Disc Tilt Research Articles

Exploring optical coherence tomography parameters in eyes with myopic tilted disc

BackgroundTo investigate the impact of optic disc torsion (ODT), horizontal disc tilt (HDT) angle, and ovality index (OI) on different retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) segments in healthy myopic eyes.MethodsODT and OI were measured from fundus photographs. HDT angle, peripapillary RNFL, and macular GCIPL were measured by swept-source optical coherence tomography (SS-OCT). The association between optic disc morphology and the RNFL/GCIPL thickness were evaluated, with age and axial length (AL) adjusted.ResultsAmong 530 healthy myopic eyes of 284 participants (mean age: 41.7 years, mean spherical equivalent: − 7.70 D, and mean AL: 26.6 mm), 335 eyes (63.2%) had temporal disc torsion (temporal group) and 195 eyes (36.8%) had nasal disc torsion (nasal group). For the nasal group, a larger OI was associated with thinner superior-to-superonasal GCIPL (β = − 7.465 to − 6.972, both P = 0.024) and temporal RNFL sectors (β = − 49.596 to − 27.748, P ≤ 0.014). For the temporal group, a larger OI was associated with thinner superior-to-nasal (β = − 50.255 to − 22.093, P ≤ 0.006) and thicker temporal RNFL sectors (β = 29.015 to 56.890, P ≤ 0.003). Additionally, a larger HDT angle was associated with thinner superior-to-nasal RNFL sectors (β = − 0.559 to − 0.242, P ≤ 0.036) and thinner superior-to-superotemporal GCIPL sectors (β = − 0.084 to − 0.069, P ≤ 0.037).ConclusionsThe optic disc tortional direction was associated with the measurement of different RNFL and GCIPL sectors independent of the AL and age. These should be considered when constructing a myopic normative database.

A New IW And-type Star: Karachurin 12 with Tilted Disks and Diverse Cycles

The IW And-type phenomenon in cataclysmic variables presents a significant challenge to the accretion disk instability model. Using photometric data from the All-Sky Automated Survey for Supernovae, the Zwicky Transient Facility, and the Transiting Exoplanet Survey Satellite, we identify Karachurin 12 as a new noneclipsing IW And-type object with a cycle period of 35.69(3) days. We also report for the first time that Karachurin 12 is a negative superhump (NSH) system featuring precessing tilted disks, with precession, orbital, and NSH periods of 4.9588(2) days, 0.3168895(13) days, and 0.2979861(8) days, respectively. Our analysis, using dips as the index and NSHs as the probe, reveals diverse cycle patterns in Karachurin 12, with NSH amplitude varying throughout the cycle. These findings offer new insights for studying tilted disks and the IW And-type phenomenon. The mass-transfer burst model has difficulty explaining the observed variations in NSH amplitude, especially given the uncertainty surrounding the origin of the mass-transfer burst. Meanwhile, the tilted thermally unstable disk model indicates a possible connection to the IW And-type phenomenon, but it also struggles to account for the detailed variations in Karachurin 12. Therefore, a wider range of factors must be considered to fully understand the complex changes in Karachurin 12.

Variability in Optic Nerve Head Morphology in High Axial Myopia and Its Association with Glaucoma

