river dolphins have very small eyes for their size, and do not have a very good sense of sight. in addition, the eyes are placed on the sides of the head, so the vision consists of two fields, rather than a binocular view like humans have. when river dolphins surface, their lens and cornea correct the nearsightedness that results from the refraction of light. they have both rod and cone cells, meaning they can see in both dim and bright light. most river dolphins have slightly flattened eyeballs, enlarged pupils (which shrink as they surface to prevent damage), slightly flattened corneas and a tapetum lucidum; these adaptations allow for large amounts of light to pass through the eye and, therefore, a very clear image of the surrounding area. they also have glands on their eyelids and an outer corneal layer that act as protection for the cornea.