Eye pain may be severe and seem sharp, aching, or throbbing, or people may feel only mild irritation of the eye surface or the sensation of a foreign object in the eye (foreign body sensation). Many causes of eye pain also cause the eye to look red. Other symptoms may be present depending on the cause of eye pain. For example, people may have blurred vision, a bulging eye, or pain worsened by bright light.
The cornea (the clear layer in front of the iris and pupil) is highly sensitive to pain. Many disorders that affect the cornea also affect the anterior chamber (the fluid-filled space between the iris and the inner part of the cornea) and cause spasm of the muscle that controls the iris (the ciliary muscle). When such spasm is present, bright light causes muscle contraction and worsening pain.