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Therapeutic Advances in Ophthalmology 2022The distance between the optic disc center and the fovea is a biometric parameter; however, it is unclear whether DFD (disc-fovea distance) affects the choroidal...
BACKGROUND
The distance between the optic disc center and the fovea is a biometric parameter; however, it is unclear whether DFD (disc-fovea distance) affects the choroidal thickness.
OBJECTIVE
The aim of this study is to investigate the association between DFD and choroidal thickness.
DESIGN
This is a prospective, and cross-sectional study.
METHODS
Two hundred fifty eyes of 250 healthy participants were examined in terms of DFD, age, axial length, spherical equivalent, and choroidal thickness. Inclusion criteria included aged between 20-40 years, no posterior segment disorders, and participants with best-corrected visual acuity (10/10 according to Snellen's chart). Participants with high hypermetropia (>4 diopter) or myopia (>6 diopter) or any systemic disease likely to affect choroidal thickness were excluded. Choroidal thickness measurements were performed at subfoveal, 1.0 mm temporal, and 1.0 mm nasal using the enhanced-depth imaging optical coherence tomography.
RESULTS
The mean age of all the participants was 26.21 ± 5.73 years, mean DFD was 4634.29 ± 274.70 µm, mean axial length was 23.62 ± 0.83 mm, and mean spherical equivalent was -0.61 ± 1.06 diopter. The mean subfoveal, nasal, and temporal choroidal thicknesses were 388.73 ± 90.15 µm, 351.26 ± 88.09 µm, and 366.50 ± 79.56 µm, respectively. A negative correlation was found between subfoveal, nasal, and temporal choroidal thicknesses and axial length ( = -0.157, = 0.013; = -0.168, = 0.008; = -0.174, = 0.006, respectively). Insignificant correlation was found between choroidal thicknesses and spherical equivalent ( > 0.05). There was not a statistically significant correlation between DFD and subfoveal, nasal, and temporal choroidal thicknesses ( = -0.028, = 0.655; = 0.030, = 0.641; = -0.025, = 0.699, respectively). In addition, there was not a statistically significant correlation between age and choroidal thickness.
CONCLUSION
This study shows that DFD and spherical equivalent do not affect choroidal thickness; axial length negatively affects choroidal thickness. In addition, age does not affect choroidal thickness between 20 and 40 years.
PubMed: 35602660
DOI: 10.1177/25158414221096062 -
Journal of Ophthalmic & Vision Research 2020To investigate the effects of refraction on retinal thickness measurements at different locations and layers in healthy eyes of Saudi participants. (Review)
Review
PURPOSE
To investigate the effects of refraction on retinal thickness measurements at different locations and layers in healthy eyes of Saudi participants.
METHODS
Thirty-six randomly selected adults aged 27.0 5.7 years who attended a Riyadh hospital from 2016 to 2017 were categorized into three groups: non-myopic (spherical equivalent refraction [SER], +1.00 to -0.50 diopters [D]), low myopic (SER, -0.75 to -3.00D), and moderate to high myopic (SER -3.25D). Full, inner, and outer retinal thicknesses were measured at nine locations by spectral-domain stratus optical coherence tomography (Optovue Inc., Fremont, CA, USA) and were compared according to refractive group and sex.
RESULTS
The mean SERs for the non-myopia, low myopia, and moderate to high myopia groups were 0.2 0.6, -1.5 0.5, and -7.5 1.9 D, respectively. Refractive error, but not sex, had significant effects on the retinal layer thickness measurements at different locations ( 0.05). The parafoveal and outer retinal layers were significantly thicker than the perifoveal and inner retina layers in all groups ( 0.05). The full foveal thickness was higher and the full parafoveal and perifoveal regions were thinner in moderate to high myopic eyes than in the non-myopic eyes ( 0.05), but were similar to those in the low myopic eyes ( 0.05). The foveal thicknesses measured in the inner and outer layers of the retina were higher but the thicknesses measured at the inner and outer layers of the parafoveal and perifoveal regions were lower in moderate to high myopic eyes.
CONCLUSION
There were regional differences in the retinal layer thicknesses of healthy Saudi eyes, which was dependent on the central refractions. This is important when interpreting retinal nerve fiber layer thicknesses in myopia and disease management in Saudi participants.
PubMed: 32308952
DOI: 10.18502/jovr.v15i2.6735 -
Journal of Ophthalmology 2021To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Swept-Source-Optical Coherence Tomography with...
OBJECTIVE
To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Swept-Source-Optical Coherence Tomography with those of Spectral-Domain-OCT in normal eyes.
