Insights on the possibility of SARS-CoV-2 transmission through the eyes.

A novel coronavirus, named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or 2019-nCOV), causing coronavirus disease 2019 (COVID-19), has rapidly spread to most countries and regions worldwide since it broke out at the end of 2019. Epidemic of the virus produces a tremendous pressure on the global health systems. With progressive insight into SARS-CoV-2, the role of eye tissue has attracted wide attention in the spread of COVID-19. Whether SARS-CoV-2 can enter the human body through eyes and cause infection? The fact that unprotected exposure of the eyes to 2019-nCoV might have allowed the virus to infect the body implies that 2019-nCOV can invade eye tissue and set foot in organism. Facing the severe challenge of preventing spread of the COVID-19, combined with the high-risk environment of ophthalmology, it is crucial to investigate ocular tropism of coronavirus. This paper explores the possibility of coronavirus transmission through the eye from aspects of probable mechanisms, clinical cases, detection of coronavirus; and puts forward precautions for ophthalmologists and nurses. Consequently, this review reveals our understanding of ocular tropism of coronavirus and contributes to determining risk of ocular transmission, raising awareness of necessary eye protection among medical workers and reducing further prevalence of SARS-CoV-2.

Bibliometric analysis and mapping knowledge domain of pterygium: 2000-2019.

AIM: To track the knowledge structure, topics in focus, and trends in emerging research in pterygium in the past 20y. METHODS: Base on the Web of Science Core Collection (WoSCC), studies related to pterygium in the past 20y from 2000-2019 have been included. With the help of VOSviewer software, a knowledge map was constructed and the distribution of countries, institutions, journals, and authors in the field of pterygium noted. Meanwhile, using co-citation analysis of references and co-occurrence analysis of keywords, we identified basis and hotspots, thereby obtaining an overview of this field. RESULTS: The search retrieved 1516 publications from WoSCC on pterygium published between 2000 and 2019. In the past two decades, the annual number of publications is on the rise and fluctuated a little. Most productive institutions are from Singapore but the most prolific and active country is the United States. Journal Cornea published the most articles and Coroneo MT contributed the most publications on pterygium. From co-occurrence analysis, the keywords formed 3 clusters: 1) surgical therapeutic techniques and adjuvant of pterygium, 2) occurrence process and pathogenesis of pterygium, and 3) epidemiology, and etiology of pterygium formation. These three clusters were consistent with the clustering in co-citation analysis, in which Cluster 1 contained the most references (74 publications, 47.74%), Cluster 2 contained 53 publications, accounting for 34.19%, and Cluster 3 focused on epidemiology with 18.06% of total 155 co-citation publications. CONCLUSION: This study demonstrates that the research of pterygium is gradually attracting the attention of scholars and researchers. The interaction between authors, institutions, and countries is lack of. Even though, the research hotspot, distribution, and research status in pterygium in this study could provide valuable information for scholars and researchers.

Trends in research related to high myopia from 2010 to 2019: a bibliometric and knowledge mapping analysis.

AIM: To evaluate the global trends in and explore hotspots of high myopia (HM) research. METHODS: This bibliometric analysis was used to reveal the publication trends in HM research field based on the Web of Science Core Collection (WoSCC). VOSviewer version 1.6.13 software was used to analyze the data and construct a knowledge map including the yearly publication number, journals, countries, international collaborations, authors, research hotspots, and intellectual base in HM. RESULTS: The search engine found 3544 peer-reviewed publications on HM between 2010 and 2019, and the yearly research output substantially elevated over the past decade. China is the top publishing country, and Sun Yat-sen University was the most active academic institution. Jonas JB is the top publishing scientist, and Investigative Ophthalmology and Visual Science (IOVS) was the most productive journal. The highest cited references mainly focused on epidemiology and management. The keywords formed 6 clusters: 1) refractive surgery; 2) etiology and clinical characteristics; 3) the mechanism of eye growth; 4) management for myopic maculopathy; 5) vitrectomy surgical treatment; 6) myopia-associated glaucoma-like optic neuropathy. CONCLUSION: The evaluation of development trends based on the data extracted from WoSCC can provide valuable information and guidance for ophthalmologists and public health researchers to improve management procedures in HM field.

