Ocular melanocytosis (melanosis oculi) is a unilateral, congenital, pigmentary lesion that is a form of a blue nevus. The nevus is located in the deep episclera, sclera and uveal tract and can manifest clinically as iris heterochromia, patchy slate-gray or bluish discoloration of the sclera, and increased pigmentation of the ipsilateral fundus. These patients are at increased risk of developing glaucoma or melanoma in the affected eye. If the nevus involves the periocular skin as well as the eye, the condition is known as oculodermal melanocytosis (Nevus of Ota).
Pictured is a 4-year-old female with patchy, slate gray discoloration of the sclera of the left eye and iris heterochromia that has been present from birth. Note that there is no cutaneous involvement. She was also noted to have diffusely increased choroidal pigmentation throughout the fundus on dilated fundus exam as well as increased pigmentation of the trabecular meshwork on gonioscopy in the left eye as compared to the right (not shown).