Soon after the publication in 1866 of Donder's work on refraction, American ophthalmologists began to busy themselves with this subject, and by the end of the century had become expert in the determination of refractive errors. Following the lead of Weir Mitchell, a neurologist, many convinced themselves that uncorrected or improperly corrected refractive errors not only often caused headaches and ocular discomfort but caused or contributed to a variety of other symptoms, and even to organic disease. They did not devise any basically new methods of testing, but applied with meticulous care methods already known. It was believed that astigmatism of ⅛ D could cause serious so-called eyestrain.
A look at the past . . .. Arch Ophthalmol. 2007;125(8):1050. doi:10.1001/archopht.125.8.1050