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DARK ADAPTATION AND NIGHT VISION

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Review of Wartime Studies of Dark Adaptation, Night Vision Tests, and Related Topics William Berry 1949 . The initial plan of this project was to summarize the articles prepared under the stimulation of military requirements during the years 1941-1946. It was assumed that it would be possible to prepare a report comparable to the reviews of scientific literature that appear from time to time in various scientific journals. During the development of the project, according to the author, it became apparent that the initial plan would have to be modified, and the decision was made to prepare informative abstracts of the original articles arranged in chronological order of their appearance. The considerations that led to the decision are summarized as follows: 1. The articles and reports are largely individual in nature, nonse- quential, and unprogrammatic. 2. In every case, the form of presentation of the results of experiments, test procedures, etc., was prescribed by the regulation military practice. 3. A considerable amount of data and information is contained in the reports, and it is of such a nature that its appraisal for scientific merit and usefulness should be made by a wide circle of competent scientists. This report consists of 106 abstracts, plus three tabular summaries of the reported data on the reliability of the test devices, their intercorre- lations, the data derived from validation studies, an index of the topics treated in the reports, and an evaluation of the work done and the results achieved. 96 pp. no figures 96 tables 100 references Availability: National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161. 35

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A Bibliography on Dark Adaptation Dorothea J. Crook, John ~ Hanson, Patricia I. McBride, and Joseph W. Wulfeck 1953 Between 1930 and 1950 probably no aspect of vision has deserved or received more attention than night vision and dark adaptation. In response to the demands of two wars, biochemical and electrophysiological research have received increased support. The requirement that specified levels of dark adaptation be maintained, the need for finding an alternative for total darkness in becoming dark adapted, and the hope of speeding up dark adaptation have resulted in widespread efforts to identify and establish the ranges of the variables affecting the instantaneous threshold and the subsequent course of dark adaptation. In addition, numerous night vision testers have been developed and masses of normative, validity, and reliability data have been accumulated. An Annotated Bibhog~aphy on Visual Performance at Low Pholopic Illu- mu~aiion Levels has been prepared by Rock The research on development, validity, and reliability of night vision testers has been summarized in a comprehensive report by Berry. Reviews by Adams in 1929 and by Lythgoe in 1940 have emphasized the mechanisms and theory of dark adaptation, but the literature dealing specifically with the experimental data on dark adaptation, especially as related to its associated variables and their ranges, has grown more and more extensive and scattered. This bibliography brings together a number of such references in an effort to make these experimental data more easier accessible. While it includes items relating dark adaptation to many variables, its basic concern is with the effects of pre-exposure variables. The heaviest emphasis is on the effects of the duration and the intensity of the preceding light, and the relation between them. There is also a fair sampling of references on the effect of wavelength of the preceding light. In addition to material on the effects of intensity, duration, and wavelength, literature from other areas is included. 27 pp. no figures no tables 417 entries Availabiluy: National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161. 36

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Report of the Working Group on Illumination and Dark Adaptation William S. Ve~planck 1953 This group was appointed for the purpose of preparing a critical review of the literature on dark adaptation as a function of antecedent conditions of illumination, with emphasis on wavelength. This summary notes that the project involved the preparation of a bibliography, the review of papers cited in this bibliography, with the preparation of evaluative abstracts of each, and finally, the publication of a paper summarizing the status of knowledge on this and closely associated topics. For a number of reasons it proved impossible for the working group to carry this task through to completion. This report describes the work achieved and the arrangements made for its completion. 3 pp. no figures no tables 9 references Availability: Committee on Vision, 2101 Constitution Ave. ington, D.C. 20418. 1 37 ~ N.W., Wash-

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Effect of Flashes of Light on Night Visual Acuity Part I . Glenn ~ Fry and Mathew Alpern 1953 The purpose of this study is to find out the ability of the eye to see a dark object against a sky background at night after the eye has been exposed to a flash of light or a series of flashes. A peripheral test object and a fixation point have been used for measuring the ability of the eye to see. This investigation has succeeded in demonstrating the operation of three basic principles: (1) The adaptation of any given part of the retina can be regarded as being independent of adaptation processes in other parts of the retina. (2) Reciprocity between time and intensity can be assumed to hold at least over a three-second interval. (3) The effect of a flash displaced from the part of the retina used in viewing an object can be accounted for in terms of stray light. The amount of stray light falling at any given part of the retina can be computed from the Stiles-Holladay equation. The exposure of the eye to a flash patch not only impairs the capacity of the photoreceptors to respond to subsequent stimulation but also produces a positive afterimage. A complete understanding of the effect of a flash of light cannot be claimed until the role played by this positive afterimage is taken into account. When the flash patch is exactly the same size and shape as the test patch, it might be questioned whether small eye movements, which cause a fresh portion of the retina to receive a portion of the image of the test patch, might affect the results. Consequently, exploratory experiments have been undertaken with much larger flash patches to investigate the role played by this factor. In all of this work, the site of the beam entering the eye has been restricted by artificial pupils, which are smaller than the natural pupil, so that variations in the size of the natural pupil have not influenced the results. There are changes in pupil size that occur as a result of a flash of light, but it was decided to study these effects in a separate investigation, which is described in another report (see Effect of Flashes of light on Light Heal Acute: PA II). 28 pp. 19 figures 1 table 7 references Availabilz~: National Technical Information Service ~S), 5285 Port Royal Road, Spnngfield, VA 22161. 38

