cisco unified video advantage, (aka VT advantage) supports video telephony functionality to the 7900 series IP phones, which does include the 7985. (albeit the video telephony is built into the 7985 and there should be no VT advantage configuraton for this device)
for you to use the 7985 phones in a multi party video conference though, you will need an MCU, (multipoint control unit), such as the MCU 3515.
see the following links for more info. on the unified video advantage and MCU:
http://www.cisco.com/en/US/products/sw/voicesw/ps5662/index.html
http://www.cisco.com/en/US/products/ps6960/index.html