| | or left up |eye, up before | | |(left hyperphoria, | left | | | left hypertropia, | | | | right hypotropia.)| | ==================+===========+===================+=================+ | Image of | | | right eye | CORRECTED BY | |as compared+-------------------+-----------------+ Name of |with that | | | diplopia | of the | (1) Turning |(2) Prism placed | | left is | | with base | ------------------+-----------+-------------------+-----------------+ {Homonymous | On the |Both eyes outward |Out before either| { | right | (divergence.) | eye. | Lat-{ | | | | eral{Heteronymous| On the |Both eyes inward |In before either | {(or crossed)| left | (convergence.) | eye. | | | | | ------------------+-----------+-------------------+-----------------+ {Right | Below |Right eye down |Down before right| Vert-{ | | and left eye up | eye or up before| ical{ | | (left | left eye. | { | | supravergence.) | | { | | | | {Left | Above |Right eye up and |Up before right | | | left eye down | eye or down | | | (right | before left. | | | supravergence.) | | ==================+===========+===================+=================+ MOVEMENT OF EACH EYE SINGLY The movements of each eye individually are effected as follows: The external rectus moves the eye directly outward; the internal rectus, directly inward. The primary action of the superior rectus is to raise the eye. Because of the way in which the muscles run, obliquely from within outward, its lifting action increases when the eye is abducted and diminishes to little or nothing when the eye is adducted. The inferior rectus carries the eye down. Owing to the oblique direction of the muscle, its depressing action increases as the eye is abducted and decreases to zero as the eye is adducted.