The iSight cameras are now PCIe rather than USB, and no drivers exist for them yet as far as I'm aware. There is some more information on the kernel.org bug tracker[1], and there's also an ongoing attempt to reverse engineer one on GitHub[2].

[1]https://bugzilla.kernel.org/show_bug.cgi?id=71131

[2]https://github.com/patjak/bcwc_pcie