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Spaceflight associated neuro-ocular syndrome (SANS) is one of the potential barriers to human long-duration spaceflight (LDSF), including a manned mission to Mars. While a large barrier, the pathophysiology of SANS is not well understood, and functional and structural findings from SANS continue to be further characterized. Currently on the International Space Station (ISS), scheduled visual assessments are static visual acuity, Amsler grid, and a self-reported survey. Additional visual assessments may help the understanding of this neuro-ophthalmic phenomenon, as well as the effects of spaceflight of overall ocular health. In this paper, a case is made for expanding scheduled visual assessments to include dynamic visual, contrast sensitivity (CS), visual field testing, and virtual reality-based metamorphopsia assessment during spaceflight. These further assessments may play a key role in helping to determine the structural and functional changes associated with SANS, which are crucial to maintain astronaut vision during LDSF, as well as for developing countermeasures. Finally, a brief discussion is provided about current challenges to expanding visual testing during spaceflight and potential solutions to these barriers, specifically head-mounted visual assessment technology.
Volume reductions in brain structures of patients with schizophrenia spectrum disorder (SSD) have repeatedly been found in voxel-based morphometry MRI studies. Hence, an underlying neurodegenerative etiological component of SSD is currently being discussed. In recent years, the imaging method of optical coherence tomography (OCT) has shown its potential in evaluating structural changes in the retina in patients with confirmed neurodegenerative disorders, providing a window into the brain.
Objectives
To evaluate potential differences in measurements of retinal layers between patients with schizophrenia spectrum disorder and healthy controls with OCT.
Methods
Twenty-six patients with schizophrenia or schizoaffective disorder and 23 age- and sex-matched healthy controls were examined with the Heidelberg Spectralis OCT system to derive a single-layer analysis of both retinas. The segmentation of retinal layers was manually corrected to minimize artifacts and software imprecisions.
Results
Compared to the control group, SSD patients showed reduced thickness and volume measurements for nearly all retinal layers, and these differences reached significance for macular volume, macular thickness, retinal nerve fiber layer (RNFL) and inner nucleiform layer (INL). Furthermore, a significant correlation between the duration of illness and the total volume of the RNFL was found.
Conclusions
Our OCT measurements demonstrate reduced single retinal layer thickness in patients with SSD. In the context of the MRI volume changes, our results provide further evidence that structural changes seen in the brain of patients are also observable in the retina, potentially allowing further insights into the different components of the nervous system that are altered in this highly etiologically complex disorder.
Idiopathic intracranial hypertension (IIH) typically presents with bilateral papilledema; however, highly asymmetric and rare unilateral cases have been reported. We report three cases of IIH meeting modified Dandy criteria presenting with unilateral papilledema. Magnetic resonance imaging (MRI) demonstrated bilateral distention of the optic nerve sheaths and computed tomography (CT) of the orbits demonstrated a smaller diameter of the optic canal in the unaffected eye in two cases. Papilledema fully resolved in all with acetazolamide. Of postulated mechanisms, we suspect that differences in bony optic canal diameter, compliance of the lamina cribrosa, and optic nerve sheath anatomy may contribute to asymmetry.
Cognitive impairment in multiple sclerosis (MS) has a complex relationship with disease progression and neurodegeneration. The aim of this study was to shed light on the importance of early detection of cognitive impairment in MS patients.
Methods:
The study comprised two groups of definite MS patients, relapsing remitting multiple sclerosis (RRMS) and secondary progressive multiple sclerosis (SPMS), each with 25 patients. Physical disability was assessed using the Expanded Disability Status Scale (EDSS), while the risk of secondary progression was assessed using the Bayesian Risk Estimate for Multiple Sclerosis (BREMS). Cognitive functions were assessed using the Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) and Controlled Oral Word Association Test (COWAT). Assessment of neurodegeneration was done using optical coherence tomography (OCT) via quantification of retinal nerve fiber layer (RNFL).
Results:
MS patients with higher RNFL thickness demonstrated a larger learning effect size than patients who had lower values in RNFL thickness regardless of MS type. RRMS patients showed significant improvement in delayed recall after giving cues than SPMS. The symbol digit modalities test was the only neuropsychological test that showed a significant negative correlation with EDSS (P = 0.009). There was a statistically significant negative correlation between BREMS scores and performance in all neuropsychological tests.
Conclusion:
Inclusion of neurocognitive evaluation in the periodic assessment of MS patients is mandatory to detect patients at increased risk of secondary progression. The thickness of RNFL is suggested as a method to estimate the expected benefit of cognitive rehabilitation, regardless of MS type.
Failure of the Fontan circulation is not a well-understood clinical phenomena.For some patients, a gradual increase in pulmonary vascular resistance (PVR) and structural changes in the pulmonary artery may be an important causative factor. To further investigate this issue, we employed optical coherence tomography (OCT) to evaluate structural changes within the pulmonary arteries of Fontan patients and compared to those with a normal pulmonary circulation.
Materials and Methods:
Pulmonary artery OCT was performed, without complications, in 12 Fontan and 11 control patients. Wall thickness and wall:vessel cross-sectional area (CSA) ratio were calculated after image acquisition, using digital planimetry.
Results:
There was no difference in wall thickness between both groups. Median wall thickness for Fontan patients was 0.12 mm (IQR, 0.10–0.14) and for controls was 0.11 mm (IQR, 0.10–0.12; p = 0.62). Wall:vessel CSA ratio for Fontan patients was 0.13 (IQR, 0.12–0.16) and for controls was 0.13 (IQR, 0.11–0.15) (p = 0.73). There was no association between wall thickness and ventricle morphology, age at catheterisation, age at Fontan, years since Fontan completion, pulmonary artery pressure, and PVR. The vessel media was more readily visualised in control patients.
