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That myopic defocus, even if restricted to the peripheral retina, inhibits eye growth in young monkey eyes has motivated the therapy of myopia control through multifocal contact lens wear in children. To understand how eye-length regulating mechanisms are triggered by light requires knowledge of retinal light spread. That is largely lacking for the multifocal contact lenses used in the therapy because empirical methods identifying just the defocus in dioptres are inadequate. "Through-focus" diffraction computations in contact lens/eye models with typical normal eye parameters, including polychromatic light, the chromatic aberrations and an M-cone phototransduction layer, offer estimates of retinal image spread for a range of viewing distances. Point- and edge-spread distributions of activation of phototransduction in the central retina show that the addition of multifocal zones produces some veiling for in-focus viewing and substantial improvement of image quality for near targets in the unaccommodated eye. These effects are much reduced in the retinal periphery. Whatever therapeutic value there is in prescribing multifocal contact lenses for myopia control, it is not particularly dependent on the precise configuration of the multifocal zones, nor can it be ascribed to changes in image quality specific to the retinal periphery; its origin is more likely less blur for near targets, reducing the stimulus to accommodation. [ABSTRACT FROM AUTHOR]

The article offers information on Horace Barlow role in the mid-20th century revision of the place occupied by neurophysiology in the study of perception. Topics incldue considered that several strategy was adopted in the early 1950 that can be well described by reference to the Artificial Neural Nets of today Artificial Intelligence.

Background: Visual acuity is measured by diminishing letter size till recognition threshold is reached, letters varying in legibility. In this experiment, size reduction was compared with other means of handicapping letter legibility.Methods: In five normal observers, discrimination thresholds for 13 sans-serif capital letters in a 5 × 4 format were obtained by a staircase procedure for size reduction, as well as for 20 minutes of arc (logMAR = 0.6) letters subjected to four kinds of image degradation: reducing contrast, convolving with blurring spread, embedding in noise and perturbing contour smoothness.Results: Threshold correlation and distribution of response errors show prominent differences and indicate the degree to which the visual processing of the various modes of image degradation is distinct.Conclusions: The validation of four other ways of impairing the recognition of optotypes in addition to size diminution reveals their potential in the differential diagnosis of defects in pattern detection, in evaluating therapeutic regimens and in developing concepts of form perception. [ABSTRACT FROM AUTHOR]

Highlights: [•] Form discrimination was measured by varying image degradation not size. [•] Performance remained stable during 7days of training, 1000trials/day. [•] There was essentially no perceptual learning of blur adaptation. [Copyright &y& Elsevier]

Abstract: Principles of the design and administration of clinical stereopsis tests are outlined. Once the presence of the distinct sense of the third dimension by binocular vision alone and without help from monocular cues has been established in a patient, the examination can proceed to the measurement of stereoscopic acuity. Best results are obtained with high-contrast, sharp, well-articulated and uncrowded elements from easily-recognized target sets, displayed with no time constraints. Polarization is the preferred method of right/left eye separation; time-sharing at a minimum of 60Hz on computer displays with counterphase occluding goggles is a feasible procedure. Random-dot stereograms are problematic because not all observers can disentangle the coherent global disparity on a first view. [Copyright &y& Elsevier]

Fourteen daily training sessions in orientation discrimination of foveal lines in the 45-deg meridian improved thresholds in the trained meridian by an average of 25 % in five observers. A substantial amount of training transferred to the other obliques, but none to the cardinal meridians, with a consequent reduction in the oblique effect. The data were interpreted as showing perceptual learning at two levels: performance facilitation specific to the trained orientation and improved proficiency globally. The failure of the cardinal orientations to share in the benefit is likely to have its origin in the fact that contour orientation in these meridians is so well established that it had already reached maximum hyperacuity thresholds. The judgment of obliques depends much more than the judgment of cardinals on whether the comparison and test stimuli are shown simultaneously or in succession, but this effect is not changed by perceptual training. [ABSTRACT FROM AUTHOR]

