Morphology of the long and short uveal nerves in the human eye.

The aim of this study was to examine the architecture of the uveal nerves in the sclera and suprachoroid of human eyes. Eyes from 17 adult human donors were investigated. The uveal nerves in different regions (retrobulbar, intrascleral, suprachoroidal, pars plana) were prepared and studied by light and electron microscopy. In addition, immunohistochemistry was performed for various neuronal markers. The long uveal nerves showed a characteristic suprachoroidal location with no branches supplying the choroid. It was found that typically they are composed of myelinated (75%) and non-myelinated (25%) nerve fibres. They mainly contain aminergic and sensory nerve fibres. A separate set of cholinergic non-myelinated nerve fibre bundles runs parallel with these long uveal nerves. The short uveal nerves supply the suprachoroidal nerve plexus with approximately 13% of their nerve fibres. The nerves and the branches supplying the choroid appear as mixed nerves containing sympathetic, parasympathetic and sensory axons. This study therefore provides new information about the quantity, type and distribution of myelinated and non-myelinated nerve fibres in the posterior uvea of the human eye.