Standardized A-scan echography and the normal optic nerve. Experience with the new Mini A equipment

The potential of making differential diagnosis in optic nerve disease with standardized A-Scan echography has been well established. With this technique it is possible to differentiate 'solid' and 'fluid' thickening. A few years ago a new standardized A-scan equipment was built: The Mini A. With this equipment, it is possible to distinguish spikes coming from the pia, the arachnoid, and the dura around the optic nerve, and to measure the thickness of these structures with a precision of 0.03 mm. We found dura distance 4.0-5.3 mm, arachnoid 3.2-4.0 mm, an pial diameter 2.8-3.4 mm. In this paper the authors discuss their preliminary findings in a normal population.