Identification of ocular refraction based on deep learning algorithm as a novel retinoscopy method.

BACKGROUND: The evaluation of refraction is indispensable in ophthalmic clinics, generally requiring a refractor or retinoscopy under cycloplegia. Retinal fundus photographs (RFPs) supply a wealth of information related to the human eye and might provide a promising approach that is more convenient and objective. Here, we aimed to develop and validate a fusion model-based deep learning system (FMDLS) to identify ocular refraction via RFPs and compare with the cycloplegic refraction. In this population-based comparative study, we retrospectively collected 11,973 RFPs from May 1, 2020 to November 20, 2021. The performance of the regression models for sphere and cylinder was evaluated using mean absolute error (MAE). The accuracy, sensitivity, specificity, area under the receiver operating characteristic curve, and F1-score were used to evaluate the classification model of the cylinder axis. RESULTS: Overall, 7873 RFPs were retained for analysis. For sphere and cylinder, the MAE values between the FMDLS and cycloplegic refraction were 0.50 D and 0.31 D, representing an increase of 29.41% and 26.67%, respectively, when compared with the single models. The correlation coefficients (r) were 0.949 and 0.807, respectively. For axis analysis, the accuracy, specificity, sensitivity, and area under the curve value of the classification model were 0.89, 0.941, 0.882, and 0.814, respectively, and the F1-score was 0.88. CONCLUSIONS: The FMDLS successfully identified the ocular refraction in sphere, cylinder, and axis, and showed good agreement with the cycloplegic refraction. The RFPs can provide not only comprehensive fundus information but also the refractive state of the eye, highlighting their potential clinical value.

LFM: A Lightweight LCD Algorithm Based on Feature Matching between Similar Key Frames.

Loop Closure Detection (LCD) is an important technique to improve the accuracy of Simultaneous Localization and Mapping (SLAM). In this paper, we propose an LCD algorithm based on binary classification for feature matching between similar images with deep learning, which greatly improves the accuracy of LCD algorithm. Meanwhile, a novel lightweight convolutional neural network (CNN) is proposed and applied to the target detection task of key frames. On this basis, the key frames are binary classified according to their labels. Finally, similar frames are input into the improved lightweight feature matching network based on Transformer to judge whether the current position is loop closure. The experimental results show that, compared with the traditional method, LFM-LCD has higher accuracy and recall rate in the LCD task of indoor SLAM while ensuring the number of parameters and calculation amount. The research in this paper provides a new direction for LCD of robotic SLAM, which will be further improved with the development of deep learning.

Dual-Arm Coordinated Control Strategy Based on Modified Sliding Mode Impedance Controller.

To meet the high-accuracy position/force control requirements of dual-arm robots for handling a target object, a control algorithm for dual-arm robots based on the modified sliding mode impedance controller MSMIC(tanh) is proposed. First, the combinative kinematics equation of the dual-arm robots and the unified dynamics model combining the manipulated object is established. Second, according to the impedance control motion model for the object, the desired joint angular accelerations of the manipulators are obtained, and the sliding mode controller based on the hyperbolic tangent function as the switch function is introduced to design the coordinated control strategy for dual-arm robots. The stability and convergence of the designed controller are proved according to the Lyapunov function theory. Finally, the operation tasks of the coordinated transport the target object for dual-arm robots are carried out in the simulated experiment environment. Simulation results show that the proposed control scheme can stably output the required internal force and achieve a high-precision trajectory tracking effect while reducing the periodic torque and joint chattering amplitude generated in the conventional sliding mode control algorithm.

Effect of short-term orthokeratology lens or ordinary frame glasses wear on corneal thickness, corneal endothelial cells and vision correction in adolescents with low to moderate myopia.

BACKGROUND: We aimed to investigate the effect of short-term orthokeratology lens or frame glasses wear on corneal thickness, corneal endothelial cells and vision correction in adolescents with low to moderate myopia. METHODS: Data of 100 adolescents with low to moderate myopia were retrospectively analyzed. The patients were assigned into two groups. The experimental group were treated with night-wear orthokeratology lens, and control group were treated with ordinary frame glasses. Follow up was carried out at the 3rd, 6th and 12th months of treatment. The naked-eye vision, diopter, corneal curvature, intraocular pressure, axial length, endothelial cell count and central corneal thickness were examined. Complications within 12 months were observed, and corneal fluorescein staining was graded. RESULTS: The naked-eye vision of the experimental group was significantly higher than that of the control group at the 3rd, 6th and 12th months, while the diopter of the experimental group was significantly lower than that of the control group at these time points. The corneal curvature of the experimental group was significantly decreased when comparing with that of the control group at the above 3 time points. The increase of axial length in the experimental group was significantly less than that in the control group at the 6th and 12th months. CONCLUSIONS: Short-term orthokeratology lens wear can effectively improve the naked-eye vision in adolescents with low to moderate myopia without significant impact on the central corneal thickness and corneal endothelial cells. It is a relatively safe method to correct myopia.