Purpose: To investigate optic disc morphology in high axial myopia and its associations with the deep-layer structure of the optic disc using optical coherence tomography and glaucoma.Methods: We retrospectively reviewed the medical records of 69 eyes (33 normal and 36 glaucomatous eyes) with an axial length of 26-27 mm. The eyes were categorized into two groups based on the optic disc tilt ratio (≥ 1.3 or < 1.3). Characteristics of optic disc morphology, including lamina cribrosa depth, peripapillary atrophy width, and Bruch’s membrane opening area, were compared between the two groups. Furthermore, factors related to mean deviation and global retinal nerve fiber layer (RNFL) thickness were analyzed.Results: The mean optic disc tilt ratio was 1.31 ± 0.23. Eyes with a tilt ratio ≥ 1.3 (30 eyes) had a higher likelihood of glaucoma (<i>p</i> = 0.035) and severe visual field (VF) defects (<i>p</i> < 0.001), a thinner global RNFL thickness (<i>p</i> = 0.046), and larger gamma peripapillary atrophy width (<i>p</i> < 0.001) compared to eyes with a tilt ratio < 1.3 (39 eyes). Linear regression analysis revealed that the optic disc tilt ratio was significantly associated with VF loss (<i>p</i> = 0.018) but not with global RNFL thinning (<i>p</i> = 0.203).Conclusions: Variations in optic disc morphology are observed in eyes with similar axial lengths, and a higher optic disc tilt ratio is associated with more severe VF defects. These findings suggest the potential influence of optic disc morphological changes due to axial elongation on the severity of glaucomatous damage.

Clinical characteristics of peripapillary hyperreflective ovoid mass-like structures in myopic children.

To describe the characteristics of peripapillary hyperreflective ovoid mass-like structure (PHOMS) in myopic children and to investigate factors associated with PHOMS. This retrospective observational study included 101 eyes of 101 children (age ≤17y) with myopia. All included patients underwent comprehensive clinical examination. Optic nerve canal parameters, including disc diameter, optic nerve head (ONH) tilt angle, and border tissue angle were measured using serial enhanced-depth imaging spectral-domain optical coherence tomography (EDI-OCT). Based on the optic disc drusen consortium's definition of PHOMS, eyes were classified as PHOMS group and non-PHOMS group. PHOMS was categorized according to height. Sixty-seven (66.3%) eyes were found with PHOMS. Small PHOMS could only be detected by optical coherence tomography (OCT). Medium PHOMS could be seen with blurred optic disc borders corresponding to OCT. The most frequent location of PHOMS was at the nasosuperior (91%, 61 of 67 eyes) to ONH disc. The axial length and spherical equivalent were more myopic in the PHOMS group than in the non-PHOMS group (both P<0.001). ONH tilt angle was also significantly greater in PHOMS group than in non-PHOMS group [8.90 (7.16-10.54) vs 3.93 (3.09-5.25), P<0.001]. Border tissue angle was significantly smaller in PHOMS group than in non-PHOMS group [29.70 (20.90-43.81) vs 45.62 (35.18-60.45), P<0.001]. In the multivariable analysis, spherical equivalent (OR=3.246, 95%CI=1.209-8.718, P=0.019) and ONH tilt angle (OR=3.275, 95%CI=1.422-7.542, P=0.005) were significantly correlated with PHOMS. There was no disc diameter associated with PHOMS. In the linear regression analysis, border tissue angle was negatively associated with PHOMS height (β=-2.227, P<0.001). PHOMS is associated with optic disc tilt and optic disc nasal shift in myopia. Disc diameter is not a risk factor for PHOMS. The changes in ONH caused by axial elongation facilitated an understanding of the mechanism of PHOMS.

Discrete element modelling of the effect of disc angle and tilt angle on residue incorporation resulting from a concave disc

Understanding crop residue behaviour during tillage is critical for improving performance of tillage tools for conservation agriculture. A laboratory experiment was conducted using a concave disc to incorporate corn residue into sandy loam soil. Dynamic attributes, including soil cutting forces and residue incorporation, were measured under different lengths (75, 125, and 200 mm) of corn residue at constant disc and tilt angles. A residue-disc-soil interaction model was developed using discrete element method (DEM). Model parameters were calibrated and validated using experimental data. The validated model was used to predict the dynamic attributes at different disc and tilt angles. Experimental results demonstrated a general increasing trend in draft force (FD) and residue incorporation rate (RI), as the corn residue length increased. The two calibrated model parameters, stiffness of soil particle and stiffness of soil-residue interface were 1.15 × 106 and 13.5 N/m respectively. The validated model had an average relative error of 9.0 % and 18.2 % for predicting RI and FD respectively, as compared with the measurements. Within the angle range of 10° to 30°, the FD and RI decreased as the tilt angle (α) increased, whereas increased as the disc angle (β) increased. The effects of β were more pronounced than those of α. The optimal angles were α = 20°, β = 25° which resulted in a minimum FD and a maximum RI. The results provided new insight into residue-disc-soil dynamics and could be used to guide the selection of disc operating parameters.

