Low Contrast Conditions Research Articles

Improving Functional Connectivity in Developmental Dyslexia through Combined Neurofeedback and Visual Training

This study examined the effects of combined neurofeedback (NF) and visual training (VT) on children with developmental dyslexia (DD). Although NF is the first noninvasive approach to support neurological disorders, the mechanisms of its effects on the brain functional connectivity are still unclear. A key question is whether the functional connectivities of the EEG frequency networks change after the combined NF–VT training of DD children (postD). NF sessions of voluntary α/θ rhythm control were applied in a low-spatial-frequency (LSF) illusion contrast discrimination, which provides feedback with visual cues to improve the brain signals and cognitive abilities in DD children. The measures of connectivity, which are defined by small-world propensity, were sensitive to the properties of the brain electrical oscillations in the quantitative EEG-NF training. In the high-contrast LSF illusion, the z-NF reduced the α/θ scores in the frontal areas, and in the right ventral temporal, occipital–temporal, and middle occipital areas in the postD (vs. the preD) because of their suppression in the local hub θ-network and the altered global characteristics of the functional θ-frequency network. In the low-contrast condition, the z-NF stimulated increases in the α/θ scores, which induced hubs in the left-side α-frequency network of the postD, and changes in the global characteristics of the functional α-frequency network. Because of the anterior, superior, and middle temporal deficits affecting the ventral and occipital–temporal pathways, the z-NF–VT compensated for the more ventral brain regions, mainly in the left hemispheres of the postD group in the low-contrast LSF illusion. Compared to pretraining, the NF–VT increased the segregation of the α, β (low-contrast), and θ networks (high-contrast), as well as the γ2-network integration (both contrasts) after the termination of the training of the children with developmental dyslexia. The remediation compensated more for the dorsal (prefrontal, premotor, occipital–parietal connectivities) dysfunction of the θ network in the developmental dyslexia in the high-contrast LSF illusion. Our findings provide neurobehavioral evidence for the exquisite brain functional plasticity and direct effect of NF–VT on cognitive disabilities in DD children.

Effects of glaucoma on detection and discrimination of image blur.

PurposeBlur is one of the most commonly reported visual symptoms of glaucoma, but it is not directly measured by current clinical tests. We aimed to investigate the effects of glaucoma on detection and discrimination of image blur.MethodsParticipants were people with glaucoma, separated into two groups with (n = 15) or without (n = 17) central visual field defects measured by 10–2 perimetry, and an age‐similar control group (n = 18). First, we measured contrast detection thresholds centrally using a 2‐interval forced choice procedure. We then measured blur detection and discrimination thresholds for the same stimuli (reference blurs 0, 1 arcmin) using a 2‐alternative forced choice procedure under two contrast conditions: 4× individual detection threshold for the low contrast condition; 95% contrast for the high contrast condition. The stimulus was a horizontal edge bisecting a hard‐edged circle of 4.5° diameter. Data were analysed by linear mixed modelling.ResultsContrast detection thresholds for the glaucoma group with central visual field defects were raised by 0.01 ± 0.004 (mean ± SE, Michelson units) (p = 0.002) and by 0.01 ± 0.004 (p = 0.03) relative to control and glaucoma without central visual field defect groups, respectively. Blur detection and discrimination thresholds were similar between groups, with small elevations in blur detection thresholds in the glaucoma groups not reaching statistical significance (detection p = 0.29, discrimination p = 0.91). The lower contrast level increased thresholds from the higher contrast level by 1.30 ± 0.10 arcmin (p < 0.001) and 1.05 ± 0.10 arcmin (p < 0.001) for blur detection and discrimination thresholds, respectively.ConclusionsEarly‐moderate glaucoma resulted in only minimal elevations of blur detection thresholds that did not reach statistical significance in this study. Despite the prevalence of blur as a visual symptom of glaucoma, psychophysical measurements of blur detection or discrimination may not be good candidates for development as clinical tests for glaucoma.

