[6][7] When colour granules are displaced from the zonules of Zinn (by friction against the lens), the irises slowly fade.

[2] Mutations in the fibrillin gene lead to the condition Marfan syndrome, and consequences include an increased risk of lens dislocation.

[2] The zonules of Zinn are difficult to visualize using a slit lamp, but may be seen with exceptional dilation of the pupil, or if a coloboma of the iris or a subluxation of the lens is present.

When colour granules are displaced from the zonules of Zinn, caused by friction of the lens, the iris can slowly fade.

This article incorporates text in the public domain from page 1018 of the 20th edition of Gray's Anatomy (1918)