If cave salamander didn’t evolve from sighted ancestors, it eyes would be a vestigial structure.
Cave salamanders live in the zone, with complete lack of light (dark zone), so this organisms adapted to that environment with blindness. It is believed that cave salamanders evolved from the ones that could see. The explanation of why they lost their sight is that they conserved energy needed to maintain sight to be more successful in reproduction.
A vestigial structure as a stunted organ that has little or no function in a particular organism. An example of this can be seen in the question above which states that some blind salamdras have eyes. These eyes have no use for these salamanders, so we can say that the eyes of the salamander is a vestigial structure.
According to the theory of evolution, organisms have undergone and undergo changes over time, with new species emerging from some common ancestor. Studying different groups of organisms, we realize several characteristics that serve as evidence for this theory. The presence of trace structures is one such evidence.
