I was in a very similar situation last month, where the RVR equipment was between the runway and a river, and reporting considerably less than the actual vis on the runway (which was visible along its full length from 10+ miles), the difference was that my R/T was 'visual, request visual approach' and the reply was 'cleared visual approach, cleared to land'.
While it may often be interpreted as such, calling 'visual' does not constitute requesting a visual approach. Doesn't help much here, but worth bearing in mind for the future.