Abstract
Purpose: :
The aim of this pilot study was to qualitatively and quantitatively evaluate near real time oculodynamic MRI (od-MRI), a new technique that allows eye movements to be recorded in vivo.
Methods: :
In 22 patients with diplopia, eye movements were tracked in the horizontal and vertical plane, using a standard 1.5 T MRI. A TrueFISP sequence (180ms/image, 1.3x1.3 mm spatial resolution) was used. The slice thickness was 5 mm. The additional MRI time for using this method was less than 15 sec. per sequence. Eye movement was assessed in the sagittal and axial plane. Visibility of extraocular muscles was graded qualitatively throughout the movement by three independent physicians. In addition, maximal monocular horizontal and vertical excursions in mm measured in the clinic were compared to the angle of the largest possible eye movements in the MRI sequence by using a see- through ruler on the computer screen and statistically by using the Pearson test.
Results: :
Mechanical adhesions could be distinguished from entrapment and paralytic eye movement disorders. Three independent assessors graded the MRI quality (from 1= not visualized to 5 = very good quality, continuous visualization). According to the plane examined, visualization was better for the horizontal and vertical rectus muscles than for the superior and inferior oblique. Complete visualization throughout the axial or sagittal sequence varied between 93,3% and 13.8% respectively. When MRIs with complete visualization were analyzed, horizontal movements of the right (p=0,015) and left eye (p=0,026) and vertical movement of the right eye (p=0,029) correlated positively to the clinical measurements.
Conclusions: :
To our knowledge, there are no other studies reported which assess od-MRI as well as clinical testing. With a good correlation to clinical findings, the od-MRI seems an advantageous tool to record and visualize normal and pathologic ocular movements. It`s potential application is particularly in the setting of preoperative planning of posttraumatic diplopia or periorbital tumors with secondary ocular motility disorders.
Keywords: eye movements • extraocular muscles: structure • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)