Physiological Optics Research Articles

Connexin 50 Influences the Physiological Optics of the In Vivo Mouse Lens.

The purpose of this study was to utilize multi-parametric magnetic resonance imaging (MRI) to investigate in vivo age-related changes in the physiology and optics of mouse lenses where Connexin 50 has been deleted (Cx50KO) or replaced by Connexin 46 (Cx50KI46). The lenses of transgenic Cx50KO and Cx50KI46 mice were imaged between 3 weeks and 6 months of age using a 7T MRI. Measurements of lens geometry, the T2 (water-bound protein ratios), the refractive index (n), and T1 (free water content) values were calculated by processing the acquired images. The lens power was calculated from an optical model that combined the geometry and the n. All transgenic mice were compared with control mice at the same age. Cx50KO and Cx50KI46 mice developed smaller lenses compared with control mice. The lens thickness, volume, and surface radii of curvatures all increased with age but were limited to the size of the lenses. Cx50KO lenses exhibited higher lens power than Cx50KI46 lenses at all ages, and this was correlated with significantly lower water content in these lenses, which was probably modulated by the gap junction coupling. The refractive power tended to a steady state with age, similar to the control mice. The modification of Cx50 gap junctions significantly impacted lens growth and physiological optics as the mouse aged. The lenses showed delayed development growth, and altered optics governed by different lens physiology. This research provides new insights into how gap junctions regulate the development of the lens's physiological optics.

Sergey V. Kravkov as a psychologist and psychophysiologist: milestones of scientific biography (to the 130th anniversary of the birth)

The article is prepared for the 130th anniversary of the birth of S.V. Kravkov (1893–1951), a preeminent Russian scientist, experimental psychologist and specialist in the field of psychophysiology of vision. The subject of this historical and psychological study is the period of his professional development between 1916 and 1935. The biographical method is used. The materials from the Archive of Russian Academy of Sciences, works of S.V. Kravkov, memories and assessments of other scientists are used. Information about his family and personality is provided. The employment positions and types of professional activities of S.V. Kravkov in the first 20 years of his work are identified. The prerequisites for the scientist’s transition from an initially wide range of psychological issues to light engineering and the psychophysiology of vision as the central area of his applied and fundamental research are revealed. The originality of the method of introspection in experimental studies of vision in the scientist’s works is shown. It is concluded that P.P. Lazarev had a predominant influence on S.V. Kravkov’s scientific development as a specialist in the field of physiological optics and psychophysiology of vision.

Gender distribution in publishing in five leading optometry journals.

To explore gender distribution in authorship and citation parameters of articles published in five optometry journals included in the Ophthalmology category of Journal Citation Reports. The Scopus database was used to retrieve all citable articles published in 2011 and 2021 in Optometry and Vision Science, Ophthalmic and Physiological Optics, Clinical Experimental Optometry, Contact Lens and Anterior Eye, and Eye and Contact Lens. Gender of the first, last and single authors of all articles, and citation parameters of articles published in 2011 up to May 2023 were determined. Gender of the editor-in-chief and members of the editorial board of these journals was investigated (May 2023). Only one journal had a female editor-in-chief and three journals had more males than females in their editorial board. In 2011 and 2021, respectively, 40.1% and 48.0% of articles had female as the first authors ( = 5.77; p = 0.02), and 32.7% and 39.6% had female as the last authors ( = 4.61; p = 0.03). Gender parity was observed in one journal for the first author and none for the last author in 2011, and in three journals for the first author and one for the last author in 2021. Regarding combinations of male (M) and female (F) first and last authorship positions, the authors of articles in 2011 were MM (44.5%), FM (22.8%), FF (17.3%) and MF (15.4%), and MM (34.6%), FM (25.8%), FF (22.1%) and MF (17.5%) in 2021. Differences between 2011 and 2021 were statistically significant ( = 9.80; p = 0.02). The proportion of authorship combinations did not show statistically significant differences among journals in 2011 or in 2021. Neither citation nor self-citation were influenced by gender. Gender disparities persist in optometry journals, with females being under-represented in senior and leadership positions. Increasing the awareness of gender disparity in authorship is a necessary step towards ensuring fairness in science in general, and optometry in particular.

