Disc Tilt Research Articles

Association Between Optic Nerve Head Deformation and Retinal Microvasculature in High Myopia

To evaluate the retinal microvasculature of peripapillary and macular regions in highly myopic eyes and investigate the association between the vascular parameters and optic nerve head (ONH) deformation. Cross-sectional study. Seventy-one subjects with highly myopic eyes and 26 subjects with emmetropic eyes were included. Horizontal B-scan images of the ONH were obtained using optical coherence tomography (OCT) and horizontal tilt angles were measured. Integrated automated algorithms in the Avanti OCT angiography were used to quantify the peripapillary vessel density and area of the foveal avascular zone (FAZ) at the level of superficial and deep vascular networks. Association between horizontal disc tilt and the vascular parameters was evaluated. The mean axial length and horizontal tilt angle were 26.73 ± 0.63mm and 9.77 ± 3.00 degrees in the highly myopic group and 23.46 ± 0.55mm and 5.95 ± 3.48 degrees in the emmetropic group, respectively. Highly myopic eyes exhibited significantly lower average peripapillary vessel density (P= .010) and larger superficial and deep FAZs (P= .001 and P < .001, respectively) compared with emmetropic eyes. Linear regression analyses showed that horizontal tilt angle significantly correlated the average peripapillary vessel density (P= .037) and the areas of superficial (P<.001) and deep (P < .001) FAZs. The retinal microvasculature was significantly different in highly myopic eyes according to the degree of horizontal optic disc tilt. In addition to peripapillary vessel density, FAZ can be affected by the degree of optic disc tilt.

Retinal Nerve Fiber Layer Protrusion Associated with Tilted Optic Discs.

This study resulted in the identification of an optic nerve head (ONH) feature associated with tilted optic discs, which might potentially contribute to ONH pathologies. Knowledge of such findings will enhance clinical insights and drive future opportunities to understand disease processes related to tilted optic discs. The aim of this study was to identify novel retinal nerve fiber layer (RNFL) anomalies by evaluating tilted optic discs using optical coherence tomography. An observed retinal nerve fiber protrusion was further investigated for association with other morphological or functional parameters. A retrospective review of 400 randomly selected adult patients with ONH examinations was conducted in a referral-only, diagnostic imaging center. After excluding other ONH pathologies, 215 patients were enrolled and evaluated for optic disc tilt and/or torsion. Gross anatomical ONH features, including size and rim or parapapillary region elevation, were assessed with stereoscopic fundus photography. Optical coherence tomography provided detailed morphological information of individual retinal layers. Statistical analysis was applied to identify significant changes between individual patient cohorts. A dome-shaped hyperreflective RNFL bulge, protruding into the neurosensory retina at the optic disc margins, was identified in 17 eyes with tilted optic discs. Available follow-up data were inconclusive regarding natural changes with this ONH feature. This RNFL herniation was significantly correlated with smaller than average optic disc size (P = .005), congenital disc tilt (P < .0001), and areas of rim or parapapillary elevation (P < .0001). This study reports an RNFL protrusion associated with tilted optic discs, which has not previously been assessed as an independent ONH structure. The feature is predominantly related to congenital crowded, small optic discs and variable between patients. This study is an important first step to elucidate diagnostic capabilities of tilted disc morphological changes and understanding associated functional deficits.

Comparison of Lumbosacral Alignment in Geriatric and Non-Geriatric patients suffering low back pain.

