A classification of retrobulbar A-mode echogram patterns is described following examination of 60 patients with unilateral proptosis. Sixty percent of 20 verified orbital neoplasms revealed one of the following axial length differences, dampening of retrobulbar echoes and tumor-cyst patterns. Five of eight undetected neoplasms were confined to the orbital apex. All patients with endocrine exophthalmos (ten) and orbital cellulitis (six) had normal echograms. Pseudoproptosis (ie, unilateral high-axial myopia or unilateral glaucoma) was easily detected due to increased ultrasonic axial measurements (five). Time-amplitude (A-mode) ultrasonography is unidirectional. All ultrasonic interpretations are subjectively made by the physician by comparing the acoustical properties of both orbits. Although this method cannot outline retrobulbar masses two-dimensionally as with intensity-modulation techniques, the ability to detect orbital neoplasms and exclude all instances of pseudoproptosis makes this technique clinically valuable and worth further clinical testing and refinement.
Gitter K, Meyer D, Goldberg R, Sarin LK. Ultrasonography in Unilateral Proptosis. Arch Ophthalmol. 1968;79(4):370-375. doi:10.1001/archopht.1968.03850040372004