Michael Francis Land. 12 April 1942—14 December 2020

Michael (Mike) Land made lasting contributions to physiological optics of diverse animals and to understanding how animals and humans move their eyes. He combined a keen interest in natural history and evolution with elegant and accessible mathematical accounts of optics and vision. In the early part of his career he discovered focusing mechanisms based on reflection in scallops' and compound eyes, and elucidated the evolutionary and functional relationships between spatial resolution and absolute sensitivity in eyes. Starting with studies of how spiders and flies use eye and body movements to track and intercept moving targets, Land went on to apply similar principles to human visuo-motor behaviour. He described where we look during routine tasks, such as making tea, and in more exacting conditions, such as driving and playing cricket. He showed how eye movements are tailored top-down for a given task, and found that typically we foveate each location a fraction of a second before each action. Finally, he suggested how behaviour and awareness are anchored to an internal representation that incorporates egocentric and allocentric frames of reference. Land's deep curiosity about the living world led him to discover visual principles of an unexcelled diversity of creatures.

Visual and Physiological Optics: introduction to the joint feature issue in Biomedical Optics Express and Journal of the Optical Society of America A.

This feature issue collects articles presented at the tenth Visual and Physiological Optics meeting (VPO2022), held August 29-31, 2022, in Cambridge, UK. This joint feature issue between Biomedical Optics Express and Journal of the Optical Society of America A includes articles that cover the broad range of topics addressed at the meeting and examples of the current state of research in the field.

Introduction to Visual and Physiological Optics feature issue of Biomedical Optics Express and JOSA A.

This feature issue collects articles presented at the tenth Visual and Physiological Optics meeting (VPO2022), held August 29-31, 2022, in Cambridge, UK. This joint feature issue between Biomedical Optics Express and Journal of the Optical Society of America A includes articles that cover the broad range of topics addressed at the meeting and examples of the current state of research in the field.

The horopter: Old and new.

The horopter's history may partly be responsible for its ambiguous psychophysical definitions and obscured physiological significance. However, the horopter is a useful clinical tool integrating physiological optics and binocular vision. This article aims to help understand how it could come to such different attitudes toward the horopter. After the basic concepts underlying binocular space perception and stereopsis are presented, the horopter's old ideas that influence today's research show their inconsistencies with the conceptualized binocular vision. Two recent geometric theories of the horopter with progressively higher eye model fidelity that resolve the inconsistencies are reviewed. The first theory corrects the 200-year-old Vieth-Müller circle still used as a geometric horopter. The second theory advances Ogle's classical work by modeling empirical horopters as conic sections in the binocular system with the asymmetric eye model that accounts for the observed misalignment of optical components in human eyes. Its extension to iso-disparity conics is discussed.

Helmholtz and the geometry of color space: gestation and development of Helmholtz’s line element

Modern color science finds its birth in the middle of the nineteenth century. Among the chief architects of the new color theory, the name of the polymath Hermann von Helmholtz stands out. A keen experimenter and profound expert of the latest developments of the fields of physiological optics, psychophysics, and geometry, he exploited his transdisciplinary knowledge to define the first non-Euclidean line element in color space, i.e., a three-dimensional mathematical model used to describe color differences in terms of color distances. Considered as the first step toward a metrically significant model of color space, his work inaugurated researches on higher color metrics, which describes how distance in the color space translates into perceptual difference. This paper focuses on the development of Helmholtz’s mathematical derivation of the line element. Starting from the first experimental evidence which opened the door to his reflections about the geometry of color space, it will be highlighted the pivotal role played by the studies conducted by his assistants in Berlin, which provided precious material for the elaboration of the final model proposed by Helmholtz in three papers published between 1891 and 1892. Although fallen into oblivion for about three decades, Helmholtz’s masterful work was rediscovered by Schrödinger and, since the 1920s, it has provided the basis for all subsequent studies on the geometry of color spaces up to the present time.

