Mantis Shrimp Has The Best Eyes – But Why (theguardian)
note: this is only in terms of photoreception abilities

As humans, we experience an amazing world of colour, but what can other animals see? Some see much more than us, but how they use this vision is largely unknown.

We see what we see because our eyes have three photoreceptors, red, green and blue. Our vision is good compared to dogs which have only two photoreceptors (green and blue), but is nothing compared to many birds who have four photoreceptors: ultraviolet (UV) as well as red, green and blue.

The addition of a UV photoreceptor is hard to imagine, but if we consider invertebrate vision it gets even more mind-boggling. Butterflies have five photoreceptors, providing them with UV vision and an enhanced ability to distinguish between two similar colours.

Octopuses do not have colour vision but they can detect polarised light. Light is made up of waves and polarised light is when these waves all vibrate in the same plane. The closest humans come to seeing polarised light is by wearing polarised sunglasses.

But this is not the end of the story. Mantis shrimp vision puts everything else to shame. These marine crustaceans may be well-known for their record breaking punch (the same acceleration as a .22 calibre bullet), but they also hold the world record for the most complex visual system.

They have up to 16 photoreceptors and can see UV, visible and polarised light. In fact, they are the only animals known to detect circularly polarised light, which is when the wave component of light rotates in a circular motion. They also can perceive depth with one eye and move each eye independently. It’s impossible to imagine what mantis shrimp see, but incredible to think about.


Problem of visual integration; retina without photo-receptors

Problem of visual integration; retina without photo-receptors

Problem of visual integration; retina without photo-receptors

The blind spot is the area on the retina without photoreceptors. Therefore, the part of an image that falls on
this region will NOT be seen. It is in this region that the optic nerve exits the eye on its way to the brain.
Humans may use different parts of their brain to discriminate objects from people. In particular, we may have

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