What can cause a corneal abrasion?

Usually injury. The most common cause for corneal abrasion is trauma, usually something striking the front surface of the eye like a fingernail, hairbrush, or tree branch. Other causes include corneal dystrophies, severe dry eye, eye surgery, contact lens removal, and many others. Most can be treated with drops to help the pain and prevent infection, although bandage contact lenses or patching may be required.