What Is the Mechanism Underlying the Interleaving Effect in Category Induction: An Eye-Tracking and Behavioral Study

Interleaved practice (i.e., exemplars from different categories are intermixed within blocks) has been shown to enhance induction performance compared to blocked practice (i.e., exemplars from the same category are presented sequentially). The main aim of the present study was to examine explanations of why interleaved practice produces this benefit in category induction (known as the interleaving effect). We also evaluated two hypotheses, the attention attenuation hypothesis and the discriminative-contrast hypothesis, by collecting data on participants’ fixation on exemplars, provided by eye-tracking data, and manipulating the degree of discriminative-contrast. In Experiments 1 and 2, participants were instructed to learn the style of 12 new artists in blocked and interleaved practice in fixed-paced and self-paced learning conditions, respectively. We examined fixation durations for six positions (temporal sequence of exemplars presented in each block) using eye-tracking. The results of the two experiments, based on eye-tracking data, suggested that attention attenuation may not be the primary mechanism underlying the interleaving effect in category induction. In Experiment 3, we manipulated the degree of discriminative-contrast to examine the impact on the interleaving effect in category induction. The results showed that the main effect of the degree of discriminative-contrast was significant, and performance in the high-contrast condition was significantly better than those in the medium-contrast and low-contrast conditions. Thus, the current results support the discriminative-contrast hypothesis rather than the attention attenuation hypothesis.

Оценка зрительных функций и сумеречного зрения у пациентов после имплантации различных видов ИОЛ

Purpose. To compare NCOSIS in the distance, at an average distance and near, twilight vision and sensitivity to blinding in patients after implantation of various IOL models. Materials and methods. Сataract phacoemulsification was performed in 60 patients, Hoya iSert 250 IOL was implanted in Group I, Lentis Comfort IOL was implanted in Group II, Acrysof IQ PanOptix IOL was implanted in Group III. In the postoperative period, twilight vision and sensitivity to bright light were evaluated. Results. The threshold value with a contrast level of 1: 23 and 1: 5 without illumination was achieved in patients of all the studied groups in 100% of cases; with a contrast of 1:2 in 90% of cases in patients of group I, in 80% of cases-in patients of group II and III; with a contrast of 1:2.7 in 60% of groups I and II, in 50% in patients of group III. The threshold value with a contrast level of 1:23 was achieved in patients of all the studied groups in 100% of cases, with a contrast of 1:5 in 100% of cases in patients of groups I and III, in patients of group II in 80% of cases; with a contrast of 1:2.7 with illumination in 80% of patients of group I and 60% of patients of groups II and III; with a contrast of 1:2 and illumination in 50% of patients of group I, 40% of group II and 20% of patients of group III of the study. Conclusion. Under mesopic conditions with high contrast indicators, all three types of IOLs show equally high results of visual quality. In light conditions, monofocal IOL allows you to get a higher quality of vision in low contrast conditions, at high and medium levels, IOL indicators do not differ statistically significantly, with a significantly larger range of vision in bifocal and multifocal IOLs. Key words: cataract phacoemulsification, intraocular lenses, twilight vision.

Self-reported driving difficulty in patients with bilateral cataract

PurposeThe presence of cataract causes reduction in visual acuity (VA) and contrast sensitivity (CS) and thus can affect individual's daily activities. The aim of this study was to investigate self-reported driving difficulty in patients with bilateral cataract. MethodsA total of 99 participants aged 50 and above, with bilateral cataract, who possessed a valid driving license and drove regularly were chosen for this cross-sectional study that looked into their visual functions (VA and CS) and driving difficulty using the self-reported Driving Difficulty Questionnaire. ResultsThe mean age of the participants was 65.04±7.22 years old. Results showed that the mean composite driving difficulty score was 83.18±11.74 and most of the participants were having difficulty for driving in the rain (73.7%) and at night (85.9%). Furthermore, the study found that there was a significant correlation between driving difficulty score and CS (rs = 0.40, p = 0.03). However, there was no significant correlation between driving difficulty score and VA (rs = -0.14, p = 0.17). A linear regression was calculated to predict driving difficulty score based on binocular CS and a significant regression equation was found (F (1,28) = 8.115, p = 0.008) with R² of 0.225. Drivers with bilateral cataract will most likely experience some forms of difficulty, especially when driving under low contrast conditions. ConclusionThe findings of this study demand that a comprehensive eye examination should be made compulsory for older adult drivers when issuing or renewing their driving license for the safety of all road users.

