The common causes of pain in one eye are: conjunctivitis, keratitis, glaucoma, uveitis and so on. 1. Conjunctivitis: it can be caused by bacterial infection or stimulated by some physical and chemical factors. It can involve one eye or both eyes. It often manifests as pain, foreign body sensation, burning sensation, increased secretion and other symptoms. Tobramycin eye drops and other drugs can be used as prescribed by the doctor. 2. Keratitis: mainly including bacterial keratitis, viral keratitis, fungal keratitis, etc., the patient often manifests as pain in one eye, photophobia, tearing, eyelid spasm and other symptoms. It is recommended to seek timely medical treatment to avoid the expansion of the disease, resulting in corneal ulceration and perforation. 3. Glaucoma: It is caused by congenital or acquired factors that prevent the circulation of aqueous humor in the eye, thus triggering an increase in intraocular pressure. Glaucoma can be characterized by swelling and pain in one eye, accompanied by headache and vision loss. It is recommended to lower the intraocular pressure in time to avoid affecting the vision. 4. Uveitis: mostly related to infection and autoimmune factors. When the disease attacks, there may be symptoms such as eye congestion, eye pain, photophobia and so on. The inflammation can affect one eye or both eyes. So it can also lead to pain in one eye. 5. Others: If there is refractive error, when wearing glasses of different prescription, one eye pain and fatigue can also occur, and it is recommended to change the glasses of appropriate prescription in time. In addition, when a foreign body enters into the eye, pain and discomfort in this eye can also occur. To summarize, if one eye hurts, it is recommended to go to the regular hospital for consultation, clear diagnosis and follow the doctor’s instructions for active treatment.