recovered spontaneously, or changed their form, and I was unable either to ignore them, or to satisfy myself with the orthodox explanations, even where such explanations were available. It seemed to me that if a statement is a truth it must always be a truth. There can be no exceptions. If errors of refraction are incurable, they should not recover, or change their form, spontaneously.
Fig. 5. The Eye As a CameraThe photographic apparatus: D, diaphragm made of circular overlapping plates of metal by means of which the opening through which the rays of light enter the chamber can be enlarged or contracted- L, lens; R, sensitive plate (the retina of the eye); AB, object to be photographed; ab, image on the sensitive plate.The eye: C, cornea where the rays of light undergo a first refraction; D, iris (the diaphragm of the camera); L, lens, where the light rays are again refracted; R, retina of the normal eye; AB, object of vision; ab, image in the normal or emmetropic eye- at b', image in the hypermetropic eye; a" b", image in the myopic eye. Note that in a' b' and a" b" the rays are spread out upon the retina instead of being brought to a focus as in ab, the result being the formation of a blurred image.
In the course of time I discovered that myopia and hypermetropia, like astigmatism, could be produced at will; that myopia was not, as we have so long believed, associated with the use of the eyes at the near-point, but with a strain to see distant objects, strain at the near-point being associated with hypermetropia; that no error of refraction was ever a constant condition; and that the lower degrees of refractive error were curable, while higher degrees could be improved.
In seeking for light upon these problems I examined tens of thousands of eyes, and the more facts I accumulated the more difficult it became to reconcile them with the accepted views. Finally, about half a dozen years ago, I undertook a series of observations upon the eyes of human beings and the lower animals the results of which convinced both myself and others that the lens is not a factor in accommodation, and that the adjustment necessary for vision at different distances is affected in the eye, precisely as it is in the camera, by a change in the length of the organ, this alteration being brought about by the action of the muscles on the out side of the globe. Equally convincing was the demonstration that errors of refraction, including presbyopia, are due, not to an organic change in the shape of the eyeball, or in the constitution of the lens, but to a functional and therefore curable derangement in the action of the extrinsic muscles.
Fig. 6. Mexican IndiansWith normal sight when tested all the members of this primitive group are now either squinting or staring.
In making these statements I am well aware that I am controverting the practically undisputed teaching of ophthalmological science for the better part of a century; but I have been driven to the conclusions which they embody by the facts, and that so slowly that I am now surprised at my own blindness. At the time I was improving high degrees of myopia; but I wanted to be conservative, and I differentiated between functional myopia, which I was able to cure, or improve, and organic myopia, which, in deference to the orthodox tradition, I accepted as incurable.
Fig. 7. Ainus, the Aboriginal Inhabitants of JapanAll show signs of temporary imperfect sight.
Notes
1. The unnatural strain of accommodating the eyes to close work (for which they were not intended) leads to myopia in a large proportion of growing children - Rosenau Preventive Medicine and Hygiene, third edition, 1917, p. 1093.
The compulsion of fate as well as an error of evolution has brought it about that the unaided eye must persistently struggle against the astonishing difficulties and errors inevitable in its structure function and circumstance - Gould The Cause, Nature and Consequences of Eyestrain, Pop Sci Monthly, Dec., 1905.
With the invention of writing and then with the invention of the printing-press a new element was introduced, and one evidently not provided for by the process of evolution The human eye which had been evolved for distant vision is being forced to perform a new part, one for which it had not been evolved, and for which it is poorly adapted The difficulty is being daily augmented - Scott The Sacrifice of the Eyes of School Children, Pop Sci Monthly, Oct., 1907
2. Ford Details of Military Medical Administration published with the approval of the Surgeon General, U.S. Army, second revised edition, 1918, pp. 498-499.
3. A diopter is the focussing power necessary to bring parallel rays to a focus at one metre.
4. Tr. Ophth. Soc. U. Kingdom, vol. xxxviii, 1918, pp. 130-131.
5. 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.
6. 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.
7. Report of the Provost Marshal General to the Secretary of War on the First Draft under the Selective Service Act, 1917.
8. Second Report of the Provost Marshal General to the Secretary of War on the Operations of the Selective Service System to December 20, 1918.
9. From the Greek myein, to close, and ops, the eye, literally a condition in which the subject closes the eye, or blinks.
10. Archiv f Augenh, vol. lxxix, 1915, translated in Arch. Ophth., vol. xlv, No. 6, Nov., 1916.
11. From the Greek hyper, over, rnetrors, measure, and ops, the eye.
12. From the Greek a, without, and stigma, a point
Chapter 2 - Simultaneous Retinoscopy
CHAPTER II
SIMULTANEOUS RETINOSCOPY
MUCH of my information about the eyes has been obtained by means of simultaneous retinoscopy. The retinoscope is an instrument used to measure the refraction of the eye. It throws a beam of light into the pupil by reflection from a mirror,; the light being either outside the instrument - above and behind the subject - or arranged within it by means of an electric battery. On looking through the sight-hole one sees a larger or smaller part of the pupil filled with light, which in normal human eyes is a reddish yellow, because this is the color of the retina, but which is green in a cat's eye, and might be white if the retina were diseased. Unless the eye is exactly focussed at the point from which it is being observed, one sees also a dark shadow at the edge of the pupil, and it is the behavior of this shadow when the mirror is moved in various directions which reveals the refractive condition of the eye. If the instrument is used at a distance of six feet or more, and the shadow moves in a direction opposite to the movement of the mirror, the eye is myopic. If it moves in the same direction as the mirror, the eye is either hypermetropic or normal; but in the case of hypermetropia the movement is more pronounced than in that of normality, and an expert can usually tell the difference between the two states merely by the nature of the movement. In astigmatism the movement is different in different meridians. To determine the degree of the error, or to distinguish accurately between hypermetropia and normality, or between the different kinds of astigmatism, it is usually necessary to place a glass before the eye of the subject. If the mirror is-concave instead of plane, the movements described will be reversed; but the plane mirror is the one most commonly used.
Fig. 8. The Usual Method of Using the RetinoscopeThe observer is so near the subject that the latter is made nervous, and this changes the refraction.
This exceedingly useful instrument has possibilities which have not been generally realized by the medical profession. Most ophthalmologists depend upon the Snellen1 test card, supplemented by trial lenses, to determine whether the vision is normal or not, and to determine the degree of any abnormality that may exist. This is a slow, awkward and unreliable method of testing