Comparison of visual performance between extended depth of focus contact lens and single-vision contact lens in eyes with monofocal intraocular lens.

To assess the visual performance of extended depth of focus (EDF) contact lenses (CL) in eyes that had undergone monofocal intraocular lens (IOL) implantation, and compare that between EDF and single-vision (SV) contact lenses. Prospective, randomized, crossover study METHODS: Seventeen patients implanted with monofocal IOLs were enrolled. The study was conducted using 1dayPure EDOF as a test CL and 1dayPure moisture (both SEED Co., Ltd.) as a control CL. Binocular visual acuity from far to near distances, photopic and mesopic contrast sensitivity (with and without glare), and stereopsis were evaluated after wearing the two kinds of CLs in random order. The obtained results were compared between the EDF and SV CLs. Binocular visual acuity at 0.3, 0.4, 0.7, 1, and 5m was 0.24 ± 0.12, 0.07 ± 0.09, - 0.02 ± 0.08, - 0.02 ± 0.08, and - 0.06 ± 0.07 logMAR during the EDF CL wear, respectively, and 0.39 ± 0.17, 0.26 ± 0.15, 0.04 ± 0.12, - 0.02 ± 0.08, and - 0.09 ± 0.09 during the SV CL wear, respectively. The EDF CL showed better results than the SV CL at 0.3, 0.4, and 0.7m (p < 0.05). There were no significant differences in contrast sensitivity between the EDF and SV CLs at 1.5 cycles per degree under all conditions; however, the sensitivity of the EDF CL was generally worse than that of the SV CL from the middle to high spatial frequencies. Stereopsis at 40cm was significantly better in the EDF CL wear than in the SV CL wear (p < 0.05). The EDF CL substantially improved visual acuity at near to intermediate distances in IOL-implanted eyes. However, far visual acuity decreased under low-contrast conditions, and contrast sensitivity slightly declined at the middle to high spatial frequencies.

Оценка контрастной чувствительности у пациентов после имплантации моно- и бифокальных ИОЛ

Purpose. To perform a comparative analysis of contrast sensitivity and glare sensitivity in patients implanted with mono- and bifocal IOLs. Material and methods. 60 patients (60 eyes) were examined: 30 cataract patients who underwent cataract phacoemulsification with bifocal IOL Lentis Comfort implantation; and 30 cataract patients who underwent cataract phacoemulsification with monofocal IOL Acrysof IQ implantation. In the post-operative period the examination of twilight vision and bright light sensitivity was carried out using a Binoptometer 4P visual function analyzer. Results. In patient of group I without flare with a contrast 1:23, the threshold value was achieved in 97.4% of patients, with a contrast 1:5 – in 87.6%; with a contrast 1:2.7 – in 49.2%; with a contrast 1:2 – in 38.3%; with flare and contrast 1:23 – in 90.3%; with flare and contrast 1:5 – in 84.8%; with flare and contrast 1:2.7 – in 41.2%; with flare and contrast 1:2 – in 22.8%. In patients of group II: without flare and with contrast 1:23 – in 98.6%; with a contrast 1:5 – in 90.1%; with a contrast 1:1.27 – in 61.9%, with a contrast – 1:2 – 44.5%; with flare and contrast 1:23 – in 95.6%; with flare and contrast 1:5 – in 86.9%; with flare and contrast 1:2.7 – in 48.7%; with flare and contrast 1:2 – in 40.5% Conclusions. In mesopic conditions IOL Acrysof IQ provides higher visual acuity in low contrast conditions with a slight decrease under flare conditions in comparison with IOL Lentis Comfort. Key words: contrast sensitivity, cataract phacoemulsification, bifocal IOL.

Evaluation of site amplification factors for shallow rock sites of Islamabad, Pakistan.

