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Background： Morphological changes of the vasculature system in patients with myopia have been observed by Doppler ultrasound and fundus fluorescein angiography （FFA）; however, these studies have limitations. Doppler ultrasound provides low-resolution images which are mainly obtained from visualized large vessels, and FFA is an invasive examination. Optic coherence tomography （OCT） angiography is a noninvasive, high-resolution measurement for vascular density. The purpose of this study was to investigate the change of vascular density in myopic eyes using OCT angiography. Methods： This cross-sectional study includes a total of 91 eyes ~Yom 47 participants including control, moderate, and high myopia that were evaluated by OCT angiography. Patients with myopia were recruited from the Refractive Department, Shenzhen Aier Eye Hospital, from August 5, 2015 to April 1, 2016. Emmetropic eyes were from healthy volunteers. The vascular density at macula and optic disc regions, ganglion cell complex （GCC） thickness, and retinal nerve fiber layer （RNFL） thickness were measured. Their relationships with axial length （AL） and refractive error were analyzed. One-way analysis of variance （ANOVA）, Pearson＇s correlation, and generalized estimating equation were used for statistical analysis, Results： Both superficial and deep macular vascular density were highest in control （25.64% ± 3.76% and 37.12% ± 3.66%, respectively）, then in moderate myopia （21.15% ± 5.33% and 35.35% ± 5.50%, respectively）, and lowest in high myopia group （ 19.64% ± 3.87% and 32.81% ± 6.29%, respectively） （F =13.74 and 4.57, respectively; both P 〈 0.001）. Both superficial （β = -0.850 and 0.460, respectively） and deep （β = -0.766 and 0.396, respectively） macular vascular density were associated with AL and spherical equivalent （all P 〈 0.001 ）. Superficial macular vascular density was associated with GCC thickness （β = 0.244, P = 0.040）, independent of spherical equivalent. The vascular density in optic disc region had no difference among the three groups, and it was not associated with AL, spherical equivalent, or RNFL thickness. Conclusion： Our results suggested that with the increase of myopia, the vascular density decreased in macular region, but not in optic disc region.

The term pachychoroid was proposed as a term indicating an abnormal increase in choroidal thickness. Eyes presenting with pachychoroid changes often exhibit dilation of the large choroidal vessels, compressing the overlying choriocapillaris and Sattler's layer. Pachychoroid spectrum diseases may present pathological findings such as pigment epitheliopathy, choroidal neovascularization (CNV), submacular serous detachment, and distinct choroidal and scleral alterations. Recent advancements in imaging modalities such as widefield indocyanine green angiography (WF-ICGA), optical coherence tomography angiography (OCTA), and enhanced depth imaging optical coherence tomography (OCT) have significantly improved our understanding of these conditions. WF-ICGA revealed venous outflow congestion in the peripheral retina as one of the characteristics of pachychoroid diseases. Scleral thickness measurements using ultrasound biomicroscopy and anterior segment OCT indicate that a thicker anterior sclera may contribute to choroidal congestion and disease pathogenesis. OCTA has emerged as a superior tool for identifying CNV and understanding the disease etiology, offering better sensitivity and specificity compared to traditional methods. These imaging advancements provide valuable insights into the structural and functional changes associated with pachychoroid diseases, potentially guiding future diagnostic and therapeutic strategies. The aim of the present review is to define the morphological characteristics of the pachychoroid spectrum of diseases, which share similar choroidal findings. Keywords: Pachychoroid disease, indocyanine green angiography, imaging, optic coherence tomography angiography, optic coherence tomography, scleral thickness

Different diseases of the optic disc may be caused by or lead to abnormal vasculature at the optic nerve head. Optical coherence tomography angiography (OCTA) is a novel technology that provides high resolution mapping of the retinal and optic disc vessels. Recent studies have shown the ability of OCTA to visualize vascular abnormalities in different optic neuropathies. In addition, quantified OCTA measurements were found promising for differentiating optic neuropathies from healthy eyes.

