How can amphibians regenerate an eye lens from iris tissue?

In certain amphibians, the regeneration of an eye lens following the loss of the original lens occurs through a process known as metaplasia, where one type of tissue is converted into another.1

When the original lens is removed, cells located at the edge of the iris on the upper margin of the pupil undergo a transformation. These iris cells, which typically contain pigment granules, lose their color and begin to proliferate rapidly. The cells then collect into a spherical mass that differentiates into a new lens.1

This regenerative process is not automatic; it relies on specific physiological conditions. Notably, lens regeneration in salamanders is dependent upon the presence of a retina, which provides the necessary stimulus for the development of the new structure.2