Objective:Lumbosacral alignment is a crucial factor for an appropriate spinal function. Changes in spinal alignment lead to diminished body biomechanics. Additionally, lumbosacral alignment may affect quality of life, sagittal balance and fall risk in elderly. In this study, we aimed to compare lumbosacral alignment in geriatric and non-geriatric patients suffering from low back pain.Methods:A total of 202 (120 male and 82 female) patients who visited to physical medicine and rehabilitation clinic with low back pain between January 2017 and August 2017 were enrolled in this study. Standing lateral lumbar radiographs were obtained from the electronic hospital database. Lumbar lordosis angle, sacral tilt, lumbosacral angle and lumbosacral disc angle were calculated on lateral standing lumbar radiographs.Results:The mean age of the non-geriatric group was 43.02 ± 13.20 years, the geriatric group was 71.61 ± 6.42 years. In geriatric patients, lumbar lordosis angle, sacral tilt and lumbosacral disc angle were significantly smaller (p = 0.042, p = 0.017 and p = 0.017). No significant differences were observed in lumbosacral angle between the groups (p = 0.508).Conclusion:Our study indicates the specific changes in lumbosacral alignment with aging. Identifying these changes in lumbosacral alignment in the geriatric population will enable to create proper rehabilitation strategies.

Topographic Relationship Between Optic Disc Torsion and ß-Zone Peripapillary Atrophy in the Myopic Eyes of Young Patients With Glaucomatous-appearing Visual Field Defects.

The purpose of this study was to assess the topographic correlation between optic disc torsion (ODT) and beta-zone peripapillary atrophy (β-PPA) in young patients with myopia and glaucomatous-appearing visual field defects (VFDs). We consecutively recruited 110 eyes of 110 young patients with myopia and glaucomatous-appearing VFDs. Retinal nerve fiber layer (RNFL) and macular ganglion cell inner plexiform layer (mGCIPL) thicknesses were measured to compare between the groups with different ODT directions. For evaluating topographic correlation, the direction and degree of ODT and the direction and angles of β-PPA and point of maximum radial extent (PMRE) of β-PPA were measured on fundus photographs. Multivariate logistic regression analysis was performed to determine the clinical factors associated with inferior ODT direction. The relationships between torsional degree and clinical variables were evaluated using linear regression analyses. Among the 110 eyes, 19 had superior ODT and 91 had inferior ODT. Compared with myopic eyes with superior ODT, those with inferior ODT showed less severity of glaucoma as determined by RNFL or mGCIPL thickness and had a longer axial length, greater amount of optic disc tilt, larger β-PPA angle, and higher ratio of β-PPA area and disc area. ODT direction was significantly associated with the locations of β-PPA and PMRE. Torsional degree was significantly correlated with the β-PPA angle. ODT direction showed a significant association with the locations of β-PPA and PMRE of β-PPA. Torsional degree was correlated with the β-PPA angle in the myopic eyes of young patients with glaucomatous-appearing VFDs.

Cryptococcal meningitis presented with irreversible binocular blindness in an HIV infected patient- A case report

Cryptococcal meningitis is a major HIV-related opportunistic infection, occurring when CD4 counts are below 100. Ocular involvement is seen with up to 30% of patients with cryptococcal meningitis. A young HIV infected male was admitted to in patient department of School of Tropical Medicine, Calcutta with complaints of headache for two months with dimness of vision for 10 days. Examination showed decreased visual acuity on both eyes, neck rigidity with right sided extensor plantar reflex, external ophthalmoplegia in the form of left 6th cranial nerve palsy, bilaterally absent light reflex, power 5/5 in all four limbs with normal tone and right eye hypermetropic tilted disc, left eye normal on ophthalmoscopy. India Ink preparation of CSF showed encapsulated budding yeast cells. Fungal culture grows Cryptococcus sp. CSF CRAG (cryptococcal antigen measured by immunochromatographic method) was positive in high titre (1:2560). MRI of brain revealed multiple tiny hypo to isointense lesions on T1 and hyperintense lesions on T2, T2 flair sequences are seen in basal ganglia, peri & paraventricular white matter and centrum semi-ovale on both sides. He was managed with injection amphotericin B deoxycholate along with fluconazole as per WHO recommendations and treatment related complications were managed accordingly. Visual acuity was followed in the entire treatment period but vision did not improve, but GCS improved to 15/15, there was no headache, no neck rigidity. Repeat MRI of brain after three weeks of treatment showed absence of above mentioned lesions. After 12 months of follow up the patient had no perception of light in both eyes and no wave in VEP study of both eyes suggestive of permanent visual loss following cryptococcal meningitis. So, cryptococcal meningitis after completion of treatment may have irreversible visual loss.

