Fig. 14. Ultrastructure of human vitreous fibers. Although centrifuged to concentrate structural elements, these specimens of adult human vitreous contained no membranes or membranous elements. Only collagen fibrils were detected. There were also bundles of parallel collagen fibrils such as the one shown here in cross-section (arrow). (From Sebag J, Balazs EA. Morphology and ultrastructure of human vitreous fibers. Invest Ophthalmol Vis Sci 30:187, 1989, with permission)