Human Eye Research Articles

The First Steps of the Visual Cycle in Human Rod and Cone Photoreceptors.

Light detection destroys the visual pigment. Its regeneration, necessary for the recovery of light sensitivity, is accomplished through the visual cycle. Release of all-trans retinal by the light-activated visual pigment and its reduction to all-trans retinol comprise the first steps of the visual cycle. In this study, we determined the kinetics of all-trans retinol formation in human rod and cone photoreceptors. Single living rod and cone photoreceptors were isolated from the retinas of human cadaver eyes (ages 21 to 90 years). Formation of all-trans retinol was measured by imaging its outer segment fluorescence (excitation, 360nm; emission, >420nm). The extent of conversion of released all-trans retinal to all-trans retinol was determined by measuring the fluorescence excited by 340 and 380nm. Measurements were repeated with photoreceptors isolated from Macaca fascicularis retinas. Experiments were carried out at 37°C. We found that ∼80% to 90% of all-trans retinal released by the light-activated pigment is converted to all-trans retinol, with a rate constant of 0.24 to 0.55 min-1 in human rods and ∼1.8 min-1 in human cones. In M. fascicularis rods and cones, the rate constants were 0.38 ± 0.08 min-1 and 4.0 ± 1.1 min-1, respectively. These kinetics are several times faster than those measured in other vertebrates. Interphotoreceptor retinoid-binding protein facilitated the removal of all-trans retinol from human rods. The first steps of the visual cycle in human photoreceptors are several times faster than in other vertebrates and in line with the rapid recovery of light sensitivity exhibited by the human visual system.

Machine Learning and Artificial Intelligence in Drug Repurposing—Challenges and Perspectives

Artificial intelligence (AI) and machine learning (ML) techniques play an increasingly crucial role in the field of drug repurposing. As the number of computational tools grows, it is essential to not only understand and carefully select the method itself, but also consider the input data used for building predictive models. This review aims to take a dive into current computational methods that leverage AI and ML to drive and accelerate compound and drug target selection, in addition to addressing the existing challenges and providing perspectives. While there is no doubt that AI- and ML-based tools are transforming traditional approaches, especially with recent advancements in graph-based methods, they present novel challenges that require the human eye and expert intervention. The growing complexity of OMICs data further emphasizes the importance of data standardization and quality.

Non-contact intelligent sensor for recognizing transparent and naked-eye indistinguishable materials based on ferroelectric BiFeO3 thin films

At present, the research on ferroelectric photovoltaic materials mainly focuses on photoelectric detection. In the context of the rapid development of the Internet of Things (IoT), it is particularly important to use smaller thin-film devices as sensors. In this work, an indium tin oxide/bismuth ferrite (BFO)/lanthanum nickelate device has been fabricated on an F-doped tin oxide glass substrate using the sol–gel method. The sensor can continuously output photoelectric signals with little environmental impact. Compared to other types of sensors, this photoelectric sensor has an ultra-low response time of 1.25 ms and ultra-high sensitivity. Furthermore, a material recognition system based on a BFO sensor is developed. It can effectively identify eight kinds of materials that are difficult for human eyes to distinguish. This provides new ideas and methods for developing the IoT in material identification.

Flavonols do not affect aphid load in green or senescing birch leaves but coincide with a decrease in Photosystem II functionality.

Instead of red anthocyanins, birches synthesise colourless (to human eye), UV-absorbing flavonols during autumn senescence. To test if flavonols protect against insects, and if leaves with high or low amounts of flavonols differ in their photosynthetic functions, aphid-free and aphid-infested green and senescing birch leaves were collected from outdoor-grown trees and analysed. Photosynthetic parameters were greatly affected by the leaf chlorophyll content (i.e. the phase of senescence). Photochemical quenching and the amount of functional Photosystem I decreased linearly with chlorophyll content, while FV/FM (Photosystem II functionality) decreased strongly only at the end of senescence. Non-photochemical quenching of excitation energy (NPQ) increased towards the end of senescence. However, no significant differences in the total flavonol amounts, nor in individual flavonol species, were found between aphid-free and aphid-infested leaves, suggesting that flavonols play no role in defence against aphid herbivory. Interestingly, both green and senescing leaves with a high flavonol content showed low FV/FM values. High flavonol content slowed down PSII photoinhibition and improved recovery, but only in green leaves. Previously, we proposed that anthocyanins provide an additional sink for photosynthates at the nitrogen resorption phase during autumn senescence, and the present data may suggest that flavonol synthesis plays a similar role.