Ametropia, retinal anatomy, and OCT abnormality patterns in glaucoma. 2. Impacts of optic nerve head parameters

Clinicians use retinal nerve fiber layer thickness (RNFLT) measured by optical coherence tomography (OCT) as an adjunct to glaucoma diagnosis. Ametropia is accompanied by changes to the optic nerve head (ONH), which may affect how OCT machines mark RNFLT measurements as abnormal. These changes in abnormality patterns may bias glaucoma diagnosis. Here, we investigate the relationship between OCT abnormality patterns and the following ONH-related and ametropia-associated parameters on 421 eyes of glaucoma patients: optic disc tilt and torsion, central retinal vessel trunk location (CRVTL), and nasal and temporal retinal curvature adjacent to ONH, quantified as nasal/temporal slopes of the inner limiting membrane. We applied multivariate logistic regression with abnormality marks as regressands to 40,401 locations of the peripapillary region and generated spatial maps of locations of false positive/negative abnormality marks independent of glaucoma severity. Effects of torsion and temporal slope were negligible. The effect of tilt could be explained by covariation with ametropia. For CRVTL/nasal slope, abnormality pattern shifts at 7.2%/23.5% of the peripapillary region were detected, respectively, independent of glaucoma severity and ametropia. Therefore, CRVTL and nasal curvature should be included in OCT RNFLT norms. Our spatial location maps may aid clinicians to improve diagnostic accuracy.

A twin study of cilioretinal arteries, tilted discs and situs inversus

PurposeTo establish the prevalence and heritability of cilioretinal arteries (CRAs), tilted discs (TDs) and situs inversus (SI).MethodsFundus photos from the Twins UK Adult Twin registry twin database were analyzed: 1812 individuals, 526 complete monozygotic (MZ) twin pairs and 336 complete dizygotic (DZ) pairs. Images were assessed non-stereoscopically on a computer screen by the same ophthalmologist for presence of CRAs, TDs or SI. Prevalence figures, probandwise concordances and heritabilities were calculated.ResultsPrevalence of a CRA in subjects’ right eyes was 28.6% (26.5–30.8). Prevalence of subjects with a CRA in at least one eye was 45.0% (42.6–47.5), with a TD in at least one eye was 1.2% (0.8–1.9), and with SI at least one eye was 0.5% (0.3–1.0). There was no association between birth weight and presence of CRA.Concordance for CRA in at least one eye (MZ twins) was 60% (95% CI 55–64), and (DZ) was 45% (95% CI 39–51). Heritability for CRAs in at least one eye was 49.4% (95% CI 38.1–59.7) and for both eyes was 32.9% (95% CI 10.4–53.3). We were unable to calculate meaningful heritabilities or concordances for TDs and situs SI, due to insufficient numbers.ConclusionsThe presence of CRAs appears to be moderately heritable, with greater variance explained by individual environmental factors or even stochastic events. They were not associated with low birth weight. Future genetic research and studies of birth/lifecourse cohorts may offer further insights into the etiology of congenital papillovascular abnormalities.

Application of the ISNT rules on retinal nerve fibre layer thickness and neuroretinal rim area in healthy myopic eyes.

