Thank you, Chimb, for some nice designs. I think you've really learned from our comments to step in and have some good ideas. First, let's try to keep "Ophthalmology Institute" on one line, a little bit larger, and then "of Orange County" on the second line, either the same font size or a touch smaller. In other words, the "of" belongs with Orange County, not with Ophthalmology Institute. Okay, now that we got that out of the way....
#18 is great. Very iconic. Very strong. Love the font choice. Very simple. Maybe modify the OC to make the O same or thicker and the C thinner, but still maintain the pupil reflection? I don't know how you could do that.
#19 builds on the idea of putting OC as the center of the eye shape. I like the subtle texturing of the eyelid contour. What really makes this one stand out is the shadowing below the eye shape; it creates a three-dimensionality that makes this logo "pop out" a little bit, gives it quite a bit of depth. There's something about the OC in the middle that's a little 'vacant'. Maybe modify the OC to add more substance. You can see how the OC in #19 is a little too empty and the OC in #18 is a little too full, if that makes sense....
#20 is just a rearrangement of #19.
#21 has an eyelid contour that is not as good as the one in #19, and there's not "pop-out" shadowing. But the one good thing about this one is that the OC in the middle creates more substance in the middle, creating a better "pupil" effect.