Spectral library and method for sparse unmixing of hyperspectral images in fluorescence guided resection of brain tumors.

Through spectral unmixing, hyperspectral imaging (HSI) in fluorescence-guided brain tumor surgery has enabled the detection and classification of tumor regions invisible to the human eye. Prior unmixing work has focused on determining a minimal set of viable fluorophore spectra known to be present in the brain and effectively reconstructing human data without overfitting. With these endmembers, non-negative least squares regression (NNLS) was commonly used to compute the abundances. However, HSI images are heterogeneous, so one small set of endmember spectra may not fit all pixels well. Additionally, NNLS is the maximum likelihood estimator only if the measurement is normally distributed, and it does not enforce sparsity, which leads to overfitting and unphysical results. In this paper, we analyzed 555666 HSI fluorescence spectra from 891 ex vivo measurements of patients with various brain tumors to show that a Poisson distribution indeed models the measured data 82% better than a Gaussian in terms of the Kullback-Leibler divergence, and that the endmember abundance vectors are sparse. With this knowledge, we introduce (1) a library of 9 endmember spectra, including PpIX (620 nm and 634 nm photostates), NADH, FAD, flavins, lipofuscin, melanin, elastin, and collagen, (2) a sparse, non-negative Poisson regression algorithm to perform physics-informed unmixing with this library without overfitting, and (3) a highly realistic spectral measurement simulation with known endmember abundances. The new unmixing method was then tested on the human and simulated data and compared to four other candidate methods. It outperforms previous methods with 25% lower error in the computed abundances on the simulated data than NNLS, lower reconstruction error on human data, better sparsity, and 31 times faster runtime than state-of-the-art Poisson regression. This method and library of endmember spectra can enable more accurate spectral unmixing to aid the surgeon better during brain tumor resection.

Consequences of eye movements for spatial selectivity

What determines spatial tuning in the visual system? Standard views rely on the assumption that spatial information is directly inherited from the relative position of photoreceptors and shaped by neuronal connectivity.1,2 However, human eyes are always in motion during fixation,3,4,5,6 so retinal neurons receive temporal modulations that depend on the interaction of the spatial structure of the stimulus with eye movements. It has long been hypothesized that these modulations might contribute to spatial encoding,7,8,9,10,11,12 a proposal supported by several recent observations.13,14,15,16 A fundamental, yet untested, consequence of this encoding strategy is that spatial tuning is not hard-wired in the visual system but critically depends on how the fixational motion of the eye shapes the temporal structure of the signals impinging onto the retina. Here we used high-resolution techniques for eye-tracking17 and gaze-contingent display control18 to quantitatively test this distinctive prediction. We examined how contrast sensitivity, a hallmark of spatial vision, is influenced by fixational motion, both during normal active fixation and when the spatiotemporal stimulus on the retina is altered to mimic changes in fixational control. We showed that visual sensitivity closely follows the strength of the luminance modulations delivered within a narrow temporal bandwidth, so changes in fixational motion have opposite visual effects at low and high spatial frequencies. By identifying a key role for oculomotor activity in spatial selectivity, these findings have important implications for the perceptual consequences of abnormal eye movements, the sources of perceptual variability, and the function of oculomotor control.

