Synergists: It refers to the muscles having the same primary action in the same eye; e.g., superior rectus and inferior oblique of the same eye act as synergistic elevators.
Antagonists: These are the muscles having opposite actions in the same eye. For example, medial and lateral recti, superior and inferior recti and superior and inferior obliques are antagonists to each other in the same eye.
Yoke muscles (contralateral synergists): It refers to the pair of muscles (one from each eye) which contract simultaneously during version movements. For example, right lateral rectus and left medial rectus act as yoke muscles for dextroversion movements. Other pairs of yoke muscles are: right MR and left LR, right LR and left MR, right SR and left IO, right IR and left SO, right SO and left IR and right IO and left SR.
Contralateral antagonists: These are a pair of muscles (one from each eye) having opposite action; for example, right LR and left LR, right MR and left MR.