144 IDA MANN

that in the future, time and personnel will be found to investigate these questions before all distinctions of diet, custom, and occupa­tion are lost in these still relatively un­touched areas which western civilization seems determined to "open up."

S U M M A R Y

1. An account is given of the occurrence of diseases of the anterior segment of the eye in four areas of Australasia—the terri­tories of Papua and New Guinea, the Kim-

INTRODUCTION

The normal human lens develops a visibly yellow coloration with age. Little is known concerning the nature of the pigment re­sponsible for this color. There is a strong discoloration of the lens in cataracta brune-scens (cataracta nigra) described by Cor-des.1 The work done on this pigment has been summarized by Duke-Elder2 who states that it may be melanin, lipofuscin, or "one of the related but little understood sub-

* From the Francis I. Proctor Foundation for Research in Ophthalmology, University of Cali­fornia Medical Center.

berleys, the southwest of Western Australia, and the Eastern Goldfields.

2. The following diseases are specially considered: glaucoma, cataract, strabismus, pterygium, trachoma, uveitis, sympathetic ophthalmitis, leprosy, nontrachomatous fol-liculosis, nutritional disease, and congenital abnormalities.

3. Possible meanings and lines for future investigation are indicated.

56 Hobbs Avenue.

stances" and that this "same substance in smaller concentration may to some extent at any rate be responsible for the yellow color of the senile lens."

Work was undertaken in this laboratory to identify more closely the yellow pigment of lenses.

M A T E R I A L AND METHODS

Lenses were obtained either from eye-bank material or from surgery. Two groups were collected.

1. Twenty yellowish cataractous lenses and one brunescent cataract were obtained after surgery through the courtesy of Dr.

REFERENCES

1. Rivers: Colour vision of the natives of Upper Egypt. Roy. Anthro. Inst, 31:229, 1901; The Torres Straits. Camb. Rep. Anthro. Exped., 11:73, 1901; Observations on the senses of the Todas. Brit. J. Psychol., 1:321, 1904-05.

2. Mann, I.: Ophth. survey of Eastern Goldfields area of Western Australia, 19S4; Ophth. survey of Kimberley division of Western Australia, 1954; Ophth. Survey of South-West portion of Western Aus­tralia, 1956; Ophth. Survey of Territories of Papua and New Guinea, 1955 (with Loschdorfer).

3. : Ophth. impressions of a leprosarium. Leprosy Rev., 26:10 (Jan.) 1955. 4. Smith, D. A., and Woodruff, M. A. F.: 1951 Spec. Rep. Ser. Med. Res. Coun. Lond. No. 274.

Livingston, P. C : Tr. Ophth., Soc. U. Kingdom, 66:19, 1946. 5. Metivier, V. M.: Am. J. Ophth., 24:1215, 1941. 6. Blumenthal, C. J.: S. African M. J., 28:967, 1954. 7. Sydenstricker, V. P., Sebrell, W. H., Cleckley, A. M., and Krause, H. D.: J.A.M.A., 33:787, 1940. 8. Mann, L: M. J. Australia, 11:610, 1957. 9. Davidson, W. S.: M. J. Australia, 11:601, 1957.

Davis, R. E., and Pitney, W. R.: M. J. Australia, 11:605, 1957. Curnow, D. H.: M. J. Australia, 11:608, 1957.

10. Mann, I., and Turner, C : Am. J. Ophth., 41:797 (May) 1956.

T H E Y E L L O W P I G M E N T O F H U M A N L E N S E S *

W. K. M C E W E N , P H . D . San Francisco, California

YELLOW PIGMENT OF HUMAN LENSES 145

F. C. Cordes and staff. These were accumu­lated in IN. NaOH.

2. Approximately a similar number of yellowish lenses were collected in alcohol from eye-bank eyes.

The absorption spectra were obtained either with a Beckman DU spectrophotome-ter or a Cary ultraviolet recording spectro-photometer.*

Urochrome was isolated from urine by slight modifications of the methods of Gar-rod and Hohlweg as reported by Fox.3

Melanin was isolated and purified from black horsehair by the method of Schmidli and Robert.4

RESULTS

The character of the absorption spectra of whole single lenses was first determined by dissolving them almost completely in thioglycolic acid. The resultant opalescent solution was clarified by centrifugation. The character of the absorption spectra of these solutions, obtained either from a yellow lens or a colorless lens or the difference spectra between a colored lens versus a colorless lens, were all similar, with increasing extinc­tion from the blue end of the visible spec­trum into the ultraviolet region and with no distinct peak. This preliminary work indi­cated that the yellow pigment is present in colorless lenses but in too low a concentra­tion to be apparent visually. It also showed that the pigment was probably among the compounds referred to earlier.2

On the assumption that the yellow mate­rial had properties similar to melanin, the first group of yellow cataractous lenses were treated according to the methods for isolat­ing melanin.* It was soon apparent that the pigment was not melanin as it was both acid and alcohol soluble. The pigment was then purified by precipitation from alcohol by ether or carbon tetrachloride. The major

* Spectra obtained with this instrument through the courtesy of Louis A. Strait, Spectrographic Laboratory, School of Pharmacy, University of California School of Medicine.

isolation procedures carried out on the sec­ond group of lenses were homogenization in a buffer at pH = 7.0, treatment with trypsin, centrifugation and dialysis of the super­natant to separate the pigment from the protein. The material isolated from both groups reacted the same to all tests and no further distinction is made between the pig­ments obtained from either the cataractous or the normal group.

