Werner Cadera

Cine Magnetic Resonance Imaging of Ocular Motility

We describe a technique of generation of a cine motion picture of ocular movements in a patient with Duane Type II exotropia. With the magnetic resonance scanning unit, multiple scans can be sequenced to give a graphic animation to the eyes as targets are fixated across the visual field. With this technique, we were able to clearly view the contractility of the extraocular muscles and note the changes in pulling directions of the muscles in this patient. The restriction of movement due to the cocontraction of the horizontal rectus muscles was readily apparent.

A magnetic resonance imaging study of horizontal rectus muscle palsies.

The assessment of extraocular muscle function is usually performed indirectly by an examination of ocular motility. We have utilized magnetic resonance imaging, in both cine and static modes, to directly observe the contractility behavior of the extraocular muscles. This noninvasive technique was applied to the study of patients with horizontal rectus muscle palsies. In all cases, the palsied muscle was of a smaller diameter than its normal counterpart. This size differential was noted in all fields of gaze. Additional studies are required to determine the relative contributions of denervation atrophy and loss of tonus to this diminution of muscle size.

Depth of Strabismic Amblyopia Determined with Neutral Density Filters

We used a neutral density filter to assess motor responses in the fixation patterns of 25 patients, ranging in age from 5 to 54 years, with strabismic amblyopia. Shifts of fixation back to the preferred eye occurred when the visual acuity of the preferred eye through the filter was marginally better than that of the amblyopic eye. Thus, we were able to correlate the level of the filter at which this shift occurred with the level of amblyopia. This technique may be particularly helpful in the examination of preliterate children and in monitoring the progress in the treatment of amblyopia.

Ocular Pursuit Movement Assessment by Magnetic Resonance Imaging

We describe a new technique for generating cinematic magnetic resonance images. This method produces more physiological imaging of extraocular muscles than our previous method. In addition, this technique provides more comfort for the study subject and results in less head movement artifact.