[New knowledge of echographic imaging of the optic nerve. Experimental and clinical studies]

The optic nerve can be displayed in vivo by A- and B-scan techniques. To achieve correlations between the anatomical structure of the optic nerve and the echograms and to answer the question if by the usual examination techniques the diameter of the nerve can be measured, experimental studies on bovine optic nerves were carried out: examination of the bovine optic nerve in vitro with the A-scan technique; measurement of the sound velocity in bovine optic nerves. Additionally, we compared the two most common A-scan techniques for the display of 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 outer sheaths of the optic nerve cause refraction of the sound beam. The sound velocity of ultrasound in bovine optic nerves was measured to 1567 +/- 25 m/s. The two most common examination techniques in vivo showed no differences in normal persons, but significant differences in patients with increased subarachnoidal fluid.