We show a textured cross-section of the retina. In the upper layers of the section are cells called photoreceptors. They form columns of tightly packed, rounded cells, specialized in capturing light and transforming it into chemical signals. In retinitis pigmentosa, these cells fail to function due to various problems, causing blindness. There are photoreceptors specialized for perceiving colors; they are larger and more elongated, called cones, but the whale lacks them. The whale only sees in black and white, as it only has rod cells.
At the bottom of the photo, a line marks the limit of the retina's thickness. This is a membrane that, when damaged for various reasons, can fold and pull on the retina, causing "retinal detachment."
In the center right of the photo, the outline of a large vessel that occupies most of the thickness of the retina is large, more than 10 times the size of the blood vessels in the human retina. Blood vessels in whales are very large and have very strong walls to withstand pressure.
Around the blood vessel there are more cells that have not been textured to simplify the figure but will be shown in the following textured sheets.