Polar alignment of a dusty circumbinary disc – I. Dust ring formation

ABSTRACT We investigate the formation of dust traffic jams in polar-aligning circumbinary discs. We use 3D smoothed particle hydrodynamical simulations of both gas and dust to model an initially highly misaligned circumbinary disc around an eccentric binary. As the circumbinary disc evolves to a polar configuration (perpendicular to the binary orbital plane), the difference in the precession between the gas and dust produces dust traffic jams, which become dense dust rings. We find the formation of dust rings exists for different Stokes number, binary eccentricity, and initial disc tilt. Dust rings are only produced while the circumbinary disc is misaligned to the binary orbital plane. When the disc becomes polar aligned, the dust rings are still present and long-lived. Once these dust rings are formed, they drift inward. The drift time-scale depends on the Stokes number. The lower the Stokes number, the faster the dust ring drifts near the inner edge of the disc. The dust rings will have an increased mid-plane dust-to-go ratio, which may be a favourable environment for the steaming instability to operate.

V892 Tau: A tidally perturbed circumbinary disc in a triple stellar system

V892 Tau is a young binary star surrounded by a circumbinary disc that shows hints of an interaction with the low-mass nearby star V892 Tau NE. The goal of this paper is to constrain the orbit of V892 Tau NE and to determine the resulting circumbinary disc dynamics. We present new ALMA observations of the V892 Tau circumbinary disc at a twice higher angular and spectral resolution. We modelled the data with V892 Tau as a triple system and performed a grid of hydrodynamical simulations testing several orbits of the companion. The simulation outputs were then post-processed to build synthetic maps that we compared to the observations. The 12CO emission of the disc shows clear non-Keplerian features such as spiral arms. When comparing the data with our synthetic observations, we interpreted these features as ongoing interactions with the companion. Our simulations indicate that an eccentricity of $e of the companion is needed to reproduce the observed disc extent and that a mutual inclination of $ i with the inner binary reproduces the measured disc tilt. In order to explain most of the features of the circumbinary disc, we propose that V892 Tau NE follows an orbit with a mild eccentricity $0.2 &lt; e &lt; 0.5$ and a mutual inclination of $30 i &lt; 60 Such a misaligned companion suggests the disc is oscillating and precessing with time, stabilising in an intermediate plane with a non-zero mutual inclination with the inner binary. Given the orbital configuration, we show that the stability of future planets is compromised in the second half of the disc once the gas has dissipated.

Hyper-Selective Posterior Fusion is Recommended When the Modified S-Line is Positive in Lenke 5C Adolescent Idiopathic Scoliosis.

