Been back "home" (Oz) for some time now, but if my memory serves me right when in the M.E. we had a correction factor to go from Vis to RVR if only one was stated and you needed the other, factor was 1.5. When I was in HK I'm pretty sure that the company had a nominated destination VIS requirement, not given as an RVR.
Also, are not Vis and RVR different?
Edit: can see some have covered this.
https://www.universalweather.com/blo...ps-visibility/3. Calculation of visibility
Visibility values are determined by both human observers and the Automated Surface Observing Systems (ASOS). The human observer determines visibility by identifying objects and landmarks at known distances throughout a 360 degree circle around the observation point. The greatest visibility observed over 50% or more of the 360 degree area is the prevailing visibility. If, however, there’s a sector of the 360 degree area that significantly differs from prevailing visibility, the observer may add a remark. ASOS measures and converts sensor-driven values to visibility values corresponding to what the human eye can see.
Pilots must be mindful that nearly half the area around an airport may have lower conditions than the reported prevailing visibility.
5. RVR considerations
RVR is distance over which a pilot of an aircraft, on the centerline of a runway, can see delineated runway surface markings and centerline. RVR values are normally determined by the human eye or with an Instrumented Runway Visual range (IRVR) trasmissometer. RVR is important as it provides the main criteria used to determine category of visual aids operational at an airport as well as criteria/minima for instrument approaches.