As Despegue says: KISS.
Deciding to land is something you do at or before minima. Being legal to make an approach is decided earlier and is dictated only by vis/rvr.
Some years ago, under PANS Ops, the visibility bore no sensible relationship to the MDA on NPA's. It was quite obvious that at MDA you might not seeing anything of the visual reference if the minimum visibility was a fact. This was to be forewarned and forearmed. I use 2000m = 320'. You can measure the approach lights, assuming 150m lateral bar spacing.
For ILS minima you will usually find different values for different lighting systems. Thus there is now a better correlation between DA & visibility. I'm not sure if the same is now applied on NPA's. It should be as most NPA's are promulgated as continuous descents and a DA is published rather than MDA.