3312 Macular corneal dystrophy in Iceland: A immunohistochemical and genealogical study of 28 cases

w The human wrnea is a densely innervated struchxe. However, data on nerve fiber (NF) distribution in tbe human cornea are scarce possibly due to fast post mortem degeneration. Therefore, moat descriptions on comeal innervation are based on studies in rats and rabbits. Tbe present study is focussed on the ulaastruaure of NF’s in the central and peripheral human cornea. Methods: Tissue samples of five corneas obtained from melanoma eyes were processed for light and electron microscopy (EM). Both frontal and cross-sections of stroma and epitbelium were studied. Ultrathin stromal and ultrathin serial sections between Bowman’s Membrane (BM) and the basal &helium were cut. Stmmai and subepitbeliai axon diameters were n&wed on EM micrographs. Egulls; Unmyelinated NF’s containing both clear and dense cored vesicles run parallel to tbe collagen fibers in the upper third of the central stroma. They consist of up to 30 fibers (diam. 0.5-2.5 pm) which are ensheathed by thin rims of Schwann cell protrusions and amorphic matrix. Some of these NF’s, containing glycogen particles, invaginate the cytoplasm of the stmmal keratocytes. After passing through BM, central stromal NF’s (diam. 0.05-0.5 @II), run parallel between BM and epitbelium. At the location of the variwsities, fibers measure up to 2 pm due to the presence of many mitochondria. These fibers turn upwards and protrude mainly into the basal cells and sometimes into the wing cells. Reconstruction of NF’s in semithin sections revealed that subepitbelial fibers, having one or more bifurcations, run in a 12h-6h direction in the centre and in a 3h-9h direction in the periphery. In contrast to the central cornea, myelinated fibers were only found in the peripheral limbal stroma. Conclusion: NF’s invaginating epitbelial cells and keratocytes suggest that both epitbelium and stromal keratocytes are directly innervated. Tbe numemua mitochondria present in tbe varicosities point at fibers from sensory nerves. Therefore, the conclusion seems to be justified that the presence of clear and dense cored vesicles in NF’s of sSroma and subepithelium point at either an adrenergic or an cholinergic input from sensory origin.