To compare angle-to-angle (ATA) distance and aqueous depth (AQD) readings produced by two different optical coherence tomography (OCT) devices and a Scheimpflug camera. ATA distance and AQD were measured in 60 eyes using the Visante time-domain OCT (TD-OCT) (Carl Zeiss Meditec AG), the Anterion swept-source OCT (SS-OCT) (Heidelberg Engineering GmbH), and the Pentacam HR Scheimpflug camera (Oculus Optikgeräte GmbH). Moreover, ATA distance was measured along the horizontal and vertical meridians. Bland-Altman analysis was used to assess the agreement between devices. All three devices did not yield similar horizontal ATA distance: 11.96 ± 0.47 mm (TD-OCT), 11.96 ± 0.42 mm (SS-OCT), and 11.05 ± 0.52 mm (Pentacam). More specifically, the Pentacam yielded significantly smaller values (approximately 0.9 mm, P <.001). Mean vertical ATA distance was 12.61 ± 0.65 and 12 ± 0.65 mm for the TD-OCT and SS-OCT, respectively (P =.983). Vertical ATA distance was significantly larger than horizontal ATA distance for both OCT devices (approximately 0.6 mm, P <.001). The lowest mean difference was found between both OCT devices (0.0068 and ?0.0415 mm, for horizontal and vertical meridians, respectively) and the highest between the Pentacam and the two OCT devices (approximately 0.9 mm). As for AQD, inter-device mean values were also statistically significant: 2.89 ± 0.48, 2.82 ± 0.49, and 2.79 ± 0.50 mm, for the TD-OCT, SS-OCT, and Pentacam, respectively (P <.001). Mean differences were similar for the TD-OCT versus SS-OCT and SS-OCT versus Pentacam (approximately 0.02 mm), and larger between the TD-OCT and Pentacam (approximately 0.05 mm). The results show that the TD-OCT and SS-OCT are interchangeable instruments for ATA distance measurement but the Pentacam is not with either of the two OCT devices. A clinical criterion should assess whether these three devices could be used interchangeably for AQD measurement.

Objectives: To evaluate the vascular changes of idiopathic macular telangiectasia type 2 (MacTel 2) patients with optical coherence tomography angiography (OCTA) and correlate these changes with the findings of spectral domain optical coherence tomography (SD-OCT). Materials and Methods: Simultaneous SD-OCT and OCTA images of 10 eyes of 6 patients who were diagnosed as MacTel 2 in Ankara University Faculty of Medicine, Department of Ophthalmology were obtained and graded according to the OCTA grading system for MacTel 2. Results: Ten eyes of 6 patients were included. Four (66%) patients were female and 2 (34%) were male. The disease was grade 0 in 2 eyes, grade 1 in 2 eyes, grade 2 in 3 eyes, grade 3 in 1 eye, grade 4 in 1 eye, and grade 5 in 1 eye. The most common findings in grade 1, 2, and 3 non-proliferative disease were thinning of the outer retinal layers, presence of intraretinal hyporeflective layers and inner limiting membrane draping. In cases with subretinal choroidal neovascularisation (CNV) in OCTA, CNV or CNV scar was present in the B-scan SD-OCT images. In a case in which OCT was within normal limits, vascular changes consistent with grade 1 disease were observed in OCTA. On the contrary, 2 patients with significant foveal atrophy and macular hole in B-scan showed changes of early disease in OCTA. In some of the eyes, OCTA revealed an intact superficial vascular layer despite visible changes in the deep layer and the presence of neovascularisation. Conclusion: OCTA yields findings which are important for understanding the pathogenesis of the disease and providing better follow-up. Contrary to fundus fluorescein angiography, changes in the deep arterial plexus in the early disease and CNV can be clearly observed with OCTA. To achieve the best results in clinical practice, en face flow maps should be evaluated together with B-scan SD-OCT images. Keywords: Macular telangiectasia type-2, optic coherence tomography angiography, spectral domain optic coherence tomography