Postoperative coronal decompensation and less fusion level are dilemmas and the proper selective posterior fusion (SPF) strategy should be investigated. We proposed a parameter, modified S-line, and aimed to investigate if the modified S-line could predict postoperative coronal decompensation in patients with Lenke 5C adolescent idiopathic scoliosis (AIS). This is a retrospective radiographic study and Lenke 5C AIS patients undergoing SPF during the period from September 2017 to June 2021 were included. The modified S-line was defined as the line linking the centers of the concave-side pedicles of the upper end vertebra (UEV) and lower end vertebra (LEV) at baseline. A modified S-line tilt to the right is established as modified S-line+ (UEV being to the right of the LEV). The patients were further categorized into two groups: the Cobb to Cobb fusion group and the Cobb-1 to Cobb fusion group. Outcomes including thoracic Cobb angle, TL/L Cobb angle, coronal balance, upper instrumented vertebra (UIV) translation, lower instrumented vertebra (LIV) translation, UIV tilt, LIV tilt, LIV disc angle, thoracic apical vertebral translation, lumbar apical vertebral translation (L-AVT), L-T AVT ratio, L-T Cobb were measured at baseline, immediately after surgery, and the last follow-up. Radiographic parameters and the incidence of both proximal and distal decompensation between the two groups were compared by chi-square test. Among 92 patients, 48 were modified S-line+ and 44 were modified S-line-. Modified S-line+ status was identified as a risk factor for postoperative proximal decompensation (p = 0.005) during follow-up. In Cobb to Cobb group, a higher occurrence of proximal decompensation in individuals with modified S-line+ status (p = 0.001) was confirmed. Also, in the Cobb to Cobb group with baseline modified S-line+ status, patients presenting decompensation showed a significantly larger baseline of the UIV tilt and postoperative disc angle below the lower instrumented vertebra. However, In Cobb-1 group, the incidence of decompensation after surgery showed no association with baseline modified S-line tilt status (p = 0.815 and 0.540, respectively). The modified S-line could serve as an important parameter in surgical decision-making for Lenke 5C AIS patients. Cobb to Cobb SPF is not recommended with a modified S-line+ status, and the Cobb-1 to Cobb fusion may serve as a potential alternative.

Analysis of the relationship between axial length, optic disc morphology, and regional variations in retinal vessel density in young adults with healthy eyes.

To investigate the relationship between optic disc morphology, axial length, and regional distribution of retinal vessels in healthy eyes of young adults. Nine hundred and two healthy eyes were enrolled in this university-based, cross-sectional study. Spectral-domain optical coherence tomography angiography was used to measure the parapapillary retinal vessel density. We automated the process of calculating optic disc tilt and rotation by using a program written in Python. Relationships between optic disc rotation, optic disc tilt, parapapillary vessel density, and other ocular parameters were analyzed using regression models. As axial length increased, optic disc morphology became more tilted and rotated inferiorly. The superficial vessel density (SVD) and radial peripapillary capillary density (RPCD) gradually decreased in all regions except for the temporal quadrant. Increased temporal SVD (OR [95% CI] = 1.081 [1.039, 1.124], p < 0.001), reduced nasal SVD (OR [95% CI] = 0.898 [0.861, 0.937], p < 0.01), and short relative lens position (OR [95% CI] = 0.126 [0.032, 0.495], p = 0.003) were significantly associated with the presence of a tilted optic disc. Inferior disc rotation was associated with decreased superior deep vessel density (DVD) and increased inferior DVD and temporal DVD after adjusting for sex and axial length. The tilted and rotated optic discs were associated with the distribution of SVD and DVD, respectively. We should fully consider the influence of optic disc morphology on parapapillary vessel density in eyes with myopia.

Deep learning-based optic disc classification is affected by optic-disc tilt

We aimed to determine the effect of optic disc tilt on deep learning-based optic disc classification. A total of 2507 fundus photographs were acquired from 2236 eyes of 1809 subjects (mean age of 46 years; 53% men). Among all photographs, 1010 (40.3%) had tilted optic discs. Image annotation was performed to label pathologic changes of the optic disc (normal, glaucomatous optic disc changes, disc swelling, and disc pallor). Deep learning-based classification modeling was implemented to develop optic-disc appearance classification models with the photographs of all subjects and those with and without tilted optic discs. Regardless of deep learning algorithms, the classification models showed better overall performance when developed based on data from subjects with non-tilted discs (AUC, 0.988 ± 0.002, 0.991 ± 0.003, and 0.986 ± 0.003 for VGG16, VGG19, and DenseNet121, respectively) than when developed based on data with tilted discs (AUC, 0.924 ± 0.046, 0.928 ± 0.017, and 0.935 ± 0.008). In classification of each pathologic change, non-tilted disc models had better sensitivity and specificity than the tilted disc models. The optic disc appearance classification models developed based all-subject data demonstrated lower accuracy in patients with the appearance of tilted discs than in those with non-tilted discs. Our findings suggested the need to identify and adjust for the effect of optic disc tilt on the optic disc classification algorithm in future development.