Current seismic provisions in Building Code of Pakistan (BCP-2007), seismic site classifications, and corresponding site amplification factors were determined similar to Uniform Building Code (UBC-1997), which were based on the local site conditions of Western United States with low impedance contrast, deep sites, and high seismicity conditions. The use of these deep sites based amplification factors to the shallow sites may not be appropriate to capture shallow sites' response. In this study, we performed a non-linear site-specific response analysis suite to compute the amplification factors for the six (06) representative shallow bedrock sites of Islamabad, Pakistan. The computed amplification factors are compared with BCP-2007 code-based design estimates; it is found that BCP-2007 code-based guidelines underestimate amplification factors at a short period whereas overestimating at an extended period. The study's findings highlight the potential implications of current code-based amplification factors for Islamabad's shallow sites and suggest improving the current seismic guidelines.

Visual Performance of Center-distance Multifocal Contact Lenses Fit Using a Myopia Control Paradigm.

The purpose of this study was to examine the visual performance of center-distance MFCLs in nonpresbyopic adults under different illumination and contrast conditions compared with a single-vision contact lens (SVCL). Twenty-five adult subjects were fit with three different lenses (CooperVision Biofinity D MFCL +2.50 add, Visioneering Technologies NaturalVue MFCL, CooperVision Biofinity sphere). Acuity and reading performance were evaluated. A statistically significant difference in high-contrast distance acuity was observed (Biofinity, -0.18 ± 0.06; Biofinity MFCL, -0.14 ± 0.08; NaturalVue MFCL, -0.15 ± 0.03; repeated-measures [RM] ANOVA, P = .02). Under mesopic, high-contrast conditions, MFCLs performed worse than SVCLs (Biofinity, -0.05 ± 0.091; Biofinity MFCL, +0.03 ± 0.09; NaturalVue MFCL, +0.05 ± 0.091; RM-ANOVA, P < .0001). Under low-contrast conditions, MFCLs performed one line worse in photopic lighting and two lines worse under mesopic conditions (RM-ANOVA, P < .0001). Glare reduced acuity by 0.5 logMAR for all lenses (RM-ANOVA, P < .001). A statistically significant difference in near acuity was observed (RM-ANOVA, P = .02), but all lenses achieved acuity better than -0.1 logMAR (Biofinity, -0.16 ± 0.06; Biofinity MFCL, -0.17 ± 0.04; NaturalVue MFCL, -0.13 ± 0.08). Reading performance in words per minute (wpm) was worse with MFCLs (Biofinity MFCL, 144 ± 22 wpm; NaturalVue MFCL, 150 ± 28 wpm) than with SVCLs (156 ± 23 wpm; RM-ANOVA, P = .02) regardless of letter size (RM-ANOVA, P = .13). No difference in acuity between the MFCLs was detected (RM-ANOVA: all, P > .05). Multifocal contact lenses perform similarly to SVCLs for high-contrast targets and display reduced low-contrast acuity and reading speed. Practitioners should recognize that high-contrast acuity alone does not describe MFCL visual performance.

High Contrast Allows the Retina to Compute More Than Just Contrast.

The goal of sensory processing is to represent the environment of an animal. All sensory systems share a similar constraint: they need to encode a wide range of stimulus magnitudes within their narrow neuronal response range. The most efficient way, exploited by even the simplest nervous systems, is to encode relative changes in stimulus magnitude rather than the absolute magnitudes. For instance, the retina encodes contrast, which are the variations of light intensity occurring in time and in space. From this perspective, it is easy to understand why the bright plumage of a moving bird gains a lot of attention, while an octopus remains motionless and mimics its surroundings for concealment. Stronger contrasts simply cause stronger visual signals. However, the gains in retinal performance associated with higher contrast are far more than what can be attributed to just a trivial linear increase in signal strength. Here we discuss how this improvement in performance is reflected throughout different parts of the neural circuitry, within its neural code and how high contrast activates many non-linear mechanisms to unlock several sophisticated retinal computations that are virtually impossible in low contrast conditions.

Assessment of the image quality of virtual monochromatic spectral computed tomography images: a phantom study considering object contrast, radiation dose, and frequency characteristics.

