The feeling of something inside the eye, or foreign body sensation, is usually caused by the following reasons: First, corneal foreign body or conjunctival foreign body, that is, a foreign body like sand does enter the eye, and with the rotation of the eye and the opening and closing of the eyelid, the foreign body will rub the cornea, thus causing a foreign body sensation in the eye. Secondly, when there is an entropion or inflammation of the lid margin, the eyelashes will no longer grow in the direction of the front, but will be directed towards the eye, which will rub the corneal epithelium and cause a foreign body sensation in the eye. Thirdly, dryness of the conjunctiva, when the tear secretion of the eye decreases, a complete tear film cannot be formed to cover the surface of the eye, and the relative friction between the eyelid and the eye lacks sufficient lubrication, leading to a foreign body sensation in the eye.