Patients with Alzheimer's Disease (AD) exhibit decreased retinal blood flow and vessel density (VD). However, it is not known whether these changes are also present in individuals with early AD (eAD) or amnestic type mild cognitive impairment (aMCI), an enriched pre-AD population with a higher risk for progressing to dementia. We performed a prospective case-control clinical study to investigate whether optical coherence tomography angiography (OCTA) parameters in the macula and disc are altered in those with aMCI and eAD. This is a single center study of 32 participants. Individuals with aMCI/eAD (n = 16) were 1:1 matched to cognitively normal controls (n = 16). We evaluated OCTA images of the parafoveal superficial capillary plexus (SCP) and two vascular layers in the peripapillary region, the radial peripapillary capillary (RPC) and superficial vascular complex (SVC). Outcome vascular and structural parameters included VD, vessel length density (VLD), adjusted flow index (AFI) and structural retinal nerve fiber layer (RNFL) thickness. We compared these parameters between the two groups and examined the correlation between OCTA parameters and cognitive performance on the Montreal Cognitive Assessment (MoCA). Cognitively impaired participants demonstrated statistically significant decrease in parafoveal SCP VD and AFI as compared to controls, but no statistically significant difference in peripapillary parameters. Furthermore, we found a significant positive correlation between MoCA scores for the entire study cohort and both the parafoveal SCP VD and peripapillary RPC VLD. OCTA shows significant decline in parafoveal flow and VD in individuals with early cognitive impairment related to AD, suggesting that these parameters could have potential utility as early disease biomarkers. In contrast, the presence of larger vascular channels in the peripapillary region may have obscured subtle capillary changes in that region. Overall, the correlation between vascular OCTA parameters and cognitive performance supports further OCTA studies in this population.

An essential ingredient of future worldwide quantum communication is the generation of long-lived entangled quantum states; a coherence time of six hours is now reported for optically addressable nuclear spins in europium-doped yttrium orthosilicate. Quantum entanglement tops six-hour mark The distribution of quantum entanglement beyond a few hundred kilometres, as would be required for a world-wide quantum communication network, is prohibited by losses accumulated during transmission. This limitation might be overcome using a repeater protocol involving storage of quantum information — provided sufficiently long-lived entanglement can be achieved. The record coherence time stands at three hours, in a system consisting of phosphorus donor in silicon-28. Here, Manjin Zhong et al . break this record, presenting a coherence time of 6 hours in europium-doped yttrium orthosilicate, a material in which coherence time had previously been limited to tens of milliseconds. The crucial advantage of this system is that the transition involved is optically addressable, which makes this finding particularly promising for long-lived quantum memory applications. Space-like separation of entangled quantum states is a central concept in fundamental investigations of quantum mechanics and in quantum communication applications. Optical approaches are ubiquitous in the distribution of entanglement because entangled photons are easy to generate and transmit. However, extending this direct distribution beyond a range of a few hundred kilometres 1 , 2 to a worldwide network is prohibited by losses associated with scattering, diffraction and absorption during transmission. A proposal to overcome this range limitation is the quantum repeater protocol 3 , 4 , which involves the distribution of entangled pairs of optical modes among many quantum memories stationed along the transmission channel. To be effective, the memories must store the quantum information encoded on the optical modes for times that are long compared to the direct optical transmission time of the channel 5 . Here we measure a decoherence rate of 8 × 10 −5  per second over 100 milliseconds, which is the time required for light transmission on a global scale. The measurements were performed on a ground-state hyperfine transition of europium ion dopants in yttrium orthosilicate ( 151 Eu 3+ :Y 2 SiO 5 ) using optically detected nuclear magnetic resonance techniques. The observed decoherence rate is at least an order of magnitude lower than that of any other system suitable for an optical quantum memory. Furthermore, by employing dynamic decoupling, a coherence time of 370 ± 60 minutes was achieved at 2 kelvin. It has been almost universally assumed that light is the best long-distance carrier for quantum information. However, the coherence time observed here is long enough that nuclear spins travelling at 9 kilometres per hour in a crystal would have a lower decoherence with distance than light in an optical fibre. This enables some very early approaches 6 , 7 to entanglement distribution to be revisited, in particular those in which the spins are transported rather than the light.

Technologies that rely on quantum bits (qubits) require long coherence times and high-fidelity operations 1 . Superconducting qubits are one of the leading platforms for achieving these objectives 2 , 3 . However, the coherence of superconducting qubits is affected by the breaking of Cooper pairs of electrons 4 – 6 . The experimentally observed density of the broken Cooper pairs, referred to as quasiparticles, is orders of magnitude higher than the value predicted at equilibrium by the Bardeen–Cooper–Schrieffer theory of superconductivity 7 – 9 . Previous work 10 – 12 has shown that infrared photons considerably increase the quasiparticle density, yet even in the best-isolated systems, it remains much higher 10 than expected, suggesting that another generation mechanism exists 13 . Here we provide evidence that ionizing radiation from environmental radioactive materials and cosmic rays contributes to this observed difference. The effect of ionizing radiation leads to an elevated quasiparticle density, which we predict would ultimately limit the coherence times of superconducting qubits of the type measured here to milliseconds. We further demonstrate that radiation shielding reduces the flux of ionizing radiation and thereby increases the energy-relaxation time. Albeit a small effect for today’s qubits, reducing or mitigating the impact of ionizing radiation will be critical for realizing fault-tolerant superconducting quantum computers. Ionizing radiation from environmental radioactivity and cosmic rays increases the density of broken Cooper pairs in superconducting qubits, reducing their coherence times, but can be partially mitigated by lead shielding.