Abstract: Classically, diffraction theory sets a boundary for the resolving capacity of optical instruments. Yet some visual thresholds have values much better than the traditional resolution limit. Recent developments in superresolution, an area of optical physics and engineering with claims of transcending the stated resolution limits of optical instruments, are reviewed and their possible relevance to visual spatial processing and to the exploration of the eye''s structure are assessed. In optical or diffractive superresolution the transmitted spatial-frequency band is not so much extended as either multiplexed with or displaced into regions that are usually beyond reach, with no overall gain in information transfer because prior knowledge is used to make inferences of possible object structure from the image. The Uncertainty Principle for photon position and momentum is never disobeyed. The study of the neural substrate of visual hyperacuity does, however, overlap that of “geometrical superresolution,” in which techniques are used for transcending limits imposed by the receptor lattice in analyzing fine image structure. [Copyright &y& Elsevier]

Citation information: Westheimer G. Spatial and spatial-frequency analysis in visual optics. Ophthalmic Physiol Opt 2012, 32, 271-281. doi: 10.1111/j.1475-1313.2012.00913.x Abstract Background: In the specification of visual targets and their transmission through the eye's optics to form retinal images, the spatial distribution of energy and its Fourier transform, the spatial-frequency spectrum, are equivalent, so long as linearity constraints are obeyed. The power spectrum, in which phase has been discarded, is an insufficient descriptor; it does not enable the original object to be reconstituted. Procedure: Not so well known, and explored here, are joint representations in the space and spatial-frequency dimensions. Their properties are outlined for some sample targets and for transforms of the Gabor, Difference-of-Gaussians and Wigner types. A related approach is one in which other kernel functions, such as the Gaussian or its derivative, are substituted for the cosines in the Fourier transform; here also graphs can be generated which jointly display properties both of the target and of its point-by-point representation in a size-tuned domain. Applications: This kind of study has application in matching the performance characteristics of optical devices to the eye's, in optical superresolution, and in the analysis of the demands placed on neural processing in, for example, visual hyperacuity. [ABSTRACT FROM AUTHOR]

Background: Changes in cortical receptive fields following deafferentation raise the question of whether interruption of optic nerve fibres engenders spatial distortion in the region bordering the resulting scotoma. Methods: The regularity and uniformity of the spatial metric surrounding a monocular Bjerrum scotoma were studied in both the affected and unaffected eyes of a glaucoma patient, using rigorous psychometric measurements and Amsler grid observations. Results: No expansion of distances towards the edge of the scotoma was found; however, such a change occurs at the border of the normal blind spot, though not binocularly and not in the corresponding field of the other eye. Conclusion: The findings argue against cortical reorganisation following monocular retinal deafferentation in the adult. [ABSTRACT FROM AUTHOR]

Procedures for three-dimensional image reconstruction that are based on the optical and neural apparatus of human stereoscopic vision have to be designed to work in conjunction with it. The principal methods of implementing stereo displays are described. Properties of the human visual system are outlined as they relate to depth discrimination capabilities and achieving optimal performance in stereo tasks. The concept of depth rendition is introduced to define the change in the parameters of three-dimensional configurations for cases in which the physical disposition of the stereo camera with respect to the viewed object differs from that of the observer's eyes. [ABSTRACT FROM AUTHOR]

Abstract: Whether position and orientation shifts induced by monocular context also act as a disparity for purposes of stereoscopy was investigated experimentally in order to examine the extent to which lateral spatial localization and stereoscopic depth share circuitry. A monocular tilt illusion in a line does not lead to a commensurate depth tilt of that line in binocular view, nor does a position shift in a bisection task caused by a gap within monocular dynamic random noise produce the commensurate depth displacement. Interocular transfer of monocularly-induced shifts, which might explain such findings, was eliminated as a factor. The results can therefore be interpreted as indicators of channeling and ordering of spatial signals paths in the visual cortex and imply that two-dimensional contextual interactions operate at a processing level beyond where disparity has already been extracted. [Copyright &y& Elsevier]

