[The development of the Schlemm's canal in human eyes]

The fetal development of Schlemm's canal of the human eye was investigated by light and electron microscopy. Schlemm's canal was not yet a circumferential structure at the 20th fetal week, and at the 26th fetal week the canal appeared to form by a process of confluence of the channels. As development proceeded, the canal positioned relatively anterior to the apex of the angle, as a result of posterior shift of the angle recess. The remarkable increase in the width of the canal during the fetal period was mainly achieved by the elongation of the endothelial cells, whereas the number of endothelial cells in meridional sections did not alter. From the 26th fetal week onward, the frequency of giant endothelial vacuoles and pores increased together with the discontinuity of the basal lamina, which corresponds with the increase of aqueous flow.