Custom contact lenses

1. Face mask

With the polygonal lasso tool draw a selection around the eyes.

On the main menu go to Select > Inverse.

Copy and paste this on a new layer and name "facemask".

2. Cutting & pasting eye

Go back to the eye layer, with the Elliptical Marquee Tool draw a perfect circle around the eye of the subject. Copy and paste the eye on a new layer and name this layer lens.

3. Color and Gradient style

First choose the color you want your eyes to be, I choose a gradient of light green to dark green. Then turn your blend mode to "Color" Then choose a pattern for your eyes, this will become the design which will take over the white area of your eyes. I choosed the pattern named "strings" which should come default with your Photoshop.

Here is finished tutorial:

Practice with different patterns and colors.