On the evolution of a twisted thin accretion disc in eccentric inclined supermassive binary black holes

ABSTRACT We propose a model of a twisted accretion disc around a Kerr black hole interacting with a secondary black hole of a smaller mass on an inclined eccentric orbit. We use parameters of the system, which may be appropriate for the so-called precessing massive model of OJ 287. We calculate expressions for torque exerted on the disc by the secondary and a contribution of the secondary to the apsidal precession of disc elements by a double averaging procedure over the periods of the secondary and the disc elements. These expressions are used at all scales of interest, including the ones inside the binary orbit. We calculate numerically the evolution of the disc tilt and twist assuming a flat initial configuration. We consider the disc aspect ratio h/r = 10−3, a rather large viscosity parameter α = 0.1 and several values of the primary rotational parameter, χ. We find that, after a few periods of Lense–Thirring precession of the orbit, the disc relaxes to a quasi-stationary configuration in the precessing frame with a non-trivial distribution of the disc inclination angle, β, over the radial scale. We propose an analytic model for this configuration. We show that the presence of the twisted disc leads to multiple crossings of the disc by the secondary per one orbital period, with time periods between the crossings being different from the flat disc model. Our results should be taken into account in the modelling of OJ 287. They can also be applied to similar sources.

Parapapillary βBM and γ Zones Played Different Roles in Axial Elongation Among Young Adolescents Using Optical Coherence Tomography.

To evaluate the influencing factors of parapapillary βBM and γ zones incidence in young adolescents and to explore their associations with axial length progression. In this prospective cohort study, 976 seventh-grade students from nine secondary schools in Beijing, China, were enrolled and followed up 1 year later. Parapapillary βBM zone was defined as retinal pigment epithelium loss while Bruch's membrane was present. Parapapillary γ zone was defined as the absence of retinal pigment epithelium and Bruch's membrane. Logistic regression model was used to analyze the influencing factors of βBM and γ zone incidence. A linear mixed model was used to analyze the associations between parapapillary zones and axial elongation. Of the 976 participants, 139 (14.2%) had only βBM zone, 398 (40.8%) had only γ zone, and 171 (17.5%) had both. At follow-up, the incidence of βBM zone was 11.5% (76/659), and the incidence of γ zone was 9.7% (39/404). Optic disc tilt, thinner subfoveal choroid, and longer axial length at baseline showed a higher risk of γ zone incidence. The absence of γ zone at baseline showed a faster axial length progression. When the baseline axial length was 25 mm or longer, the βBM zone was also related to the axial elongation. The γ zone was associated with axial length progression, and the βBM zone was also associated with the axial length progression when the axial length exceeded 25 mm, which was consistent with the notion that excessive axial length growth not only is the extension of the eyeball but also has its own pathologic changes.

Progression of Myopic Maculopathy Based on the ATN Classification System

Introduction: Myopic maculopathy is a sight-threatening disease, which causes irreversible vision faults and central vision loss. The purpose of this study is evaluating the risk factors of the myopic maculopathy progression according to the ATN classification system. Methods: Clinic data of 69 high myopia patients aged older than 40 years with a follow-up time of more than 2 years, who underwent fundus photography and OCT examination were retrospectively collected. Fundus changes were evaluated with ATN classification at the first and last follow-up times. The related factors affecting progress including axial length (AL), spherical equivalence (SE), subfoveal choroidal thickness (SFCT), disc-foveal distance (DFD), optic disc tilt, and parapapillary atrophy (PPA) were analyzed. Results: This study included 69 high-myopia patients with mean age 54.29 ± 10.41 years. The progression rate of myopic maculopathy (MM) was approximately 25.56%. Elongated DFD (5.37 ± 0.11 mm vs. 4.86 ± 0.37 mm; p < 0.001) and thinner SFCT (138.52 ± 29.38 μm vs. 184.87 ± 48.72 μm; p = 0.008) at baseline were linked with MM progression. In multiple logistic regression analysis, DFD was a substantial hazard risk factor (adjusted OR = 1.672, 95% CI: 1.135–2.498, p < 0.05) after adjusting for age, AL and SFCT. Receiver operating characteristic curve showed that DFD might serve as a predictor to discriminate the MM progression with a cut-off value of 5.15 mm and a substantial receiver operating characteristic curve area (AUC: 0.794). Compared with the non-progression group, the progression group had older age (p < 0.001), longer AL (p = 0.001), higher optic disc tilt rate (p < 0.001), and higher proportion of pre-existing PPA (p = 0.038) at baseline, the differences were statistically significant. Conclusion: Based on the ATN classification system, we found that the progression of MM was related to older age, longer AL, high disc tilt, pre-existing PPA, thinner SFCT, and longer DFD. The parameter of DFD was an important factor affecting the progression of MM, which is considered to have a higher probability of progression when the length is beyond 5.15 mm.