Liquid-alloy-based dual sensing elements contact lens sensor for continuous intraocular pressure monitoring

Intraocular pressure (IOP) fluctuation is an independent risk factor for glaucoma and a key to clarify its pathogenesis. We have developed a contact lens integrated with a conformal LC resonance circuit made of liquid alloy (Galinstan) for non-invasive continuous IOP monitoring. The contact lens is fabricated using polydimethylsiloxane (PDMS), in which the LC resonance circuit can sense corneal strain proportionally caused by IOP variation. The Galinstan configuration is formed to the designed pattern by UV-laser treating the carbon-doped Ecoflex (c-Ecoflex) stamps and then selectively transferring the Galinstan onto the stamp to form the LC resonance circuit pattern. The tests conducted on silicone model eyes demonstrate high sensitivity in the frequency responses to variations in IOP, reaching 649 ppm/mmHg. IOP measurement on human eyes during head-down tilt bedrest confirms its applicability. With process optimization, this contact lens sensor has great potential for mass production and wide application in monitoring IOP.

Computational modelling of scleral photocrosslinking: from rat to minipig to human.

Selective scleral crosslinking has been proposed as a novel treatment to increase scleral stiffness to counteract biomechanical changes associated with glaucoma and high myopia. Scleral stiffening has been shown by transpupillary peripapillary scleral photocrosslinking in rats, where the photosensitizer, methylene blue (MB), was injected retrobulbarly and red light initiated crosslinking reactions with collagen. Here, we adapted a computational model previously developed to model this treatment in rat eyes to additionally model MB photocrosslinking in minipigs and humans. Increased tissue length and subsequent diffusion and light penetration limitations were found to be barriers to achieving the same extent of crosslinking as in rats. Per cent inspired O2, injected MB concentration and laser fluence were simultaneously varied to overcome these limitations and used to determine optimal combinations of treatment parameters in rats, minipigs and humans. Increasing these three treatment parameters simultaneously resulted in maximum crosslinking, except in rats, where the highest MB concentrations decreased crosslinking. Additionally, the kinetics and diffusion of photocrosslinking reaction intermediates and unproductive side products were modelled across space and time. The model provides a mechanistic understanding of MB photocrosslinking in scleral tissue and a basis for adapting and screening treatment parameters in larger animal models and, eventually, human eyes.

Perception-action Dissociations as a Window into Consciousness.

Understanding the neural correlates of unconscious perception stands as a primary goal of experimental research in cognitive psychology and neuroscience. In this Perspectives paper, we explain why experimental protocols probing qualitative dissociations between perception and action provide valuable insights into conscious and unconscious processing, along with their corresponding neural correlates. We present research that utilizes human eye movements as a sensitive indicator of unconscious visual processing. Given the increasing reliance on oculomotor and pupillary responses in consciousness research, these dissociations also provide a cautionary tale about inferring conscious perception solely based on no-report protocols.

Book Review: Optics of the Human Eye, 2nd ed.

Book Review: Optics of the Human Eye, 2nd ed.

The Role of Heat Shock Protein 70 (HSP70) in the Pathogenesis of Ocular Diseases-Current Literature Review.

Heat shock proteins (HSPs) have been attracting the attention of researchers for many years. HSPs are a family of ubiquitous, well-characterised proteins that are generally regarded as protective multifunctional molecules that are expressed in response to different types of cell stress. Their activity in many organs has been reported, including the heart, brain, and retina. By acting as chaperone proteins, HSPs help to refold denatured proteins. Moreover, HSPs elicit inhibitory activity in apoptotic pathways and inflammation. Heat shock proteins were originally classified into several subfamilies, including the HSP70 family. The aim of this paper is to systematise information from the available literature about the presence of HSP70 in the human eye and its role in the pathogenesis of ocular diseases. HSP70 has been identified in the cornea, lens, and retina of a normal eye. The increased expression and synthesis of HSP70 induced by cell stress has also been demonstrated in eyes with pathologies such as glaucoma, eye cancers, cataracts, scarring of the cornea, ocular toxpoplasmosis, PEX, AMD, RPE, and diabetic retinopathy. Most of the studies cited in this paper confirm the protective role of HSP70. However, little is known about these molecules in the human eye and their role in the pathogenesis of eye diseases. Therefore, understanding the role of HSP70 in the pathophysiology of injuries to the cornea, lens, and retina is essential for the development of new therapies aimed at limiting and/or reversing the processes that cause damage to the eye.

