Hi Michael,
I guess you have treated yourself to a high spec microscopy camera and want to be able to manipulate slides in real time while still being able to capture high resolution stills and video.
If you want low latency imaging direct to the Mac, have a look here:
http://www.cloudmakers.eu/
The reason I suggest this is that planetary imaging poses many of the same issues, namely capturing huge amounts of video data in real time, typically with USB2.
Most 'HD' resolution cameras can handle full frame at 15-30 fps in real time over USB2.
If you want faster, astro software allows good access to the camera controls, and can often support things like reduced resolution, region of interest and choice of data format (which can speed things up if you choose a compressed format).
This might allow you to achieve what you want using USB2.
I don't know the details of the applications at that website, but if you had a PC I'd be recommending Sharpcap.
Another possibility is astro imaging software on the RPi (get a used monitor for £30 off eBay or use your TV), and then just port the captures to the Mac for processing. Typically you can pre-process the view for gamma, histogram stretch, contrast, white balance, sharpness etc.in real time while still saving the data as full bit depth RAW for processing.
(Note – most astro capture software has vastly more capability than medical capture software, and it tends to be free. Other advantages are saving stills as FITS and raw video as SER).
Neil