Abstract: Viewing the trajectory of the discipline through the first half-century of VISION RESEARCH it is of interest to sketch what it is was like to conduct vision research at the time of the founding of the journal and counterpoise that with the situation at present. The most notable change has been the increase in the number of researchers, in the volume of publication and in the incorporation of computers into the research enterprise at every level. A few topics that were cutting-edge at the earlier time turned out to have led into culs-de-sac, others have been forgotten because their solution opened up new territories, others yet have remained unanswered, challenging researchers now as they did 50years ago. [Copyright &y& Elsevier]

Abstract: The orientation of a test line appears shifted away from that of contextual contours. This repulsion in the orientation domain manifests itself in, for example, the tilt aftereffect, the simultaneous orientation contrast, and the Zöllner illusion. Attractive rather than repulsive interaction has been reported for collinear inducing configurations at small inducing angles. Here it is shown that the tilt induced in a monocular vertical foveal test line by a single centered inducing line is repulsive when both are in the same eye, but becomes attractive for dichoptic stimulation. This occurs for only a narrow range of test-line/inducing-line separations and varies somewhat between and, by ocularity, within observers. The phenomenon might be related to stereoscopy which involves the processing of dichoptic orientation differences around the vertical. [ABSTRACT FROM AUTHOR]

The explosive growth of automatic examination of the eye, in particular for determining refractive corrections, invites an analysis of the strengths and limitations of these devices and their role in clinical decisions. Subjective refraction procedures are based on a patient's visual responses and these embrace many levels of additional optical and neural processing and factors involving the higher-order nervous system and perception. Because the ultimate mission is the maintenance and improvement of a patient's visual experiences, the optometric examination necessarily extends beyond the employment of automatic devices and therefore, should include engaging the patients in tests of their visual functions. [ABSTRACT FROM AUTHOR]

Anatomical superposition of the cortical projections from the overlapping visual fields of the two eyes does not make it obvious how the disposition of objects in the third dimension is encoded. Hubel and Wiesel's demonstration that units in the primary visual cortex of the mammal respond preferentially to elongated contours of specific orientation encouraged the inquiry into whether binocular disparity might not similarly be represented as an attribute interdigitated within the orderly progression of position. When this was found to indeed be the case, this entrained a brisk research activity into the disparity of receptive fields of single units in the primary visual cortex and the influence on their response of the three-dimensional locations of outside world stimuli. That cells’ preferred orientations covered the whole gamut whereas space perception required only horizontal disparity was an apparent paradox that needed resolution. A connection with an observer's stereoscopic performance was made by the discovery that cells in the primate primary visual cortex display good tuning to the disparity in random-dot stereograms. But a wide gap still remains between the properties of these cortical units and human stereo thresholds in simple target configurations, let alone depth judgments in which perceptual and cognitive factors enter. When the neural circuits in the primary visual cortex that are involved in processing depth are eventually traced in detail they will also need to have properties that allow for the plasticity in learning and experience. [ABSTRACT FROM AUTHOR]

Abstract: The traditional view of the resolving power of the eye as based on the Rayleigh Criterion needs extension in view of insight gained from information theory. As first pointed out by Toraldo di Francia, the image of a double line is subtly different from that of a single line even when there is no central dip. Given an image, the uncertainty concerning the generating object can be expressed numerically in bits. With the available data on the optical performance and anatomical structure of the normal human eye, details of the distribution of light and of receptor activation have been characterized for foveal two-line resolution. They allow a comparison with the actual performance of the human observer and some conclusions concerning the strategy employed in resolution decisions as well as a more comprehensive analysis of the processes involved in the measurement of visual acuity. The discussion is extended to the case of laser-illuminated targets where the difference between image formation in coherent and incoherent light becomes relevant. [Copyright &y& Elsevier]

