In vivo three-dimensional confocal laser scanning microscopy of the epithelial nerve structure in the human cornea

Purpose Evaluation of a new method for in vivo visualization of the distribution and morphology of human anterior corneal nerves. Method The anterior cornea was examined to a depth of 100 mu m in four human volunteers with a confocal laser scanning microscope (CLSM) using a Rostock Cornea Module (developed in house) attached to a Heidelberg Retina Tomograph II (Heidelberg Engineering, Germany). Optical sections were digitally reconstructed in 3D using AMIRA (TGS Inc., USA). The scanned volumes had a greatest size of 300x300x40 mu m and voxel size of 0.78x0.78x0.95 mu m. Results The spatial arrangement of the epithelium, nerves and keratocytes was visualized by in vivo 3D-CLSM. The 3D-reconstruction of the volunteers' corneas in combination with the oblique sections gave a picture of the nerves in the central human cornea. Thin nerves run in the subepithelial plexus aligned parallel to Bowman's layer and are partially interconnected. The diameter of these fibres varied between 1.0 and 5 mu m. Thick fibres rose out of the deeper stroma. The diarneter of the main nerve trunks was 12 +/- 2 mu m. Branches penetrating the anterior epithelial cell layer could not be visualized. Conclusions 3D-CLSM allows analysis of the spatial arrangement of the anterior corneal nerves and visualization of the epithelium and keratocytes in the living human cornea. The developed method provides a basis for further studies of alterations of the cellular arrangement and epithelial innervation in comeal disease. This may help to clarify alterations of nerve fibre patterns under various clinical and experimental conditions.