You have a blind spot in each eye. Every human does. It's where your optic nerve punches through your retina to connect to your brain, creating a small area that can't detect light. Your brain fills in the gap so seamlessly you never notice it.

The octopus? No blind spot whatsoever.

A Different Design From the Ground Up

This isn't just a minor variation - it's a fundamentally different architectural solution to the same problem. Vertebrate eyes have what's called an inverted retina. The light-detecting photoreceptor cells point away from incoming light, and the nerve fibers that carry signals to the brain run across the front of the retina, blocking the view like cables draped over a camera lens.

To get those nerve signals out to the brain, they all have to converge at one exit point, bundling together and punching through the retina to form the optic nerve. That exit point is packed with nerve fibers - no room for photoreceptors. No photoreceptors means no light detection. Hence: blind spot.

Octopuses solved this with an everted retina. Their photoreceptor cells point toward the light, exactly where you'd logically want them. The nerve fibers route behind the retina, not across the front of it. This means there's no need for nerves to pierce through the light-detecting layer, and therefore no blind spot.

Convergent Evolution's Plot Twist

Here's what makes this even more remarkable: octopus eyes and human eyes look strikingly similar from the outside. Both have a lens, an iris, a pupil, and a camera-type structure. They evolved to solve the same problem - seeing clearly underwater and on land respectively.

But they evolved these solutions completely independently. The last common ancestor of octopuses and humans was a simple worm-like creature that lived over 500 million years ago, long before either lineage had anything resembling a complex eye. Octopuses are mollusks, more closely related to snails and clams than to any vertebrate.

When evolution ran the same experiment twice, cephalopods arguably got the better design - at least when it comes to blind spots. Their photoreceptors are rhabdomeric (microvillous) rather than ciliary, and they're sensibly oriented toward the light source from the start.

The Tradeoff

Does this mean octopus vision is superior? Not necessarily. While they lack our blind spot, they also lack color vision - most octopus species have only one type of photoreceptor. They see the world in grayscale, though they compensate with extraordinary motion detection and the ability to detect polarized light.

Still, for sheer elegance of design when it comes to routing nerve fibers, the octopus eye is hard to beat. No blind spot. No awkward workaround. Just a straightforward solution to capturing light and sending signals to the brain.

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