The Cure of Imperfect Sight by Treatment
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The Original Bates Method, for correcting vision defects

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26 Accepted Theory of Accommodation
Subsequently Helmholtz, working independently, made a similar observation, but by a somewhat different method. Like Donders, he found the image obtained by the ordinary methods on the front of the lens very unsatisfactory, and in his "Handbook of Physiological Optics" he describes it as being "usually so blurred that the form of the flame cannot be definitely distinguished."1 So he placed two lights, or one doubled by reflection from a mirror, behind a screen in which were two small rectangular openings, the whole being so arranged that the lights shining through the openings of the screen formed two images on each of the reflecting surfaces. During accommodation, it seemed to him that the two images on the front of the lens became smaller and ap« proached each other, while on the return of the eye to a state of rest they grew larger again and separated. This change, he said, could be seen "easily and distinctly."2 The observations of Helmholtz regarding the behavior of the lens in accommodation, published about the mid dle of the last century, were soon accepted as facts, and have ever since been stated as such in every text-book dealing with the subject.
"We may say," writes Landolt, "that the discovery of the part played by the crystalline lens in the act of accom modation is one of the finest achievements of medical physiology, and the theory of its working is certainly one of the most firmly established; for not only have "savans" furnished lucid and mathematical proofs of its correctness, but all other theories which have been ad vanced as explaining accommodation have been easily
1  Handbuch der physiologischen Optik, edited by Nagel, 1909-11, vol. i. p. 121.
2  Ibid, vol. i, p. 122.