Depict eyes accurately
Notice how the eyelid bends inside the eye socket, causing a horizontal folding over the eye – that’s the key. The ocular globe is basically a sphere that’s half inserted inside the eye socket surrounded by two very prominent areas: the supraorbital and the cheekbone.
Once you’ve grasped the physical structure, try to simplify the volumes of the eye to understand them better. The ocular globe and the eyelids can be depicted as a sphere with a depression in the middle. Eyes are spheres, so there will be highlights, shadows and so on.
Once you understand the basic shape of the ocular globe, the eyelid, the supra orbital, the cheeks and nose, painting the eye should be easy. It’s just a matter of representing the volumes using lights and shadows, according to the light sources. Studying references will help.