This is an indept drawing of the eye with the goal of getting every detail.
The eye has been one of the most challenging aspects in making portrait.
Failure to make a propore detail of the eye could make the work look like some other person or creature instead of the real model.
In this I made sure there is a relationship between light and shade.
As you can see in this drawing I left a portion of the eye blank - This where bright light feel on and makes it to look as real as possible.
Here is my outline sketching.
The final piece.
Did you observe something? The eye is looking at you :)