[Avodah] Brussel sprouts and halachic ramifications of vision strength

[Moshe Y. Gluck]

RMB writes (on Areivim):
> One of my suggested resolutions is that the definition of "visible bug"
> actually changes with improvements in lighting and eye health. That
> whatever excludes magnification doesn't exclude changes we can make to
> the context that further empowers naked human senses.

And R'n CL responds (also on Areivim):
> I find this suggestion difficult. I don't know of any sources that
> suggests that a Torah issur changes with improvements that we make in
> science, ie that bug X was mutar to them, but assur to us. There are
> ideas around that the teva changes - but our ability to view the
> world? This is very different from saying that what the Torah assured
> were visible bugs. I think you need some sort of source for such a
> radical idea. And the other problem is that the boundary is very fuzzy.
> Some people even in those days had better eyesight than others. Does it
> vary from person to person? Can Rachel eat a fruit checked by Rachel,
> but not by Leah, and does Leah have to check that Rachel has at least
> as good eyesight as she does before she eats in her house? What about
> husband and wife?

You could be mechaleik (wasn't that an old Avodah meme - VIDC? Something
like that?), but I do have one situation in which the halachah changes
based on vision - the Biur Halachah in Siman 79 (DH Oy SheHu Suma) says
that a person has to distance himself from Tzoah when saying Shema at
night based on how well he sees during the day. One who sees farther
will have to make sure he's farther away. (A blind person, though,
evaluates the distance based on the vision of an average person. 20/20,
maybe? Or is the average _uncorrected_ vision?)

KT,
MYG