I've been kicking around story ideas about how much different this pandemic would be if human beings could actually see the virus on our hands, on surfaces, in the air, etc. This lead me to wonder: can a human head host eyes with sufficient resolution to be able to see bacteria? How about viruses? To do smaller and smaller resolutions, my understanding is that you need greater precision in the lens. Is there some fundamental biological limit we would hit trying to achieve such perfection? What about mechanical replacements? Is there enough space in a human head for the cameras/machinery needed to do such resolution?

In summary, is there anything that prevents humans from having both the ability to see as well as we do today for macroscale objects and the ability to see all the tiny bits of life on all the surfaces around us?

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    $\begingroup$ Viruses cannot be resolved with visible light, sorry. (Because they are smaller than the wavelength of visible light. That's why they were so mysterious before the invention of the electron microscope in the 1930s -- optical microscopes working with visible light could not see them.) (P.S. Have you tried to find out what is the depth of field of a microscope and how precisely one needs to position the sample being observed so that it is in focus? Or do you plan to give your enhanced humans micrometer screws in their necks?) $\endgroup$
    – AlexP
    Commented Jul 14, 2021 at 23:00
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    $\begingroup$ Seeing is only part of the solution. Humans can see lice, but that does not stop lice from proliferating. Eyes should be able to scan faster, brain should be able to process a much large stream of visual information, and hands should be able to move with quick surgical precision. And even then humans can be simply overwhelmed by numbers. $\endgroup$
    – Alexander
    Commented Jul 15, 2021 at 0:20
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    $\begingroup$ Limited resolving power means that either eyes would have to be huge or your humans would have to position them a millimeter or so from the surface without shaking at all. $\endgroup$
    – Robert
    Commented Jul 15, 2021 at 1:10
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    $\begingroup$ Frame challenge : maybe you should go with the smelling. $\endgroup$
    – Jemox
    Commented Jul 15, 2021 at 8:01
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    $\begingroup$ If you could see bacteria, you would see a carpet of them. Everywhere. Even on yourself. People might become less scared. I think many actually think that they live in a sterile evironment and that any "germ" or virus or bacteria is like a little enemy monster.. $\endgroup$
    – Manuki
    Commented Jul 15, 2021 at 12:58

6 Answers 6


The limitations of microscopy:

I work with microscopes all the time, viewing bacteria (Gram stains). There are a couple of issues at play here that would seriously disrupt the ability of a person to see bacteria in the way you are describing.

First, microscopes focus on things in a very specific distance to be precise. It would be possible to have a big-ish microscope essentially head-mounted on a person, and flip the objective out of the way, so this isn't a total deal breaker. It just means you'd need to be able to hold the head very still and at the perfect distance. Even the vibration of a running refrigerator nearby will throw off the focus.

Second, at the focus levels you're needing to see bacteria, the light scatter is such that in a hospital lab, I apply oil to the sample so the change in density between the air and the lens doesn't scatter the light. You'd need to be applying oil and essentially plastering your optics right up to what you wanted to see, or else it would be too fuzzy.

additionally, bacteria are tiny things in an environment FILLED with tiny things that look a bit like bacteria. Not to mention that the environment is FILLED with otherwise harmless bacteria. To get around this, we Gram stain - use stains that selectively colorize the cell walls of bacteria so we can even see that they are there and what shapes they are (to distinguish approximately what kind of bacteria they are; a complex series of tests verifies what kind they are, and if they are pathogenic). The actual Gram stain is a relatively imprecise tool, but quick.

Finally, viruses are generally so small that you need an electron microscope to visualize them. While it might someday be possible (but totally impractical) to place an electron microscope on a person's head, the other issues are all magnified (pardon the Dad joke) a thousand-fold with this technique. Not to mention that most of these images are actually visualizing thin coatings of metal bombarded on to the objects being viewed rather than the actual objects themselves.

