It is not easy to have eyes, especially big ones. A research by Sweden's Lund University has unveiled that larger eyes are developed at the cost of other body organs. Between 5 and 15% of total energy is used to build big eyes in infant stage. The researchers said that a Mexican cavefish has lost its visual system due to weakening.

The researchers observed the fish, which lives in very dark, nutrient-poor environment. It does not have any use for eyes, but that is not true for surface-dwelling variant, known as a morph.

Study researchers have said that the fish being sightless gets a lot of boost as they have to save a lot of energy. As mentioned above, the researchers have even looked at members of the same fish living aboveground in rivers of Texas and Mexico and having perfect vision.

The researchers acquired captive cavefish and measured the energy cost of their sight. The researchers found that the energy cost of sight ids 15% more for young, developing fish than if they were have been blind.

Study’s lead researcher Damian Moran said vision is a costly affair as photoreceptive cells and neurons continuously demand energy. Moran affirmed, “Any animal that lives in permanent darkness and doesn’t need vision to find food or avoid predators won’t really need their eyes or visual centers in the brain”. The researchers have also found that blind A. mexicanus has a smaller midbrain that deals with vision.