Regression of the tunica vasculosa lentis in the postnatal rat.

Involution of the tunica vasculosa lentis (TVL) was examined in albino rats from 1 to 21 days after birth. Scanning electron microscopy demonstrated that as the lens increased in size, the larger vessels became straight and the small interconnecting vessels disappeared. Transmission electron microscopy revealed that the endothelial cells lost their close relationship with the posterior lens capsule. In the endothelial cells and pericytes the cytoplasm was dense, and many of the organelles became to recognize. However, the cells appeared to remain intact for into regression, shrinking until a basement membrane-like remnant remained. Vitreal cells were close to the TVL throughout the period studied, but few contained phagosomes. During regression the TVL appeared to (1) change its shape in order to accommodate the enlarging ocular structure, (2) maintain separation of the vitreal and vascular compartments by remaining intact during regression and (3) be associated with vitreal cells, which did not seem to play a prominent role in the involution of these vessels.