STUDY OF THE INFERIOR OBLIQUE MUSCLE OF THE EYE BY MRI

The utility of the inferior oblique m. radioanatomical study by a FLAS H 3D sequence in magnetic resonance imaging (MRI). Twenty eyes (ten he althy volunteers aged 21-32 years, without any history of significant ocular pathology) were explored by MRI (1 Tesla; cranial coil) and com parisons wen made between spin 1 echo (SE) T1 sequence (through the ne uro-ocular and coronal planes; thickness of slices = 3 mm) and a gradi ent echo FLASH 3D sequence (thickness of slices = 1 mm). This enabled a mm by mm reformation of the inferior oblique m. through the frontal- oblique plane, made possible by new SE T1 sequences through the same p lane. Position, height, and signal of the m. were estimated. The mean frontal angle formed by the muscle and the sagittal axis measured 29 d egrees for the light eye and 27 degrees for the left eye. The muscle w as always identifiable in the reformation despite its thin dimensions: 1.9 mm (1.5-2.8) on the right and 2 mm (1,7-2.5) on the left, in low signal silhouetted by the high signal of orbital fat. Thus, thanks to mm by mm reconstructions using FLASH 3D sequence, a good radioanatomic study of the inferior oblique m. by MRI is possible. This could be us eful particularly for the strabismus of children.