Ernst Wilhelm Brücke on stereoscopic vision

ABSTRACT In the early 19th century the doctrine of identical retinal points, linked with the Vieth-Müller circle, was a pillar of German physiological optics. It was challenged by Wheatstone’s observations of stereoscopic depth perception announced in 1838; he also advanced a cognitive theory of binocular vision that attacked physiological interpretations. In 1841 Brücke mounted a defense of the doctrine by questioning Wheatstone’s observations and offering an alternative interpretation in terms of the integration over time of a rapid sequence of convergence eye movements. The theory could not be sustained because of evidence that stereoscopic depth occurred without eye movements. Brücke also questioned Wheatstone’s observations that with some stereoscopic displays stimulation of identical retinal points could result in double vision. The binocular combination of circles differing in size was accounted for by differentially dissociating accommodation in opposite directions for each eye from convergence. Despite the negative reaction to Brücke’s proposals, his speculations about the nature of rapid eye movements and of their neural basis were ahead of his time.

An image reconstruction framework for characterizing initial visual encoding.

We developed an image-computable observer model of the initial visual encoding that operates on natural image input, based on the framework of Bayesian image reconstruction from the excitations of the retinal cone mosaic. Our model extends previous work on ideal observer analysis and evaluation of performance beyond psychophysical discrimination, takes into account the statistical regularities of the visual environment, and provides a unifying framework for answering a wide range of questions regarding the visual front end. Using the error in the reconstructions as a metric, we analyzed variations of the number of different photoreceptor types on human retina as an optimal design problem. In addition, the reconstructions allow both visualization and quantification of information loss due to physiological optics and cone mosaic sampling, and how these vary with eccentricity. Furthermore, in simulations of color deficiencies and interferometric experiments, we found that the reconstructed images provide a reasonable proxy for modeling subjects' percepts. Lastly, we used the reconstruction-based observer for the analysis of psychophysical threshold, and found notable interactions between spatial frequency and chromatic direction in the resulting spatial contrast sensitivity function. Our method is widely applicable to experiments and applications in which the initial visual encoding plays an important role.

Functional integration of eye tissues and refractive eye development: Mechanisms and pathways

Refractive eye development is a tightly coordinated developmental process. The general layout of the eye and its various components are established during embryonic development, which involves a complex cross-tissue signaling. The eye then undergoes a refinement process during the postnatal emmetropization process, which relies heavily on the integration of environmental and genetic factors and is controlled by an elaborate genetic network. This genetic network encodes a multilayered signaling cascade, which converts visual stimuli into molecular signals that guide the postnatal growth of the eye. The signaling cascade underlying refractive eye development spans across all ocular tissues and comprises multiple signaling pathways. Notably, tissue-tissue interaction plays a key role in both embryonic eye development and postnatal eye emmetropization. Recent advances in eye biometry, physiological optics and systems genetics of refractive error have significantly advanced our understanding of the biological processes involved in refractive eye development and provided a framework for the development of new treatment options for myopia. In this review, we summarize the recent data on the mechanisms and signaling pathways underlying refractive eye development and discuss new evidence suggesting a wide-spread signal integration across different tissues and ocular components involved in visually guided eye growth.

Helmholtz at 200.

Hermann von Helmholtz was born 200 years ago, but his influence on vision research is enduring. His legacy in vision is celebrated visually with anaglyphs that combine portraits of him with illustrations from his publications. Emphasis is directed principally to his Treatise on Physiological Optics. Among the optical instruments Helmholtz invented were the ophthalmoscope, ophthalmometer, and telestereoscope. Mention is made of his investigations into accommodation, colour vision, eye movements, stereoscopic vision, binocular rivalry, and lustre. Helmholtz also presented his analyses of vision and art in several of his Popular Lectures.

The vision of Helmholtz

ABSTRACT Hermann Ludwig Ferdinand von Helmholtz (1821–1894) began investigating vision at a time when its study was undergoing a revolution. Laboratory experiments were augmenting the long history of naturalistic observations. Instruments of stimulus control enabled the manipulation of time and space in ways that had not been possible previously, and Helmholtz added to their tally. Vision was a central issue in his early years as an academic, and the bicentenary of his birth is here celebrated visually. Much of his research on vision was described in his Handbuch der physiologischen Optik, which was translated into English to mark the centenary of his birth. The history of his Handbuch is examined, together with illustrating highlights from it. Helmholtz’s contributions to understanding the eye as an optical instrument, the sensations of vision, and perception were expressed in the three parts of the Handbuch, which became the three volumes of his Treatise on Physiological Optics.

