RVR transmissometers are pointed in one direction...they are not valid for the opposite runway.
Ha Ha Ha. Nice try!!
as someone else said, RVR transmissometers measure the opacity of the atmosphere between the sender and the receiver and work out an RVR.
RVR is a measurament of the visual range at a point. It is not directional. i.e. the RVR can be different as soon as one moves away from that point in any direction.
As many Garwick operators will remember, the RVR at the sensors can be 50m while the runway is CAVOK!!
If there is no touchdown RVR then use CMV to check if you can shoot the approach.
The mid-point (and stop end) RVRs are not limiting in terms of shooting the approach. However, they are indeed of interest when it comes to roll-out and if one expects to pass the midpoint at more than 60Kt then one would expect to have an RVR in excess of the take-off minima. One will usually be at less than 60Kt before passing the far end touchdown point so something like 75m can be acceptable. (All subject to appropriate LV-Ops approval).
So in the example given, I would use the vis to get a CMV and use that as the touchdown figure and then use the approved figures eg 125m (take-off minima)for the mid-point and 75m for the stop-end as minimums.
If there are are no RVR reports then you use CMV for the touchdown and that is it.