We determined the applicability of inferior>superior>nasal>temporal (ISNT) rules on retinal nerve fibre layer (RNFL) thickness and rim area and evaluated the impact of various ocular factors on the performance of the ISNT rules in healthy myopic eyes. A total of 138 eyes from 138 healthy myopic subjects were included in this cross-sectional observational study. The peripapillary RNFL and optic disc in each eye were imaged with Cirrus HD optical coherence tomography (OCT) and Heidelberg Retina Tomograph II (HRT2), respectively. The performance of the inferior>superior (IS), inferior>superior>nasal>temporal (IST) and ISNT rules on RNFL thickness and rim area was determined and compared between low-to-moderate myopia and high myopia. The effects of ocular factors [including axial length, disc area, disc tilt, disc torsion, disc-fovea angle (DFA) and retina artery angle] on the performance of ISNT rules were evaluated with logistic regression analysis. The mean axial length and refractive error were 25.57±1.09mm (range, 22.52-28.77mm) and -5.12±2.30D [range, -9.63 to -0.50dioptres (D)], respectively. Sixty-three per cent of the healthy eyes were compliant with the ISNT rule on rim area, while ISNT rule on RNFL thickness was followed in only 11.6% of the included eyes. For rim area, smaller disc area was significantly associated with increased compliance of the IS rule (odds ratio: 0.46, p=0.039), IST rule (odds ratio: 0.46, p=0.037) and ISNT rule (odds ratio: 0.44, p=0.030). For RNFL thickness, greater DFA was significantly associated with increased compliance of the IS and IST rules (odds ratio: 1.30, p<0.001; odds ratio: 1.19, p=0.006, respectively). In healthy myopic subjects, 88.4% and 37% of eyes did not comply with the ISNT rule on RNFL thickness and rim area, respectively. Due to significant low compliance in healthy eyes, the ISNT rule and its variants have limited potential utility in diagnosing glaucoma in myopic subjects.

Three-Dimensional Evaluation of Posterior Pole and Optic Nerve Head in Myopes with Glaucoma

The degree of myopia is represented by a global index, such as refractive error or axial length. However, the progression of myopia mainly develops in the posterior eyeball. Therefore, it is reasonable to assume that the evaluation of myopia should be confined to the posterior segment, where most of the growth and lengthening occurs. Swept source optical coherence tomography software can reconstruct the scans to the coronal view of the posterior pole, which provides additional anterior-posterior depth (z axis in the Cartesian coordinates) that is not provided with the common fundus photograph. We deduced that the parameter of deepest point of the eyeball (DPE) as a surrogate for posterior pole configuration. Between myopes with and without normal tension glaucoma (NTG) with similar axial length, myopes with NTG had deeper and more distant location of the DPE from the optic disc. The difference of the DPE position between the myopes with and without NTG may have implications for the larger optic disc tilt and torsion characteristic of myopes with NTG. Furthermore, these data suggest that myopes with NTG go through excessive posterior scleral remodeling, which may result in vulnerable optic nerve head.

Visual field assessment in high myopia with and without tilted optic disc

BackgroundThe aim was to evaluate the effect of the tilted optic disc on the visual field in highly myopic eyes.MethodsA total of 58 eyes from 58 highly myopic individuals underwent detailed ophthalmic examination and were categorised into two groups according to the presence of a tilted optic disc. The visual field of 20 eyes (mean age of 28.95 ± 7.22 years) with tilted optic discs were compared with 38 eyes (mean age of 27.87 ± 6.08 years) of control subjects without tilted optic discs using the 30‐2 SITA standard protocol with a Humphrey Field Analyzer – HFA II‐i. Optic disc tilt was assessed from retinal photographs exported to Adobe Photoshop software. Disc ovality was assessed using the ratio of minimum to maximum disc diameter. A ratio of up to 0.80 was considered a tilted optic disc.ResultsFoveal threshold sensitivity showed no statistically significant difference between tilted and non‐tilted groups (35.16 ± 2.71 dB versus 35.37 ± 2.35 dB, p = 0.76). The mean deviation was −3.29 ± 2.03 dB in the tilted group and −3.49 ± 2.56 dB in the non‐tilted group (p = 0.77). Additionally, there were no significant differences in the average deviation between the two groups in four quadrants and four hemifields; however, the lowest average deviation was observed in the superotemporal quadrant in the tilted group (−4.54 ± 3.16 dB). In the non‐tilted group, 29 per cent had no visual field defect, 24 per cent had an arcuate scotoma and 20 per cent had generalised depression. In the tilted group, 30 per cent had an arcuate scotoma, 30 per cent had generalised depression and 13 per cent had no visual field defect. Other visual field defects occurred at frequencies less than 15 per cent in both groups.ConclusionsThe investigation of visual field patterns may be more appropriate than quantitative indices (for example, total mean deviation, foveal threshold sensitivity, average deviation) to assess the visual field in highly myopic patients with tilted optic discs.

