Starfish, which are more scientifically known as sea stars, don't have any visible body parts that look like eyes. So how do they see?
While it may not look like starfish have eyes, they do, although they're not like our eyes. A starfish has eyespots that cannot see much in the way of details but can detect light and dark. These eyespots are at the tip of each of the starfish's arms. That means that a 5-armed starfish has five eyespots, and a 40-armed starfish has 40!
How to See a Starfish's Eyespots
A starfish's eyespots lie underneath its skin, but you can see them. If you get a chance to gently hold a starfish, often it will tilt the end of its arms upward. Look at the very tip, and you might see a black or red dot. That's the eyespot.
Cartoons that portray starfish with a face with eyes in the center of their body are therefore inaccurate. A starfish is actually looking at you with its arms, not from the center of its body. It's just easier for cartoonists to portray them that way.
Structure of the Sea Star Eye
The eye of a sea star is very small. On a blue star, they are only about half a millimeter wide. They have a groove on the underside of each arm that has the tube feet that stars use to move. The eye is made of a couple hundred light-collecting units and is located at the end of one of the tube feet on each arm. It is a compound eye like that of an insect, but it doesn't have a lens to focus the light. This reduces its ability to see anything but light, dark, and large structures such as the coral reef it needs to live on.
What Sea Stars Can See
Sea stars can't detect color. They don't have the color-detecting cones that human eyes do, so they are colorblind and see only light and dark. They also can't see fast-moving objects as their eyes work slowly. If something swims by them fast, they simply won't detect it. They can't see any details because they have so few light-detecting cells. Experiments have shown they can detect large structures, and even that was a surprise for scientists, who for a long time thought they could only see light and dark.
Each eye of the sea star has a large field of vision. If all of their eyes weren't blocked, they could see for 360 degrees around themselves. They could probably limit their field of vision using their other tube feet on each arm as blinders. Sea stars likely see just enough to be able to get to where they want to be, on a rock or coral reef where they can feed.