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The punctumeter is an instrument for ascertaining the range of accommodation. Its name signifies a point-measurer, i. e., to measure the far and near points of vision. The difference between these two points equals the range of accommodation. For several years I have been impressed with a lack of reliable methods for making these measurements. No instrument for obtaining this information being in existence, I began to study whether it would not be possible to have one constructed on scientific principles. After the usual history of trials and failures I am at last able to present to the profession an instrument which I believe to be absolutely reliable. It is so constructed that it can also be used as a rapid test for any of the errors of refraction and in this respect I know of no instrument that is superior to it.
A 10 D. convex lens is placed
HUIZINGA JG. THE PUNCTUMETER, FOR MEASURING THE RANGE OF ACCOMMODATION.. JAMA. 1902;XXXVIII(17):1095. doi:10.1001/jama.1902.62480170036025