Static performance analysis of gas foil thrust bearings under inclined thrust disc considering the slip flow effect

As one of the important components in air compressors for fuel cell vehicles, the static performance of the gas foil thrust bearings greatly affects the operating stability of the rotor system. In actual operation, thrust disc tilt and the slip flow effect often occur, which will change the characteristics of bearings. Therefore, this paper focuses on the static performance of gas foil thrust bearings under tilting conditions with account of the slip flow effect. Firstly, the gas film thickness equation is established when the thrust disc is inclined, and the Reynolds equation is modified by the boundary slip conditions. Secondly, the load capacity and friction torque of bearings are solved by the finite difference method and successive over-relaxation method. Finally, the sensitivity of rigid and elastic bearings to tilt angles is analyzed by comparing the static characteristics under tilting conditions. The results show that the load capacity will be overestimated without considering the slip flow effect, and the tilting of the thrust disc increases both the load capacity and friction torque. Furthermore, compared with rigid bearings, elastic foil bearings have better adaptability to tilting conditions, which is conducive to the stable operation of the rotor system.

Quantification of peripapillary nerve fibre elevation and its association with axial length, optic disc tilt, and parapapillary atrophy area in young, healthy eyes.

Eyes with peripapillary nerve fibre elevation (pNFE) may have a gap between the optic nerve papillary margin on colour fundus photography and Bruch's membrane opening on cross-sectional optical coherence tomography (OCT). This study was conducted to evaluate the quantification of the height of pNFE in young healthy eyes and examine the relationship between pNFE height and axial length. A prospective, observational, cross-sectional study was performed involving 117 right eyes. All participants (mean age 25.8 years) underwent comprehensive ophthalmologic examination involving axial length, fundus photography, and peripapillary and optic disc OCT. pNFE height was defined as the distance between the retinal surface plane and the upper edge of the pNFE in optic disc cross-sectional OCT images. Optic disc tilt was evaluated using a sine curve on retinal nerve fibre layer B-scan images. Parapapillary atrophy (PPA) area in colour fundus images was calculated using ImageJ and corrected using Bennett's formula. We evaluated relationships between pNFE height, axial length, optic disc papillary tilt, and PPA area using Spearman's correlation analysis. Sixty-five eyes had pNFE, with a mean pNFE height of 84.7 μm. pNFE height was significantly positively correlated with axial length (r = 0.32, p < 0.001), optic disc tilt (r = 0.25, p = 0.008), and PPA area (r = 0.27, p = 0.004). pNFE is not rare in young healthy eyes. Eyes with higher pNFE had a longer axial length and larger optic disc tilt and PPA area.

