This is the report of an experiment conducted in November, 1958, in the Department of Ophthalmology of Falk Clinic, University of Pittsburgh School of Medicine.
The purpose of the experiment was to determine what percentage of refracted patients could detect any difference in their wearing of genuinely first-quality lenses versus their wearing of lenses of substandard quality, or "second quality."
Because a lens may be pronounced substandard, or second quality, for any one or more of several reasons (weak or strong in power, malpositioned optical center or axis, scratches, incomplete polish, bubbles, aberration due to striae, aberration due to "invisible" grooves in one or both surfaces of the lens), the one factor tested in the subject experiment was that of aberration due to "invisible" grooves on the concave surface of the glass lenses. Except for that
McCASLIN MF. Effects of "Invisible" Lens AberrationsA Clinical Experiment. AMA Arch Ophthalmol. 1959;62(3):434-437. doi:10.1001/archopht.1959.04220030090013