Normally the retina appears on a B-mode ultrasonogram as a concave, smooth white surface, which is indistinguishable and inseparable from the choroid and sclera. In retinal detachment, however, the retina will appear as a white membrane separate from the choroid and sclera.
The extent of any retinal detachment is best ascertained by performing many B-mode scans in serial, horizontal places, starting from the superior limbus and scanning toward the inferior limbus at 2-mm intervals. One can then mentally assemble all the two-dimensional scans to make a three-dimensional construct of the detachment.
Very shallow detachments can be observed by ultrasonography, but the space between the detached retina and choroid-sclera complex is narrow and may be difficult to discern.