Stereo scanning electron microscopy of the crystalline lens.

We have used an improved protocol to prepare human, human neonatal, rat and frog lenses for examination by stereo scanning electron microscopy. In this manner, complete and accurate images of the changes in lens cell shape, size and surface complexity are revealed as they differentiate and develop from cuboidal epithelial cells into elongate fiber cells. This method also shows that the apical ends of elongating fibers are variably expanded as they interface with the overlying lens epithelium. Apical ends are most expanded as they contact pre-germinative zone epithelial cells and least enlarged as they contact transitional zone cells. By examining the interlocking devices on opposed fibers in frog, rat and human lenses we determined that there are standard types and interlocking patterns in all lens species. Finally, stereo SEM reveals that the ridges previously reported on aged human nuclear fibers are also seen on human neonatal cortical fibers and that these ridges may actually be interlocked villous or fingerlike projections.