Hi MiguelS
great sb start 
Doing anatomy studies is one great way to improve your skills.
About your eye studies…
The eye is a spherical form contained in a socket.
Try to see the complete eyeball as a spherical shape, draw the sphere lightly if you have to.
The spherical shape of the eyeball has a direct impact on the shape of the iris. When you see the iris from a frontal view, it will look like a circle. From an angle it will be an ellips.
Check the eyelids, how do they relate to eachother?
How does that work, when an eye is being closed? Do the lower eyelid and upper eyelid both move towards eachother? It’s got something to do with their position in comparison with eachother and the eyeball.
About shading…
I see your sketches and I remember thinking my drawings looked too flat but I couldn’t point out where the cause was.
Shading can help a lot in creating a feeling of depth, volume, mass.
How it works? By the use of contrast.
If you study the art of masters (ancient and contemporary), you will notice that our eyes are drawn to the area’s with the highest contrast first.
Some good contrast exercises: take a HB pencil and draw some simple shapes (cylinders, spheres, boxes,…). Try to get as high contrast as possible. Do the same with a black pencil (2B or 4B or…). You will see that with a HB pencil you can go only as dark as a really dark grey of some kind, while the 2B pencil will allow you to go black.
In time you will learn that you can often go really dark, adding volume to your shapes and depth to your overall composition.
Anyway,
keep up the good work!
Draw, draw, draw!
















