That is a beautiful portrait ,looking through your process of drawing I like most that you have showed us the structure of your drawing starting with the proportion and help-lines to orientate the position of facial features. I immediately recalled the time of Art classes when I was fascinated how from geometric figures we were able to build up such amazing thing like a human face. Beautiful work, as to eyes as you say some people have too dark Iris and if the eyebrows dropping shadow on eyes, then they look just dark :)