Sharp, severe eye pain with redness, tearing, light sensitivity, and a foreign body sensation can occur when the ocular surface is scratched. This is a common occurrence and is usually due to a corneal abrasion.
The cornea is the clear, dome-like window on the front surface of the eye; it is the structure on which contact lenses rest. The epithelium is a thin carpet like layer of cells that cover the cornea. These cells protect the deeper layers of the cornea against infection and help to provide a smooth ocular surface to focus light onto the retina. When these cells are traumatized, the nerve endings that run in this layer are exposed, resulting in knife-like pain. This pain is similar to the pain experienced by the exposed nerve endings in a tooth cavity.
If you experience ocular trauma with pain, or if you feel that there is something in your eye that you cannot seem to get out, don't delay; see one of the HEA ophthalmologists promptly. Your Eye M.D. will examine the eye and likely start an antibiotic drop to help prevent infection. Neglect of this problem could lead to more serious problems such as a potentially sight threatening corneal ulcer. Unfortunately, the only true cure for the pain is complete healing of the abrasion, but luckily these usually heal in 24 to 48 hours.
Since prevention is the best medicine, try to avoid corneal abrasions by wearing protective eyewear anytime you are using machinery, striking metal on metal (i.e. hammering), or working in the yard.