Why are caecilian eyes often covered by skin or bone?

Caecilians have degenerate eyes that are covered by skin or bone because they are primarily subterranean animals that live in environments where vision is of little importance.12

These specialized adaptations allow caecilians to navigate, feed, and avoid enemies within their underground habitats. Because their lifestyle is largely fossorial, they rely on other senses, such as chemoreception, to interact with their environment. The name "caecilian" itself is derived from the Latin word caecus, meaning "sightless" or "blind," reflecting this evolutionary reduction of visual capability.1234