What causes pain in the left eye?

Normally, eye pain can be divided into three categories, one is severe eye pain, then severe eye pain, can be due to corneal foreign body or upper eyelid conjunctiva foreign body, there is trichiasis, mechanical or chemical corneal damage, and keratitis, glaucoma, endophthalmitis or trigeminal neuralgia and so on. If only the discomfort of the eye, then often due to refractive error, or eye muscle balance imbalance caused; If the eyeball is only burning, dry itching or dry feeling, then it may be chronic conjunctivitis or excessive smoking and drinking, keratoconjunctivitis sicca, blepharitis and ametropia, or spring catarrhal conjunctivitis and so on. Therefore, there are many reasons for eyeball pain, we should go to the ophthalmology department for a comprehensive and systematic examination, identify the cause, symptomatic treatment.