The cornea is the clear, dome-shaped area that covers the front of the eye. Light passes through the cornea before reaching the retina in the back of the eye, and so it must remain clear so light can pass through. Corneal opacities can cause anything from minor irritation to vision problems and even blindness. In fact, corneal problems are the fourth leading cause of blindness (after glaucoma, cataracts, and age-related macular degeneration).
Most of the focusing power in the eye occurs along the front surface, called the cornea, which is the clear "window" in the front of the eyeball. The next structure involved in focussing is the lens, which sits behind the cornea inside the eye. The ideal cornea has a round, symmetrically curved surface, like a basketball. Astigmatism is caused by an "out of round" cornea or a lens that is not symmetrical. As a result, people with significant astigmatism may have distorted or blurry vision.
Injury, infection, and certain eye diseases can cause corneal opacities. Here is an overview of the symptoms, causes, and treatment of conditions that affect the cornea.
Corneal Opacity Symptoms
The cornea is formed by strong, tough tissue composed of five different layers, each with a specific function. The cornea protects the eye from dust, germs, UV rays, and other foreign substances. Along with the lens, it bends light rays onto the retina so that images appear in focus. If the corneal shape is excessively steep, flat, or not completely round, it can cause nearsightedness, farsightedness, or astigmatism. These are called refractive errors. Certain types of corneal diseases can change the shape of the cornea.
Depending on the cause, symptoms of corneal damage may include:
Redness and swelling of the eye tissues and eyelid
Corneal injuries can occur when a foreign object gets in the eye or from something striking the eye. This can cause cuts or scratches to the cornea. Common causes of cornea injury include:
An object in the eye, such as sand or dust
Something striking the eye, such as a tree branch
Radiation injury from the sun, sun lamps, welding, or sun reflected on snow (snow blindness)
Complications of contact lens wear
Minor corneal abrasions heal quickly, usually within two days. More serious wounds take longer to heal and can cause irritation, pain, tearing, and redness. If the cornea becomes deeply scarred it can cause vision problems. Treatment may include patching the eye, using a temporary contact lens, and prescription eye drops or ointments. If vision problems remain or the cornea becomes permanently damaged, you may need a cornea transplant. This surgery removes the damaged cornea and replaces it with a healthy donor cornea.