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    $\begingroup$ And there is also the fact that you need to have as close to one single layer as possible to have any chance to identify things. If you have multiple layers of bacteria and viruses, it will be come an undiscernible mess. $\endgroup$ Commented Jul 15, 2021 at 12:39
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    $\begingroup$ The oil is irrelevant, you do not need to apply oil to do anything, though it is possible to design a lens that uses oil to increase its numerical aperture to be manufactured more cheaply than one that does not use oil, which is necessarily larger and more expensive, hence most lenses for biological use are designed to use oil to focus the other side of the coverslip. A lens that is designed for use with oil is of course useless without oil. $\endgroup$
    – camelccc
    Commented Jul 16, 2021 at 14:52
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    $\begingroup$ I wouldn't call an electron microscope "human eyes" anymore, it's just a totally different mechanism, so I think it's just a hard no for viruses. $\endgroup$
    – Mark
    Commented Jul 16, 2021 at 21:11

can a human head host eyes with sufficient resolution to be able to see bacteria? How about viruses? To do smaller and smaller resolutions, my understanding is that you need greater precision in the lens

It would not be enough. The problem here is that when you "see" a very small object, what you actually see is the light reflected by that object. The smallest the object, the less light it reflects in absolute terms.

That is why microscopes use a light source to light up the sample. This is not possible with just an eye.

What you could do is have a laser-like illuminator target an area, and gather the light scattered by that. You probably don't want coherent light though, so no laser, just a focused light source.

Then you'd have the problem of stabilizing the image. Imagine looking at a bacterium one meter distant; a bacterium is maybe two microns in diameter. One micron at one meter is on the order of two arcseconds; this means that even the minutest wobble of the head (due to heartbeat, let alone breathing) would make the focused area sweep away. Some really clever image stabilization technique would be needed.

These are the first difficulties that spring to my mind, but this is totally not my area, so there could be worse traps lurking in the concept.

As to not give up normal vision, that's no problem. You could have microscopic vision replace on demand the vision out of one eye. With a little training it's perfectly possible to be looking at two different scenes from the two eyes at the same time; the brain learns to concentrate on whichever detail catches your attention, but does not go blind to the other eye.

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    $\begingroup$ What you could do is have a laser-like illuminator target an area… Oh! Is that why the Borg have random laser pointers on their heads? $\endgroup$ Commented Jul 16, 2021 at 1:43

The lens in the human eye would not allow it, even if it would be perfect

Note: below is about limits of a perfect lens. Answers/comments that take the wavelength of visible light into account are right, of course.. in fact, no optical device for visible light will be able to show corona viruses !

  • Focal distance. This property limits the minimal view distance to objects that can be sharp. For the human eye, depending on age, it is around 30-40mm in practice and 17 mm theoretically. At that distance, the retina will never have enough cells to see viruses.

  • MTF. For a lens geometry, you also have an built-in theoretical limit on resolution. The maximum MTF is the resolution of the ideal lens and it only depends on the wavelength and on the curvature, size and refraction index of the lens itself. Our eyes do contain a high quality lens, but the size of that lens and its power (about 20D) will not allow us to discern particles below ca 0.02mm at 17mm focal distance. Even the perfect android robot with endless retina resolution, having a single diamond eye lens shaped like ours, would not be able to see most bacteria. Let alone viruses..


Humans can already detect objects down to the nano-scale using their touch (ref). You might like to play with the idea of "seeing" being a bit broader and instead use sensory inputs like touch, or smell (à la suggested superior olfactory senses of canines).

Secondly there is a quite a bit of research that shows the dose of a virus or bacteria is important to survival / damage e.g. ref (use search times like: dose response LD50 bacteria). Clean surfaces don't necessarily need to be 100% clean as removing 99% of the microorganisms still might leave tens, thousands or millions but might downgrade what would be a fatal infection to a serious, serious to mild, mild to asymptomatic. And or a communicable (transmissible) to non-communicable.

Finally and perhaps most usefully: what if we could see in UV light like various insects like bees and also not be overly harmed by it (e.g. higher melanin)? UV light is absorbed by various chemical bonds; which is why it can then break them / generate free radicals that can damage / kill the organism. But this means it also "looks" different due to difference reflectance / absorbance. Secondly UV light, upon being absorbed can be re-emitted at a different wavelength through fluorescence. (ref)

... of course that air is also stuffed full of dust, pollen, mould spores etc so this might not be very useful after all.


