Elucidation of restrictive motility in high myopia by magnetic resonance imaging
T. H. Krzizoh, H. Kaufmann and H. Traupe
Department of Strabismus and Neuro-ophthalmology, Justus-Liebig-University, Giessen, Germany. Thomas.H.Krzizok@augen.med.uni-giessen.de
OBJECTIVE: To elucidate the cause of an acquired, restrictive motility
disorder in patients with high myopia. METHODS: Magnetic resonance imaging
(MRI) scans were obtained from 37 patients with high myopia (axial length
of globe, 29.4 mm; refractive error, > -15 diopters). Additional dynamic
MRI scans were obtained in which the patient fixated in various positions
with the less restricted eye for 50 seconds. Twenty normal orbits were
studied in control MRI scans. RESULTS: The path of the lateral rectus, in
the anterior and midorbital regions, was displaced downward an average of
3.4 mm in 13 patients with typical esotropia and hypotropia. This
mislocation reduces abducting torque of the lateral rectus and creates
depressing and extorting moments. The muscle insertions were normal, except
where previous strabismus surgery relocated them. Contact between the
enlarged globe and the bones of the orbital apices that would cause
esotropia was not observed. CONCLUSIONS: This eye muscle abnormality in
patients with high myopia is another strabismus syndrome related to
abnormalities of orbital connective tissues and muscle paths. Orbital MRI
scans may be useful before strabismus surgery in patients with high myopia.
If an abnormal lateral rectus path is found, surgery should be directed to
normalize it. Magnetic resonance imaging morphometry in high myopia may
give additional information on orbital anatomy and biomechanical mechanisms
of strabismus.
