Oil droplet

Oil droplets are found in the eyes of some animals, being located in the photoreceptor cells.

[1] They are found in cone cells far more often than in rods, suggesting a role in colour vision.

They are located in the cone inner segment, where they intercept and filter light before it can pass through to the cone outer segment where the opsins are,[3] the molecules that sense light.

The adaptive advantage of oil droplets is not firmly established.

Coloured oil droplets have a cost in that they reduce the amount of light available to the visual system.