DuPont Guerry

Action Spectrum for Retinal Injury from Near-Ultraviolet Radiation in the Aphakic Monkey

We found that the action spectrum for retinal damage (determined by the fundus photographic appearance of a minimal lesion immediately after exposure) extends into the near-ultraviolet by exposing three aphakic eyes from rhesus monkeys to 405-, 380-, 350-, and 320-nm wavelengths produced by a 2,500-W xenon lamp equipped with quartz optics and 10-nm interference filters. Exposure times were 100 and 1,000 seconds and the spot diameter on the retina was 500 micrometers. The retina was six times more sensitive to 350- and 325-nm wavelengths than to blue light (441 nm). Both ophthalmoscopic and histologic data showed that near-ultraviolet lesions differed in important respects from blue-light lesions. Near-ultraviolet produced irreparable damage to rod and cone photoreceptors.

The incidence of congenital impatency of the nasolacrimal duct

Summary In a study of 1,000 consecutive, unselected, full-term newborn infants, fifty-seven cases (5.7 per cent) of congenital impatency of the nasolacrimal duct were found.

AGING, ANOMALIES AND RADIATION EFFECT OF THE RABBIT LENS

A causal relationship between the effects of aging on biological structures and that of ionizing radiation has been suggested by various investigators (1-4). If this suggestion is valid, one might expect to find: a) that tissue subjected to doses of ionizing radiation would develop prematurely certain changes which one customarily recognized as aging effects; b) that these “aging effects” might be present to a more pronounced degree than is usually apparant; and c) that a continuum might be detectable between the changes which are ascribed to aging and those which are known to follow ionizing radiation. The mammalian lens represents an ideal “medium” for providing points of comparison between the two “insults” i.e. age and radiation effect. The lens is easily studied in vivo by means of biomicroscopy. It naturally develops changes with age, and characteristic changes take place after exposure to ionizing radiation. In order that lens variations and anomalies which may occur can be distinguished from changes due to aging and radiation, such observations are described first. The present study is therefore divided into two sections. 1) Normal lens, variations and anomalies 2 ) Aging and lens irradiation effects The reported findings were obtained by slitlamp examinations ( X 16). Detailed drawings of each lens were made showing changes in an anterior-posterior

ENZYME ACTIVITY IN THE COAGULATED RETINA: A MEANS OF STUDYING THERMAL CONDUCTION AS A FUNCTION OF EXPOSURE TIME

A short definition of .retinal thermal threshold lesions< seems justified because the data presented in the following papers in this supplement have to do with such lesions. Since the introduction of the term .retinal thermal threshold lesions<< by Ham and his coworkers (I) a considerable number of misunderstandings in regard to this term have occurred, both in the literature and in the minds of investigators concerned with the problem of retinal thermal injury. The original definition of a threshold burn was an ophthalmoscopically observable lesion barely visible five minutes after exposure. A burn of this type is of course *threshold<< only in the sense that it fits this particular definition, but it is not *threshold<< according lto other examination methods. The ultimate in threshold lesions, therefore, is a retinal burn of such degree as to just perceptibly irreversibly impair retinal function. In order to evaluate a retinal burn of this type, obviously, the most sensitive method would be a subjective one; i. e. visual acuity and visual fields testing in intelligenit human volunteers following light coagulation. For obvious reasons this approach is not feasible. However it has been suggested by Newton (12) that primates trained by psychologists to perform certain tests might be utilized as likely substitutes, and in the future, data obtained from such experiments may prove valuable. Our basic research, as previously reported and as outlined in this supplement, has been carried out on rabbits. This readily available animal is quite

ELECTRORETINOGRAPHY AFTER LIGHT COAGULATION.

The term ,threshold burn* has produced a number of contradictory arguments and a number of misquotations, as has been pointed out previously (1). The question of what happens foIlowing extensive light exposure is not only of academic interest but also has a bearing on the clinical use as well as the development of adequate devices. To obtain exact data with regard to the functional status of the human retina after light exposure, presents, for obvious reasons, many problems. Conventional in vitro experimentation however is usually difficult to apply to in vivo situation. In the past the transfer mechanisms in visual function have been studied extensively in the horseshoe crab and the frog. However, even with very precise experimentation, it is exceedingly difficult to transfer those data to the human eye. Preliminary studies on chincilla rabbits (2) have shown that B wave changes may be obtained after light exposure with energies about 50 per cent below that required for production of ophthalmoscopically visible retinal lesions if a sufficient area of the retina was involved. These observations led to more extensive studies which are presented in this paper. Although the rabbit eye does not have a fovea, it has been situdied more than any other with regard to thermal injury. Quite accurate data have been accumulated from such studies and marly comparisons and correlations exist between the rabbit and human eye with respect to light coagulation. Several approaches to measuring electrical responses from the retina after light coagulation have been tried; the one described here is probably the simplest one of these and has provided the most accurate and reproducible data.

SOME IMMUNOLOGICAL ASPECTS IN KERATOPLASTY

In previous studies (1, 2 ) on heterogenous corneal transplants from dog to rabbit, it was noted by in vitro methods that the precipitating antigenicity of the graft had greatly diminished within the first ten deys following transplantation. The purpose of this study is to examine this ten-day period in order to determine more precisely when and how rapidly this process takes place and whether storing of the graft in other media will result in similar observations. The following study is, therefore, divided into four sections: 1 ) Dog corneal grafts transplanted into rabbit cornea, 2) Dog corneal grafts submerged in rabbit serum, 3 ) Dog corneal grafts stored in various other media, 4) Dog corneal grafts and whole dog eyes placed in a moist chamber and stored by deep freezing for various periods of time. The agar diffusion technique was used in these studies.

AN EXPERIMENTAL STUDY ON THE INFLUENCE OF VITAMIN C ON ALKALI CORNEAL BURNS AND CORNEAL SENSITIVITY1

Alkali burns of the eye and its adnexa have always been and, even with more modern methods of treatment, still are a problem in ophthalmology. A few years ago Hydrosulphosol captured our attention in that particular field because of the excellent clinical results reported by Kuhn. Experimental studies conducted by Narlay, however, could not show any superiority of this kind of treatment over the use of pure castor oil. Recently Nemec reported the local use of Ascorbic Acid in alkali burns of the human eye. He used local instillations of Vitamin C solutions and subconjunctival injections routinely in all his patients with fresh akali burns and claimed this method to be superior to other methods of treatment. Lyle and McLean, in 1941, reported rapid improvement in ten cases of corneal ulcer, keratitis, and chronic corneal opacities after intravenous and oral medication with Vitamin C. Since no experimental study could be found in the literature where Ascorbic Acid had been used subconjunctivally, we have conducted these experiments on rabbits to ascertain whether or not Ascorbic Acid employed locally is of value in the treatment of alkali burns of the cornea.

LASER RADIATION PROTECTION

Abstract Although most health physicists and others in the field of radiation protection have confined their efforts primarily to the hazards from the so-called ionizing radiations (X-rays, gamma-rays, neutrons, high energy particles, etc.), an increasing number of workers in this field are being called upon to protect personnel from laser radiation. The phenomenal development of laser technology during the past three years has introduced new hazards for industry, for governmental agencies, particularly the military and space agencies, and for universities and medical schools. The necessity for such criteria will be examined. Since the eye is the most vulnerable organ of man to laser radiation, the effects of wavelength, pulse duration, intensity of irradiation (power density), energy density, and other factors on the eye will be given. Current data from several laboratories will be reviewed briefly. Finally, protective practices and equipment in current use in the United States will be discussed.