Fig. 1

Schematics of three models of left eye. a Non-pulley model; b passive-pulley model; c active-pulley model (Revised from work by Demer et al. [20]). P_L, P_M, and P_S are the pulleys of LR, MR, and SR, respectively. The EOMs are plotted by the red lines. Not all the six EOMs are plotted. I _i : the insertion point of the ith EOM; T _i : the tangency point of the ith EOM; A _i : the origin point of the ith EOM