182 IRE TRANSACTIONS ON MEDICAL ELECTRONICS July

Penetration of Corneal Opacities byInfrared Electronics*

JOEL FRIEDMANt, D.D.S.

Summary-Some areas of application of the infrared image prints of iris detail visualized through a corneal opacityconverter to diagnostic procedures in cases of corneal opacifica- by infrared photography.tion are presented. Further extension of areas of usefulness willbe paced by technical advances in infrared optics, quality of Dekking rals post t the nearl quant intae irescreen image, and simplification of design to facilitate the adap- flection of infrared rays by the brown pigment in the iristation of the tube as an auxiliary for direct ophthalmic examina- provides a protective barrier against heat absorption bytion. the retina. This is not a specifically biologic phenomenon,

however; the same effects of brown reflection as lightINFRARED PHOTOGRAPHY IN MEDICINE gray, and absorption of blues so that they are rendered

HE phenomenon of tissue penetration by infrared dark gray or black, are observable in oil paintings, whereT radiation as a diagnostic aid has been applied in mineral pigments are used.

peripheral and collateral circulatory problems, neo- Mann [9] later demonstrated how infrared photographicplastic disease, and dermatologic and ophthalmologic techniques disclosed abnormalities of contour and size ofstudies with varying success. Soon after the first relatively iris, and the presence or absence of marginal blood vesselsstable infrared photographic plates became commercially (and synechiae) which tend to impair corneal transparency.available in 1933, demonstrations of the superficial venous Mann used panchromatic film for the clinical rendition,patterns in the legs in peripheral vascular disease appeared and Eastman Type 1-R Infrared Sensitive Plates for evalu-in the literature [ 1 ]. The progress of collateral circulatory ating the penetration of opacities.repair in the extremities after thrombosis, and the enlarge- INFRARED ELECTRONICS IN OPHTHALMOLOGYment of superficial veins on the abdominal wall were dis-played [2]. Altered thoracic venous configuration in neo- Perhaps the earliest infrared-sensitive image converterplastic and Paget's disease were recorded [3]. Varicosity was developed in the middle 1930's by Zworykin and Mor-of the lower limbs, superficial vascular tumors, and heal- ton. Improved during the World War II years for use ining of skin under the scabs of lupus erythematosus were the "sniperscope," the application of the instrument todemonstrated [4]. The progressive increase in prominence medical diagnostic fields has proven most fruitful in theof superficial vessels of the breasts in pregnancy were visualization of the anterior chamber of the eye in casesshown graphically [5]. of corneal opacification.

Gross specimens, especially after arterial injection with Used in conjunction with routine ophthalmic diagnosticred cinnabar, and India ink in the veins, produced excel- instruments such as the slit-lamp microscope, an accuratelent black and white contrast plates of circulatory distribu- appraisal of the status of structures in the anterior por-tion [6]. Infrared studies of the patterns of venous dis- tion of the globe may be made.tribution in the oral mucous membranes have been made A direct view of the size, shape, and position of the[7], indicating that disclosure of veins under moist epi- pupil, unusual pupillary contours, surface texture of thethelial surfaces could be done in the same manner as sub- iris, turbidity of the aqueous humor, and transparency ofepidermal studies. the crystalline lens is obtained. Because many of these pa-

tients are potential candidates for corneal transplantation,INFRARED PHOTOGRAPHY IN OPHTHALMOLOGY it is essential that the information thus made available be

Among the first to apply infrared photographic tech- appraised in estimating the likelihood of success of a cor-niques to ophthalmology, Dekking [8] noted the altered neal graft. Abnormalities such as atrophy of the iris are-recording of colors of the iris by infrared. A typically sometimes disclosed, which would preclude restoration ofdark brown iris appeared light on the infrared plate while vision, and thus influence the decision against surgicala blue iris photographed dark. He published the earliest transplant.

Beginning with Vasko and Peleska [10] in 1947, sev-eral workers [11], [12], have applied war surplus tubes

* Received by the PGBME, December 11, 1959. Presented at the to the study of opacities and the observation of eye move--Biology, Philadelphia, Pa., November 10-12, 1959. This researchdakesOg [13]uizdaBrthWolwas aided by loan of equipment by the Office of Naval Research. War II electronic image converter (CV-147) adapted toTihel clinical Istuldies were mnade at the Brooklyn Eye and Ear Hos- one eyepiece of a slit lamp to study eyes afflicted with

t Chief of Prosthodontics, Jewish Chronic Disease Hospital of opaque corneas. The unit, operated with a filtered tungstenBrolyn, N.Y.P Asst VistinDureontst, nst. forCanverst Res. Col- lgh suce, penetrated the opacities easily, and in one in-Neg of Phscin an'ugos ouba nvriy e ok stance provided a clear view of a malignant melanoma of

1960 Friedman: Penetration of Corneal Opacities by Infrared Electronics 183

the choroid, while the secondary retinal detachment wastransparent. He also performed pupil measurements indark adaptation studies with the image converter. U-

THIEORY OF OPERATIONThe studies in this paper were made with a U.S. Navy Fig. 1-E.B.: Reproduction of films detailing corneal graft which

developed a cloudy result. (Left) Clinical condition of the graft.infrared receiver utilizing a No. 6032 image converter [ 14]. (Center) Iris and pupil via infrared photography. (Right) StillIn this tube, electrons activated in the infrared-sensitive photograpli taken on Ilford HP3 film through an infraredimage converter. The grain of the phosphor screen, on whichcathode are directed electromagnetically to the phosphor the eyepiece optics are set in fixed focus, is markedly apparent.screen anode (type P20) with the aid of a 19-kv power In use, the observer is no more aware of this than of the scanlines of a television screen. The single tungsten lighit source ispack. The erect image on the Yg-inch diameter screen is reflected from the patient's lens. This reflex can be moved aboutviewed through an enlarging lens eyepiece. The curvature by clanging the viewing angle. The opacity appears to be morein evidence over the iris than in the infrared phiotograph, whereof the face of the photocathode produces a curved field it is only faintly seen.which is partly compensated by a correcting lens beforethe cathode. Although the observer has the impression ofseeing through the viewer, his eye sees only the imageformed on the phosphor screen.

