The title says it all. What would the person be able to see?
By harmless, I mean that it is non-corrosive, non-toxic, etc. The liquid doesn't cause any biological damage to the eye or any other organ related to it, simply put.
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If it's significantly different, then not a whole lot. Your vision is very sensitive to the focal length of the lens of your eye, and changing the refractive index of the fluids in your eye changes that focal length. Depending on the refractive index, it would just make you nearsighted or far
The focal length of a lens depends on its refractive index, and the refractive index of the media on both sides, so opening your eyes underwater does a similar thing. Relevant: Eyes open under water.