If there’s one part of your image that is absolutely critical to have in sharp focus, it’s the eyes. If the eyes aren’t sharp, the whole photo’s a bust, so we take extra steps to make sure we sharpen them. In this case, we’re going to use the most advanced sharpening Photoshop has to offer: the Sharpen tool. By the way, it wasn’t always this way. Adobe went and reworked the math behind the sharpening just a couple of years ago, and now we can apply more sharpening with fewer of the distracting halos and artifacts (junk) you’d get anytime you really sharpened something a bunch.
Open the image you want to retouch in Photoshop, and then press Command-J (PC: Ctrl-J) to duplicate the Background layer. I generally do this type of sharpening on a duplicate of the Background layer so (1) I can easily toggle the layer on/off to see a before/after while I’m sharpening, (2) I can lower the Opacity amount of the layer if I think I’ve over-sharpened the eyes, or (3) I can delete the layer altogether if I decide I don’t want any sharpening at all.
Get the Zoom tool (Z; it looks like a magnifying glass) from the Toolbox, and then zoom in on the eyes. Also in the Toolbox, nested under the Blur tool, you’ll find the Sharpen tool (seen here). It has been in Photoshop for many years, but was pretty much unusable because it was so harsh we avoided it all costs. But, in Photoshop CS5, Adobe’s engineers decided to not only fix this tool, but to make it Photoshop’s most advanced sharpening tool (I got that straight from one of Adobe’s own Photoshop product managers). However, this new math is only turned on if the Protect Detail checkbox up in the Options Bar is turned on, so make darn sure that it is (as shown here, circled in red), or you’ll be using the old version of the Sharpen tool (with the old results).
Also in the Options Bar, lower the Strength amount to 20% (as seen here). Using a lower amount like this gives you more control because the sharpening builds up each time you paint, rather than all at once. Then take the Sharpen tool, and paint a few times over an entire iris, including the outside edge of it (as shown here). Do the same thing with the other eye, and keep in mind that since you did this on a layer, if you need to, you can lower the layer’s opacity, which lowers the amount of sharpening you’ve applied. Doing this much sharpening can sometimes sharpen random bits of noise or shift the colors in your image a bit, so change the top layer’s blend mode from Normal to Luminosity, so it just sharpens the detail and not the color, and you’re done. Now, flatten the layers (from the Layers panel’s flyout menu) before you save the image and take it back to Lightroom.