Sorry, there is no full screen mode. If vision impaired you may already be familiar with your TV’s zoom features, if not this may provide some relief. But many full screen modes do not increase the font size anyway; merely consume the entire screen showing more data that might be uncomfortably small.
Not vision impaired, just getting older. I just do not like the distraction of having something happening on the left hand side of the screen. This makes the facebook widget unattractive to me. I will just continue to use the computer instead of the TV. Maybe a future enhancement?