Abstract: Differences between the geometrical properties of simple configurations and their visual percept are called geometrical–optical illusions. They can be differentiated from illusions in the brightness or color domains, from ambiguous figures and impossible objects, from trompe l’oeil and perspective drawing with perfectly valid views, and from illusory contours. They were discovered independently by several scientists in a short time span in the 1850’s. The clear distinction between object and visual space that they imply allows the question to be raised whether the transformation between the two spaces can be productively investigated in terms of differential geometry and metrical properties. Perceptual insight and psychophysical research prepares the ground for investigation of the neural representation of space but, because visual attributes are processed separately in parallel, one looks in vain for a neural map that is isomorphic with object space or even with individual forms it contains. Geometrical–optical illusions help reveal parsing rules for sensory signals by showing how conflicts are resolved when there is mismatch in the output of the processing modules for various primitives as a perceptual pattern’s unitary structure is assembled. They point to a hierarchical ordering of spatial primitives: cardinal directions and explicit contours predominate over oblique orientation and implicit contours (Poggendorff illusion); rectilinearity yields to continuity (Hering illusion), point position and line length to contour orientation (Ponzo). Hence the geometrical–optical illusions show promise as analytical tools in unraveling neural processing in vision. [Copyright &y& Elsevier]

Modern developments in machine vision and object recognition have generated renewed interest in the proposal for drawing inferences put forward by the Rev. Thomas Bayes (1701–1759). In this connection the epistemological studies by Hermann Helmholtz (1821–1894) are often cited as laying the foundation of the currently popular move to regard perception as Bayesian inference. Helmholtz in his mature writings tried to reconcile the German idealist notions of reality-as-hypothesis with scientists' quests for the laws of nature, and espoused the view that we "attain knowledge of the lawful order in the realm of the real, but only in so far as it is represented in the tokens within the system of sensory impressions". His propositions of inferring objects from internal sensory signals by what he called 'unconscious inferences' have made Helmholtz be regarded as a proto-Bayesian. But juxtaposing Bayes's original writings, the modern formulation of Bayesian inference, and Helmholtz's views of perception reveals only a tenuous relationship. [ABSTRACT FROM AUTHOR]

Abstract: Vision scientists long ago pointed to black and white as separate sensations and saw confirmation in the fact that in the absence of light, one perceives the visual field as gray against which the negative after-image of a bright light appeared blacker. The first recordings from optic nerve fibers in vertebrates revealed ON and OFF signals, later associated with separate streams, arising already at the synapse between receptors and bipolar cells. These can be identified anatomically and physiologically and remain distinct all the way to the lateral geniculate nucleus, whose fibers form the input to the primary visual cortex. The dichotomy has been probed by electroretinography and analyzed by means of pharmacological agents and dysfunction due to genetic causes. The bi- rather than a unidirectional nature of the retinal output has advantages in allowing small signals to remain prominent over a greater dynamic range. The two streams innervate cortical neurons in a push–pull manner, generating receptive fields with spatial sensitivity profiles featuring ON and OFF subregions. Manifestations of the dichotomy appear in a variety of simple visual discriminations where there are often profound threshold differences in patterns with same polarity as compared with mixed contrast-polarity components. But even at levels in which the spatial, contrast and color attributes have already been securely established and black and white elements participate equally, a categorical difference between blackness and whiteness of a percept persists. It is an opponency, akin to the ones in the color domain, derived from the original ON and OFF signals and subsequently bound with the other attributes to yield a feature''s unitary percept. [Copyright &y& Elsevier]

