Perfect Sight Without Glasses - William Horatio Bates

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disappears, and when the inferior rectus is cut the hypermetropic part disappears, and the eye becomes normal - adjusted for distant vision - although the same amount of traction is maintained. It is evident that these muscles are essential factors in the production of myopia and hypermetropia.

      After one or both of the obliques had been cut across, or after they had been paralyzed by the injection of atropine deep into the orbit, accommodation could never be produced by electrical stimulation; but after the effects of the atropine had passed away, or a divided muscle had been sewed together, accommodation followed electrical stimulation just as usual. Again when one oblique muscle was absent, as was found to be the case in a dogfish, a shark and a few perch, or rudimentary, as in all cats observed, a few fish and an occasional rabbit, accommodation could not be produced by electrical stimulation. But when the rudimentary muscle was strengthened by advancement, or the absent one was replaced by a suture which supplied the necessary countertraction, accommodation could always be produced by electrical stimulation.

      After one or both of the oblique muscles had been cut, and while two or more of the recti were present and active,3 electrical stimulation of the eyeball, or of the nerves of accommodation, always produced hypermetropia, while by the manipulation of one of the recti, usually the inferior or the superior, so as to strengthen its pull, the same result could be produced. The paralyzing of the recti by atropine, or the cutting of one or more of them, prevented the production of hypermetropic refraction by electrical stimulation; but after the effects of the atropine had passed away, or after a divided muscle had been sewed together, hypermetropia was produced as usual by electrical stimulation.

      It should be emphasized that in order to paralyze either the recti muscles, or the obliques, it was found necessary to inject the atropine far back behind the eyeball with a hypodermic needle. This drug is supposed to paralyze the accommodation when dropped into the eyes of human beings or animals, but in all of my experiments it was found that when used in this way it had very little effect upon the power of the eye to change its focus.

      Fig. 17.No. 1. - Production of mixed astigmatism in the eye of a carp by pulling strings attached to the conjunctiva in opposite directions. Note the oval shape of the front of the eyeball.No. 2. - With the cutting of the strings the eyeball returns to its normal shape, and the refraction becomes normal.

      Fig. 18. Demonstration Upon the Eyeball of a Rabbit That the Obliques Lengthen the Visual Axis in MyopiaR, rest. The eyeball is of normal length and emmetropic - that is, perfectly adjusted for distant vision. My, myopia. The pull of the oblique muscles has been strengthened by advancement and the retinoscope shows that myopia has been produced. It can easily be noted that the eyeball is longer. It was impossible to avoid some movement of the head between the taking of the two pictures as a result of the manipulation of the strings, but the rule shows that the focus of the camera was not appreciably changed by such movements.

       Astigmatism was usually produced in combination with myopic or hypermetropic refraction. It was also produced by various manipulations of both the oblique and recti muscles. Mixed astigmatism, which is a combination of myopic with hypermetropic refraction, was always produced by traction on the insertion of the superior or inferior rectus in a direction parallel to the plane of the iris, so long as both obliques were present and active; but if either or both of the obliques had been cut, the myopic part of the astigmatism disappeared. Similarly after the superior or the inferior rectus had been cut the hypermetropic part of the astigmatism disappeared. Advancement of the two obliques, with advancement of the superior and inferior recti, always produced mixed astigmatism.

      Fig. 19. Demonstration Upon the Eye of a Carp That the Recti Shorten the Visual Axis in HypermetropiaR, rest. The eyeball is of normal length and emmetropic. Hy, hypermetropia. The pull of the external and internal recti has been strengthened by advancement, and the retinoscope shows that hypermetropia has been produced. It may easily be noted that the eyeball is shorter. The rule shows that the focus of the camera was not appreciably changed between the taking of the two pictures.

       Eyes from which the lens had been removed, or in which it had been pushed out of the axis of vision, responded to electrical stimulation precisely as did the normal eye, so long as the muscles were active; but when they had been paralyzed by the injection of atropine deep into the orbit, electrical stimulation had no effect on the refraction.

      Fig. 20. Lens Pushed Out of the Axis of VisionIn this experiment on the eye of a carp the lens was pushed out of the axis of vision. Accommodation took place after this displacement just as it did before. Note the point of the knife in the pupil in front of the lens.

       In one experiment the lens was removed from the right eye of a rabbit, the refraction of each eye having first been tested by retinoscopy and found to be normal. The wound was then allowed to heal. Thereafter, for a period extending from one month to two years, electrical stimulation always produced accommodation in the lensless eye precisely to the same extent as in the eye which had a lens. The same experiment with the same result was performed on a number of other rabbits, on dogs and on fish. The obvious conclusion is that the lens is not a factor in accommodation.

      Fig. 21. Rabbit With Lens RemovedThe animal was exhibited at a meeting of the Ophthalmological Section of the American Medical Association, held in Atlantic City, and was examined by a number of ophthalmologists present, all of whom testified that electrical stimulation of the eyeball produced accommodation, or myopic refraction, precisely as in the normal eye.

       In most text-books on physiology it is stated that accommodation is controlled by the third cranial nerve, which supplies all the muscles of the eyeball except the superior oblique and the external rectus; but the fourth cranial nerve, which supplies only the superior oblique, was found in these experiments to be just as much a nerve of accommodation as the third. When either the third or the fourth nerve was stimulated with electricity near its point of origin in the brain accommodation always resulted in the normal eye. When the origin of either nerve was covered with a small wad of cotton soaked in a two per cent solution of atropine sulphate in a normal salt solution, stimulation of that nerve produced no accommodation, while stimulation of the unparalyzed nerve did produce it. When the origin of both nerves was covered with cotton soaked in atropine, accommodation could not be produced by electrical stimulation of either or both. When the cotton was removed and the nerves washed with normal salt solution, electrical stimulation of either or both produced accommodation just as before the atropine had been applied. This experiment, which was performed repeatedly for more than an hour by alternately applying and removing the atropine, not only demonstrated clearly what had not been known before, namely, that the fourth nerve is a nerve of accommodation, but also demonstrated that the superior oblique muscle which is supplied by it is an important factor in accommodation. It was further found that when the action of the oblique muscles was prevented by dividing them, the stimulation of the third nerve produced, not accommodation, but hypermetropia.

      Fig. 22. Experiment Upon the Eye of a Cat Demonstrating That the Fourth Nerve, Which Supplies Only the Superior Oblique Muscle, Is Just as Much a Nerve of Accommodation As the Third, and That the Superior Oblique Muscle Which It Supplies Is a Muscle of Accommodation.No. 1. - Both nerves have been exposed near their origin in the brain, and a strip of black paper has been inserted beneath each to render it visible. The fourth nerve is the smaller one The superior oblique muscle has been advanced by a tucking operation, as this muscle is always rudimentary in cats, and unless its pull is strengthened accommodation cannot be produced in these animals. Stimulation of either or both nerves by the faradic current produced accommodation.No. 2. - When the fourth nerve was covered with cotton soaked in a normal salt solution, the application of the faradic current to the cotton produced accommodation. When the cotton was soaked in a one per cent solution of atropine sulphate in a normal salt solution, such application produced no accommodation, but stimulation of the third nerve did produce it.No. 3. When the third nerve was covered with cotton soaked in a normal salt solution, the application of the faradic current to the cotton produced accommodation. When the cotton was soaked with atropine sulphate in a normal salt solution, such application produced no accommodation, but the stimulation of the fourth nerve did produce it.No. 4. - When both nerves were covered with cotton soaked in atropine sulphate in a normal salt solution,

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