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I've read that unlike humans, octopuses have eyes "designed" the "right way", i.e. with the nerve fibers behind the retina, thus getting rid of the blind spot we humans have as well as theoretically improving eyesight.

Have there been tests to compare octopus sight with that of humans, and do they indeed have better vision than us?

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    $\begingroup$ I'd suggest adding the tag "cephalopods". $\endgroup$
    – Nathaniel Bubis
    Commented Jan 7, 2013 at 12:20
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    $\begingroup$ Why would removing the blind spot result in better vision? $\endgroup$
    – terdon
    Commented Jan 7, 2013 at 12:30
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    $\begingroup$ the blind spot perhaps not, (although it could come in ahndy if the eyes are on the side of your head and not in front), but mostly one would think that the lack of nerve fibers would somehow improve resolution, vision in dim light, etc. $\endgroup$
    – Nathaniel Bubis
    Commented Jan 7, 2013 at 12:37
  • $\begingroup$ But octopus do not have fovea - so no more keen vision! They may have more photoreceptors , but they have no more complex brains than humans - the brain behind the eye is more important than eye itself. $\endgroup$
    – user9126
    Commented Sep 7, 2014 at 19:38
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    $\begingroup$ monkey eyes can move so fast as to examine 10 branches and stems every second while they jump through the trees with awesome focus and positional mapping. chimps eyes have positional mapping for tree climbing that is 10x faster than human eye movement, so eyes have specializations for fine movement, distance, speed, narrow, wide, all very refined. eyes and ears are extremely advanced and perfected for the given environment. animal's primary senses are normally very near to perfection for their actions and needs. probably octopi trade range of eye movement for a more fixed structure. $\endgroup$
    – bandybabboon
    Commented Apr 15, 2017 at 12:56

2 Answers 2

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There are a couple of advantages and disadvantages of possessing the eyes of octopuses.

  • The first advantage of the octopus eye is that it has no blind spot. This means that octopuses can see everything that is going on in their environment, and are more aware of predators and prey than some vertebrates. Also, they have many more photoreceptors than vertebrates, at roughly 20,000-50,000/mm2 which means that their vision is much better than that of any human.

  • The disadvantage of the octopus eye is that it can not see in colour. The eyes possess no cones, only the invertebrate equivalent of rods. This means that octopuses can only distinguish between light and dark.

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  • $\begingroup$ So if a diver and an octopus where to be threatened by a shark, the octopus would see the shark first? $\endgroup$
    – Nathaniel Bubis
    Commented Jan 7, 2013 at 19:01
  • $\begingroup$ Of course it depends, As I cleared above both have some advantages and disadvantages. So, It's completely depends. But In some manner of course the Octopus will see the Shark first because they didn't have blind spot so their field of view is more than a common person. $\endgroup$
    – Saharsh
    Commented Jan 8, 2013 at 5:38
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    $\begingroup$ Nice answer, +1. Do you have a reference for the photoreceptor claim? $\endgroup$
    – terdon
    Commented Jan 8, 2013 at 17:19
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    $\begingroup$ "Like other cephalopods, they can distinguish the polarization of light. Color vision appears to vary from species to species, being present in O. aegina but absent in O. vulgaris." - en.wikipedia.org/wiki/Octopus#Sensation $\endgroup$
    – MCM
    Commented Jan 8, 2013 at 18:58
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    $\begingroup$ Would the blind spot matter? The respective blind spots of the two eyes don't overlap, so unless you are a pirate (I suppose a frequent victim of sharks), you will still see all the things in either of your blind spots, there will just be two small spots in your FOV where you don't have depth perception. $\endgroup$
    – Superbest
    Commented Apr 21, 2014 at 20:59
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Adding to the answer above, another advantage of cephalopod eyes is the lower risk of retina detachment. (HumanEvolution)

Also, cephalopod eye focus image by moving the lense (like a camera or telescope), not by changing the lense's curvature, as in vertebrate eye (Wiki). Hence, I speculate that cephalopod would not experience either myopia or hyperopia. Cephalopod may still have problem with presbyopia at old age, affecting both near and far vision, however.

Furthermore, this article comparing human and cephalopod eyes might be of interest: QuarkPhysics

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  • $\begingroup$ I thought presbyopia would not affect cephalopods. In vertebrates it's due to the lense becoming stiffer with age so it can't change shape, but as you say this is not how cephalopod eyes focus. $\endgroup$
    – uUnwY
    Commented Apr 5, 2020 at 19:09
  • $\begingroup$ Ah, I mean if the muscles that move the eyes are not working properly when the animal ages, cephalopod would suffer presbyopia as vertebrates do. $\endgroup$
    – Nam Tran
    Commented Apr 7, 2020 at 1:39
  • $\begingroup$ Thanks, that's a good point (although I have no idea if old octopusses suffer a similar kind of muscle stiffness as humans, there's probably a lot more here that we don't know!). $\endgroup$
    – uUnwY
    Commented Apr 7, 2020 at 9:29

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