Ok here goes:
Met this woman outside of the chip shop in Selby North Yorkshire and took her photo don't know who she is but thought she had nice eyes for this tutorial. I WISH HA HA!!!
Once you have opened your image in photoshop zoom in to the eye you want to enhance first. I am going to do the left eye only so that you can see the difference.
The first step is to make a selection of the eye, you can do this several ways, I tend to use the pen tool but you can use the lasso tools the choice is yours. Try and be as accurate as possible and follow the contour of the eye.
If you used pen tool use make selection - feather radius 3 pixels press ok.
If using lasso go to select- modify-feather radius 3 pixels press ok
Either way you should end up with the marching ants.
Next go to Image-Adjustments Curves.
Angelina has blue greenish eyes so I made 3 curve adjustments.
First I adjusted the overall brightness as below using the RGB channel (arrowed) Take notice of the output and input numbers (circled) as you will need to make the same adjustments to the other eye,
I then altered both the blue and green channels in the same way to get the effect I required.
You can use whatever setting you want to gain the effect you require but try and match the eye colour and don't overdo it be subtle.
Next we have to use the dodge and burn tools if your not sure which these are they are on the lefy toolbar and look like this
Select the dodge tool first and make sure that highlights is selected on the top toolbar and exposure around 30 like so.
Choose a brush size that covers an area of the lightest area around the black part of eye.
Then paint around the area to lighten it further, again don't go over the top. You should end up with something like this.
Next select the burn tool making sure that shadows is selected in the top toolbar, I reduced the exposure to 7 as 30 was far too dark. This time paint around the outside of the pupil which will darken as you paint again be very gentle. You should end up with an eye looking like this.
The next thing to do is to select the pupil you can use the elliptical marque tool for this.
Once you have made the selection go to select-modify-feather and dial in around 5 pixels then clock ok.
it should look like this
Next make sure that black is selected as the background colour as so:
Then on your keyboard press clear on my Mac it is the back tab button not sure what it is on Pc. You should end up with a completely black pupil.
Now select the brush tool on the left toolbar the foreground colour should be white as below,
Now click on the pupil where the highlight should be and you should end up with this. (consider the position of the highlight carefully if no highlight appears in original image.)
Finally select the sponge tool, it's in the same place as Dodge and Burn, make sure that Desaturate and 100% is selected on the top toolbar. Pick a brush size that covers the size of he eye and place it over the eye and click once. There done.
I think you can see the difference all be it very subtle.
This process can be used with all eye colours, for blue eyes you would only use RGB and Blue channels in curves, Green eyes RGB and green and for brown which is the most difficult a mixture of RGB red, blue and green depending on the effect.
I hope these instructions are clear give it a go and let me know the results. Any problems let me know and I will contact you directly.