Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 127, April 1974

This special bibliography lists 279 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1974

Quantifying the colour appearance of displays.

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Visual effects of respiratory disturbance

BACKGROUND Mild hypoxia is well known to impair scotopic (night) vision while moderate to severe hypoxia is required to compromise photopic (day) vision. However, the severity of hypoxia required to affect mesopic (twilight) vision, when both rod and cone photoreceptors contribute to visual perception, is unknown. This question is relevant to night flying at low altitude when mild hypobaric hypoxia might influence the visual performance of healthy aircrew operating in dimly illuminated cockpits and flight decks. Comparative studies indicate that increased rod oxygen consumption in dim light promotes outer retinal hypoxia under normal respiratory conditions. This might increase the susceptibility of the outer retina to the deleterious effects of exogenous hypoxia. This thesis aims to identify and quantify effects of respiratory disturbance on visual performance across the low photopic to mid-mesopic range. As well as mild to moderate hypoxia, the effects of hype roxi a and hypocapnia (hyperventilation) are considered. METHODS Cardio-respiratory status was monitored closely in all experiments, including breath-by-breath mass spectrometry for respired partial pressures of oxygen and carbon dioxide. An initial dark adaptation study in a hypobaric chamber assessed the effects of hypoxia, hyperoxia and hypocapnia on threshold sensitivity to dim flash stimuli, enabling definition of a mesopic adaptation procedure that was independent of respiratory condition. Hyperventilation increases flicker sensitivity, so the potential for hypocapnia to lower mesopic flicker thresholds and thereby confound subsequent studies was assessed under progressive hypocapnia. Subsequent experiments examined the visual perception of 12 healthy volunteers (6 male and 6 female) under low photopic, upper mesopic and mid-mesopic viewing conditions while breathing gas mixtures to establish normoxic, mildly hypoxic or hyperoxic respiratory states. Visual parameters comprised spatial contrast sensitivity, threshold chromatic sensitivity, visual processing speed, temporal contrast sensitivity and low contrast acuity, the last incorporating assessment of pupil size at each light level and respiratory condition. Visual stimuli were display-based and comprised foveal Gaussian Gabor patch gratings; the City University Colour Assessment and Diagnosis Test; the Useful Field of View® Test; threshold Frequency Doubling Technology perimetry; and the City University Contrast Acuity Assessment Test. Breathing gases were masked from the subjects and exposure orders were balanced and randomised between males and females. In some experiments hypocapnia was induced by voluntary hyperventilation. Vision testing was conducted binocularly and monocularly where practicable. Repeated measures designs favoured initial statistical analyses using balanced Analysis of Variance followed by various parametric and non-parametric post hoc analyses. RESULTS The achievement of scotopic sensitivity during dark adaptation is oxygen dependent, being delayed progressively by worsening hypoxia but hastened by hyperoxia and hypocapnia, such that rod photoreceptors are functionally hypoxic, in the dark, under normal respiratory conditions. Mesopic flicker sensitivity is highly correlated with the severity of hypocapnia but the magnitude of the effect is slight and unlikely to be meaningful. At the fovea, spatial contrast sensitivity is resistant to respiratory disturbance but threshold chromatic sensitivity is increasingly vulnerable to hypoxia as light level decreases in the mesopic range. Both spatial contrast sensitivity and chromatic sensitivity exhibit clear binocular summation. Mild hypoxia tends to delay visual processing speed and may be relevant to the extraction of visual information from complex scenes. Effects of hypoxia to impair and hyperoxia to enhance temporal contrast sensitivity vary with light level and retinal eccentricity but also support a progressive effect of hypoxia with decreasing mesopic luminance. Low contrast acuity is compromised by mild hypoxia at photopic and mesopic luminance but is enhanced by hyperoxia, relative to normoxia, in the mesopic range, implying further oxygen-dependent functional impairment. Mild hypoxia consistently induces pupillary miosis in the low photopic to mid-mesopic range. CONCLUSIONS Mild hypoxia compromises numerous visual attributes and its effects may be promoted by endogenous, rod-driven, outer retinal hypoxia with decreasing mesopic luminance. In dim light hyperoxia enhances some aspects of visual sensitivity relative to performance breathing air, implying oxygen-limited functional impairment under normal respiratory conditions, presumably due to increasing rod oxygen consumption in dim light. These effects have implications for the use by aircrew of supplementary oxygen at modest altitudes. Hypocapnia enhances visual sensitivity but is unlikely to be meaningful except, perhaps, in the scotopic range. The outer retina is functionally hypoxic in the mesopic range under normal respiratory conditions and this may have implications for the aetiology of retinal pathology. Effects of respiratory disturbance on pupil size warrant further consideration

Fundus-controlled perimetry (microperimetry): Application as outcome measure in clinical trials

