Robinson's Computerized Strabismus Model Comes of Age

Abstract

In this article we review our further development of D.A. Robinson's computerized strabismus model. First, an extensive literature study has been carried out to get more accurate data on the anatomy of the average eye and the eye muscles, and about how these vary with age and with refraction. Secondly, the force-length relations that represent the mechanical characteristics of the eye muscles in the model have been determined more accurately in vivo recently, and the model was changed accordingly. Thirdly, many parameters that were free in the original model and not derived from in vivo measurements were replaced by derivatives from in vivo measurements or made redundant. Fourthly, the ease of operation was improved greatly and the algorithms were made so much faster that a calculation for nine positions of gaze now takes ten seconds on a handheld HP 200LX Palmtop. The predictions of the model compared well with clinical results in horizontal muscle surgery, oblique muscle surgery, forced duction tests and abducens, oculomotor or trochlear palsies. Consequently, complex strabismus surgery in our clinic is now guided by the predictions of the computerized model.

Dynamic Magnetic Resonance Imaging of the Levator palpebrae superioris Muscle

“…Oblique-sagittal MRI scan in a plane along the optic nerve on downgaze. The LPS (1) originates from the lesser wing of the sphenoid and courses superiorly in a curved path to a culmination area superoposteriorly to the equator of the globe from where the LPS aponeurosis (and the superior tarsal muscle) course inferiorly to insert into the upper border of the tarsal plate (arrow) and the posterior surface of the orbicularis muscle (4). The slope of the aponeurosis is steep in this gaze position.…”

“…In eye muscle surgery, the dose-response relationship has been based on biomechanical and physiological principles [2][3][4]. Currently, the amount of surgery on the levator muscle is based on empirically derived values [5] and no biomechanical model of upper eyelid movements has been presented so far.…”

Ocular Rotation Axes during Dynamic Bielschowsky Head-Tilt Testing in Unilateral Trochlear Nerve Palsy

“…Although detailed biomechanical models of the eye plant, such as Orbit 16 or the computerized strabismus model, 17 have the advantage of being anatomically more realistic, a simple geometric model makes it easier to understand, why the dynamic Bielschowsky head-tilt test evokes the eye movements that we observed. The geometric model presented here computes rotation vectors, but, for convenience, the results are projected stereographically on the Hess screen chart.…”

Simulation of Active Eye Motion Using Finite Element Modelling

“…To the best of our knowledge, muscle pretension magnitude is not obtained experimentally so far. As mentioned earlier, it is common to assume medial and lateral rectus muscles pretension equivalent to 80Nm Spekreijse 1996 andSchutte et al 2006 . In this subsection, we are trying to study the effects of this assumption.…”

“…Descartes pioneering work for eye modelling in 1630 see Descartes 1972 has been continued by Listing, Ruete, Donder, Helmholtz and many others until now details can be found in works by Simonsz & Spekreijse 1990, Donders 1864and Fetter et al 1997. Simonsz & Spekreijse 1996, Clement 1982and Miller & Robinson 1984 suggested some computerized model for studying eye behaviour.…”