The cornea is the transparent, dome-shaped "window" that covers the front of the eye. A nick, scratch or scrape of the cornea is called a corneal abrasion.
Corneal abrasions are one of the most common forms of eye injury. In some cases, they are caused by the direct impact of a sharp object, such as a pencil, staple, nail or sewing pin. They also can be caused by small, airborne particles, such as dust, sand or flying debris from soldering, woodworking or weed trimming. Even fingernails can cause a corneal abrasion.
Although corneal abrasions can occur in people of all ages, people more likely to have this happen include:
Infants who scratch their eyes unintentionally with untrimmed fingernails
School children who play with pencils, pens and other pointed objects
Athletes who play sports without using some form of eyewear to protect against dust, sand or an accidental scratch from another player's finger. More eye injuries occur in baseball and football than in other sports.
People who have hobbies or crafts that use pointed tools, such as sewing and wood carving, or that produce dust, such as woodworking and gardening
Workers who are exposed to eye hazards on the job, especially those involved in farming or construction
Anyone who inserts contact lenses without properly cleaning their hands and their lenses beforehand
The cornea has several layers of cells and membranes. The thin top layer, called the epithelium, is composed of sensitive cells that are similar to skin. Below this surface layer lies a tough, protective structure called Bowman's membrane. The epithelium and Bowman's membrane together make up only 10% of the thickness of the cornea. They are the two layers most involved in corneal abrasions. Abrasions that involve only the surface epithelium have a good chance of healing without any long-term effects. However, deeper abrasions that penetrate through the Bowman's membrane are more likely to cause permanent corneal scars. These scars are opaque, whitish areas in the cornea that may interfere with normal vision.
In the United States, corneal abrasions are the most common eye injury in children. Boys get corneal abrasions twice as often as girls between the ages of 5 and 15. Most corneal abrasions are superficial injuries that involve only the surface layer of the cornea. Although these abrasions can be very painful, they don't usually cause permanent vision problems.