Histopathological and cell biological analyses of the formation mechanism of anterior polar cataract.

Anterior polar cataract, defined as an opacification limited to the anterior polar region of the crystalline lens, results in a significant decline of vision even though the area of opacification is generally small. Having performed histopathological and cell biological studies in an attempt to identify the formation mechanism of anterior polar cataract, we found that lens epithelial cells (LECs) in contact with the opacified region were arranged in a monolayer and contained vacuoles. Furthermore, compared to LECs obtained from cortical and nuclear cataractous lenses and cultured for the study, these LECs revealed a significantly diminished proliferation, suggesting that their physiological activity had been reduced. On the other hand, LECs existing within the opacified region were multi-layered, and there were structureless deposits including remnants of organelles among the cells. Based on these findings, we have concluded that the formation mechanism of anterior polar cataract is as follows: LECs contacting the opacified region initially undergo significant mitosis; rather than migrating towards the equator, these proliferating cells accumulate and form a multilayer in the anterior polar region. Since multi-layered cells are surrounded by the anterior lens capsule and the lens cortex, there is a limit as to how many layers the cells can continue to form; when this limit is reached, these cells next undergo endocytosis and exocytosis. Because the physiological activity has been reduced as a result of having undergone significant proliferation, the cells contacting the opacified area are no longer able to force the proliferating cells towards the anterior polar region; hence multi-layering of the cells and the entire cellular movement are terminated at this point and result in cells with vacuoles and diminished physiological activity. While further studies are required to confirm our hypothesis, we believe this is the first study to suggest a possible mechanism of formation of anterior polar cataract.