Comparison of measurements of anterior chamber angle via anterior segment optical coherence tomography and ultrasound biomicroscopy.

BACKGROUND: Glaucoma is an irreversible optic neuropathy with the loss of visual field and decrease of vision. The variable clinical manifestations may result in differential diagnostic difficulties. The early screening and diagnosis of glaucoma are currently experiencing a demand for anterior segment analysis tools that can gather more information with one short measurement. Therefore, we analyzed the agreement, difference, and correlation of chamber angle parameters such as angel opening distance at 500 µm (AOD500) and trabeculo-iris space area at 500 µm2 (TISA500) measured by anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM). AIM: To compare the differences, correlation, and agreement in measuring AOD500 and TISA500 by AS-OCT and UBM. METHODS: Both AS-OCT and UBM were performed to measure AOD500 and TISA500 in 45 subjects (72 eyes). All subjects without glaucoma were collected from October 2015 to August 2016 at the Ophthalmology Department of the Fourth Affiliated Hospital of China Medical University. Data of the two groups (AOD500 and TISA500) were compared by nonparametric tests. Pearson correlative analysis and Bland-Altman analysis were used to compare the correlation and agreement. RESULTS: There were no significant differences between AS-OCT and UBM in measuring AOD500 (P1 = 0.110, P2 = 0.633, P3 = 0.078, and P4 = 0.474) and TISA500 (P1 = 0.584, P2 = 0.889, P3 = 0.297, and P4 = 0.550) of the four quadrants of the anterior chamber angle. There was a high correlation in measuring AOD500 (r1 = 0.562, r2 = 0.671, r3 = 0.635, and r4 = 0.720; P < 0.001) and TISA500 (r1 = 0.584, r2 = 0.889, r3 = 0.297, and r4 = 0.550; P < 0.001). There was a good agreement in measuring AOD500 and TISA500 by the two modalities. CONCLUSION: There is a high correlation and agreement between AOD500 and TISA500 measurements by AS-OCT and UBM. They are interchangeable under some circumstances. AS-OCT proves to be a better early screening tool for glaucoma.

Engineering of an enhanced synthetic Notch receptor by reducing ligand-independent activation.

Notch signaling is highly conserved in most animals and plays critical roles during neurogenesis as well as embryonic development. Synthetic Notch-based systems, modeled from Notch receptors, have been developed to sense and respond to a specific extracellular signal. Recent advancement of synNotch has shown promise for future use in cellular engineering to treat cancers. However, synNotch from Morsut et al. (2016) has a high level of ligand-independent activation, which limits its application. Here we show that adding an intracellular hydrophobic sequence (QHGQLWF, named as RAM7) present in native Notch, significantly reduced ligand-independent activation. Our enhanced synthetic Notch receptor (esNotch) demonstrates up to a 14.6-fold reduction in ligand-independent activation, without affecting its antigen-induced activation efficiency. Our work improves a previously reported transmembrane receptor and provides a powerful tool to develop better transmembrane signaling transduction modules for further advancement of eukaryotic synthetic biology.

Changes in corneal endothelial cell density in patients with primary open-angle glaucoma.

BACKGROUND: Glaucoma is a group of diseases characterized by a specific pattern of optic nerve neuropathy and retinopathy. Increasing evidence demonstrates glaucoma associated corneal endothelium loss. Direct-compression mechanism due to elevated intraocular pressure (IOP), cell toxicity after long term exposure to preservatives and glaucoma surgery have been reported to be the possible mechanism. Herein, we compare the specular endothelial microscopy in primary open-angle glaucoma (POAG) patients and healthy controls of the same age group to observe the corneal endothelium changes and the correlations to the mean IOP in a Chinese case control study. AIM: To investigate corneal endothelial cell density in Chinese patients with POAG. METHODS: A case control study was performed on 60 eyes of 60 patients with POAG. Exclusion criteria included history of corneal diseases, intraocular diseases, contact lens use, ocular trauma or surgery (including intraocular surgery and laser treatment), congenital abnormalities or systemic diseases such as diabetes. Intraocular pressure was measured using Goldmann tonometry. Indirect specular microscopy (TOPCON SP-2000P) was performed on central corneas and endothelial images were acquired. Endothelial cell density, area and cell counts were analyzed. RESULTS: Endothelial cell density was 2959 ± 236 cells/mm2 in healthy controls and 2757 ± 262 cells/mm2 in patients with POAG. The POAG eyes had significantly lower endothelial cell density compared to healthy control eyes (P < 0.001). In the POAG group, endothelial cell density was 2686 ± 233 cells/mm2 in the patients receiving medication and 2856 ± 272 cells/mm2 in the untreated subgroup. The eyes receiving medication had significantly lower endothelial cell density compared to untreated eyes. There was a negative correlation between cell density and mean IOP (r = -0.286, P = 0.004), positive correlation between the average cell area and mean IOP (r = 0.228, P = 0.022), maximum cell area and mean IOP (r = 0.218, P = 0.029) and minimum cell area and mean IOP (r = 0.290, P = 0.003). The percentage of hexagonal cells was not correlated with mean IOP. CONCLUSION: Patients with POAG have lower corneal endothelial cell density than healthy controls of the same age. This may be attributed to mechanical damage from elevated IOP and toxicity of glaucoma medications.