Fast kilovoltage (kVp)-switching technology cannot obtain conventional 120kVp images; thus, 70keV virtual monochromatic spectral computed tomography (CT) images (VMSI) are generally used. The contrast-to-noise ratio (CNR) is used to evaluate the image quality of VMSI; however, CNR does not include frequency characteristics. The present study aimed to investigate the evaluation methods of VMSI considering frequency characteristics by comparing the image quality of 70keV VMSI with that of conventional 120kVp images. The evaluated object contrasts were 70 and 300 Hounsfield units (HU). Scans used two radiation dose levels: low (LD) and standard (SD). The volume CT dose index of LD and SD was 4.8- and 12mGy, respectively. Images were reconstructed by filtered back projection, evaluating CNR, noise power spectrum (NPS), task transfer function (TTF), and system performance (SP) function calculated as TTF2/ NPS. The total NPS values (spatial frequency range: 0.2 ~ 0.4mm-1) of 70keV VMSI were higher than those of 120kVp images. The spatial frequency TTF values that reached 10% (f10%) of the 70keV VMSI changed based on object contrast. For the low-contrast condition, a lower f10% was observed with 70keV VMSI. The CNR of 70keV VMSI was comparable to that of 120kVp images in low- and high-contrast conditions. However, for 70keV VMSI, SP of low-contrast was low, and SP of high-contrast was high, compared with those of 120kVp images. This study suggested that only CNR was not sufficient to evaluate the image quality of VMSI; thus, evaluation methods considering frequency characteristics should be used.

Salient target detection algorithm based on dual-channel multi-scale pyramid pooling model

To improve the detection accuracy for armored targets in complex environment, a salient target detection algorithm was proposed. The low-level features and multi-scale pooling semantic features constrained by visual attention mechanism were respectively obtained by visual attention mechanism and joint pyramid upsampling module. Then the aggregation strategy was used to fuse, so as to improve the ability of target representation in low contrast or occlusion conditions. The experimental results show that the proposed algorithm obtains good detection results for multi-scale targets in complex scenes, the precision, recall rate and mean average precision (mAP) are 72.2%, 71.4% and 77.1%, respectively, which can meet the practical application requirements.

Contrast Enhancement for Improved Detection of Ananas Comosus from Aerial Imagery

This paper describes contrast enhancement method used in detecting Ananas Comosus from aerial images. The main challenge faced by many researchers is to deal with image under low contrast conditions. Under low contrast, target images of Ananas Comosus often blends with the background features such as leaves and ground, making detection difficult. This study is set out to investigate the usefulness of implementing contrast enhancement technique on existing image to improve detection performance. Aerial images under study were obtained at Simpang Renggam pineapple plantation using DJI Phantom 3 and subjected to two image pre-processing methods-intensity adjustment method and contrast-limited adaptive histogram equalization methods. As a control, these images were also evaluated against pre-processing method without any contrast enhancement. The performance of the techniques for detecting Ananas Comosus is then assessed using relative error, RE and mean absolute percentage, MAPE. The best results were obtained by using contrast-limited adaptive histogram equalization method; yielding RE of 0.125 and MAPE of 0.008% compared to intensity adjustment technique yielding maximum RE of 0.286 and MAPE of 0.027%. Meanwhile detection without image enhancement had resulted maximum RE of 0.250 and MAPE is 0.024%.

A Fully Automated Method for Segmenting Arteries and Quantifying Vessel Radii on Magnetic Resonance Angiography Images of Varying Projection Thickness.

PurposePrecise quantification of cerebral arteries can help with differentiation and prognostication of cerebrovascular disease. Existing image processing and segmentation algorithms for magnetic resonance angiography (MRA) are limited to the analysis of either 2D maximum intensity projection images or the entire 3D volume. The goal of this study was to develop a fully automated, hybrid 2D-3D method for robust segmentation of arteries and accurate quantification of vessel radii using MRA at varying projection thicknesses.MethodsA novel algorithm that employs an adaptive Frangi filter for segmentation of vessels followed by estimation of vessel radii is presented. The method was evaluated on MRA datasets and corresponding manual segmentations from three healthy subjects for various projection thicknesses. In addition, the vessel metrics were computed in four additional subjects. Three synthetically generated angiographic datasets resembling brain vasculature were also evaluated under different noise levels. Dice similarity coefficient, Jaccard Index, F-score, and concordance correlation coefficient were used to measure the segmentation accuracy of manual versus automatic segmentation.ResultsOur new adaptive filter rendered accurate representations of vessels, maintained accurate vessel radii, and corresponded better to manual segmentation at different projection thicknesses than prior methods. Validation with synthetic datasets under low contrast and noisy conditions revealed accurate quantification of vessels without distortions.ConclusionWe have demonstrated a method for automatic segmentation of vascular trees and the subsequent generation of a vessel radii map. This novel technique can be applied to analyze arterial structures in healthy and diseased populations and improve the characterization of vascular integrity.

