Verify Time Machine backups


I have recently got a 2TB NAS drive which I'm now using to keep a backup of my Mac with Time Machine. Everything seems to be going fine with it so far, but when I've read up on Time Machine, I discovered there was a "verify backups" option which can be used to check that the backups are definitely working correctly. Sighted people access this option by holding the option key down and clicking into the Time Machine menu. How can this option be accessed with VoiceOver?

I have tried pressing CMD + F5 to put the mouse pointer on the Time Machine menu, then turning the trackpad commander off, then clicking the trackpad while holding down the option key but this just brings up the standard time machine status menu. That method works fine on the volume menu for switching inputs and outputs, so not sure why it doesn't work here.

Any help appreciated.