Broadband and highly efficient quadratic interactions in double-slot lithium niobate waveguides through phase matching.

We propose and study in detail a phase-matched quadratic optical interaction in a realizable 2D double-slot lithium niobate (LN) waveguide. As opposed to the single-slot waveguide, the field can be well confined in the nanometric nonlinear material, and it is also more flexible for birefringence and dispersion design. The proposed compact double-slot structure could not only achieve form birefringence phase matching but also effectively enhance the modal overlap integral and expand the working wavelength. The calculated results on second harmonic generation show an extremely large bandwidth of ~40 nm. The modal overlap integral up to 0.035 W(3/2)/V can be realized by optimizing the waveguide geometry, and it is much better than previous results on single-slot waveguides. Its temperature dependence is low--around 25 °C. The geometry is practical considering the current micromachining technique of LN.

Polarization independent quasi-phase-matched sum frequency generation for single photon detection.

Polarization independent sum frequency generation (SFG) is proposed in an electro-optic (EO) tunable periodically poled Lithium Niobate (PPLN). The PPLN consists of four sections. External electric field could be selectively applied to them to induce polarization rotation between the ordinary and extraordinary waves. If the domain structure is well designed, the signal wave with an arbitrary polarization state could realize efficient frequency up-conversion as long as a z-polarized pump wave is selected. The applications in single photon detection and optical communications are discussed.

Tunable broadband isolator based on electro-optically induced linear gratings in a nonlinear photonic crystal.

We theoretically propose a broadband optical isolator based on second-harmonic generation in a one-dimensional quadratic nonlinear photonic crystal (NPC) with an embedded defect. An external electric field along the z axis is applied to modulate the NPC refractive index periodically. Complete optical isolation always could be reached with the help of an external field. Influences of the defect position and thickness are discussed. The spectral and power tolerances of the isolator also have been investigated and show high contrast within a wide wavelength range at different power levels.

A bidirectional tunable optical diode based on periodically poled LiNbO3.

We propose a bidirectional tunable optical diode based on a periodically poled lithium niobate (PPLN) with defect. An acoustic wave propagates together with the light beam so that a collinear photon-phonon interaction happens, which affects the nonlinear optical processes in PPLN. The fundamental wave exhibits an optical diode effect, i.e., the light only may travel toward a single direction while the opposite way is isolated. However, the acoustic wave could be used to adjust the contrast of optical isolation from -1 to 1. A direction-optional operation is thus realized. Moreover, the advantages of our tunable PPLN optical diode are also discussed.

Acousto-optic tunable second harmonic generation in periodically poled LiNbO3.

Acousto-optic (AO) tunable second harmonic generation (SHG) was proposed in periodically poled lithium niobate (PPLN). The acoustic wave could either be induced from an external transducer or self-generated in PPLN driving with a cross-field radio frequency field. The reciprocal vector of PPLN compensates the SHG wave-vector mismatch when quasi-phase- matching (QPM) condition is satisfied, while phonons with suitable frequencies may affect it by scattering photons to different polarization state. The QPM SHG and AO polarization rotation are coupled together. Second harmonic waves' intensities, polarization states and even phases thus could be manipulated instantly through AO interaction.