Pigment-containing cells in extraocular tissues of the primate.

In the present study pigment-containing (PC) cells, localized in extraocular tissues of man and the cynomolgus monkey, were investigated to establish their localization, nature and relationships with the autonomic nervous system. In the orbit of man as well as the cynomolgus monkey three localizations of PC cells were detected: (1) Tenon's capsule along the ciliary arteries at the level of the entrance of the arteries into the eyeball, (2) Tenon's capsule along the ciliary nerves at the level of the entrance into the eyeball, and (3) the sclera around the ciliary arteries and nerves. Moreover in the orbit of the cynomolgus monkey PC cells were found along and around the accessory lateral rectus muscle. Histological, histochemical and electron microscopical studies led to the conclusions that PC cells are similar in nature to melanocytes and do not have neuronal properties. In contrast to the melanocytes in the anterior segment of the eye in both man and monkey, melanocytes in the extraocular tissues are not innervated either adrenergically or cholinergically.