I hear ya on that one. I just got the ST300 (full size version) and it actually leaves me seeing stars after I use it (30yo eyes with glasses). The speed and sensitivity are amazing however, so I can't part with it. I'm thinking of picking up a pack of these guys:
LightDims Original Strength\xae: Amazon.ca: Home & Kitchen
Can stick one of the square ones over the screen and put the display back to a normal level of brightness. It might work for your polytune as well.
LightDims Original Strength\xae: Amazon.ca: Home & Kitchen
Can stick one of the square ones over the screen and put the display back to a normal level of brightness. It might work for your polytune as well.