How does eye always ache to return a responsibility

The eye is always ophthalmological symptoms, mainly due to the following reasons. First, it is caused by keratitis, such as virus, bacteria or fungi infection of the cornea will cause inflammation, so stimulate the pain nerve fibers distributed in the corneal stroma, causing obvious eye pain. Second, it is caused by visual fatigue, long-term close use of the eye will cause eyeball, internal ciliary muscle spasm, resulting in spasticity. Third, it is due to glaucoma caused by glaucoma when the intraocular pressure rises, will make the eye wall by traction and stimulation, the formation of eye pain. Fourth, due to dry eye caused by insufficient eye tear secretion, will make corneal tissue dry and damaged, so the formation of obvious eye pain.