PubMed ID: 19578020
Author(s): Flügel-Koch C, Neuhuber WL, Kaufman PL, Lütjen-Drecoll E. Morphologic indication for proprioception in the human ciliary muscle. Invest Ophthalmol Vis Sci. 2009 Dec;50(12):5529-36. doi: 10.1167/iovs.09-3783. Epub 2009 Jul 2. PMID 19578020
Journal: Investigative Ophthalmology & Visual Science, Volume 50, Issue 12, Dec 2009
PURPOSE To search for proprioceptive nerve terminals in human ciliary muscle.
METHODS In 48 human donor eyes, histologic and ultrathin sections cut in different planes and wholemounts of the ciliary muscle were studied. Immunohistochemical staining with antibodies against pan-neuronal antigens and antigens reported as markers for sensory terminals in other organs was performed.
RESULTS Among the markers for proprioceptive terminals, only calretinin was present in the ciliary body. Calretinin-immunoreactive (IR) nerve terminals surrounded the posterior and reticular ciliary muscle tips and their elastic tendons. Terminals in that region contained mitochondria and neurofilaments. At the anterior tips larger terminals with numerous membrane-filled vesicles were located between the muscle fibers. The most elaborate network of calretinin-IR nerve fibers was present in the ground plate covering the circular muscle portion. Here calretinin-IR neurons with morphologic features of mechanoreception were present. Within the circular muscle portion numerous calretinin-IR ganglion cells were found. Their processes were connected to the calretinin-IR network but also surrounded ciliary muscle cells and NADPH-diaphorase-positive ganglion cells.
CONCLUSIONS These morphologic findings indicate that there are proprioreceptors in the ciliary muscle that morphologically and presumably functionally differ at different locations. At the posterior muscle tips, the receptors could measure stretch of the tendons, whereas the large receptor organs located at the anterior muscle tips morphologically resemble mechanoreceptors measuring shear stress. The presence of the numerous intrinsic nerve cells indicates that contraction of the circular muscle portion can be modulated locally via a self-contained reflex arc.