Aqueous outflow in the beagle. I. Postnatal morphologic development of the iridocorneal angle: pectinate ligament and uveal trabecular meshwork.

The present study examined the postnatal development of the pectinate ligaments and uveal trabecular meshwork of the normal canine chamber angle of the Beagle breed at one day, one through ten weeks, three, four and six months, and one and two years of age. Angle tissue was prepared and examined by standard techniques for light microscopy and scanning and transmission electron microscopy. Developmentally, pectinate ligaments matured by the third week although areas continued to develop through the eighth week. Each primary pectinate ligament possessed a large, posterior extracellular space at its iridal attachment. The uveal meshwork, which developed by rarefaction, was not formed at birth and did not appear adult-like until the end of the second month. Adult trabecular cells were ultrastructurally identical throughout the angle, having been characterized by having cilia and "special" rough endoplasmic reticulum.