The muscle which makes an angle of about 51deg with the optical axis is
The extraocular muscles rotate the eyeball around veical, horizontal and antero-posterior axes. Medial and lateral rectus muscles are almost parallel to the optical axis of the eyeball; so they have got only the main action. While superior and inferior rectus muscles make an angle of 23deg and reflected tendons of the superior and inferior oblique muscles of 51degwith the optical axis in the primary position. Ref:- A K KHURANA; pg num:-315
Superior oblique
Superior rectus
Inferior rectus
Lateral rectus
Ocular motility and squint