At higher magnification, examination of sections stained with DiI and SYTOX green revealed ultrastructural differences between alphaA/BKO lenses and wild type lenses (Figure 3). Anterior epithelial staining in 5 wk old alphaA/BKO (Figure 3A) and 5 wk old wild type lenses were similar (Figure 3K) with respect to nuclear staining with SYTOX green. However, some differences in 54 wk old alphaA/BKO lenses (Figure 3F) were observed in the central anterior epithelium compared to 5 wk (Figure 3K), 46 wk (Figure 3P), and 72 wk (data not shown) wild type lenses. These differences included changes in central epithelial nuclear staining, nuclear shape and epithelial thickness and continuity. Superficial and deep anterior cortical staining was grossly different between alphaA/BKO (Figure 3A,3D,3F and 3I) and wild type lenses (Figure 3K,3N,3P and 3S). In 5 and 54 wk old alphaA/BKO lenses, superficial and deep anterior cortical regions, stained for lipid membranes, did not reveal any patterns typical of fiber cells cut in cross-section or longitudinal section. In 5 wk alphaA/BKO lenses there was a high density of stained membranes per unit area throughout the cortex, with no nucleic acid staining in these regions. In 54 wk alphaA/BKO lenses, large, irregularly shaped cells were observed, interspersed among regions of high membrane staining density per unit area. These large objects were not vacuoles, because examination of the interior of these structures by transmitted and reflected light microscopy showed that the membranes encompassed cellular material (data not shown). In addition, nucleic acid staining was observed (Figure 3F and 3I) within many of these cells exhibiting large cross-sectional profiles. In the wild type lenses, typical cross-sectional patterns of fiber cells organized in radial columns were observed (Figure 3K,3N,3P and 3S).