Discussion:
OCT of the pulmonary arteries in Fontan patients is safe and feasible. Our OCT findings suggest that during childhood, pulmonary artery wall dimensions are normal in Fontan children with reassuring hemodynamics. Further evaluation of Fontan patients with abnormal hemodynamics and serial evaluation into adulthood are required to conclude on the utility of OCT for identifying early pulmonary artery structural changes.
To investigate choroidal thickness using enhanced-depth imaging optical coherence tomography in paediatric patients with adenotonsillar hypertrophy, with comparison to healthy children, three months after adenotonsillectomy.
Methods:
The patients were assigned to three groups: an adenotonsillar hypertrophy group, an adenotonsillectomy group and a healthy control group. In all groups, subfoveal, temporal and nasal choroidal thickness measurements were taken.
Results:
In the subfoveal, temporal and nasal regions, choroidal tissue was found to be significantly thinner in adenotonsillar hypertrophy children than healthy children (p = 0.012, p = 0.027 and p = 0.020). The subfoveal and temporal choroidal thickness measurements of adenotonsillar hypertrophy group cases were significantly decreased compared to those in the adenotonsillectomy group (p = 0.038 and p = 0.048).
Conclusion:
There was a significant association between decreased choroidal thickness and adenotonsillar hypertrophy. Adenotonsillar hypertrophy may play an important role in decreased choroidal thickness.
Zebrafish (Danio rerio) provide many advantages as a model organism for studying ocular disease and development, and there is great interest in the ability to non-invasively assess their photoreceptor mosaic. Despite recent applications of scanning light ophthalmoscopy, fundus photography, and gonioscopy to in vivo imaging of the adult zebrafish eye, current techniques either lack accurate scaling information (limiting quantitative analyses) or require euthanizing the fish (precluding longitudinal analyses). Here we describe improved methods for imaging the adult zebrafish retina using spectral domain optical coherence tomography (OCT). Transgenic fli1:eGFP zebrafish were imaged using the Bioptigen Envisu R2200 broadband source OCT with a 12-mm telecentric probe to measure axial length and a mouse retina probe to acquire retinal volume scans subtending 1.2 × 1.2 mm nominally. En face summed volume projections were generated from the volume scans using custom software that allows the user to create contours tailored to specific retinal layer(s) of interest. Following imaging, the eyes were dissected for ex vivo fluorescence microscopy, and measurements of blood vessel branch points were compared to those made from the en face OCT images to determine the OCT lateral scale as a function of axial length. Using this scaling model, we imaged the photoreceptor layer of five wild-type zebrafish and quantified the density and packing geometry of the UV cone submosaic. Our in vivo cone density measurements agreed with measurements from previously published histology values. The method presented here allows accurate, quantitative assessment of cone structure in vivo and will be useful for longitudinal studies of the zebrafish cone mosaics.
Shear bond strength (SBS) and the interfacial adaptation (IA) of self-adhesive resin (SAR) composites to dentin were evaluated. Two SARs [Vertise Flow (VTF) and Fusio Liquid Dentin (FLD)] were evaluated and compared with a conventional restorative system [adhesive: OptiBond FL and composite: Herculite Précis (OBF/HP)]. Human third molars were used for SBS testing and IA imaging (n=7) using optical coherence tomography (OCT). Flattened dentin disks were prepared and the composites were applied into molds (2.4 mm diameter) that were positioned on dentin. Samples were subjected to SBS testing and OCT analysis, which considered an increase in signal intensity at the bonded interface as evidence of internal gaps. SBS data were analyzed by one-way analysis of variance and Tukey’s test and IA data (% distribution of high brightness values) by Kruskal–Wallis and Dunn’s test (p≤0.05). No statistically significant difference in SBS was observed between VTF (13.9±3.6 MPa) and FLD (11.3±3.2 MPa), whereas OBF/HP showed higher average strength (27.3±6.1 MPa). However, there was a statistically significant difference in IA when VTF (33.3%) was compared with FLD (1.2%) and OBF/HP (1.5%). The conventional restorative system exhibited superior SBS performance compared with SARs. However, the IA of FLD to dentin had values that were not significantly different from OBF/HP.
The emergence of optical coherence tomography (OCT) technologies has allowed measurements of retinal nerve fiber layer (RNFL) and macular thickness that complement the history and clinical examination in distinguishing forms of acute optic neuropathy and retinal disease. High-resolution Fourier domain OCT has allowed for rapid imaging of the retina as well as three-dimensional imaging and improved volumetric measurements. Ongoing studies of OCT in clinical trials and research examine patterns of axonal degeneration and visual loss over time, and establish the role for OCT and other ocular imaging modalities as structural markers. With the emergence of a variety of OCT techniques, including Fourier Domain OCT, future studies will also help establish the protocols for data analysis to provide meaningful information about changes in structure from baseline. OCT is likely to play an increasing role in multiple sclerosis (MS) trials for measuring both axonal integrity and neuronal preservation.
To introduce the use of optical coherence tomography with an operating microscope for intra-operative evaluation of the human larynx.
Methods:
A specially equipped operating microscope with integrated spectral domain optical coherence tomography apparatus was used during microlaryngoscopy.
Results:
Technical improvements in optical coherence tomography equipment (e.g. pilot beam, variable focal distance, improved image quality and integration into an operating microscope) have enabled greater sensitivity and imaging speed and a non-contact approach. Spectral domain optical coherence tomography now enables a better correlation between optical coherence tomography images and histological findings. With this new technology, the precision of biopsy can be improved during microlaryngoscopy.
Conclusions:
Use of this new optical coherence tomography technology, integrated into an operating microscope, enables the surgeon to define the biopsy site location and resection plane precisely, while the optical zoom of the operating microscope can be used over the complete range.
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