The pressure determined in ophthalmodynamometry is not the local pressure in the central retinal artery, but rather the pressure somewhere in the much larger ophthalmic artery. Using a steady flow analysis, this communication mathematically determines (1) the site corresponding to the systolic dynamometric pressure, and (2) the actual central retinal artery pressure before the ophthalmodynamometry was performed. The systolic pressure determined by ophthalmodynamometry is shown to be 14 to 17 mm Hg higher than the normal central retinal artery systolic pressure. The magnitude of this discrepancy is due primarily to the small lumen of the central retinal artery, which produces a very large pressure gradient.
Werff TJV. The Pressure Measured in Ophthalmodynamometry. Arch Ophthalmol. 1972;87(3):290-292. doi:10.1001/archopht.1972.01000020292011