Relationship between the structure and microcirculation of the optic disc region and myopic traction maculopathy in highly myopic eyes

PurposeTo explore the characteristics and influencing factors structural and microcirculatory of optic disc and peripapillary tissue in eyes with myopia traction maculopathy (MTM).MethodsThere were 100 eyes from 77 patients in this study. We used 1:1 matching axial length in myopic eyes. Patients were divided into two groups according to the presence or absence of MTM. Fundus structure parameters were obtained by swept source optical coherence tomography (SS-OCT), and the optic disc microcirculation parameters were obtained by OCT angiography (OCTA).ResultsMTM group were older (P = 0.001) and had poorer Best-corrected Visual Acuity (BCVA) (P = 0.011), the optic disc-fovea distance (DFD) was longer (P < 0.019), optic disc tilt was greater (P < 0.001), area of peripapillary atrophy (PPA) was larger (P < 0.001), and PPA/optical disc area (ONH) was higher (P < 0.001). The peripapillary scleral thickness (PST) was lower in the MTM group (P < 0.001). The mean peripapillary choroidal thickness (PCT) (P < 0.001) and PCT in the 10 orientations were significantly lower in the MTM group than in the NMTM group (all P < 0.01). Vascular density in the nasosuperior (NS) region of the optic disc was significantly lower in the MTM group (P = 0.037). The generalized estimating equation suggested that PPA area (P = 0.028), mean PCT (P = 0.008), superior PCT (P = 0.027), inferonasal PCT (P = 0.040), temporoinferior PCT (P = 0.013), and PST (P = 0.046) correlated with MTM. Age, axial length, optic disc tilt, PPA area, mean PCT, and optic disc central zone (0–2 mm) vascular density (all P < 0.05) were significantly correlated with PST.ConclusionsThe enlarged PPA area and thinner PCT and PST in eyes with MTM are more significant. Lower PST in high myopia was related to abnormalities of PCT and microcirculation.Trial registrationClinical Trial Registration number: ChiCTR2100046590

Formation of misaligned second-generation discs through fly-by encounters

ABSTRACT Observations reveal protoplanetary discs being perturbed by fly-by candidates. We simulate a scenario where an unbound perturber, i.e. a fly-by, undergoes an inclined grazing encounter, capturing material and forming a second-generation protoplanetary disc. We run N-body and three-dimensional hydrodynamical simulations of a parabolic fly-by grazing a particle disc and a gas-rich protoplanetary disc, respectively. In both our N-body and hydrodynamic simulations, we find that the captured, second-generation disc forms at a tilt twice the initial fly-by tilt. This relationship is robust to variations in the fly-by’s tilt, position angle, periastron, and mass. We extend this concept by also simulating the case where the fly-by has a disc of material prior to the encounter but we do not find the same trend. An inclined disc with respect to the primary disc around a misaligned fly-by is tilted by a few degrees, remaining close to its initial disc tilt. Therefore, if a disc is present around the fly-by before the encounter, the disc may not tilt up to twice the perturber tilt depending on the balance between the angular momentum of the circumsecondary disc and captured particles. In the case where the perturber has no initial disc, analysing the orientation of these second-generation discs can give information about the orbital properties of the fly-by encounter.

Deep Optic Nerve Head Morphology in Tilted Disc Syndrome and Its Clinical Implication on Visual Damage.

To study deep optic nerve head (ONH) morphology in tilted disc syndrome (TDS) and identify factors associated with retinal nerve fiber layer (RNFL) defect. In patients with TDS, we evaluated the optic disc shape using the Bruch's membrane opening (BMO)-anterior scleral canal opening (ASCO) offset and measured the border tissue (BT) length, depth, and angle in the direction of the tilt, using radial ONH optical coherence tomography (OCT). We compared the parameters between the TDS groups with and without RNFL defects. Twenty-one eyes had no glaucomatous RNFL defect, and 38 eyes had a glaucomatous RNFL defect. The group with RNFL defects had a higher baseline IOP, larger tilt axis of BMO-ASCO optic disc margin (76.4° ± 14.5° vs. 87.9° ± 15.4°, P = 0.012), larger BMO-lamina cribrosa insertion (LCI) angle (25.6° ± 9.3° vs. 43.6° ± 15.2°, P < 0.001), and more lamina cribrosa (LC) defects (4.3% vs. 30.6%, P = 0.028) than without RNFL defects. The tilt axis and BMO-LCI angle were significant factors after adjusting for baseline IOP and LC defect. The BMO-LCI angle had excellent diagnostic power for glaucomatous RNFL defect in TDS, similar to the visual field mean deviation. OCT-based large deep ONH BT angle and tilt axis were factors associated with the presence of RNFL defects in TDS. The results suggest a mechanism of RNFL defect associated with structural ONH deformation. Further investigations are warranted to understand the role of ONH structures in a general population with and without optic disc tilt.

