Arguments against a role for selection in the regression of cave-fish eyes cited the insignificant cost of their development, but we argue that the energetic cost of their maintenance is sufficiently high for eyes to be detrimental in the cave environment.
“Third, the manner of eye degeneration in Astyanax cavefish does not appear to be economical. Instead of undergoing eye loss at a very early stage, the cavefish eye develops to a relatively mature stage prior to the beginning of degeneration, presumably at high energetic cost.”
(See the effect of lens transplant.)