You will need:
Versafine or versafine clair ink
13 x 18cm canvas or board
First stamp the eye onto the watercolour card using a waterproof ink such as versafine or versafine clair
2 or 3 Eggshells (soak these in antibacterial hand wash and make sure all the membrane is removed, then leave to dry)
Mixed media or watercolour card
Put modelling paste around the outline and put bits of eggshell into it before leaving to dry.
When this is dry, use the irridescent paint to go over the eggshells to give the appearance of scales.
Finally glue the eye in place (I used 3d glue gel) and add a coat of spray varnish, mod podge or something similar to protect it if you wish.