Create a “curves” based adjustment layer.
Menu: Layer -> New ->New
adjustment layer -> Curves
Select the eye portion the curve by holding down
the Ctrl key while clicking on the bright part of the eye.
Raise the brightness on the eye
Use the up arrow on the keyboard or drag that portion of the curve
upward.
Repeat steps 2-3 on the dark portion of the eye to
make it darker.
Fill in the mask (created automatically for
adjustment layers) with black.
Menu: Edit -> Fill -> black
Select the brush tool and brush the areas of the eyes you wish to
improve.
Select an opacity in the range of 20-50%, select the appropriate
diameter, select a soft edge.