Unfortunately, this is a very easy thing to create. The inner cavity of the eyeball has a certain size. I do not remember the frequency but it is in the sub megahertz band. Used to work with in car police radios and if you were to close to the antenna, radios with certain frequencies they will give you eye irritation. Directional antenna and the right frequency could definitely cause eye injury. But also very easy to detect and locate since the power needed is fairly high. Probably over 50 watts.
Like all RF, the inverse square law applies. Power, antenna gain, and distance determines the field strength. As you say, different tissues respond to different frequencies.
I think Trump speaks from behind a bullet-proof glass shield now, which would probably attenuate the energy enough that Trump himself wasn’t affected.
Maximum power transfers in radio waves to receptors according to resonance, or comparable size with the wavelength. So the Sizes of the various parts of the eye (e.g., retina cones, etc. are very small) the viscous eyeball cavity is what? About and inch, inch and a half? I’d be looking at high frequency RF in the high GHz region (26.5-40 GHz).