The eye can't see inside of itself. The metaphor breaks down though, because the inside of an eye are in principle _seeable_ (mirrors and microscopes etc), while the "nature of language" or whatever, is in principle _unspeakable_ , no so much as a coherent thing to ask after.
Even better, you absolutely see things in your eye. They're called "floaters". Your brain learns to mostly ignore them.
And if you develop cataracts, your vision tends to "yellow", and you'll be seeing more and more of the lens of your eye, as it becomes less transparent. Cataract surgery (= replacing natural lens with plastic lens) can lead to the operated eye seeing "bright" and un-operated one "yellow".
Well, you are not really seeing an eye in a mirror, you are just seeing a representation of it. The medium cannot depict all the dimensions and details of the object, so again you are able to see depictions, representations, and simplifications of it, but never truly be able to grasp the object itself.
Sure you can say that everything I see is technically a representation in my head. But there is very much a shared reality, a domain of objects and state of affairs for which we both agree about the presence or absence of the same representations. There's a difference between a value and our measurement of a value. If every multimeter we touch to a battery reads 5.9v, its possible the battery is actually 6v and every single multimeter was coincidentally wrong. However from the inside the situation is indistinguishable from a 5.9v battery. We may as well accept the reality of our perception and its representations as the real thing per se, because even if it is delusion we are still stuck playing by its rules as if it were real.
I am "really" seeing an eye in the mirror in the sense that I'm seeing the same thing other people would call an eye, and thus it exists in the shared domain. To have a shared domain of objects and facts is to have a common ground. There is no "object itself" for us to reach out and grasp outside of our mutual perception of objects. We might all be in a computer simulation. Doesn't matter. The conversational/perceptual reality is reality.
Right, it's a three dimensional object projected onto a two dimensional surface and your knowledge about it, from looking into the mirror, is merely superficial. What's to say our world isn't a five dimensional space projected onto four dimensions? What can language say about anything, everything, and the universe when great amounts of it is hidden from us?