Fig. 1. As demonstrated, the iris is derived from both neural crest cells and the optic cup. The Anterior Epithelial Layer (AEL) and Posterior Epithelial Layer (PEL) are derived from the optic cup and are oriented in an apex-to-apex pattern with basement membranes (BM). When the five layers of the iris are seen in cross section, one can see that the Anterior Border Layer (ABL) and stroma (colored in blue) are derived from the neural crest cells and the iris muscles; AEL and PEL (shaded in orange) come from the optic cup.