Background: How current visual acuity standards were established. - Printable Version +- Eyesight Improvement Forum (https://www.iblindness.org/forum) +-- Forum: General Discussion (https://www.iblindness.org/forum/forumdisplay.php?fid=4) +--- Forum: Complementary Methods (https://www.iblindness.org/forum/forumdisplay.php?fid=7) +--- Thread: Background: How current visual acuity standards were established. (/showthread.php?tid=205) |
Background: How current visual acuity standards were established. - otis - 10-30-2006 Bate2040.txt Subject: What is the origin of the DMV Visual Acuity Standard? The visual acuity test (20/20) means reading 3/8 inch letters at 20 feet. The DMV standard is for 20/40, or 3/4 inch letters at 20 feet. For some states, the standard is 20/70 (Florida), 20/60 (Georgia) and 20/50 (Texas). In working to clear your vision, it is necessary to be close to passing these "standards". Here is the reason why the standard was change. The term "normal 20/20" in reality meant that the retina had the capability of 20/20 -- with a proper strength minus lens. The idea that a large number of people have naked-eye 20/20 is simply in error. The various "qualifying" agencies recognized this truth, and made the decision to use a REASONABLE visual-acuity standard as stated below. For anyone working to "clear" his vision, I think he should set the major goal of personally passing the DMV standard to be legal. Here is the background of these standards. ======================================== Statements by W. Bates about the change from 20/20 to 20/40 -- 20/100 for visual acuity. Up to 1908 the United States required normal vision in recruits for its military service. In that year Bannister and Shaw made some experiments from which they concluded that a perfectly sharp image of the target was not necessary for good shooting, and that, therefore, a visual acuity of 20/40 (the equivalent in feet of 6/12 in meters), or even 20/70, in the aiming eye only, was sufficient to make an efficient soldier. This conclusion was not accepted without protest, but normal vision had become so rare that it probably seemed to those in authority that there was no use insisting upon it; and the visual standard for admission to the Army was accordingly lowered to 20/40 for the better eye and 20/100 for the poorer, while it was further provided that a recruit might be accepted when unable with the better eye to read all the letters on the 20/40 line, provided he could read some of the letters on the 20/30 line. (1) +++++++++++++++ 1. Harvard Manual of Military Hygiene for the Military Services of the United States, published under the authority and with the approval of the Surgeon General, U. S. Army third revised edition, 1917, p. 195. +++++++++++++ In the first enrollment of troops for the European war(WWI OSB) it is a matter of common knowledge that these very low standards were found to be too high and were interpreted with great liberality. Later they were lowered so that men might be "unconditionally accepted for general military service" with a vision of 20/100 in each eye without glasses, provided that the sight of one eye could be brought up to 20/40 with glasses, while for limited service 20/200 in each eye was sufficient, provided the vision of one eye might be brought up to 20/40 with glasses. (2) ++++++++++ 2. Standards of Physical Examination for the Use of Local Boards, District Boards, and Medical Advisory Boards under the Selective Service Regulations, issued through the office of the Provost Marshal General, 1918. +++++++++++ Yet 21.68 per cent of all rejections in the first draft, 13 per cent more than for any other single cause, were for eye defects, (1) while under the revised standards these defects still constituted one of three leading causes of rejection. They were responsible for 10.65 per cent of the rejections, while defects of the bones and joints and of the heart and blood vessels ran, respectively, about two and two and a half per cent higher. For more than a hundred years the medical profession has been seeking for some method of checking the ravages of civilization upon the human eye. The Germans, to whom the matter was one of vital military importance, have spent millions of dollars in carrying out the suggestions of experts, but without avail; and it is now admitted by most students of the subject that the methods which were once confidently advocated as reliable safeguards for the eyesight of our children -- have accomplished little or nothing. Some take a more cheerful view of the matter, but their conclusions are hardly borne out by the army standards just quoted. By Dr. W. H. Bates |