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Effect of Flashes of Light on Night Visual Acuity: Part II Glenn ~ Fry and Merrill J. Allen 1953 The objective of this study is to discover a satisfactory method of pre- dicting the course of constriction of the pupil of a dark-adapted eye when exposed to a flash of any duration or a series of flashes involving a complex and changing distribution of brightness in the visual field. This problem is quite complicated for several reasons. It involves the differential distri- bution of rods and cones over the retina with their independently varying states of adaptation and speeds of reaction. It involves the distribution of ganglion cells and their connections through the bipolars with the rods and cones. It involves the mechanism in the midbrain for summating the impulses received simultaneously from various areas of the retina and also the mechanism for summating impulses spread out in time; it also involves the response of the sphincter muscle of the iris to the pattern of impulses relayed to it by the ciliary ganglion from the Edinger-Westphal nucleus. The role played by stray light has to be taken into consideration; this is particularly important in the case of a bright patch subtending a small solid angle and having a dark background. The small number of photoreceptors stimulated director by the bright patch might well have a negligible effect on pupil constriction in comparison with the effect produced by the thousands of photoreceptors that are stimulated only by the stray light in the eye. In the experiments described in this report, the beams of light entering the eye are restricted by artificial pupils normal to the axes of the beams. 17 pp. 18 figures no tables 12 references Availability: Committee on Vision, 2101 Constitution Ave., N.W., Wash- ington, D.C. 20418. 39

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The Effect of Pre-Exposure on Dark Adaptation: An Annotated Bibliography Patricia I. McBride, Dorothea E. Johannsen, and Joseph W. Wulfeck 1955 The relation between pre-exposure and the course of the subsequent dark adaptation is of special interest from both the theoretical and practical points of view. This bibliography summarizes research concerned with the effects of different pre-exposure variables on subsequent dark adaptation. Since this bibliography is concerned only with the effects of pre- exposure variables, only those parts of experiments that include the effects of pre-exposure are described. In a few instances, holding to this policy resulted in the elimination of large portions of a study; most of the experi- ments are fully described, however. Coverage of references is intended to be comprehensive through spring 1954. An attempt was made to summarize the important results. The manner in which the data were originally presented (tabular or graphic) is indicated. If an experiment consisted of several parts, the results from each part are identified by numbers. 60 pp. no figures no tables 69 references Availability: National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161. 40

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Flash Blindness Symposium: Proceedings of the U.S. Army Natick Laboratories John M. Davies and David T. Randolph, Editors 1967 The purpose of this symposium, and the report based on it, was to arrive at an understanding of the state of knowledge in flash blindness technology, with the underlying aim of determining how this information could or should be applied to military problems. Considering our use of light as a weapon, the eye is among the most valuable targets. The cornea and lens of the eye may be damaged in various ways by exposure to intense light, but the most critical visual component is the retina. Injury to the retina may take the form of retinal lesions; the effect of the injury then will depend partly on the location. Small lesions may cause very little decrement; if on the fovea, the loss of vision may be nearly complete. Even if not on the fovea, a severe chonoretinal lesion may allow blood to flow into the vitreous body; this type of blindness may be temporary. This symposium concentrated upon the temporary degradation of vision caused by bleaching of the visual pigments, such as rhodopsin and cyanolate, chlorolate and erythorolabe, and the effects that may follow that bleaching. In recent flash blindness studies, rather short-duration blinding flashes have been used, sometimes as short as the microsecond range, but now even shorter pulses are available. Lasers with pulse durations as short as perhaps 30 nanoseconds have been used to produce retinal lesions. Apparently, these devices have not been used to produce flash blindness. Another phase of the symposium needs specific mention. A part of it was concerned with eye protection; the discussion was based primarily upon classified information and is not included in the written summary. 265 pp. 95 figures 17 tables 49 references Availability: AD 697793, National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161. 41

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Night Vision: Current Research and Future Directions Symposium Proceedings 1987 Night vision encompasses many different visual functions under a variety of ambient lighting conditions. Since night operations are a crucial part of around-the-clock combat readiness, the U.S. Air Force has been interested in evaluating visual performance at night. A working group addressed the topic of night vision with four specific objectives in mind: (1) a definition of the relevant parameters of night vision; (23 an update of the literature pertaining to night vision, especially new findings, test procedures, and concepts since 1950; (3) the development of guidelines for establishing a comprehensive night vision laboratory; and (4) recommendations for the development of night vision screening tests. The first two objectives were addressed by convening a symposium at Brooks Air Force Base in 1985. The proceedings of the symposium form the basis of this report. The findings and recommendations presented here are based on working group discussions following that meeting. Reference is made throughout this section to the papers in this volume that have some relevance to the recommendations under discussion. The recommendations address five broad topics: (1) the specification of ambient illuminance levels; (2) task analysis and characterization of the work environment; (3) research areas of potential utility to the development of night vision tests; (4) the development of night vision screening tests; and (5) recommended equipment for a night vision laboratory. This report contains 19 papers in addition to the summary report. 335 pp. 80 figures 13 tables 511 references . Availability: Publication on Demand, National Academy Press, 2101 Con- stitution Ave., N.W., Washington, D.C. 20418. 42