AMERICAN JOURNAL OF OPHTHALMOLOGY PUBLISHED MONTHLY BY T H E 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. W H E E L E R 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.

COLOR F I L T E R S I N T H E R E T I N A F o r more than a century the macula

lutea, or yellow spot of Sommer ing , has figured in all descr ipt ions of the re t ina . H u x l e y pointed out tha t it quickly dis­appears after death. Gul ls t rand, on ac­count of the difficulty of seeing it w i th the ophthalmoscope, t h o u g h t it was a pos t -mor tem phenomenon . But V o n der Hoeve , and others , have demons t ra t ed it du r ing life. Vog t , wi th his red-free l ight made it easy for m a n y observers to s tudy it. Of late years it has taken its place in the color pla tes of the fundus, as seen by such i l luminat ion. In the ret ina of man , and the p r imates mos t near ly related to man , there is cer ta inly a yellow spot.

Abou t n inety years ago Valent in and H a n n o v e r discovered colored oil drop­lets in the ret inal cones of some ver te ­bra tes . These are general ly s i tuated at the outer end of the inner segment of the cones. In the same eyes there a re also similarly placed dr'oplets tha t are not colored. F r o m t ime to t ime such

drople t s have been observed in m a n y widely scat tered species. An extensive l i te ra ture has g rown about this subject, inc luding independent observat ions , somet imes contradic tory , wi th sugges­t ions of the probable function of such droplets and their colors. Recent ly this l i te ra ture has been studied and checked wi th new observat ions , by W a l l s and Judd . (Br i t i sh Journa l of Oph tha lmol ­ogy, N o v emb er and December , 1933.)

In the grea t major i ty of observat ions the color of the drople ts has been yel­low. In some species red droplets are found, and in one bird they are dist inct­ly green. O the r colors have been re­por ted ; bu t chiefly in the earl ier years , when the microscope objectives were not s tr ict ly achromat ic . Observa t ions recent ly repeated wi th object ives more completely achromat ic seem to show tha t the o the r colors are not present . Such droplets are ei ther red, yellow, or near ly yel low, as the yel lowish green. Fo r species not o therwise accessible, W a l l s and J u d d have secured the co-

644

EDITORIALS 645

operation of other observers, so that this prevalence of the yellow color seems well established.

The vascularity of the retina has also been studied; and in some species where no yellow was found in the retinal tis­sue, a similar color light may be pro­duced by the blood in the capillary net­work. In some species devoid of capil­laries and of yellow in the retina, the cornea or the crystalline lens has been distinctly yellow. The mass of evidence thus brought together seems to show that the yellow tissue and droplets serve as a color screen, such as has been found serviceable in photography and glasses for outdoor use.

The species that have this yellow screen in their eyes are not confined to any one division of the animal kingdom but occur among fish, reptiles, birds and mammals. Often in two closely related species, one will have oil drops that are yellow, and the other will have those that are all colorless, and both yellow and colorless drops are found in the same eye. A wide review of the habits of these animals seems to show that those which have the yellow color filter are diurnal—use their eyes in strong light. Those that have no such color screen are nocturnal, and use their eyes chiefly, or wholly by feeble light. Walls and Judd are convinced that this is the significance of the distribution of these color filters.

The most brilliant part of the solor spectrum that gives us the ordinary white light, or daylight, is in the yellow. Chromatic aberration, the inability of a lens to focus light of different colors at the same distance, hindered the perfect­ing and use of optical instruments for hundreds of years. Nature seems to have met this difficulty by the color filter; cutting out the light that could not be focussed close to the yellow, where the greater part of the light would focus. The blue and violet rays, for which the aberration is greatest, and the red rays, for which the brightness rapidly dimin­ishes as they depart from the yellow, are excluded, without greatly diminishing the brightness. This works well only in good light. At night the proportion of the blue, or violet, would leave the il­

lumination greatly diminished, if they were excluded. Red droplets exclude the blue, and may be of special advan­tage to some animals, as some birds that feed chiefly in the dawn and twilight.

The general existence of uncolored droplets, along with those that are yel­low, would suggest that the droplet may perform the function of a condensing lens, even where no color filter is needed. The wide distribution and varied character of uses they might serve, should stimulate further investi­gation of their frequency and variation.

, Their absence from many eyes should suggest that colored glasses in front of the eye are by no means so widely help­ful, or necessary, as the makers of such glasses would have the profession and the public believe. It may also explain the lasting popularity of the yellow and yellow-green glasses as eye protectors.

Edward Jackson.

THE PROBLEM OF REBATING In theory the medical profession and

the organizations of those who limit their practice to ophthalmology, or to ophthalmology in combination with otology, laryngology, and rhinology, have set their faces strongly against what is known as rebating, that is against acceptance from a wholesale or retail optician of the difference between a trade or wholesale price and the retail price paid by the patient for his spec­tacles and lenses.

Pious resolutions or rules condemn­ing this procedure have been adopted by various national and local ophthal-mological societies. A "pious resolu­tion" is one which does not produce sub­stantial results, and the expression is here applied because the practice is still carried on by members of every organ­ization which has condemned it. Quite probably, in the larger cities, at least sixty-five percent of all prescriptions written by physicians for glasses are filled through wholesale or retail op­ticians who collect the retail price from the patient and credit to the prescrib­ing physician the difference between re­tail and wholesale.

A sort of rebating exists very widely