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Cylinder Rotation Test
CORRESPONDENCE will be turned downward. . . . In a similar manner does the ray act within the pupil." He accounted for the experience of a straightforward image by supposing that a second inversion of the rays took place at the crystalline lens. Leonardo was the first to explain the crea tion of three-dimensional imagery through the differing perspective produced by the two eyes. He concluded also that the eye requires time to absorb impressions, from his observations of the apparent doubling of a vibrating metal strip, and of the circle of light formed by a rapidly revolving torch. He suggested the phenomenon of irradiation on perceiving that when one end of an iron rod is made red-hot it seems thicker than the other end. He recognized that the twinkling of the stars was an optical illusion which he could eliminate by use of the pinhole. He detected that the hue of an illuminated ob ject is affected by that of the luminous body. As he became older, he reflected on the de creasing strength of vision that accompanied advancing age and had stronger lights hung from the ceiling. Leonardo appreciated the optical impor tance of the pinhole and in the following passage anticipated experiments independ ently described by Scheiner in 1619: "Let a fine opening be made with the point of a needle in paper, and then let objects on the opposite side of the paper be viewed through the perforation. If, now, the needle is moved between eye and paper straight from above downwards, then the motion of the needle will appear on the opposite side of the opening in a direction contrary to that of its real motion." In Leonardo's analysis of the acceleration of freely falling bodies, he illustrated his text with a diagram showing horizontally the intervals of time and vertically those of distance, probably the first graph in the his tory of science. His personal studies fore shadowed the discoveries of Copernicus, Galileo, Harvey, Newton, and Vesalius. Had his work been published, the knowledge of
595
nature would have advanced at one bound at least a century, and he would have justly been acclaimed the first modern man of sci ence. But to award Leonardo priorities for the numerous truths he first envisioned is to lose the true perspective of the march of progress. Yet the fact that such a unique man once lived who could demonstrate equal preeminence in art and science has proved in itself an inspiration to mankind. James E. Lebensohn.
CORRESPONDENCE CYLINDER ROTATION TEST
Editor, American Journal of Ophthalmology: There are one or two points in Dr. Fantl's article on "The cylinder rotation test" in the December, 1951, issue of the JOURNAL which call for some comments. Dr. Fantl says "the English literature does not bestow a name on this angle," referring to the angle termed by Lindner, Kramer, and others, "Richtwinkel." In my book Modern Retinoscopy (Lon don, Hatton Press, 1930) and in subsequent articles (for example, "Fundamental princi ples of cylinder retinoscopy," Am. J. Ophth., 17:120 (Feb.) 1934; "Cylinder retinoscopy—simplified," Am. J. Ophth., 26:1304 (Dec.) 1943) I termed this angle, "guide angle," as it is by the size and posi tion of this angle that the examiner guides himself in estimating the correctness of the cylinder axis or the cylinder power. Some earlier English writers had called this angle, "direction angle," a term which conveys nothing of the meaning or significance of this angle. Lindner in describing the rotation test uses throughout his discussion the term "Richtwinkel" (guide angle) and only in one place does he use the term "Drehwinkel" (rotation angle). I believe the latter is just a slip of the pen as he does not define
596
BOOK REVIEWS
anywhere the term "Drehwinkel." The "Richtwinkel," or guide angle in Eng lish, when plus cylinders are used, is the angle between the axis of the inserted plus cylinder and the "myopic meridian," that is, the meridian in which there is "against" movement or in which lies the "hyperopic (with-moving) astigmatic band." Similarly, when minus cylinders are used, the guide angle is the angle between the axis of the inserted minus cylinder and the "hyperopic meridian," that is the meridian in which there is a "with" movement or in which lies the "myopic (against-moving) astigmatic band." By derivation and significance this angle is called "guide angle" because the examiner guides himself by the size and position of this angle as to the correctness of the in serted cylinder both as to power and axis. This is the real meaning and origin of the German term, "Richtwinkel," and is so used by all writers on the subject. I think it is unwise, and certainly it may lead to confusion, to apply the term "rota tion angle" to this angle. Since the publica tion of my book, various articles in English dealing with cylinder retinoscopy have al ways referred to this angle as the "guide angle." The term rotation angle may be applied to what Dr. Fantl calls "angle alpha" and is, as a matter of fact, so called "Drehwinkel" (ro tation angle) by Dr. Kramer in his discus sion of the cylinder rotation test. It is a suitable name in this particular test as it is the angle through which the cylinder has been rotated in order to check on the correct ness of the cylinder strength. Lindner refers to the angle between the correct axis of the required cylinder and the false axis of the inserted cylinder, in all cases, as the angle of "Fehlstellung," which in my book I rendered into English as the angle of "malplacement or malposition." In fact, Dr. Fantl himself uses the term mal position once for this angle though every where else he refers to it as angle alpha.
However, in this special case the angle may also be termed "rotation angle" as Kramer has done. But by no means can this latter term be applied to replace the term "guide angle" for the "Richtwinkel." One other point worth noting is the author's statement, "it is often advantageous to postpone the final estimation of the spherical component of a refractive error until a correct cylinder has been found." Unless one has a very keen eye and a great deal of experience it is very difficult to note and appraise the phenomena of cylin der retinoscopy before one meridian has been neutralized as accurately as possible with a sphere. Dr. Lindner emphasizes this point and I have always done so in my teach ing. In fact, otherwise one may not even get the characteristic phenomenon of oblique opposite movements in the newly created false mixed astigmatism. In bringing up these points I do not mean to detract from the very excellent presenta tion of this test which is relatively little known in the English-speaking countries. (Signed) Joseph I. Pascal, New York.
