The overall ambient light can't be too low. Any ambient light will eventually strike the display, affecting the perception of its blackest black. That said, too low could cause you to bump into objects! Ambient light can be TOO HIGH.
With the older CRTs, those that might be able to hit 95cd/m2, the recommended ambient light was 16-25 lux which is dim. Since you can drive LCD's higher, you can also work with higher ambient lighting but again, it should be lower than the display.
There's a very old ISO standard if we can call it that for viewing conditions but its kind of out dated.