Correlations between local peripapillary choroidal thickness and axial length, optic disc tilt, and papillo-macular position in young healthy eyes.

Optical coherence tomography (OCT) has made it possible for clinicians to measure the peripapillary choroidal thickness (ppCT) noninvasively in various ocular diseases. However, the ocular factors associated with the ppCT have not been conclusively determined. The purpose of this study was to determine the relationship between the local ppCT and the axial length, optic disc tilt, and the angle of the papillo-macular position (PMP) in healthy eyes. This was a prospective, observational cross-sectional study of 119 right eyes of 119 healthy Japanese volunteers. The ppCT was manually measured at eight sectors around the optic disc using the B-scan images of the Topcon 3D OCT RNFL 3.4 mm circle scan. The trajectory of the retinal pigment epithelium in the B-scan image was fitted to a sine curve using ImageJ, and the amplitude of the sine curve was used to determine the degree of the optic disc tilt. The PMP angle was determined in the color fundus photographs. The relationships between the ppCT and the axial length, the optic disc tilt, and PMP angle were determined by Spearman and multiple correlation analyses. The mean age was 25.8 ± 3.9 years and the mean axial length was 25.5 ± 1.4 mm. The ppCT was significantly and negatively associated with the axial length (R = -0.43 to -0.24, P<0.01) and positively associated with the PMP angle (R = 0.28 to 0.37, P<0.01) in all eight circumpapillary sectors. The temporal and infratemporal ppCTs were significantly and negatively associated with the optic disc tilt (R = -0.31, -0.20, P<0.05). The results of multiple regression analyses were similar to that of Spearman correlation analysis. In conclusion, the axial length and PMP angle can affect the ppCT in all circumferential sectors, however the tilt of the optic disc is correlated with only some of the sectors. This should be remembered in interpreting the ppCT.

Compressed 3D and 2D digital images versus standard 3D slide film for the evaluation of glaucomatous optic nerve features

SynopsisClinicians can feel confident compressed three-dimensional digital (3DD) and two-dimensional digital (2DD) imaging evaluating important features of glaucomatous disc damage is comparable to the previous gold standard of stereoscopic slide...

Sub-classification of myopic glaucomatous eyes according to optic disc and peripapillary features.

PurposeTo investigate the sub-classification of myopic glaucomatous eyes by optic disc and peripapillary features.MethodsOptic disc tilt and torsion were determined from retinal nerve fiber layer photographs. Based on the location of the Bruch’s membrane (BM) opening within the β-zone of the peripapillary atrophy (PPA) area, the widths of β-zone PPA (PPA1W), PPA+BM (PPA2W), and PPA-BM (PPA3W) were measured with enhanced depth imaging spectral-domain optical coherence tomography. Cluster analysis that employed partitioning around medoids was performed with these parameters, the presence of inward rotation of BM ending axial length (AXL), and central corneal thickness.ResultsA total of 115 eyes (AXL≥24 mm) were included. Two clusters produced maximum overall silhouette widths (average = 0.43). Visual field (VF) mean deviation was not different between cluster 1 (52 eyes; -4.02±3.01 dB) and cluster 2 (63 eyes; -5.21±5.62 dB; p = 0.174). In cluster 1 compared to cluster 2, optic disc tilt was significantly greater, PPA1W and PPA3W were longer, and AXL was longer (all p<0.001). The presence of an inward rotation of BM ending was more frequent in cluster 2 (p = 0.043). Forty-one eyes (78.8%) in cluster 1 had superior VF defects while 10 eyes (19.2%) had inferior defects, and only one eye (2%) had defects in both hemifields. Eyes in cluster 2 were more evenly distributed: 55.6% had superior defects, 34.9% had inferior defects, and 9.5% had defects in both hemifields (p = 0.023).ConclusionsMyopic glaucomatous eyes characterized by optic disc and peripapillary configurations can be classified as two distinct types, and the most distinct difference between the two was degree of optic disc tilt and width of PPA. The location of VF defects were also significantly different between two clusters.