YesFundus-controlled perimetry (FCP, also called 'microperimetry') allows for spatially-resolved mapping of visual sensitivity and measurement of fixation stability, both in clinical practice as well as research. The accurate spatial characterization of visual function enabled by FCP can provide insightful information about disease severity and progression not reflected by best-corrected visual acuity in a large range of disorders. This is especially important for monitoring of retinal diseases that initially spare the central retina in earlier disease stages. Improved intra- and inter-session retest-variability through fundus-tracking and precise point-wise follow-up examinations even in patients with unstable fixation represent key advantages of these technique. The design of disease-specific test patterns and protocols reduces the burden of extensive and time-consuming FCP testing, permitting a more meaningful and focused application. Recent developments also allow for photoreceptor-specific testing through implementation of dark-adapted chromatic and photopic testing. A detailed understanding of the variety of available devices and test settings is a key prerequisite for the design and optimization of FCP protocols in future natural history studies and clinical trials. Accordingly, this review describes the theoretical and technical background of FCP, its prior application in clinical and research settings, data that qualify the application of FCP as an outcome measure in clinical trials as well as ongoing and future developments

Factors affecting brightness and colour vision under water

Both theoretical and practical importance can be attached to attempts to model human threshold and supra-threshold visual performance under water. Previously, emphasis has been given to the integration of visual data from experiments conducted in air with data of the physical specification of the underwater light field. However, too few underwater studies have been undertaken for the validity of this approach to be assessed. The present research therefore was concerned with the acquisition of such data. Four experiments were carried out: (a) to compare the predicted and obtained detection thresholds of achromatic targets, (b) to measure the relative recognition thresholds of coloured targets, (c) to compare the predicted and obtained supra-threshold appearance of coloured targets at various viewing distances and under different experimental instructions, (d) to compare the predicted and obtained detection thresholds for achromatic targets under realistic search conditions. Within each experiment, observers were tested on visual tasks in the field and in laboratory simulations. Physical specifications of targets and backgrounds were determined by photometry and spectroradiometry. The data confirmed that: (a) erroneous predictions of the detection threshold could occur when the contributions of absorption and scattering to the attenuation of light were not differentiated, (b) the successful replication of previous findings for the relative recognition thresholds of colours depended on the brightness of the targets, (c) the perceived change in target colour with increasing viewing distance was less than that measured physically, implying the presence of a colour constancy mechanism other than chromatic adaptation and simultaneous colour contrast; the degree of colour constancy also varied with the type of target and experimental instructions, (d) the successful prediction of the effects of target-observer motion and target location uncertainty required more than simple numerical corrections to the basic detection threshold model. It was concluded that further progress in underwater visibility modelling is possible provided that the tendency to oversimplify human visual performance is suppressed

Engineering Data Compendium. Human Perception and Performance, Volume 1

The concept underlying the Engineering Data Compendium was the product an R and D program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design of military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by system designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is Volume 1, which contains sections on Visual Acquisition of Information, Auditory Acquisition of Information, and Acquisition of Information by Other Senses

Chromatic Properties of Bipolar Cells in the Mouse Retina

The retina performs a wide range of computations to process visual signals. Feature extrac-tion, such as the detection of edges, motion, and color originate in specialized retinal circuits. In this study we investigated the circuits underlying chromatic processing in the mouse retina. Although color vision is wide spread among mammals, its research tends to focus on primates. Studying non-primate mammals can be advantageous in understanding the general principles of retinal chromatic processing. Like most mammals, mice feature dichromatic color vision based on short (S) and medium (M) wavelength-sensitive cone types. It is thought that mammals share a common retinal circuit that compares S- and M-cone output (in trichromats S- and M+L-cone) to generate blue/green (blue/yellow) opponent signals, with distinct bipolar cells providing separate chromatic channels. While S cone selective ON-bipolar cells (in mouse “type 9”) have been anatomi-cally identified, little is known about other cone selective channels, such as, for instance, M-cone selective OFF-bipolar cells. Here, we characterized cone connectivity and light responses of selected mouse bipolar cell types using immunohistochemical and electrophysiological methods. Our anatomical data indicate that four of the five mouse OFF-bipolar cell types (types 2, 3a/b and 4) as well as type 7 (as an example for ON-bipolar cells) indiscriminately contact both S- and M-cones. Using a marker that labels dendrites of both type-1 and -2 OFF-bipolar cells we found reduced immunofluorescence at S-cone, suggesting that type 1 avoids S-cones. Recordings of light responses showed that the chromatic tuning of bipolar cells strongly depended on their position along the dorso-ventral axis – due to the dorso-ventral gradient in S-opsin co-expression in mouse M-cones. In dorsal retina, where co-expression is low, most type-2 (and type-7) cells were green-biased, with a fraction of cells (≈ 14 %) displaying strongly blue-biased responses, likely reflecting S-cone input. Type 1 cells were also green biased but did not include blue-biased “outliers”, consistent with type-1 cells avoiding S-cones. We therefore suggest that type 1 represents the greenOFF pathway in mouse. In addition, we confirmed that type-9 bipolar cells display blueON responses. In ventral retina, all bipolar cell types studied here displayed similar blue-biased responses, suggesting that color vision may be only supported in the dorsal mouse retina. In conclusion, our data supports an antagonistically organized blue/green circuit with bipolar cells functioning as chromatically defined channels, which form the common basis for mammalian dichromatic color vision