Eyes construction

[cafe_claro]

For being able to represent anything in painting it is necesary to comprehend the escense and the nature of its form and its volume. Right now and always I'm having so much trouble understanding this hole concept of eyes, the eyes I do are somkind fake because there is something I'm not being able to understand.
It would be great if you guys could talk of the way you construct and uderstand this hole eye thing.
Thank you!