The Location of the Deepest Point of the Eyeball Determines the Optic Disc Configuration

Tilted and rotated appearances are hallmarks of the myopic optic disc. As the eyeball grows axially, the posterior pole elongates not only globally but in a localized manner as well. In this process, the optic disc is pulled towards the deepest point of the elongated eyeball, which might result in a change in optic disc configuration. Thus, we hypothesized that analyzing the variation of posterior pole contour can play a major role in understanding optic disc configuration in myopic subjects. By analyzing consecutive images of swept source OCT coronal sections at the posterior pole, the deepest interface between Bruch’s membrane and the choroid could be identified as the deepest point of the eyeball (DPE). The location and the properties of the DPE differed significantly between the 125 eyes of non-glaucomatous myopic group and the 40 eyes of non-glaucomatous emmetropic group classified based on 24 mm axial length. The results suggested that the larger disc to DPE angle and the larger disc to DPE depth strongly predicts the optic disc torsion degree and the optic disc tilt. Our findings suggest that identifying the posterior pole profile plays a major role in understanding the optic disc alterations found in myopic subjects.

Optic Nerve Tilt, Crescent, Ovality, and Torsion in a Multi-Ethnic Cohort of Young Adults With and Without Myopia.

PurposeThe purpose of this article is to evaluate optic nerve head (ONH) characteristics in an ethnically diverse cohort of young U.S. adults.MethodsIn this study, 409 myopes and 206 nonmyopes (median age 22 years) completed measures including biometry and spectral domain optical coherence tomography from enface (ovality and torsion) and cross-sectional (tilt and crescent width) scans. Associated factors were evaluated using multivariable models.ResultsIn myopic versus nonmyopic right eyes, median tilt (6.0° vs. 2.4°; P < 0.0001) and frequency of crescents (49% vs. 10%; P < 0.0001) were higher in myopes. Right eyes with crescents had higher median tilts (8.8° [myopic], 9.0° [nonmyopic]) than those without crescent (2.5° [myopic], 2.1° [nonmyopic]), irrespective of refractive group (both P < 0.0001). Torsion was similar between groups, with a slight difference in ovality (0.89 vs. 0.91; P < 0.03). Data in the left eyes were similar, and modeling was done only for the right myopic eyes. Multivariable models showed that an increased tilt was associated with ethnicity (P < 0.001), the presence of crescent (P < 0.001), and smaller ONH diameter (P < 0.0031), with interactions between ethnicity and crescent (P = 0.002). Specifically, ONH tilt was significantly higher in Asian eyes without crescent (P < 0.0001 for all comparisons), and crescent width was associated with increased tilt in non-Asian eyes (P < 0.02). Crescent width was associated with ethnicity (greatest in Asians) and disc tilt. Interactions were observed between tilt and ethnicity, whereby tilt had a greater effect on crescent width in non-Asian eyes, and crescent width was associated with increased tilt in non-Asian eyes.ConclusionsThe data clarify the influence of ethnicity and myopia on ONH characteristics in young adults and may inform future studies of biomechanical properties or of retinal pathology of the myopic eye.

Structural parameters associated with location of peaks of peripapillary retinal nerve fiber layer thickness in young healthy eyes.

