Haven't looked at any of the research, but I had the same problem you
are describing.   I became more nearsighted during pregnancy, and the
nearsightedness worsened during lactation.  This became a real issue,
as I went back to school soon after the birth.  I was able to
compensate by recording class and sitting up front, but these
solutions don't apply to this mother's situation.

Would it be a real problem (financially or otherwise) for the mom to
get some new lenses for use during lactation?  The optician could
just pop the lenses out of the eyeglasses she has now, and she could
save them for use after her eyesight returns to pre-bf level.  Can't be
more than $50 or so just for new lenses, unless she has unusual
prescription.

Good luck,
Gina
nursing student and future LC