To confirm that the pigment was not mel­anin it was subjected to treatment with al­kaline KMn0 4 with subsequent addition of oxalic acid. The melanin control was bleached by the permanganate but the yellow lens material had a slightly higher optical density. This intensification of color is char­acteristic of urochrome.3

There are a number of naturally occur­ring yellow animal biochromes which may be identifiable with the yellow lens pigment. These include principally urochome, uro-bilin, stercobilin, lipofuscins, thiochrome, and riboflavins.

Urochrome is apparently a decomposition product of protein and is the principal pig­ment of normal urine. Urobilin in urine is the same as stercobilin in feces and they may be distinguished from urochrome by an ab­sorption peak at 494 mp.5 and by the Gmelin test6 which is positive for most linear tetra-pyrrole compounds. The vague class of com­pounds known as lipofuscins or chromoli-poids are oxidative derivatives of fat. They are easily distinguished from urochrome by their solubility in fat solvents. Both thio­chrome, the yellow oxidation product of thi-amine, and the riboflavins have strong ab­sorption peaks.

The yellow pigment of the lens and uro­chrome are soluble in dilute acids and bases and alcohol and insoluble in ether and chloro­form. They both yield negative Gmelin tests. They give similar absorption spectra from 300 to 700 m[j. but the spectra have no char­acteristic maxima or minima. When applied to filter paper they show blue fluorescent spots. It is not known if this material is the

146 W. K. McEWEN

same fluorescent material of the lens as measured by Brolin and Cederlund.7

DISCUSSION

The various chemical and physical tests made on the lens pigment indicate that it is related to urochrome rather than to several other naturally occurring animal biochromes which have been postulated to this time.

Because urochrome8 is as yet so ill-defined chemically, it is difficult to identify unam­biguously the yellow pigment of the lens as urochrome.

The evidence indicates that this same pig­ment occurs in both normal and cataractous lenses. Since only one brunescent cataract was included in the cataractous group, it is not known if the pigment in this type of cataract is the same as that which was iso­lated. There is apparently no casual relation­ship between the pigment and cataracts.

It might be difficult to explain the pres­ence of melanin or pyrrole compounds de­rived from blood because of the nonpig-mented, avascular nature of the lens. Since

REFERENCES

1. Cordes, F. G: Cataract Types. A Manual of the American Academy of Ophthalmology and Otolaryngology, 1954, ed. 3, p. 60.

2. Duke-Elder, S.: Textbook of Ophthalmology. St. Louis, Mosby, 1945, v. 3, p. 3199. 3. Fox, D. L.: Animal Biochromes and Structural Colours. London, Cambridge Univ. Press, 1953,

p. 236-237. 4. Schmidli, B., and Robert, P.: Pigment studies VI Mitterlung Physikalische und Chemische Unter-

suchungen an Naturlichen Melanin, Dermatologica, 108:343, 1954. 5. Takesi, Y.: Spectrochemical studies on bilirubinoids. Igaku Kenkyu, 24:1395-1438, 1954. (As ab­

stracted in Chem. Abst, 49:1121d, 1955.) 6. Hawk, P. B., Oser, B. L,, and Summerson, W. H.: Practical Physiological Chemistry, 12th Edition.

The Blakiston Co., Philadelphia, 1947, p. 376. 7. Brolin, S. E., and Cederlund, C.: Fluorescence of the lens of the eyes of different species. Acta

Ophthal., 36:324, 1958. 8. Ekman, B.: Oxydation Zyklischer Verbindungen Durch Vitamin C. Acta Phsiol. Scand., 8 Suppl.

22 (1944).

urochrome is probably derived from non-specific protein material, its presence in the lens may be accepted on a physiologic basis.

SUMMARY

1. The yellow pigment isolated from nor­mal and cataractous lenses appears to have similar physical and chemical properties to urochrome isolated from urine.

2. This pigment is probably a nonspecific degradation product of proteins and appar­ently increases in concentration with age, finally becoming clearly visible in the older age group.

3. Its presence in both normal and cata­ractous lenses indicates only a casual rela­tionship.

University of California Medical Center (22).

ACKNOWLEDGMENT Dr. Louis A. Strait, professor of biophysics and

director of the Spectrographic Laboratory, School of Pharmacy, gave most valued help and advice during the whole course of this investigation.