The manifestation of painful eyeball pressure in one eye may be caused by scleritis, glaucoma and keratitis. 1. Scleritis: scleritis occurs in one eye due to the lowering of the patient’s own immunity, which can cause localized congestion and redness of the conjunctiva on the patient’s white eyeball, and there is also pain in the eyeball after pressing. 2. Glaucoma: due to genetic and developmental abnormalities, patients with glaucoma have increased intraocular pressure, which can cause eye swelling and pain, blurred vision. Pressing on the eyeball can cause the pressure inside the patient’s eyeball to rise further, thus aggravating the pain. 3. Keratitis: If the patient has monocular keratitis, under the stimulation of inflammation, it can lead to pain in a single eyeball after pressing the patient. It is recommended that patients with significant pain in one eye should seek prompt medical attention to evaluate their condition and follow the doctor’s instructions for treatment.