Development of Automated Physical Defect Inspection Systems in Greige Tarpaulin Fabric Based on Machine Learning Algorithms

The textile industries in Indonesia have challenges, one of which is improving the efficiency of processes. PT NTX is a weaving industry company that produces gray tarpaulin textile products. In this industry, the inspection process for gray cloth resulting from the weaving process is generally carried out conventionally, using a cloth inspection machine and visually with the human eye. Traditional inspection methods cannot be applied to greige tarpaulin textile products since the characteristics of the greige tarpaulin textile are very prone to shifting or slipping of the woven thread construction if it is pulled, touched, or rewound. The process of detecting defects and quality control of greige tarpaulin textile products is carried out by the operator on the loom during the weaving process. This process, of course, will result in the need for inspection operators with high skills, and the consistency of inspection results is very dependent on the condition of the inspection operator. This research has used image processing techniques based on machine learning algorithms to overcome this problem by examining the product directly on the machine. This research has used the Mean Pixel Value method combined with the Logistic Regression Model and the Local Binary Pattern method combined with the Support Vector Machine as image process techniques. Based on the research results, the Mean Pixel Value method combined with the Logistic Regression Model had an accuracy rate of 61% on greige tarpaulin images, and the Local Binary Pattern method with the Support Vector Machine had an accuracy rate of 68%.

HISTORICAL ANALYSIS OF SPECIES AND COLOR IN ANTHROPOCENTRIC PROVERBS

The world around us is always colored in one way or another, and then, of course, we need to use terms to define color. The dictionary of any language always contains a limited number of color names (usually 100-150). In this case, the human eye can distinguish several times more colors (up to 100,000 shades). Color is of great importance in the life of a modern person. Often, people’s mood, emotions, and even physical well-being directly depend on this. This explains why research in the field of color is so popular among psychologists. However, when considering certain aspects, experts often overlook the deep historical and cultural experience of a person who constantly strives to name the objects and phenomena that surround him. This article examines the conceptual features of flowers in proverbs and sayings. The article examines from a historical point of view the poetic features of anthropocentric proverbs with black and white colors and concludes that they form the basis of a stable antonymy that helps to understand the features of the artistic image of the world, as well as clarify philosophical and aesthetic points of view. The relevance of the study lies in the fact that black and white colors are little studied in proverbs and sayings. To continue and complement these studies, the authors focus on the color palette of proverbs when conducting the study. The color scheme is ideological and thematic, attracts characteristic sharp contrasts, and most importantly performs certain functions. It is proved that the values «black» and «white» can have both positive and negative characteristics.

EVALUATION OF EFFICACY OF COLOUR CORRECTED LIGHT SOURCE IN DETERMINING THE ACCURACY OF SHADE MATCHING DONE WITH A COMMONLY USED SHADE GUIDE SYSTEM BY CONVENTIONAL VISUAL METHOD AND AN INTRA ORAL SPECTROPHOTOMETER