Some adjustment of the electromagnetic optical fielddistortion may be made on the instrument, but the bestdistortion may be made on the instrument, but the best

Fig. 2-E.E.: Diffuse corneal scar after graft and partial iridec-resolution is not synchronous with optimal flatness of field. tomy. (Left) Corneal opacity with cloudy postoperative result.The tube provides a good response to radiant energy (Center) The eye via infrared photography, providing a distinct

view of the extent of the iri(lectomy. (Ri~qht) Through the elec-in the near infrared, 0.8 to 1.2 microns, and a high ratio of tronic receiver, mainifesting a comnparable view of the rigltpiotolight input to infrared energy output. It has a resolution of Fig. 1.of 18 line-pairs per mm at the center of the semitrans-parent photocathode. to problems of fundus photography by infrared light, that

infrared is of limited value in the diagnosis of fundusDIscussIoN disease because the blood vessels, the macula, an(l optic

Utilizing the longer, more penetrative wavelengths of disk lack (lefinition. In general the retina is grossly re-the near-infrared segment of the spectrum, examiniation flective to infrared, wvith no absorptive elements. Only aof the anterior chamber of the eye beneath relatively dense, bluish or blue-gray lesion such as melanotic pigmentationlong-standing corneal opacities is facilitated. There are would possess the necessary contrast. To date, these ob-some instances of mild corneal opacity where it is possible servations made by Kugelberg in 1934 hold true for elec-to "burn through" with strong visible light from the oph- troiiic receivers as well.thalmoscope or slit lamp and gain a reasonable visualiza- BIBLIOGRAPHYtion of subcorneal tissues. For the most part, a distinctly [1] H. L. Gibson, "Infrared photography of patients," Radiog. andsuperior penetration is gained by the use of the image con- CiNn. Photog., vol. 21, pp. 72-86; March, 1945.verter combined with the routine diagnostic instruments. [2] E. F. Gooel, "Varicose veins of the abdominal wall," Am. J.

in thesesudies, theinstrument Surg., vol. 64, pp. 135-138; April, 1944.However, as applied in these studes, the instrument [3] L. Massopust, "Infrared photography," J. Biol. Photog. Assoc.,has definite technical and biological limitations. The 18 vol. 13, pp. 139-145; March, 1945.

[4] W. Clark, "Photography by Infrared," John Wiley & Sons,line-pirs pemmcopare fvorabl with he aveage of Inc., New York, N. Y., 2nd ed., pp. 218-252;1946.12 line-pairs per mm of the 1P25A American World War [51 L. Massopust, "Infrared photographic study of the changingII orits Britsh (CV-147) an German (Vain- pattern of the superficial veins in a case of human pregnancy,"II sniperscope or its British (CV-147) and German (Vam- Surg. Gyn., and Obstet., vol. 63, pp. 86-89; January, 1936.pire) counterparts. The coarseness of the grain structure [6] P. F. Swindle, "The architecture of the blood vascular net-in the phosphor screen interferes with good photographic works in the erectile and secretory lining of the nasal pas-in th phoshorsreenintereres ith ood potogrphic sages," Ann. Otol., Rhinol., and Laryngol., vol. 44, pp. 914-rendition of observations made through the No. 6032 932; I)ecember, 1935.

[7] J. Friedman, T. Lite and H. Fischler, "Infrared phiotographiyviewer, although this too is appreciably better than the of the oral mucosa," N. Y. J. Dent., vol. 28, pp. 7-13; January,coarser grained cesium silver oxide phosphor screens of 1958.the earlier tubes, which in addition were fitted with optics [8] H. M. Dekking, "Infrarot Photographie des Auges," Graefe'sthe erliertube,whih inadditon wre fited ith otics Arch. Ophthal., vol. 130, pp. 373-374, August, 1933; vol. 133,partially obscured by reticles. pp. 20-25, November, 1934.

Pincushion field distortion is marked, despite the cor- [9 W. A. Mann, "Infrared photography of the eye," Arch.Pincusion filddisortionis mared, depite te cor- Ophthal., vol. 13, pp. 985-991; June, 1935.recting lens built into the optics, and peripheral blurring [10] A. Vasko and M. Peleska, "Visual diagnosis of eye diseases

is apparent. ~~~~~~~~~~~~bymeans of infrared radiation," Brit. J. OphthaL., vol. 31,is apparent. pp. 419-422; June, 1947.Limitations to the penetration of opaque corneas have [11] M. Marshall, "Infrared image converter in rod scotometry,"

Brit. J. Ophthal., vol. 37, pp. 316-318; May, 1953.been noted in six patients in a series of twenty-one studied. [12] IH. Knoll, "An infra-red skiascope," Am. J. Optom., vol. 30,Difficulty was experienced chiefly in long-standing, thick pp. 346-349; July, 1953.Opacities with marked formation of new scar tissue and [13] A. Ogg, "Examination of the eye with infra-red radiation,"opacites wit marke formaion ofnew scr tisse and Brit. J. OphthaL, vol. 42, pp. 306-310; May, 1958.well-organized circulatory elements. Recognition should be [14] Radio Corp. of America.given to the observations of Kugelberg [151 with respect [15] I- Kugelberg, "Der Augenhintergrunid in Infrarotem Licht,"