The location of the peaks of the circumpapillary retinal nerve fiber layer (cpRNFL) thickness is affected by several ocular parameters. In this study, we have generated equations that can determine the peaks of the cpRNFL. This study was a prospective, observational, cross sectional study of 118 healthy right eyes. The axial length, optic disc tilt, superiortemporal (ST)- and inferiortemporal (IT)-peaks of the cpRNFL thickness, and angles of the ST and IT retinal arteries (RA) and veins (RV) were determined. The correlations between the location of the ST- and IT-peaks and ocular structural parameters and the sex, body height and weight were calculated. The best fit equations to generate the location of the ST/IT-peaks were determined using corrected-Akaike Information Criteria. The location of the ST-peak was 0.72+(0.40 x ST-RA)+(0.27 x ST-RV)+(0.14 x height)–(0.47 x papillo-macular-position)–(0.11 x disc tilt) with a coefficient of correlation of 0.61 (P<0.0001). The location of the IT-peak was 21.88+(0.53 x IT-RA)+(0.15 x IT-RV)+(0.041 x corneal thickness)-(1.00 x axial length) with a coefficient of correlation of 0.59 (P<0.0001). The location of ST/IT peaks is determined by different parameters of the ocular structure. These equations allow clinicians to obtain an accurate location of the peaks for a more accurate diagnosis of glaucoma.

Multiple Temporal Lamina Cribrosa Defects in Myopic Eyes with Glaucoma and Their Association with Visual Field Defects

To investigate characteristics of lamina cribrosa (LC) defects in myopic eyes with open-angle glaucoma (OAG) using spectral-domain (SD) optical coherence tomography (OCT). Cross-sectional study. One hundred thirty-three eyes with OAG and 83 eyes without OAG, with axial length of 24 mm or more. Serial enhanced depth imaging SD OCT B-scans of the optic disc were acquired and reviewed for LC defects (diameter, ≥100 μm) and large pores (diameter, 60-100 μm). The numbers and locations of LC defects and large pores in each eye were assessed. In eyes with OAG, factors related to the number of LC defects were evaluated, as well as the association between the locations of LC defects and visual field (VF) defects (e.g.,paracentral scotoma [PCS] and superior or inferior hemifield defects). Numbers and locations of LC defects and large pores. In myopic eyes with and without OAG, the average numbers of LC defects were 3.8 and 0.8 and numbers of large pores were 1.9 and 1.6, respectively. In both groups, LC defects and large pores were located predominantly at the temporal periphery. Among eyes with OAG, the number of LC defects was relatively high in the eyes with greater optic disc tilt angle and worse mean deviation of the VF (both P < 0.001). The number of temporal LC defects and tilt angle were associated with presence of PCS, whereas the number of inferior and superior LC defects and torsion direction were associated with presence of superior and inferior VF defects. Myopic eyes with OAG exhibited LC defects and large pores at similar locations as those without OAG, but in greater numbers, suggesting that these focal alternations of the LC in myopic eyes may evolve into larger defects when glaucoma develops in the eye. The number of LC defects, which was related to the optic disc tilt angle, was associated significantly with glaucomatous VF defects in both severity and location. This suggests that myopia may influence glaucomatous VF defects through optic disc tilt by way of an increased number of LC defects at the temporal periphery.

A tilted and warped inner accretion disc around a spinning black hole: an analytical solution

