteria or fungi enter the cornea. These
microorganisms can enter the eye after deep injury, causing
infection, inflammation, and ulceration of the cornea. Though
uncommon, this type of infection can also arise after injury from
wearing contact lenses.