Nevus of Ota.

It is usually present at birth in the two thirds of patients who have ocular involvement.It is more common in females with 5% being bilateral.4 It was first described by Ota in 1939. It can be unilateral or bilateral. Exact etiology and pathology of NOO is not known. Unconfirmed hypothesis is that it represents melanocytes that have not migrated completely from the neural crest to the epidermis during the embryonic stage. The variable prevalence among different populations suggests genetic influence although familiar cases of nevus of ota are very rare. It is most prevalent in Japanese population and comparatively rare in Indian subcontinent.5 It is uncommon in white population. Male to female ratio is 1:4.8. First peak of onset occurs in infancy (50%). Second peak of onset occurs in adolescence . Important differential diagnoses for NOO are Blue Nevi, Hori macule, Lentigo, Malignant Melanoma, Melasma, Mongolian Spot, Ochronosis and Phytophotodermatitis. Cosmetic camouflage makeup can m i n i m i z e t h e d i s f i g u r i n g f a c i a l pigmentation resulting from NOO. Otherwise, topical therapy is of no value in the treatment. Since childhood NOO is likely to be more superficial than adult NOO, early laser treatment might have some beneficial effects.6 Hydroquinone preparations are also he lpful in par t ia l ly t reat ing th is condition. Patients with NOO are at greater risk for the development of intraocular and central nervous system malignant melanomas are more common and occur in as many as 4% of cases. Therefore it is reasonable for all patients with the NOO to have yearly examinations.