This is a congenital defect in which there is an aperture in the iris.
Hering figures the two eyes of a horse in which these appeared in the
direction of the outer canthus. Renner records a case in a foal in
connection with intra-bulbar enchondroma. Dochtermann and Berlin record
that among 64 pigs the result of breeding a boar on his daughters and
grand-daughters no less than 36 showed coloboma. Möller figures a dog
with the same affection.
The condition is not known to prove hurtful to the affected animal so
that it may be wisely let alone.