ENERGY EFFICIENCY OF A SYSTEM FOR PRIMARY PROCESSING OF SIGNALS IN AN OPTO-ELECTRONIC DEVICE OPERATION UNDER LOW-CONTRAST CONDITIONS

The energy efficiency of systems for primary processing of signals in optoelectronic devices is analyzed for the case of identification and study of remote objects against a bright background and under low-contrast conditions. A criterion is determined for evaluating the energy efficiency of the major unit of the system for primary signal processing the optic system, and some expressions are derived, relating the value of the signal-to-noise ratio at the device’s input with these criteria (amplification factor) and other “ideal” or “real” optic systems’ parameters. The specific thing here is the operation of the system for primary processing of signals when the value of recorded contrast equals 1 percent or less. As an evaluation criterion for the energy efficiency of this system, the signal-to-noise ratio is used. Comparative evaluation of various systems for primary processing of signals operating under low-contrast conditions and specific values of the signal-to-noise ratio is performed. The operation analysis for the system for primary processing of information (signals) under low-contrast conditions is performed accounting for the impact of the optic system. The evaluation criterion for the energy efficiency of the major unit of the system for primary processing of information (the optic system) is the amplification factor, which determines the limit value for the signal-to-noise ratio at the output of the optic-electronic device. The assumption is made that the flow, which determines the circle’s area, is uniformly distributed, which does not cause significant errors in evaluating the energy efficiency of the optic- electronic system.

Revisiting contextual cueing effects: The role of perceptual processing.

Incidental learning of invariant configurations of items can facilitate visual search, which is termed contextual cueing effect. Previous debates about the mechanisms of the contextual cueing effect mainly focused on the roles of attentional guidance and response-related components. Because the time for perceiving displays is very short, few studies have revealed the role of initial perceptual processing. Thus, in the present study, we manipulated the key variable of display contrast to prolong the perceptual processing duration in low-contrast displays. With response-time and eye-movement recording, the study explored the role of initial perceptual processing. In addition, we examined the roles of attentional guidance and response-related components. From three experiments we found: In addition to the role of attentional guidance, the initial perceptual processing could also contribute to a contextual cueing effect in a low-contrast condition; there was only the facilitation from attentional guidance in a high-contrast condition. These results suggest that perceptual processing can also play a role if the perceptual processing time is prolonged, but the main role involves improved attentional guidance.

Diagnostic and Gradation Model of Osteoporosis Based on Improved Deep U-Net Network.

The measurement of bone mineral density for osteoporosis has always been the focus of researchers because it plays an important role in bone disease diagnosis. However, because of X-ray image noise and the large difference between the bone shapes of patients under the condition of low contrast, existing osteoporosis diagnosis algorithms are difficult to obtain satisfactory results. This paper presents an improved osteoporosis diagnosis algorithm based on U-NET network. Firstly, the bone in the original image are marked and used to construct the data set. And then, by normalizing the input of each layer, it can be ensured that the input data distribution of each layer is stable, so that the purpose of accelerated training can be achieved. Finally, the energy function is calculated by combining the value of the softmax prediction class for each pixel on the final feature map with the Cross entropy loss function and all the segmented images are extracted to obtain the diagnostic result. As the experimental results show that the improved U-net can accurately solve the influence of image interference in the process of bone mineral density measurement. The recognition rate of U-net automatic diagnosis method is above 81%, and the diagnosis effect is better than other comparison methods.

