Titanium - as a rule of thumb we use 1nm = 300'
1nm = 1852m so therefore 1000m per 160' wouldn't exactly work.
Another rule of thumb is RVR REQ = DA/MDA x 6 again this is a ball park figure.
Its an interesting topic, but it wouldn't be so critical on an ILS where on a Non precision approach it would (taking cloud ceiling into account).
If you take for example a VOR approach with MDA = 660'(50' added) and RVR 2km
Using the above conversions, you will need a minimum of 4km to see the runway.
Question is why is the RVR down to 2km?