Aim: The objective of this study was to evaluate the efficiency of colour corrected light source in shade matching and to determine accuracies and inter-rater agreement of three shade matching methods (conventional visual method, visual method using colour corrected light source and spectrophotometric method). Methodology: In the conventional visual method and the visual method using colour corrected light source, four examiners with normal colour vision matched five target control shade tabs taken from the VITAPAN 3D MasterTM shade guide, with other full set of the same shade guide. Shade matching with the colour corrected light source was done under daylight mode simulating 5500K or natural daylight. Each tab was matched three times to determine repeatability of visual examiners. In the spectrophotometric method, two independent examiners matched the control tabs with three repetitions for each tab. The data was collected and statistical analysis was performed. Results: Visual method using colour corrected light source produced more accurate results (80%) than the conventional visual method (68.3%) and spectrophotometric method (0%), thus proving the efficacy of colour corrected light source (p<0.05). All three methods exhibited poor inter-rater agreement. Conclusion: The question is whether handheld light correcting devices and digital assessments are clinically useful or are they unreliable andunnecessary costly. Even though visual shade matching is subjective, it is not inferior and should not be underrated. The low accuracy value obtained for the spectrophotometer may be a misrepresentation of the machines capabilities due to its inability to measure any reading asclose to the correct value. If both analyses are combined, digital determination of the basic shade and visual determination of the effects, can provide the best possible esthetic outcome. Although human eye will be the finalarbitrator, success can best be achieved by combining traditional artistic techniques with advancements in technology, complemented with innovations in colour-related research, education, and training of dental professionals.

Deteksi Tingkat Kematangan Buah Tomat Dengan Transformasi Ruang Warna HSI

Among the vegetables most commonly consumed by people around the world are tomatoes. One of the potential vegetable commodities to be developed is tomato plants. This plant can thrive in rice fields, dry land, and highlands. Use of Technology Digital images are images that can be processed by computers directly. A matrix with M columns and N rows can be used to describe a digital image. The smallest element in an image is called a pixel or image element, and is the intersection between columns and rows. image processing is the process of processing an image numerically; in this case, each pixel or point in the image is treated. One method of image processing is to use computer software to process each pixel in the image. It is easier for object recognition applications in image processing to identify objects based on differences in hue values when the hue values of objects are limited to a certain value. The color space system that mimics the capabilities of the human eye is called the HSI color space model. HSI incorporates the grayscale or color components of an image. The test image of Tomato fruit with a value of H = 32 S = 0.675 I = 83 can be considered ripe, according to the range of fruit reference values that have been established through the use of the HSI method.

Integrating eye rotation and contrast sensitivity into image quality evaluation of virtual reality head-mounted displays

Visual perception on virtual reality head-mounted displays (VR HMDs) involves human vision in the imaging pipeline. Image quality evaluation of VR HMDs may need to be expanded from optical bench testing by incorporating human visual perception. In this study, we implement a 5-degree-of-freedom (5DoF) experimental setup that simulates the human eye geometry and rotation mechanism. Optical modulation transfer function (MTF) measurements are performed using various camera rotation configurations namely pupil rotation, eye rotation, and eye rotation with angle kappa of the human visual system. The measured MTFs of the VR HMD are inserted into a human eye contrast sensitivity model to predict the perceptual contrast sensitivity function (CSF) on a VR HMD. At the same time, we develop a WebXR test platform to perform human observer experiments. Monocular CSFs of human subjects with different interpupillary distance (IPD) are extracted and compared with those calculated from optical MTF measurements. The result shows that image quality, measured as MTF and CSF, degrades at the periphery of display field of view, especially for subjects with an IPD different than that of the HMD. We observed that both the shift of visual point on the HMD eyepiece and the angle between the optical axes of the eye and eyepiece degrade image quality due to optical aberration. The computed CSFs from optical measurement correlates with those of the human observer experiment, with the optimal correlation achieved using the eye rotation with angle kappa setup. The finding demonstrates that more precise image quality assessment can be achieved by integrating eye rotation and human eye contrast sensitivity into optical bench testing.

Method for determination of the spectral mismatch correction factors for the luminous responsivity of photometers when measuring the characteristics of LED lamps

This paper describes the challenges associated with the metrology of LED sources. The main problem is the difference between the spectra of LED lamps and the spectrums of reference lamps, which are mainly highly stable and well-reproducible incandescent lamps. The difference in spectra leads to the fact that the luminous responsivity of the calibrated photometer will be different for the reference incandescent lamp and for the LED lamp. The difference is caused by the fact that a relative spectral characteristic of the photometer responsivity is always different from the spectral responsivity of the human eye (V(λ) curve), which determines all luminous quantities. The greater the difference between the relative spectral responsivity of the photometer and V(λ) is, the more the luminous responsivity of the photometer will differ for the reference lamp and for the LED lamp. The paper describes a method developed at the NSC “Institute of Metrology” for experimental determination of mismatch correction factors of luminous responsivity that account for the difference in the LED spectra to solve the problems of metrological support of LED sources. Methods of experimental study of mismatch correction factors for measuring instruments of luminous quantities of LED radiation sources are presented.

