Aniridia is a congenital absence of the iris. Complete aniridia is more often apparent than real, for if sections are made through an eye that appears to possess no iris, apron-like vestiges of iris tissue will usually be found projecting a short distance from the ciliary attachment of the root of the iris. They are feebly expressed and are so rudimentary that the most careful macroscopic examination will usually fail to reveal the presence of vestiges of iris.
The most common embryologic defects of the eye are those of the iris and the pupil. The iris does not begin to grow until after the lens is ensheathed with the hyaloid vascular membrane, at which time it is in contact with the forming cornea. The edge of the secondary optic vesicle must now force itself between the fibrovascular sheath and the lens. The branches of the ciliary vessels which anastomose