Nevus of Ota, also known as brownish-bronze nevus of the upper frontal part of the eye, ocular dermal melanocytosis, ocular dermal melanosis, and melanocytosis of the mucous membranes and skin of the eye, was first reported by Masao Ota of Japan in 1938, and is often called nevus of Ota, which is a dark-brown, blotchy lesion of the sclera and the skin of the face innervated by the trigeminal nerve. It is present at birth in 65% of patients, with the remainder appearing mostly between the ages of 10-20 years. The lesions are pale greenish, brownish-black, black or tawny patches with a dark center and fading edges. The color of the lesions is aggravated by sun exposure, exertion, menstruation, etc., and some of them become darker and enlarged during puberty. The most common areas of this disease are around the eyes, temporal, forehead, zygomatic, and nose, that is, equivalent to the area where the first and second branches of the trigeminal nerve are distributed, mostly unilateral distribution, occasionally bilateral. Nowadays, the treatment of nevus of Ota is mainly based on laser treatment, and there are three types of commonly used lasers for nevus of Ota treatment: Q-switched ruby laser, Q-switched emerald green gemstone laser, and Q-switched Nd:YAG (garnet) laser. The difference lies mainly in the gemstones used in the core of the laser, which are ruby, emerald and garnet. Ruby and emerald composition is very similar, ruby for the Al2O3 and chromium complex, emerald for the Be-containing Al2O3 and chromium complex and garnet for man-made stone, the three have their own advantages and disadvantages, as described below. From the purchase of equipment, ruby and emerald green laser purchase price are higher, and the above two types of lasers are only original imports, and no domestic. But the main thing is that the failure rate of the two is relatively high, the cost of maintenance and repair is very high, much higher than the Nd: YAG laser, so the promotion of the equipment is limited by some economic conditions. Ruby laser is mainly suitable for white people and is the best-selling laser in Europe and America, but in Asia and the continent, where yellow people are mainly found, it is prone to the complications of pigment loss and has fewer users. The emerald green laser is most suitable for yellow people and is the best-selling laser in developed areas of Asia such as South Korea, Japan and Taiwan, but due to the price and other reasons, it has not been entered into the mainland market until the second half of 2009, when it began to formally start sales in the mainland market. The purchase price of Nd:YAG laser is relatively low, and domestic manufacturers are able to produce, such as domestic, the price is even lower, while its biggest advantage lies in the low failure rate, maintenance and repair costs are much lower than the first two types of lasers, so it is the domestic use of the longest time, the best-selling laser. From the therapeutic effect, Nd:YAG laser emits a wavelength of 1064nm, the wavelength of the pigment selectivity is low, and its energy is absorbed by the pigment at the same time will also be absorbed by the blood vessels, resulting in blood vessel rupture and bleeding, so in the treatment of Nd:YAG laser, there must be obvious bleeding and thick scabs. However, since its energy is partially absorbed by blood vessels, its therapeutic effect is also reduced accordingly. The ruby and alexandrite lasers emit wavelengths of 694nm and 755nm respectively, which are very close to each other and have similar effects, except that the alexandrite laser is more suitable for yellow people. These two wavelengths have high selectivity to pigment, the blood vessels absorb very little, so there will be no bleeding phenomenon during the treatment, only local whitening at the treatment place and slight scabs, and its therapeutic effect is better than that of Nd:YAG laser.