Nevus of Ota
What is Nevus of Ota?
Nevus of Ota is typically a bluish or gray-brown lesion of the eye and the surrounding skin innervated by the first and second branches of the trigeminal nerve. It is caused by the entrapment of melanocytes in the upper third of the dermis. The sclera is involved in two-thirds of cases (causing an increased risk of glaucoma). It should not be confused with Mongolian spot, which is a birthmark caused by entrapment of melanocytes in the dermis but is located in the lumbosacral region. Women are nearly five times more likely to be affected than men, and it is rare among white people. Nevus of Ota may not be congenital, and may appear during puberty.
This serious cosmetic problem occurs in 0.6 percent of Japanese,' but is also seen in Chinese, East Indians, blacks, and white. Treatments have included surgical removal, skin grafting, dermabrasion, and cryotherapy.
Surgical treatment causes scarring. Cryotherapy, though somewhat effective depending on the site of the lesion, is not reliable and may cause atrophy or scarring if over applied.
Selective photothermolysis produces specific, heat-mediated injury to pigmented skin cells and other structures by means of brief and selectively absorbed laser pulses. Melanin, the pigment in melanosomes, is a potential target for selective photothermolysis, because it is the primary light-absorbing compound of cells exposed to laser energy of a certain wavelength.
The Q-switched Nd: YAG laser can produce very short high-energy pulses and can selectively target cells that contain pigment, such as dermal melanocytes.
The patients are treated with topical anesthesia (5 percent lidocaine hydrochloride ointment). During all treatment sessions, the eyes of the patients and the clinical staff are protected. The treatment intervals ranged from 6-8weeks.
A white square appears immediately after pigmented skin was exposed to the Q-switched Nd;YAG
laser. A wheal-and-flare response is seen around the irradiated sites about five minutes later. This response is pronounced when periorbital areas are treated. The whitening is more intense in pigmented skin than in the surrounding skin. This white color fades within 20 minutes.
Superficial punctate erosions limited to the pigmented area was seen in some patients immediately after laser treatment.
The wheal-and-flare response last for several hours, and erythema is seen for upto 24 hours.
Periorbital oedema sometimes persist for 2-3 days. Vesicles are occasionally seen during the first three days after laser treatment followed by formation of a brown crust over the treated pigmented area during the first two weeks. Gradual lightening of the lesions is usually evident after two or three laser treatments. Dermal tissue in nevus of Ota contains large amounts of melanin, which provides an excellent target for the laser.
The Q-switched Nd:YAG laser appears to cause selective destruction of pigmented cells, wIth negligible damage to surrounding tissues. The Q-switched Nd: YAG laser is also useful in removing tattoos, in particular those with blue-black pigment.
Safety and Effectiveness
In conclusion, selective photothermolysis with the Q-switched ruby laser is a safe and effective method for lightening nevi of Ota. Multiple treatments increase the response rate.