The position of a black – white border is perceived somewhat towards the black side of its physical location. New measurements were performed of the magnitude of this effect for foveal vision in the normal observer and it was found to be about 0.4 min of arc at medium photopic luminances. The border shift can be accounted for by postulating that the retinal light spread caused by the optics of the eye is subjected to a compressive nonlinearity of light intensity (Naka — Rushton equation). Such irradiation-induced apparent enlargement of the white elements does not fully account for the shifted-chessboard illusion. When an additional stage of center — surround (DoG) transformation is introduced, a hypothetical excitation distribution can be generated, whose contours, at the appropriate scale, can outline quite well the seen shape deviations from rectangularity of the illusion. Contributing to the final percept, in addition to the light-spread, compressive nonlinearity, and center — surround reorganization, which would be retinal in origin, there are some cortical stages: the generation of the experience of sharp, straight borders and pointed corners, the emergence of a monotonic slope of the demarcation lines made of 'saw-tooth' position and angle shifts, and, finally, when all the retinal effects have been nulled out, a Zöllner kind of orientation deviation, due to offset pattern elements acting as tilted virtual contours. [ABSTRACT FROM AUTHOR]

Abstract: A review covering the trends that led to the current state of knowledge in the areas of: [(a)] schematic models of the eye, and the definition of the retinal image in terms of first-order optics; [(b)] the description of the actual image on the retina and methods for accessing and characterizing it; [(c)] available procedures for controlling the quality of the retinal image in defined situations; and [(d)] intra-receptoral optical effects that cause differences between the light distribution on the retinal surface and at the level of interaction with photopigment molecules. [Copyright &y& Elsevier]

Vernier acuity for short horizontal, vertical and oblique target lines was measured in many locations in the periphery of the visual field in normal human observers. In the 10 deg periphery, the average alignment threshold with oblique vernier lines in eight locations for three observers was 2.29 times higher than that with vertical and horizontal target lines. This oblique effect was found everywhere in the visual field. Similar conclusions are drawn for configurations in which the lines were replaced by just their distal endpoints, but here, additionally, performance was distinctly better when the dot pair was collinear with the fixation point, i.e. oriented radially, than when it was oriented tangentially. Both for vernier lines and for dot pairs, in all observers, horizontal configurations showed somewhat better thresholds than vertical ones. These results suggest an inherent pattern of connectivity throughout the visual field favoring processing in the cardinal orientations over the obliques, the radial over the tangential and, to a limited extent, the horizontal over the vertical. [ABSTRACT FROM AUTHOR]

Mach and Hering had early advanced a model of spatial visual processing featuring an antagonistic interaction between adjoining areas in the visual field. Spatial opponency was one of the first findings when single-unit studies of the retina were begun. Not long afterwards psychophysical experiments revealed a center-surround organization closely matching that found in the mammalian retina. It hinged on the demonstration of reduction of sensitivity in a small patch of the visual field when its surround was changed from dark to bright. Because such patterns inevitably produce borders, well-known phenomena of border interaction could be seen as providing alternative explanations, whose substrate would most likely be in the visual cortex. These competing viewpoints are discussed especially as they pertain to the recent demonstration of spatial differences in the center/surround organization between the normal and affected eyes of amblyopes. To the extent that most findings favor a retinal site for the psychophysically measured antagonism, and that evidence is accumulating for a direct effect on the mammalian retina of stimulus manipulation during visual development, the difference in spatial parameters of center/surround antagonism in amblyopia suggests that the dysfunction in amblyopia begins already in the retina. [Copyright &y& Elsevier]

The contention is examined that the oblique effect, i.e., the well-known performance deficit in detecting orientation difference in oblique lines as compared to vertical and horizontal ones, has its origin in a relative deficiency of neurons with obliquely-oriented receptive fields in the primary visual cortex. Psychophysical observations demonstrate a prominent oblique effect also in visual tasks involving widely-separated elements and other stimuli that would elicit little or no response in oriented neurons in the visual cortex. Conversely, some tasks, e.g. position discrimination, exhibit no oblique effect even with short, high-contrast lines. When the comparison with the reference can be accomplished during a single brief exposure rather than sequential ones, thresholds for orientation differences between adjacent contours in oblique meridians are also elevated compared to those in the vertical and horizontal, but to a lesser extent. In one particular texture discrimination task some but not all observers have a conspicuous oblique effect. The discrimination only of the direction of streaming random dots, not of their speed, is poorer for motions in oblique meridians. The findings imply that the neural locus for the oblique effect is more central than the primary visual cortex. [Copyright &y& Elsevier]