Yes, in some sense

Do not repeat that thypical mistake of genetically modified creatures adapting for each and everyone planet.

Use google glasses or equivalent and appropriate, technology based sensors and convert their signals to visual information.

Optical means for shure do not help you see vuruses, and apparently you have no idea how messy skin would look like under a microscope, and that many bacterias are part of our symbiosis.

But what you are looking for, partially, called AFM which is basically a micro wisker scanning a surface.

So it can be not like you solve the problem of how much optical component you can squish in someones head, but by some technology you have array of such wiskers on a tip of ones finger and you move it across some surface and get the information, already filtered for features you are looking for.

It may be part of efforts of controlling spreading and elemination antibiotic resistant bacterias, and other microbiological stuff, but it does not describe it in full - how it should be done and alone it is definitely not an ultimate answer for the situation. Capacities of our bodies aren't that bad and it can be used as a detector, or part of the detector - I mean body contains tools which can be used on cellular level and it just needs better and digital/chemical interface.

As potencial technology - nanomachines son - really that could be useful, a lot of things can be done with our ability to work more freely in confines of few microns. Including that we could eliminate all harmfull microbiological materials, in a way which they can't adapt for, and/or create additioanl barriers for them, and bug fix the responses of immune system etc.

So what you are looking for is nanotech.


Assuming the fact that no one will ever remove one of his working eyes to see if a plate is full of bacteria, the reply is - everything is already full of bacteria. Probably will be more usefull to distinguish between kind of bacteria.

Assuming you know how to distinguish the bacteria, the minimal resolution is a 400x magnification. It can be done by a normal (normal by scientist range) microscope lab. Your skull is not enough to host such optics, and we don't know any being able to do a 400x magnification (1000x if you want details). Some predator is able to spot more details but not to "zoom in". Anyway, once you own such magnification by some special mean, there's no issue for your optical nerves to transfer the stimulation to the brain - so you'll see the figure.

Does this could help against pandemics? If every human being was able to distinguish evil bacteria on top of a surface, probably so. To be honest, I can't figure out how to write a pandemic story if that skill or technology was developed for more than two generations. There will be no contagion at all - the actual problem we have with viruses is we cannot scan the entire world surface - having such granularity of detection is in fact what we first did with COVID! Good luck.

(on a side note: I've spoken just of bacteria, as viruses work differently, but if your story can assume people can see bacteria, is already "fantasy" enough to see viruses the same).

(side note 2: now that I'm thinking about... why the sense of view?!? It's not efficient. You can create an organ that work like a nose, inspire and have a reaction. A natural buffer. That's what I'll develop!)

  • $\begingroup$ So, your answer is, "No." Correct? $\endgroup$
    – SRM
    Commented Jul 15, 2021 at 2:26
  • $\begingroup$ We already have other senses that can detect infections, most notably smell and touch -- both of these already trigger deep immune responses if we get bacteria/viruses in our nose or on our skin. But these senses require us to have physical contact with the entities that we do not want to physically contact! Those two senses do not let us look at an object ahead of time and say, "Oh, I should avoid that thing because it is covered in germs." That's why I've been exploring vision solutions. If bacteria/viruses made noise (I've checked: scientists don't think they do), I'd be exploring hearing. $\endgroup$
    – SRM
    Commented Jul 15, 2021 at 13:26
  • $\begingroup$ @SRM I think nose operates on volatile chemicals basis rather than direct touch? It allows you to detect spoiled food without direct exposure to bacteria. $\endgroup$ Commented Jul 17, 2021 at 5:12
  • $\begingroup$ @maciej that isn’t direct detection of bacteria. That is detection of spoiled food that is result of bacterial process — indirect evidence. Not the same thing at all, especially since many harmful bacteria do not trigger such processes. $\endgroup$
    – SRM
    Commented Jul 17, 2021 at 12:35

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