Dynamic changes in higher-order aberrations after correction of lower-order aberrations with adaptive optics in myopic and emmetropic eyes.

This study investigated the instantaneous changes of higher-order aberrations (HOAs) following lower-order aberrations (LOAs) correction with a closed-loop adaptive optics (AO) system in myopic and emmetropic eyes. Data were analyzed using generalized additive mixed models. Time-related changes in HOAs were modeled with two-piecewise linear regressions and were compared between myopic and emmetropic eyes. Both vertical coma and spherical aberrations shifted to the positive direction immediately after LOA correction. The fluctuations of the above values were significantly faster in myopic than in emmetropic eyes. Understanding these changes in HOAs following LOA correction may help in achieving better visual outcomes.

Mechanism of two styryl BODIPYs as fluorescent probes and protective agents in lipid bilayers against aqueous ClO.

Two styryl BODIPY derivatives, BOH and BOE, with different hydrophilic properties, were investigated for their reaction mechanisms in lipid bilayers against aqueous ClO-, by both experimental and theoretical methods. Density functional theory (DFT) calculations confirmed their identical conformations in solution. Fluorescence spectra and high-resolution mass spectra corroborated the central vinyl group as a common antioxidation moiety against ClO- oxidation. In giant unilamellar vesicles (GUVs), distinct reaction kinetics with ClO- suggested that BOE provided superior protective effects compared to BOH on lipids. Molecular dynamics simulations indicated that the lipophilic octyloxy group in BOE led to its deeper localization within the lipid phase, bringing it closer to the corresponding lipid target group. This study establishes the two styryl BODIPYs as promising fluorescent probes for detecting aqueous ClO- in lipid-water polyphasic systems.

Rhodobacter sphaeroides as a model to study the ecotoxicity of 1-alkyl-3-methylimidazolium bromide.

The purple non-sulfur bacterium Rhodobacter sphaeroides was selected as a biological model to investigate its response to the toxicity of 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br), a type of ionic liquid (IL), with different alkyl chain lengths (n describes the number of carbon atoms in the alkyl chain). The inhibition of bacterial growth by [Cnmim]Br was positively correlated with n. Morphological characterization revealed that [Cnmim]Br caused cell membrane perforation. The signal amplitude of the electrochromic absorption band shift of endogenous carotenoids showed a negatively linear correlation with n, and the amplitude of the blue-shift of the B850 band in light-harvesting complex 2 showed a positively linear correlation with n. Furthermore, an increase in blocked ATP synthesis and increase in antioxidant enzyme activity were observed in chromatophores treated with ILs containing longer alkyl chains. In summary, the purple bacterium can be developed as a model to monitor ecotoxicity and examine the mechanism of IL toxicity.

Association of Axial Length and Refraction with Near Horizontal Heterophoria in Chinese Children: An Observational Cross-Sectional Study.

Purpose: To evaluate the association of near heterophoria with refraction and axial length (AL) in Chinese school children. Methods: This school-based cross-sectional study included 15,081 Chinese primary school children (grades 1-6) examined during 2017. Near heterophoria was measured at 33 cm using the Maddox rod and prism test. Noncycloplegic refraction and AL were also measured. A generalized additive model with a Gaussian link was used to determine the association of near heterophoria with refraction and AL. Analyses were adjusted for age to account for differences in the age distribution of the sample. Results: Overall, data were analyzed for 11,013 students ranging in age from 6 to 13 years. The most common type of near heterophoria was exophoria (64.96%), the proportion and value of which increased according to grade. Exophoria accounted for 62.53% (2,328/3,723), 65.03% (2,501/3,846), and 67.51% (2,325/3,444) of near heterophoria cases for grades 1-2, grades 3-4, and grades 5-6, respectively. Prism diopter (PD) values for near heterophoria in these grades were -6.30 ± 3.69, -6.81 ± 4.01, and -8.32 ± 5.12 PD, respectively. The average spherical equivalent (SE) in children with orthophoria was 0.23 D and 0.25 D lower than those in children with exophoria and esophoria, respectively (P < 0.001). The mean AL in children with orthophoria was 0.11 mm shorter than that in children with either exophoria or esophoria (P < 0.001). Near heterophoria exhibited a significant correlation with refraction and AL, irrespective of age. Conclusions: Exophoria represents the most common type of near heterophoria in children. Children with more severe near heterophoria, whether exophoria or esophoria, exhibited a higher degree of myopia and longer AL than those with relatively less severe near heterophoria. These results highlight the need for further, long-term investigation regarding the role of near heterophoria in visual development.