Lutein, a carotenoid found in numerous plants and the human eye, demonstrates the capacity to bundle collagen fibrils

Collagen fibrils serve as the building blocks of the extracellular matrix, providing a resilient and structural framework for tissues. However, the bundling of collagen fibrils is of paramount importance in maintaining the structural integrity and functionality of various tissues in the human body. In this scenario, there is limited exploration of molecules that promote the bundling of collagen fibrils. Investigating the interactions of well-known carotenoids, commonly associated with ocular health, particularly in the retina, with collagen presents a novel and significant area of study. Here, we studied the influence of lutein, a well-known carotenoid present in many plant tissues and has several biological properties, on the structure, thermal stability, self-assembly, and fibrillation of collagen. Fibrillation kinetics and electron microscopic analyses indicated that lutein did not interfere with fibrillation process of collagen, whereas it enhances the lateral fusion of collagen fibrils leading to the formation of compact bundles of thick fibrils under physiological conditions. The hydrophobic and hydrogen bonding interactions between lutein and collagen fibrils are most likely the cause of the bundling of the fibrils. This study establishes the first investigation of collagen-carotenoid interactions, showcasing the unique property of lutein in bundling collagen fibrils, which may find potential application in tissue engineering.

Visually encoding orthogonal planar graph drawings as graph mazes: An eye tracking study

There are various styles to visually represent relational data in the form of node-link diagrams. In particular, for planar graphs we can find orthogonal node-link diagrams consisting of links bending only at ninety degrees a successful and prominent variant. One of the benefits of such drawings is the tracking of longer paths through a network with the eyes due to their limited number of link orientations, changes, and variations, but on the negative side the links can have arbitrary bending shapes. In this article we developed a novel way to visualize such orthogonal planar drawings by making use of mazes that look more natural to the human eye due to the street-like visual metaphor that many people are familiar with. Tracking paths is one of the major tasks in such graph visualizations, similar to orthogonal node-link diagrams, however, we argue that mazes are a more natural way to find paths. To get insights in the visual scanning behavior when reading graph mazes we conducted a comparative eye tracking study with 26 male versus female participants of different experience levels while also alternating between orthogonal node-link drawings and graph mazes as well as different graph size levels. The major result of this comparative study is that the participants can track paths in both representation styles, including a geodesic path tendency in their visual search behavior, but typically have a longer fixation duration at branching nodes and locations in the mazes that lead to opposite directions to the geodesic path tendency, maybe the viewers had to start a reorientation phase in their visual scanning behavior. We also found out that the size, that is the number of graph vertices has an impact on the visual scanning behavior for both orthogonal node-link diagrams as well as street-like maze representations, but for the mazes we found this impact to be less strong (in terms of the eye movement data metrics fixation durations and saccade lengths) compared to the node-link diagrams. To conclude the article, we discuss limitations and scalability issues of our approach. Moreover, we give an outlook and future work for possible extensions.

Linear Regression Based Machine Learning Model for Cataract Disease Prediction

Blindness and visual impairment have become major health problems today, with one major source of impairment being the formation of cataract disease. Cataract disease affects around 20 million individuals worldwide, with three out of every four being above the age of 60. A cataract is a clouding of the lens that impairs vision and can lead to blindness. Accurate and convenient detection of cataracts is essential for improving this condition. This paper presents a model based on linear regression to predict the presence of cataracts from images of the human eye. Experiments were conducted to validate the model. Various image processing techniques have also been used to perform image preprocessing and contrast enhancement, with patients notified about their eye health via SMS.