This section deals with how the 
extra ocular muscles move the eyeball.
As you now know, there are 6 extra-ocular muscles concerned with movements of the eyeballs - the four recti muscle and the two obliques. But if the eye is a sphere, why should it need six muscles to move it ? Wouldn't four do just as well ?

Let's set out to answer this question - and look at the individual actions of the muscles.

 
Muscle
Primary Action
Superior Rectus
Raises the eyeball
Inferior Rectus
Lowers the eyeball
Medial Rectus
Adducts the eyeball
Lateral Rectus
Abducts the eyeball
Superior Oblique
Lowers the eyeball when the eyeball is adducted
Inferior Oblique
Raises the eyeball when the eyeball is adducted