Nothing better than direct eye to lens contact! When that happens, fire away!
Here I am on a tripod, and I will usually take multiple shots, manually tweaking the focus on the eyeball between bursts of the shutter.
In other words, I autofocus on the eye (click, click, click), then manually tweak the focus (click, click, click), and manually tweak again (click, click, click). Out of 9 (or more) shots, That usually assures that at least one will be tack sharp on the eyeball.
Great Horned Owl. Block Creek Natural Area, Texas Hill Country. I just set up a workshop at Block Creek for April 24-27.
Canon 1d Mark IV. 500 mm lens + 2x teleconverter. Aperture Priority. f.22 @ 1/250 sec. +2/3 EV.