Inner accretion disc around a black hole provides a rare, natural probe to understand the fundamental physics of the strong gravity regime. A possible tilt of such a disc, with respect to the black hole spin equator, is important. This is because such a tilt affects the observed spectral and timing properties of the disc X-ray emission via Lense-Thirring precession, which could be used to test the theoretical predictions regarding the strong gravity. Here, we analytically solve the steady, warped accretion disc equation of Scheurer and Feiler (1996), and find an expression of the radial profile of the disc tilt angle. In our exact solution, considering a prograde disc around a slowly spinning black hole, we include the inner part of the disc, which was not done earlier in this formalism. Such a solution is timely, as a tilted inner disc has recently been inferred from X-ray spectral and timing features of the accreting black hole H1743-322. Our tilt angle radial profile expression includes observationally measurable parameters, such as black hole mass and Kerr parameter, and the disc inner edge tilt angle $W_{\rm in}$, and hence can be ideal to confront observations. Our solution shows that the disc tilt angle in $10-100$ gravitational radii is a significant fraction of the disc outer edge tilt angle, even for $W_{\rm in} = 0$. Moreover, tilt angle radial profiles have humps in $\sim 10-1000$ gravitational radii for some sets of parameter values, which should have implications for observed X-ray features.

Une série continue de 27 patients adultes opérés d’un spondylolisthésis isthmique L5-S1 par voie combinée : résultats cliniques et radiologiques à 1 an de suivi

Through this single-center consecutive prospective study, we evaluated the results of a combined approach for L5-S1 isthmic spondylolisthesis, using a polyetheretherketone (PEEK) interbody lordotic cage during anterior approach and pedicle screw-based posterior fixation. Between 2010 and 2014, 27 adult patients were treated for L5-S1 isthmic spondylolisthesis (high and low grades) by a combined approach with a minimum follow-up of one year. Clinical outcome was assessed before surgical treatment and at four months and one year after surgery by: VAS, Oswestry Index (ODI) and Rolland-Morris scores. Two observers evaluated the following radiological parameters: pelvic incidence, pelvic tilt, lumbar lordosis, segmental lordosis L5-S1, anterior and posterior disc height, spinal vertical axis (SVA), SVA/sacro-femoral distance (SFD) ratio. Fusion was evaluated on the CT scan at one-year follow-up. Blood loss, surgery time and complications were also collected. The mean age was 47.7 years (±16.9). The VAS, ODI and Rolland-Morris scores were significantly improved postoperatively, decreased from 7.5 (±1.45); 48 (±19.25); 15.3 (±4.67) before the surgery to 3.8 (±2.55); 28.7 (±19.58) and 7.76 (±7.21) respectively at one year after the surgery (P=0.05). The mean follow-up was 3.3 years. Mean surgery time was 193.7min (±37). Fusion was obtained in 100% of cases. Segmental lordosis L5-S1, pelvic tilt, slippage, anterior and posterior L5-S1 disc height were significantly improved postoperatively, they passed from 20.1; 22.6; 35.3%; 26.4%; 17.9% to 29.5; 20.6; 20.3%; 64.4%; 36.3% respectively. Combined surgical procedure meets the required goals of surgery in the treatment of adults L5-S1 isthmic spondylolisthesis.

Kozai–Lidov disc instability

Recent results by Martin et al. (2014) showed in 3D SPH simulations that tilted discs in binary systems can be unstable to the development of global, damped Kozai-Lidov (KL) oscillations in which the discs exchange tilt for eccentricity. We investigate the linear stability of KL modes for tilted inviscid discs under the approximations that the disc eccentricity is small and the disc remains flat. By using 1D equations, we are able to probe regimes of large ratios of outer to inner disc edge radii that are realistic for binary systems of hundreds of AU separations and are not easily probed by multi-dimensional simulations. For order unity binary mass ratios, KL instability is possible for a window of disc aspect ratios H/r in the outer parts of a disc that roughly scale as (n_b/n)^2 < H/r < n_b/n, for binary orbital frequency n_b and orbital frequency n at the disc outer edge. We present a framework for understanding the zones of instability based on the determination of branches of marginally unstable modes. In general, multiple growing eccentric KL modes can be present in a disc. Coplanar apsidal-nodal precession resonances delineate instability branches. We determine the range of tilt angles for unstable modes as a function of disc aspect ratio. Unlike the KL instability for free particles that involves a critical (minimum) tilt angle, disc instability is possible for any nonzero tilt angle depending on the disc aspect ratio.