The lens receives nutrition and blood supply from the hyaloid artery, a branch of the primitive ophthalmic artery. The hyaloid artery first enters the eye through the optic fissure (see Fig. 1-12) and then becomes incorporated into the center of the optic nerve as the optic fissure closes. The hyaloid vessels form a network around the posterior lens capsule and then anastomose anteriorly with the network of vessels in the pupillary membrane (Fig. 1-16). The pupillary membrane consists of vessels and mesenchyme that overlie the anterior lens capsule (see Development of Anterior Segment). This hyaloid vascular network that forms around the lens is called the tunica vasculosa lentis. The hyaloid vasculature reaches its greatest development at approximately 10 weeks gestation. The tunica vasculosa lentis and hyaloid artery regress during the end of the fourth month of
gestation. The clinical lens anomaly, Mittendorfs dot, is a small (1-2mm) area of fibrosis on the posterior capsule and is probably a manifestation of incomplete regression of the hyaloid artery where it attaches to the posterior capsule. The regression of the pupillary membrane begins during the sixth month and is usually complete by the eighth month. Persistent pupillary membranes result from incomplete regression. These iris strands may connect to an anterior polar cataract (Fig. 1-17) or area of corneal endothelial fibrosis.
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