Fig 1.
A process of simulation model setup.
Fig 2.
Construction of a 3D eye model with extraocular muscles and the pulley system.
An eyeball was constructed as a homogenous sphere with a 12-mm radius. The rectus muscles were supposed to act as a spring model, and the origin of the rectus muscle was fixed at a single point. A pulley system was incorporated into the rectus muscles based on previous geographic data [18].
Fig 3.
Relationship between tension record and temporal rotations of a normal eyeball.
The angle of orbital rotation according to force within the scope of eyeball rotation established the linearity [28]. Based on the result, we assumed that the extraocular muscle acts as a spring.
Table 1.
Biomechanical properties of the model eyeball and rectus muscle.
Table 2.
Calculated bearing tension of the four rectus muscles.
We first set the medial rectus muscle tension obtained from a previous study and evaluated the subsequent reaction forces of the other rectus muscles to maintain the standard eyeball position established based on geometric data. In the standard model, superior rectus and inferior rectus were more medially located, so the relative lateral rectus tension was estimated to be larger than medial rectus tension.
Table 3.
Degree of ocular deviation according to the abduction vector force of lateral rectus muscle.
Fig 4.
Simulation of the various muscle transposition procedure.
(A) Hummelsheim, (B) Jensen, (C) Foster, (D) muscle union procedure (MUP) (blue line: superior rectus, green line: inferior rectus, red line: lateral rectus, purple line: medial rectus, red dot: pulley, black dot: original insertion of the superior rectus muscle). We changed muscle vectors, origins, and pulley locations consistent with each surgical method to realize the surgical effect and then evaluated temporal rotation degree of the eyeball using each biochemical model.