A small black spot on the black eye can be caused by many reasons. Clinically it is more common to be a corneal foreign body, such as the eye with congestion, and foreign body sensation and other symptoms, mostly seen in workers in the workshop, mostly caused by iron filings foreign body, after the diagnosis needs to be promptly performed corneal foreign body removal, otherwise it is easy to lead to secondary infection. Some patients who have been there for a long time and do not have any symptoms may be caused by metallic pigmentation, for example, after occupational exposure to various foreign bodies such as iron, copper and silver, which are not removed in time, and the pigment is deposited in the corneal stroma. If small black dots appear at the edge of the cornea, it may also be a malignant melanoma of the corneal rim. Some patients may present with localized elevation of the corneal rim, which is yellowish or dark brown in color, and may also be caused by corneal dermatomal cysts.