To explore the utility of intraoperative optical coherence tomography (iOCT) in the determination of phacoemulsification groove depth and remaining lens thickness from the posterior capsule before lens cracking. In this retrospective analysis of 22 eyes, a remaining lens thickness (RLT) of less than 1.5 mm was defined as a suitable remainder to be achieved before initiating lens cracking. Phacoemulsification of the primary groove was carried out to a depth judged to be adequate by assessment of red reflex. An iOCT image was obtained; if the RLT was greater than 1.5 mm, further grooving was performed and a second iOCT measurement was obtained. Once the RLT was 1.5 mm or less, the surgeon proceeded with nucleus cracking. The RLT was less than 1.5 mm in 90.9% of eyes (20/22). In 2 eyes (9.1%), the RLT was greater than 1.5 mm (cataract grade 2 and 5), which prompted further sculpting to deepen the groove. The final RLT was 0.99 and 0.90 mm in these 2 eyes, followed by lens cracking. Quantitative iOCT measurement enabled objective intraocular visualization of cataract groove depth prior to splitting the nucleus. Groove depth judgment using the red reflex resulted in an inadequate depth of grooving and a RLT of greater than 1.5 mm in 9% of eyes, even for an experienced surgeon. Greater difficulty was found in one dense cataract. The iOCT measurement may have helped dictate the need for further grooving before initiating lens cracking, thus minimizing the risk of a difficult or failed lens cracking. Objective confirmation of groove depth will be particularly useful for novice surgeons as they gain experience with the red reflex assessment and could be a helpful adjunct to phacoemulsification training.

To compare angle-to-angle (ATA) distance and aqueous depth (AQD) readings produced by two different optical coherence tomography (OCT) devices and a Scheimpflug camera. ATA distance and AQD were measured in 60 eyes using the Visante time-domain OCT (TD-OCT) (Carl Zeiss Meditec AG), the Anterion swept-source OCT (SS-OCT) (Heidelberg Engineering GmbH), and the Pentacam HR Scheimpflug camera (Oculus Optikgeräte GmbH). Moreover, ATA distance was measured along the horizontal and vertical meridians. Bland-Altman analysis was used to assess the agreement between devices. All three devices did not yield similar horizontal ATA distance: 11.96 ± 0.47 mm (TD-OCT), 11.96 ± 0.42 mm (SS-OCT), and 11.05 ± 0.52 mm (Pentacam). More specifically, the Pentacam yielded significantly smaller values (approximately 0.9 mm, P < .001). Mean vertical ATA distance was 12.61 ± 0.65 and 12 ± 0.65 mm for the TD-OCT and SS-OCT, respectively (P = .983). Vertical ATA distance was significantly larger than horizontal ATA distance for both OCT devices (approximately 0.6 mm, P < .001). The lowest mean difference was found between both OCT devices (0.0068 and −0.0415 mm, for horizontal and vertical meridians, respectively) and the highest between the Pentacam and the two OCT devices (approximately 0.9 mm). As for AQD, inter-device mean values were also statistically significant: 2.89 ± 0.48, 2.82 ± 0.49, and 2.79 ± 0.50 mm, for the TD-OCT, SS-OCT, and Pentacam, respectively (P < .001). Mean differences were similar for the TD-OCT versus SS-OCT and SS-OCT versus Pentacam (approximately 0.02 mm), and larger between the TD-OCT and Pentacam (approximately 0.05 mm). The results show that the TD-OCT and SS-OCT are interchangeable instruments for ATA distance measurement but the Pentacam is not with either of the two OCT devices. A clinical criterion should assess whether these three devices could be used interchangeably for AQD measurement.