Nozzle Shocks, Disk Tearing, and Streamers Drive Rapid Accretion in 3D GRMHD Simulations of Warped Thin Disks

The angular momentum of gas feeding a black hole (BH) may be misaligned with respect to the BH spin, resulting in a tilted accretion disk. Rotation of the BH drags the surrounding spacetime, manifesting as Lense–Thirring torques that lead to disk precession and warping. We study these processes by simulating a thin (H/r = 0.02), highly tilted () accretion disk around a rapidly rotating (a = 0.9375) BH at extremely high resolutions, which we performed using the general-relativistic magnetohydrodynamic code H-AMR. The disk becomes significantly warped and continuously tears into two individually precessing subdisks. We find that mass accretion rates far exceed the standard α-viscosity expectations. We identify two novel dissipation mechanisms specific to warped disks that are the main drivers of accretion, distinct from the local turbulent stresses that are usually thought to drive accretion. In particular, we identify extreme scale height oscillations that occur twice an orbit throughout our disk. When the scale height compresses, “nozzle” shocks form, dissipating orbital energy and driving accretion. Separate from this phenomenon, there is also extreme dissipation at the location of the tear. This leads to the formation of low-angular momentum “streamers” that rain down onto the inner subdisk, shocking it. The addition of low-angular momentum gas to the inner subdisk causes it to rapidly accrete, even when it is transiently aligned with the BH spin and thus unwarped. These mechanisms, if general, significantly modify the standard accretion paradigm. Additionally, they may drive structural changes on much shorter timescales than expected in α-disks, potentially explaining some of the extreme variability observed in active galactic nuclei.

Quantization of Optic Disc Characteristics in Young Adults Based on Artificial Intelligence

Purpose This study aimed to automatically and quantitatively analyse the characteristics of the optic disc by applying artificial intelligence (AI) to fundus images. Methods A total of 1084 undergraduates were recruited in this cross-sectional study. The optic disc area, cup-to-disc ratio (C/D), optic disc tilt, and the area, width, and height of peripapillary atrophy (PPA) were automatically and quantitatively detected using AI. Based on axial length (AL), participants were divided into five groups: Group 1 (AL ≤ 23 mm); Group 2 (23 mm < AL≤ 24 mm); Group 3 (24 mm < AL≤ 25 mm); Group 4 (25 mm < AL< 26 mm) and Group 5 (AL ≥ 26 mm). Relationships between ocular parameters and optic disc characteristics were analysed. Result A total of 999 undergraduates were included in the analysis. The prevalence of optic disc tilting and PPA were 47.1% and 92.5%, respectively, and increased with the severity of myopia. The mean optic disc area, PPA area, C/D, and optic disc tilt ratio were 1.97 ± 0.46 mm2, 0.84 ± 0.59 mm2, 0.18 ± 0.07, and 0.81 ± 0.08, respectively. In Group 5, the average optic disc area (1.84 ± 0.41 mm2) and optic disc tilt ratio (0.79 ± 0.08) were significantly smaller and the PPA area (1.12 ± 0.61 mm2) was significantly larger than those in the other groups. AL was negatively correlated with optic disc area and optic disc tilt ratio (r=–0.271, –0.219; both p < 0.001) and positively correlated with PPA area, width, and height (r = 0.421, 0.426, 0.345; all p < 0.01). A greater AL (β = 0.284, p < 0.01) and a smaller optic disc tilt ratio (β=–0.516, p < 0.01) were related to a larger PPA area. Conclusion The characteristics of the optic disc can be feasibly and efficiently extracted using AI. The quantization of the optic disc might provide new indicators for clinicians to evaluate the degree of myopia.