Changes in Refractive Error Under COVID-19: A 3-Year Follow-up Study.

INTRODUCTION: To investigate changes in refractive error in schoolchildren before and during the coronavirus disease 2019 (COVID-19) pandemic. METHODS: This study included 2792 students, who underwent a 3-year follow-up from 2018 to 2020. All participants underwent yearly noncycloplegic refraction and ocular examinations. Time-related changes in sphere, cylinder, and spherical equivalent (SE) measurements in both genders were analyzed. RESULTS: The myopic sphere (- 0.78 ± 1.83 vs. - 1.03 ± 1.91 D; P = 0.025) and SE (- 1.04 ± 1.90 vs. - 1.32 ± 1.99 D; P = 0.015) progressed significantly from 2018 to 2019. Female participants had a significantly greater change in SE than male participants (P < 0.05), and the low hyperopia, emmetropia, and mild myopia groups significantly deteriorated (P < 0.001) from 2018 to 2019. Significant differences in sphere change (- 0.21 ± 0.97 vs. - 0.36 ± 0.96 D; P < 0.001) and SE change (- 0.23 ± 0.99 vs. - 0.38 ± 0.98 D; P < 0.001) were noted between 2019-2018 and 2020-2019, respectively. The respective changes in cylinder were statistically similar (- 0.03 ± 0.53 vs. - 0.05 ± 0.62 D; P = 0.400). CONCLUSIONS: The refractive status of schoolchildren showed an increasing myopic shift trend before and during the COVID-19 pandemic. The low hyperopia, emmetropia, and mild myopia groups were more sensitive to environmental changes during COVID-19 than before. The myopic shift was greater in female participants than male participants.

A Highly Sensitive and Selective Probe for the Colorimetric Detection of Mn(II) Based on the Antioxidative Selenium and Nitrogen Co-Doped Carbon Quantum Dots and ABTS•.

Herein, selenium and nitrogen co-doped carbon quantum dots (Se/N-CQDs) were hydrothermally synthesized by using citric acid, histidine, and sodium selenite, which had sp3 and sp2 hybridized carbon atoms and showed excitation-dependent fluorescence behavior. Furthermore, due to the redox reaction of ABTS•+ and Se/N-CQDs, Se/N-CQDs had the excellent antioxidant capacity that it was demonstrated by scavenging ABTS•+ with the fading of blue. Based on the synergistic effect of Se/N-CQDs and Mn(II) on ABTS•+, Se/N-CQDs and ABTS•+, as a stable, sensitive, selective, and reproducible colorimetric sensor, was applied to the detection of Mn(II) with a detection limit of 1.69 µM and a linear range of 0 to 142.90 µM. More importantly, the probe was successfully applied to detecting Mn(II) in tap water, illustrating that it could be a promising tool for Mn(II) detection in water environments.

Conjugation Length Dependence of Free Radical Scavenging Efficiency of Retinal and Retinylisoflavonoid Homologues.

Retinal (C20) and the C25 and C30 homologues were compared as radical scavengers together with their C22, C27, and C32 homologues linked with daidzein through a B'3 (isoflavonoid) to oxo-carbon (aldehyde) covalent bond. Oxidation potential in acetonitrile determined by cyclic voltammetry and ionization potential calculated by density functional theory for the aldehydes and dyads (conjugates), of which the two longer are new, decreased linearly with the wavenumber for absorption maximum. The logarithm of the second-order rate constant for scavenging of the ABTS•+ increased linearly with decreasing oxidation potential suggesting that longer conjugation in the antioxidant increases the rate of electron transfer. A similar linear free energy relationship was found for the rate of scavenging DPPH•, including daidzein, which may indicate involvement of hydrogen atom transfer from an isoflavonoid phenol. Prediction of radical scavenging efficiency from visible absorption spectra was demonstrated with the perspective of rational design of bifunctional amphiphilic antioxidants.