Orientation discrimination was measured for line targets in the fovea and in locations along four meridians (vertical, horizontal, 45 degrees and 135 degrees ) in the peripheral visual field. In all locations, the performance for vertical and horizontal contours was on average almost twice as good as for oblique ones. In addition, especially in peripheral locations along oblique meridians, thresholds tend to be better for radially-oriented contours compared to tangential ones. These effects are robust to length of the test lines and to small changes in position and cannot therefore be due to cortical singularities (pinwheels). The results suggest that the advantage of horizontal and vertical contours, as well as possibly of radial ones, is a manifestation of a characteristic structural property of the organization of the visual pathway. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the role of the primary visual cortex in the integration of visual information of alert monkeys. Methodology of the study; Results and discussion.

Of 188 unselected biology students participating in one or both of two tests measuring stereoscopic depth detection ability, 183 (97.3%) were able to see a depth difference at horizontal disparities of 2.3 min arc or smaller. At least 80% could detect depth differences at 30 sec arc disparity. These findings indicate that most people are able to take advantage of the increasing utilization of stereoscopic displays. [ABSTRACT FROM AUTHOR]

Abstract: When the separation between the incoherent point sources is decreased, in the limit a decision whether the image distribution arises from one or two points or a short bar rests, in the absence of prior information, on the detection of an indentation. That, in essence, is the concept of resolution. [Copyright &y& Elsevier]

Strasburger et al.'s welcome translation of Hering's seminal paper, and reminder of what Hering actually said about eye movements and spatial averaging in vernier acuity, is supplemented by references to further trends on how the subject has evolved to the present state of knowledge. [ABSTRACT FROM AUTHOR]

The law of equal innervation of the two eyes, positing that conjugacy of movement of our two eyes is basic and innate, was enunciated in Hering's 1868 persuasively argued monograph. It has prevailed over Helmholtz's contrary view that conjugacy is learned. Yet 100 years earlier, Thomas Reid (1710-1796), Scottish clergyman and professor of philosophy, advanced exactly the same view as Hering, using almost identical arguments. Reid also considered whether the eyes' parallelism might have its origin in "custom" or "habit" rather than "nature" and reached the now accepted conclusion that it is innate. [ABSTRACT FROM AUTHOR]

Presents an obituary for Fergus W. Campbell, a member of the editorial board of the journal "Ophthalmic and Physiological Optics," who died on May 3, 1993.

This article focuses on the resignation of professor Fergus W. Campbell of the University of Cambridge, England. According to the author, the occasion of Campbell's retirement from the personal chair of neurosensory physiology in Cambridge was marked not by a weighty symposium and a severe Festschrift but by a lighthearted get-together of his many collaborators and students. Opened by a reception in the gardens of Saint John's College, of which he has been a long-time fellow, the gathering included banquet at New Hall and a farewell garden reception in Pembroke College featuring a grating-decorated cake and the singing of "Happy Festspiel to Fergus."

Discusses the existence of center/surround opponency in spatial vision. Discovery of D.H. Hubel and T.N. Wiesel on the preferential response of the neurons in the mammalian cortex; Connection with orientation-selective receptive fields; Response to illusory contours; Entry of illusory contours at the edge or border-processing apparatus; Stages of visual processing.

A correction to the article "Spatial and spatial-frequency analysis in visual optics" that was published in the 2012 issue is presented which discusses the error in the biography of author Gerald Westheimer.

The article presents an obituary for Meredith W. Morgan, a professor of physiological optics and optometry and dean of the School of Optometry at the University of California in Berkeley, California.