New results about the echographic examination of the optic nerve. Experimental and clinical investigations

Abstract

The optic nerve can be displayed in vivo by A- and B-scan techniques. To correlate the anatomical structures of the optic nerve with the echograms, and to determine whether the diameter of the nerve can be measured by routine examination techniques, we conducted experimental studies on bovine optic nerve in vitro with the A-scan technique, and measured the sound velocity in bovine optic nerves. We also compared the two A-scan techniques most frequently used to display the optic nerve in vivo in 47 normal persons and in 35 patients with changes of the optic nerve. The experimental studies showed that the orbital fat and the outer sheaths of the optic nerve cause refraction of the soundbeam. The sound velocity of ultrasound in bovine optic nerves was 1567 ± 25 m/s. The two most widely used in vivo examination techniques showed no differences in healthy subjects, but significant differences in patients with increased subarachnoidal fluid.