Doppler ultrasound velocity mapping of extra-ocular muscles: a preliminary report

Colour doppler imaging and conventional spectral doppler/B-mode techniques were used to detect and quantify rectus muscle movement during voluntary saccades. A velocity gradient was evident in all muscles studied--low velocities near the muscle origin at the back of the orbit increasing linearly to a maximum near the muscle insertion on the globe. A consistent reduction in velocity occurred along muscles injected with botulinum toxin. Doppler ultrasound complements current clinical eye movement recording techniques--electronystagmography, infrared light reflection methods and magnetic induction methods--insofar as it detects movement in parts of the muscle itself rather than movement of the globe secondary to muscle contraction. Future developments in colour doppler imaging will make the technique clinically more applicable.