Col4a1 heterozygosity results in mild ocular phenotypes with incomplete penetrance. (A) Representative slit-lamp images of eyes from 6-mo-old mice. Most Col4a1^+/− eyes were grossly normal while a small portion had slightly enlarged and tortuous iris blood vessels (arrowheads). Top panels, frontal view of the eyes; bottom panels, side view of the eyes. White arrows indicate anterior chamber depth. n = 14 and 50 eyes for R26^Flpe;Col4a1^+/+ and Col4a1^+/− mice, respectively. (B) Representative H&E-stained ocular sections from 6-mo-old mice. Both R26^Flpe;Col4a1^+/+ and Col4a1^+/− eyes have normal morphology, as indicated by well-developed and open Schlemm’s canal (SC) and trabecular meshwork (asterisks), fully foliated ciliary body (open arrowheads), continuous ganglion cell layer (black arrowheads), thick nerve fiber layer (black arrowheads), and normal optic nerve heads. n = 7 and 9 eyes for R26^Flpe;Col4a1^+/+ and Col4a1^+/− mice, respectively. Scale bar = 20 μm.