HERMANN VON HELMHOLTZ, EWALD HERING AND COLOR VISION: A CONTROVERSY OVER STYLES OF REASONING?

During the second half of the 19th century, in the field of physiological optics, there was a strong controversy between Hermann von Helmholtz and Ewald Hering. This controversy has been usually characterized as “empiricism” vs. “nativism”. In the field of physiology of visual perception, several subjects demanded attention, among them, color vision. Helmholtz and Hering suggested different theories for the physiological correlate of color sensation and different color spaces to give an account of the relationships between colors. In this article, I will argue that the controversy between the two authors could be understood as differences between styles of reasoning, and these different styles express different presuppositions. More specifically, I want to suggest that the disagreements could be linked to the discussions on how vital phenomena should be studied.

Perspectives of people with late age-related macular degeneration on mental health and mental wellbeing programmes: a qualitative study.

People with age-related macular degeneration (AMD) experience high rates of depression, but rarely engage in or have access to tailored mental wellbeing programmes. This qualitative study investigated the perspectives of those primarily with late AMD on mental health and mental wellbeing programmes. Twenty-eight people with late AMD in at least one eye, and one person with early AMD in both eyes, aged 56-87years (mean age 78years) attending a private eye clinic between December 2019 and January 2020 in Sydney, New South Wales, Australia, participated. Individual semi-structured interviews were conducted and analysed deductively using content analysis, following the individual level factors for health promotion interventions in the behaviour change wheel: Capability (Physical & Psychological), Opportunity (Physical & Social), and Motivation (Reflective & Automatic). Six major themes were identified: Capability: (1) Impact of vision loss on mobility and leisure pursuits; (2) Adjustment to living with vision loss; Opportunity: (3) Program considerations for those with AMD; (4) Stigma and self-perception of vision loss and mental health; Motivation: (5) Accumulation of vision-related issues as a barrier to participation; (6) Examples of others living with vision loss. General personal factors relevant to delivery of a programme in this age group were also identified: Comorbidities; Limitations using technology; Isolation; Financial concerns and Beliefs that undesired effects of aging are inevitable. Complex individual, environmental and social factors influence the perspectives of people with late AMD on mental health, and potential participation in mental wellbeing programmes. These factors should be considered when developing and implementing mental wellbeing programmes to improve the emotional and functional rehabilitation outcomes for people with AMD.

Research on Improvement of Optical Model of Human Vision

In retrospect, visional researches mostly focused on vision sensitivity. However, a vision model suitable to human eye shall be built to further explore human eye visional characteristics. Most of the vision models in the fields of optometry and physiological optics must be modified to bring them more closer to actual human eye characteristics. While the aforementioned potential problem would not impede the visual capability of a person with normal eye sight, it tends to cause significant implication for a patient with retina illness during the initial syndrome and recuperation period after surgical operation. Under some special circumstances, such as in a battle field when lack of light is norm due to weather and landform conditions, human eye recognition capability would be significantly compromised as well. The CSF (Contrast sensitivity function) curve is proposed to be applied to the analysis in evaluating human eye recognition characteristics problems. this is the first literature to incorporate CS(contrast sensitivity) correction into human vision multi-parameter model. The modified modeling is validated by the experiment results showing the modified model is closed to human eye’s CSF curve.

Vanishing optotypes and objective measurement of human visual acuity

The eye resolving power and human visual acuity are the most important parameters of physiological optics. In this study, we compare our results of psychophysics, subjective measurement of visual acuity, with the results of electrophysiological measurement, objective measurement of visual acuity using vanishing optotypes that differ in spatial (sharp or non-sharp) and semantic (animate or inanimate) properties. The subject is instructed to provide consciously the classification of images: are they sharp, or are they non-sharp. At the same time the subject unconsciously provides another classification: what objects presented to him as images are animate or inanimate. This unconscious classification was provided by the subject without instruction to do it, and it was independent of his conscious decisions made during testing of the presented images of the objects (sharp or non-sharp). We see the observer’s unconscious classification (animate or inanimate) only using electrophysiological measurements. The markers of unconscious recognition are the visual evoked potential components P200 and N170, recorded from the frontal brain area. The discovered effect works as an instrument for objective visual acuity measurements.

