How to make Eyes sparkle as such...

This is a photo done by Eric Vega of www.Vegablue.com

Notice how her eyes sparkle.

Now how in d world can u get dat!?

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Looks like they may have been over-sharpened to me.

I see what looks like a reflection of something in her left eye, but nothing unusual otherwise.

I've seen a series of posters in one of the UK High Street fashion retailers where a different shaped "catchlight" has been artificially created in each shot.

I would not show a client a picture with eyes like those, I really don't like what has been done there. There are many ways to get the results that you want. One of the more simpler ways has been mentioned here is over sharpening. I will move the eyes to their own layer and then adjust them in curves and then over sharpen. I can then adjust the opacity of this layer to the point where I am happy with it.