A New Self-Reference Image Decomposition Algorithm for Strip Steel Surface Defect Detection

Automatic vision-based defect detection on the steel surface is a challenging task due to miscellaneous patterns of defects, low contrast between the defect and the background, and so on. Image-decomposition-based method can analyze the structure and texture to inspect the defective objects. Currently, the state of the art of image decomposition-based defect detection methods is the one guided by a given fixed template. However, a fixed template cannot be suitable for all situations. In this article, a new self-reference template-guided image decomposition algorithm for strip steel surface defect detection is developed. Combined with the statistical characteristics of a large number of defect-free images, a specific template can be built for each test defect image. Then, a total variation (TV)-based image decomposition algorithm guided by the self-reference template is developed to decompose the test image into the structural component and textural component. Moreover, the decomposition is optimized by developing a new index-gradient similarity to measure the similarity between the self-reference template and decomposed textural component. Experimental results show that the proposed method can detect various types of defects on the homogeneously textured surface, including miscellaneous defects, even for tiny defects and under the low contrast condition, and the precision, recall, and F-measure of the proposed algorithm are better than the state-of-the-art algorithms.

Visual Performance and High-Order Aberrations with Different Contact Lens Prototypes with Potential for Myopia Control

ABSTRACT Purpose Contact lenses (CLs) used for myopia control incorporate variable power distribution across the optic zone potentially creating degradation of the high-order aberrations. The present study aims to evaluate the retinal image quality and visual performance in three prototypes of CLs intended to control axial elongation of the eye before they are considered for clinical trials. Methods This is a non-dispensing cross-over, double-blind study where 30 right eyes of myopic subjects worn 3 multifocal test lenses and 1 monofocal control lens in random order. Lens 1 was a radial refractive gradient design (center distance) and Lens 2 and 3 center-near with an additional annular ring for near. Nominal add power was 2.00D, 1.50D, and 2.00D, respectively. Subjects had an age 21.96 ± 2.23 years [18–30] and mean spherical equivalent refraction M = −2.23 ± 1.50D [−0.75 to −5.50] with refractive astigmatism below −0.75D. Higher-order aberrations (HOA), glare formation (halo), high- and low-contrast LogMAR visual acuity (VA), and contrast sensitivity function (CSF) was measured under monocular conditions. Results All individual terms of HOA and total root mean square from 3rd to 8th order increased significantly with the 3 test lenses compared to control. Between test lenses, Lens 1 increased significantly the higher HOA compared with Lens 2 and Lens 3. Halo size was significantly larger with test lenses compared with control, with Lens 1 showing the largest. VA under high-contrast conditions was similar for all lenses. Under low-contrast conditions, Lens 1 and Lens 2 performed significantly worse than control (Bonferroni post hoc correction, p < 0.001). CSF was below normal limits with Lens 1 for 3 and 6 cpd spatial frequency but was not significantly different between test lenses and control. Conclusions Lenses with larger stabilized areas for distance vision interfere less with VA and induce lower values of HOA and image degradation.

AUTOMATION OF RESEARCH AREA RECOGNITION UNDER WEAK- CONTRAST BORDERS ON A PICTURE OF TRANSPARENT OBJECTS

Recently, due to the active development of computer technologies, in the field of science dealing with visual objects, there are problems of creating systems for automatic image recognition. This class of problems does not have a universal way of solving and this leads to the fact that, depending on the needs of a particular branch of science and engineering, the developers of such systems are forced to solve problems of a private nature.&#x0D; The purpose of this work is to create a software product by the authors that would allow automatic recognition of the study area of objects having a weakly expressed boundary between the separation of object and background to further determine the values of the optical characteristics of transparent objects, as common features in identification trace evidence analysis the whole by parts.&#x0D; One of the main problems of detecting the boundaries of the separation of objects in an image is the poor contrast of the transition region between adjacent areas of the divided space, which leads to the need for image processing to segment and correct the contrast. To develop an effective way to limit the recognition area and identify the boundaries of the studied object under the condition of low contrast between the light background and the space occupied by a transparent medium, which differs from the background in optical properties, there is a need to analyze existing image enhancement algorithms and their further practical implementation using mathematical software products of numerical analysis.&#x0D; Thus, the paper reviews modern algorithms for image recognition methods and algorithms for changing image quality by segmentation and contrast correction. The proposed algorithms are implemented in a computer program developed by the authors of the Sumy Research Institute of the Ministry of Internal Affairs of Ukraine on the basis of the mathematical software MATLAB, which allows to carry out automatic comparative analysis of the studied samples on the basis of their digital images. The questions posed to the authors for further development of this topic are outlined.