1. Find or open your eye file. I used this one: www.sxc.hu
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2. Optimize levels and other settings. (How? Look here -> Optimizing Photo)
3. Make a new layer. Choose Elliptical Marquee Tool and select eye.
4. Select Gradient Tool. Set Foreground Color to #0aa5ed and Background Color to #42c502. Set Gradient type to Radial Gradient, fill the selection with it.
5. Set layer's mode to Overlay and remove unnecessary areas using Eraser.
6. You can use other colors! Duplicate (Ctrl+J) your gradient layer for more contrasted image.
7. Filter -> Render -> Lightning Effects, Flashlight, Point it to your eye.
8. Edit -> Fade Li
Click to enlarge