VioBio lab adaptive optics: technology and applications by women vision scientists.

Adaptive Optics allows measurement and manipulation of the optical aberrations of the eye. We review two Adaptive Optics set-ups implemented at the Visual Optics and Biophotonics Laboratory, and present examples of their use in better understanding of the role of optical aberrations on visual perception, in normal and treated eyes. Two systems (AOI and AOII) are described that measure ocular aberrations with a Hartmann-Shack wavefront sensor, which operates in closed-loop with an electromagnetic deformable mirror, and visual stimuli are projected in a visual display for psychophysical measurements. AOI operates in infrared radiation (IR) light. AOII is provided with a supercontiniuum laser source (IR and visible wavelengths), additional elements for simulation (spatial light modulator, temporal multiplexing with optotunable lenses, phase plates, cuvette for intraocular lenses-IOLs), and a double-pass retinal camera. We review several studies undertaken with these AO systems, including the evaluation of the visual benefits of AO correction, vision with simulated multifocal IOLs (MIOLs), optical aberrations in pseudophakic eyes, chromatic aberrations and their visual impact, and neural adaptation to ocular aberrations. Monochromatic and chromatic aberrations have been measured in normal and treated eyes. AO systems have allowed understanding the visual benefit of correcting aberrations in normal eyes and the adaptation of the visual system to the eye's native aberrations. Ocular corrections such as intraocular and contact lenses modify the wave aberrations. AO systems allow simulating vision with these corrections before they are implanted/fitted in the eye, or even before they are manufactured, revealing great potential for industry and the clinical practice. This review paper is part of a special issue of Ophthalmic & Physiological Optics on women in visual optics, and is co-authored by all women scientists of the research team.

Ray tracing 3D spectral scenes through human optics models.

Scientists and engineers have created computations and made measurements that characterize the first steps of seeing. ISETBio software integrates such computations and data into an open-source software package. The initial ISETBio implementations modeled image formation (physiological optics) for planar or distant scenes. The ISET3d software described here extends that implementation, simulating image formation for three-dimensional scenes. The software system relies on a quantitative computer graphics program that ray traces the scene radiance through the physiological optics to the retinal irradiance. We describe and validate the implementation for several model eyes. Then, we use the software to quantify the impact of several physiological optics parameters on three-dimensional image formation. ISET3d is integrated with ISETBio, making it straightforward to convert the retinal irradiance into cone excitations. These methods help the user compute the predictions of optics models for a wide range of spatially rich three-dimensional scenes. They can also be used to evaluate the impact of nearby visual occlusion, the information available to binocular vision, or the retinal images expected from near-field and augmented reality displays.

Should Pearson's correlation coefficient be avoided?

To survey the use of Pearson's correlation coefficient (r) and related statistical methods in the ophthalmic literature, to consider the limitations of r, and to suggest suitable alternative methods of analysis. Searching Ophthalmic and Physiological Optics (OPO), Optometry and Vision Science (OVS), and Clinical and Experimental Optometry (CXO) online archives using correlation and Pearson's r as search terms resulted in 4057 and 281 hits respectively. Coefficient of determination, r square, or r squared received fewer hits (65, 8, and 22 hits respectively). The assumption that r follows a bivariate normal distribution was rarely encountered (3 hits) although several studies applied Spearman's rank correlation (70 hits). The intra-class correlation coefficient (ICC) was widely used (178 hits), but fewer hits were recorded for partial correlation (43 hits) and multiple correlation (13) hits. There was little evidence that the problem of sample size was addressed in correlation studies. Investigators should be alert to whether: (1) the relationship between two variables could be non-linear, (2) the data are bivariate normal, (3) r accounts for a significant proportion of the variance in Y, (4) outliers are present, the data are clustered, or have a restricted range, (5) the sample size is appropriate, and (6) a significant correlation indicates causality. In addition, the number of significant digits used to express r and the problems of multiple testing should be addressed. The problems and limitations of r suggest a more cautious approach regarding its use and the application of alternative methods where appropriate.