AMERICAN JOURNAL OF OPHTHALMOLOGY PUBLISHED MONTHLY BY THE OPHTHALMIC PUBLISHING COMPANY

EDITORIAL STAFF LAWRENCE T. POST, Editor

640 S. Kingshighway, Saint Louis WILLIAM H. CRISP, Consulting Editor

530 Metropolitan building, Denver EDWARD JACKSON, Consulting Editor

1120 Republic building, Denver HANS BARKAN

Stanford University Hospital, San Fran­cisco

HARRY S. GRADLE 58 East Washington street, Chicago

EMMA S. BUSS,

H. ROMMEL HILDRETH 824 Metropolitan building, Saint Louis

PARK LEWIS 454 Franklin street, Buffalo

M. URIBE TRONCOSO 350 West 85th street, New York

M. F. WEYMANN 903 Westlake Professional building, Los Angeles

JOHN M. WHEELER 30 West Fifty-ninth street, New York

Manuscript Editor Address original papers, other scientific communications including correspondence,

also books for review and reports of society proceedings to Dr. Lawrence T. Post, 640 S. Kingshighway, Saint Louis.

Exchange copies of medical journals should be sent to Dr. William H. Crisp, 530 Metropolitan building, Denver.

Subscriptions, applications for single copies, notices of change of address, and com­munications with reference to advertising should be addressed to the Manager of Sub­scriptions and Advertising, 640 S. Kingshighway, Saint Louis. Copy of advertisements must be sent to the manager by the fifteenth of the month preceding its appearance.

Authors' proofs should be corrected and returned within forty-eight hours to the editor. Twenty-five reprints of each article will be supplied to the author without charge. Additional reprints may be obtained from the printer, the George Banta Publishing Com­pany, 450-458 Ahnaip street, Menasha, Wisconsin, if ordered at the time proofs are re­turned. But reprints to contain colored plates must be ordered when the article is accepted.

L I G H T AND COLOR SENSE Living matter is widely sensitive to

electro-magnetic radiations, or vibra­tions. The effects of heat, light and the x-ray, and radium emanations, that are now understood, show the great range of this sensitivity. Vision depends on the special adaptation of the eyes to radiations of certain wave lengths. Every one who uses a radio set knows how important it is to get accurate ad­justment for the kilocycle frequency of the station he wants to hear. Any mix­ture of wave frequencies brings confu­sion and the listener hears nothing.

The first step in the evolution of the eye was the production of a tissue sensi­tive to certain radiations and insensitive to all others. The eye thus has the pow­er to pick out and discriminate certain wave-lengths, which we call light. These wave-lengths are all within one "octave," of the more than fifty "oc­taves" of electro-magnetic vibrations that have been recognized and measured by the methods of experimental physics. The shortest wave-length of violet that

the eye can perceive as light, 390 milli­microns, is more than half as long as the longest wave-length of red light 770 millimicrons that can be seen. We know from music how similar are the sounds of notes that vary just an octave in pitch, giving perfect chords. Looking at the solar spectrum, we can see in the violet end, as it fades out, how similar in appearance it becomes to the red end. If it were possible to see several octaves of the solar radiations, the confusion might be as great as the interference of "static" with the radio.

With the production of the sensitive retina and its sensitiveness confined to one octave of radiation, it was important to protect the retina from radiations so close to light as might cause confusion. The infrared, or heat radiations, are taken care of by the circulation of blood, that keeps the various parts of the body at approximately one temperature, most favorable for the continuance and bal­ance of the different processes of meta­bolism. The ultraviolet radiations near the other end of the light spectrum, are

858

EDITORIALS 859

prevented from reaching the retina. The great mass of them are "absorbed"—• converted into other forms of force—by the corneal epithelium. This is directly derived from the primitive ectoderm.

It is probable that this selective power of the ectodermal layer early became a dominating factor in the selection of light radiations, that fixed the limits of visible wave-lengths. Such ultraviolet radiations as do pass through the cor­neal epithelium, are arrested and altered by the crystalline lens—a later deriva­tive from the ectodermal epithelium. The lens has the notable power of fluor­escence, changing invisible radiations into light of bluish or greenish color.

There is no known evidence that eyes of lower animals perceive radiations outside the spectrum of colors known to the human eye. Even the phototropism, turning to light, or the turning from light, of the youngest fish, seems to be due to the wave-lengths that are known to us as light. Experiments as to sight in birds and insects seem to indicate the same limits of vision as for the human eye. It would appear that living matter in general has a fixed relation to the visible radiations known as light, and that evolution has worked out, in the eye, an organ quite fitted to utilize the serviceable radiations, and exclude those that might be confusing and dangerous. This basis, in evolution and physiology, should be made the starting point for all schemes to "protect" the eye from radiations that might be harmful.

Evolution, that has confined vision to the use of such limited range of wave­lengths of radiations, has given us a wonderful variety of sensations that mav be perceived within the limits of visible lieht. These sensations depend on the discriminating powers of the visual brain centers. All consciousness of sensations comes through the brain ; and the evolution of minute brain struc­ture is but little known. Probably varia­tions in the power to discriminate and recognize color, depend upon differ­ences in brain organization, rather than upon differences in the retina, or the im­pressions made upon it. Cerebral irrita­tion and fatigue are the immediate causes of pain, or discomfort, that are

blamed to excessive stimulation of the retina by light. The nerve element is predominant in photophobia and in col­or perception. This too must be borne in mind, in connection with the problem of relief from symptoms ascribed to ex­cessive light. Edward Jackson.

1934 MEETING OF THE AMERI­CAN OPHTHALMOLOGICAL

SOCIETY A more delightful spot for a medical

meeting in the month of July than the Seigniory Club, Lucerne-in-Quebec, Canada, could not be imagined. The Log Chateau situated on the Ottawa River, and surrounded by an immense wooded tract containing numerous lakes, was the location of the seventieth annual meeting of the American Ophthalmo-logical Society. Recreation in the form of hiking, tennis, swimming, boating, and golf was enjoyed by those in at­tendance. It seems to the writer that a great advantage lies in holding a medi­cal meeting in some such isolated club or resort, rather than in a large city be­cause under such conditions there is a greater tendency for the members to gather in informal discussions, in addi­tion to the sessions, than in a city where too many distracting amusements are offered to fill the time not occupied by the sessions. Also those members who reside in the city chosen for the meeting usually have their time partially ab­sorbed by trying to maintain a sem­blance of a practice during the meeting and do not enjoy the full advantages thereof.

The scientific session, which occupied three mornings as usual, was repre­sented by twenty-six papers. When pos­sible, these were so arranged as to fall in groups where similar subjects were under discussion. It would have been difficult to ' choose any papers which might have been omitted, but a certain amount of tension was produced by the knowledge that such a large number of papers had to be read and discussed in a given length of time. This feeling doubtless cut down or caused the omis­sion of some valuable discussion of those