BOOK R E V I E W S SURGERY OF THE OBLIQUE MUSCLES OF THE
EYE. By Walter H. Fink, M.D. St. Louis, Missouri, C. V. Mosby Company, 1951. 350 pages, 93 illustrations (18 in color), 130 references. Price: $8.75. The author presents the detailed surgical anatomy of all of the extraocular muscles of the eye, as well as of the obliques from the posterior aspect. H e . includes the embryol ogy, comparative anatomy, and miscroscopic anatomy. The prodigious amount of work in the dissections and preparations for this volume have been appreciated at the exhibits that have been prepared for the Academy of Ophthalmology and Otolaryngology in the past several years, and it is good to see the
595
nature would have advanced at one bound at least a century, and he would have justly been acclaimed the first modern man of sci ence. But to award Leonardo priorities for the numerous truths he first envisioned is to lose the true perspective of the march of progress. Yet the fact that such a unique man once lived who could demonstrate equal preeminence in art and science has proved in itself an inspiration to mankind. James E. Lebensohn.
CORRESPONDENCE CYLINDER ROTATION TEST
Editor, American Journal of Ophthalmology: There are one or two points in Dr. Fantl's article on "The cylinder rotation test" in the December, 1951, issue of the JOURNAL which call for some comments. Dr. Fantl says "the English literature does not bestow a name on this angle," referring to the angle termed by Lindner, Kramer, and others, "Richtwinkel." In my book Modern Retinoscopy (Lon don, Hatton Press, 1930) and in subsequent articles (for example, "Fundamental princi ples of cylinder retinoscopy," Am. J. Ophth., 17:120 (Feb.) 1934; "Cylinder retinoscopy—simplified," Am. J. Ophth., 26:1304 (Dec.) 1943) I termed this angle, "guide angle," as it is by the size and posi tion of this angle that the examiner guides himself in estimating the correctness of the cylinder axis or the cylinder power. Some earlier English writers had called this angle, "direction angle," a term which conveys nothing of the meaning or significance of this angle. Lindner in describing the rotation test uses throughout his discussion the term "Richtwinkel" (guide angle) and only in one place does he use the term "Drehwinkel" (rotation angle). I believe the latter is just a slip of the pen as he does not define
596
BOOK REVIEWS
anywhere the term "Drehwinkel." The "Richtwinkel," or guide angle in Eng lish, when plus cylinders are used, is the angle between the axis of the inserted plus cylinder and the "myopic meridian," that is, the meridian in which there is "against" movement or in which lies the "hyperopic (with-moving) astigmatic band." Similarly, when minus cylinders are used, the guide angle is the angle between the axis of the inserted minus cylinder and the "hyperopic meridian," that is the meridian in which there is a "with" movement or in which lies the "myopic (against-moving) astigmatic band." By derivation and significance this angle is called "guide angle" because the examiner guides himself by the size and position of this angle as to the correctness of the in serted cylinder both as to power and axis. This is the real meaning and origin of the German term, "Richtwinkel," and is so used by all writers on the subject. I think it is unwise, and certainly it may lead to confusion, to apply the term "rota tion angle" to this angle. Since the publica tion of my book, various articles in English dealing with cylinder retinoscopy have al ways referred to this angle as the "guide angle." The term rotation angle may be applied to what Dr. Fantl calls "angle alpha" and is, as a matter of fact, so called "Drehwinkel" (ro tation angle) by Dr. Kramer in his discus sion of the cylinder rotation test. It is a suitable name in this particular test as it is the angle through which the cylinder has been rotated in order to check on the correct ness of the cylinder strength. Lindner refers to the angle between the correct axis of the required cylinder and the false axis of the inserted cylinder, in all cases, as the angle of "Fehlstellung," which in my book I rendered into English as the angle of "malplacement or malposition." In fact, Dr. Fantl himself uses the term mal position once for this angle though every where else he refers to it as angle alpha.
However, in this special case the angle may also be termed "rotation angle" as Kramer has done. But by no means can this latter term be applied to replace the term "guide angle" for the "Richtwinkel." One other point worth noting is the author's statement, "it is often advantageous to postpone the final estimation of the spherical component of a refractive error until a correct cylinder has been found." Unless one has a very keen eye and a great deal of experience it is very difficult to note and appraise the phenomena of cylin der retinoscopy before one meridian has been neutralized as accurately as possible with a sphere. Dr. Lindner emphasizes this point and I have always done so in my teach ing. In fact, otherwise one may not even get the characteristic phenomenon of oblique opposite movements in the newly created false mixed astigmatism. In bringing up these points I do not mean to detract from the very excellent presenta tion of this test which is relatively little known in the English-speaking countries. (Signed) Joseph I. Pascal, New York.
BOOK R E V I E W S SURGERY OF THE OBLIQUE MUSCLES OF THE
EYE. By Walter H. Fink, M.D. St. Louis, Missouri, C. V. Mosby Company, 1951. 350 pages, 93 illustrations (18 in color), 130 references. Price: $8.75. The author presents the detailed surgical anatomy of all of the extraocular muscles of the eye, as well as of the obliques from the posterior aspect. H e . includes the embryol ogy, comparative anatomy, and miscroscopic anatomy. The prodigious amount of work in the dissections and preparations for this volume have been appreciated at the exhibits that have been prepared for the Academy of Ophthalmology and Otolaryngology in the past several years, and it is good to see the