Etiology: Unknown. Clinical features: The onset is usually in infants and children (50%), and in a few cases in adolescence (10%). The typical symptom is a well-defined, uniform greenish-black patch centered around the eye, ranging in size from a few centimeters to the whole area. If the discoloration is close to the eye, the sclera (white of the eye) may be involved in the blue staining. Clinical type: The vast majority are unilateral, only a few are bilateral (5%). Greenish-black and greenish-blue colors are common, but greenish-gray and grayish-brown colors are also seen. Differential diagnosis: Bilateral nevus of Ota should be distinguished from zygomatic nevus of brownish-blue color (nevus of Ota-like spots). The color is similar to that of nevus of Ota, and the spots are distributed in the form of dots, and normal skin color can be seen between them. Treatment methods: Before the new skin laser was introduced to the market, some people treated the disease with internal herbal medicine, external chemical peeling and isotope patching methods without success, but left scars and white spots with lifelong regret. The emergence of modern new skin lasers provides the perfect means for the complete treatment of the disease, commonly treated with Q-modulated Nd:YAG laser 1064nm or Q-modulated emerald laser 755nm wavelength, with mild local bleeding and swelling for 2 to 3 days after the procedure, and generally 10 to 14 days to remove the scab. The treatment interval is about 6 months. Effectiveness: Usually the treatment varies from 2 to 8 times, but the clinical application in China for more than 10 years proves that most patients can be cured with 4 to 5 treatments. According to the experience of greenish gray and gray-brown healing effect is slightly worse. The disease has individual recurrence after treatment (the probability is not clear), but most of them are not completely cured that stop treatment.