What constitutes "the lights delineating the runway"? ICAO defines RVR as "The range over which the pilot of an aircraft on the centerline of a runway can see the runway surface markings or the lights delineating the runway or identifying its centerline."

What are "the lights delineating the runway" here? Do they just point to runway edge lights? Or do they include approach lighting systems as well?
Presumably it's your runway lighting (edge lights, such as HIRL, MIRL, etc, plus runway end identifier lights - REIL), centerline lights, and touchdown zone lights only, because being able to see the nearest approach light miles away isn't helpful if, by the time I'm at 200' half a mile from the runway (and past that outer-most approach light), I'm inside a dense fog bank with an RVR of 600 feet.

That said, it's a much more common case where the RVR at the runway (where it's measured) is about the same as the in-flight visibility farther out on final, so with an RVR of 4000' you can expect to see the threshold at typical Cat I ILS minimums of 200' AGL (okay, ATDZE for the pedantic &amp; precise), but at 1800 RVR at the same point, you expect to see approach lights but little else.