Trigeminal innervation of the scleral spur in cynomolgus monkeys.

Degeneration induced by intracranial section of the ophthalmic branch of the trigeminal nerve was used as a marker to trace the ocular passage and termination of fibres in ocular filtration angle structures of 3 cynomolgus monkeys. Fine supraciliary nerves branched from precorneal nerves as they entered the sclera from the uvea, passed forwards radially in the lamina fusca, entered the scleral spur, turned circumferentially and terminated. Many of the fibres were degenerated. Other less numerous branches advanced in the ciliary muscle close to the lamina fusca and were distributed either to the spur or to the trabecular meshwork. Spur fibres were approximately 4 times as numerous as trabecular fibres. The position, arrangement and ophthalmic identity of most of the spur terminals suggest a capacity to record tension produced by ciliary muscle contraction.