There are black spots in the eyes. What's the cause?

What is the cause of black spots in the eyes? The outermost layer of normal eyeball is white scleral tissue, and the scleral surface is covered with transparent bulbar conjunctiva. The black spots are conjunctival pigment spots, also known as conjunctival pigment nevus. It is the bulbar conjunctiva of the palpebral fissure, irregular round, different in size, clear in boundary, slightly raised on the conjunctival surface, generally black, pigment shades. Generally benign, no effect on vision, and will not cause any uncomfortable performance. If it affects the appearance, it can be surgically removed. The operation is very simple. After the pigmented nevus is cut off, 1 to 2 stitches are sewn on the conjunctiva, and the patient generally recovers quickly. If the pigmented nevus is progressively enlarged, it is necessary to immediately operate, and the excised tissue is sent for pathological examination.