METHODS
30 normal eyes of 30 patients were assessed by 3 trained operators with SS-OCT and SD-OCT.
RESULTS
The central and minimum ET obtained with both devices were correlated: central ET, = 0.86, < 0.05; minimum ET, = 0.72, < 0.05. Compared with SD-OCT, SS-OCT tended to underestimate these figures by 1.4 and 1.9 m on average. The central and minimum CT obtained with both devices were strongly correlated: central CT, = 0.994, < 0.05; minimum CT, = 0.995, < 0.05. SS-OCT tended to overestimate these figures by 11 and 14 m on average. Repeatability was good for both devices with a mean coefficient of variation of measurements <6% for ET and <2% for CT. Interoperator variability (standard deviation and COV) was significantly higher for SS-OCT than for SD-OCT for all local epithelial thicknesses and significantly lower for the central CT and several local corneal thicknesses, whereas no significant differences between both technologies were found for the central and minimum ET and the minimum CT.
CONCLUSION
SS-OCT and SD-OCT provide reproducible measurements of CT and ET in normal corneas with a strong correlation between both technologies. However, both technologies are not interchangeable when the main thickness parameters (i.e., central and minimum CT and minimum ET) are used for diagnosing early keratoconus or calculating the expected residual stromal bed thickness before corneal refractive surgery or anterior lamellar keratoplasty.
PubMed: 34650817
DOI: 10.1155/2021/3444083 -
Journal of Ophthalmology 2021To evaluate the differences in macular choroidal thickness and volume between patients with primary open-angle glaucoma (POAG) and healthy controls to assess the...
PURPOSE
To evaluate the differences in macular choroidal thickness and volume between patients with primary open-angle glaucoma (POAG) and healthy controls to assess the correlation between macular choroidal thickness and visual field mean defect (MD).
METHODS
Case-control study. A total of 101 patients (101 eyes) with POAG who were hospitalized in our hospital and 102 healthy subjects (102 eyes) matched by age, sex, and axial length were consecutively selected as the POAG group and the control group, respectively. The macular choroidal thickness and volume in nine regions were measured in all subjects by enhanced-depth imaging optical coherence tomography (EDI-OCT).
RESULTS
The mean thicknesses of the choroid in the macular area in the POAG group and healthy group were 207.97 ± 62.83 m and 208.24 ± 47.97 m, and the mean volumes were 0.63 ± 0.19 m and 0.64 ± 0.14 m. There were no significant differences in macular choroidal thickness, volumes of various macular regions, or mean choroidal thickness or volume between the POAG and healthy groups (all > 0.05). The macular choroidal thickness of various macular regions was not correlated with visual field MD in the POAG group (all > 0.05).
CONCLUSION
The macular choroidal thicknesses and volumes in POAG patients were not significantly different from those in healthy individuals. The macular choroidal thickness was not correlated with MD in POAG patients. Therefore, macular choroidal thickness is not an appropriate parameter to evaluate damage caused by POAG, and the role of the macular choroid thickness in POAG needs to be further investigated.
PubMed: 34007481
DOI: 10.1155/2021/5574950 -
Acta Stomatologica Croatica Mar 2022Dentin thickness in concave areas of the root creates risk for complications such as strip perforation during endodontic treatment. The study aims to examine dentin...
OBJECTIVES
Dentin thickness in concave areas of the root creates risk for complications such as strip perforation during endodontic treatment. The study aims to examine dentin thickness of the danger (DZ) and safety zone (SZ), canal configuration, and the presence of isthmus in the mesiobuccal root of maxillary molars.
MATERIAL AND METHODS
Cone-beam Computed Tomography (CBCT) images of 1251 teeth belonging to 642 patients were retrospectively reviewed. The dentin thicknesses at DZ and SZ in maxillary molars with one (MB) or two mesiobuccal canals (MB1, MB2) were measured at the 3 mm apical to the furcation level. Vertucci's canal configurations and the isthmus rate were recorded. The Chi-square test andThe Student's t-test were performed.
RESULTS
MB2 rate was higher in maxillary first molars (61.68%) than second molars (39.36%). Isthmus rates were 27.3% and 44.11% in first and second molars. DZ thickness was thinner than the dentin thickness in the SZ in both first and second molars with one or two mesial canals (p< 0.05). In teeth with single canal, the mean DZ thickness was 0.88mm. In teeth with two canals, the mean DZ thicknesses were 0.83mm and 0.80mm for MB1 and MB2 canals, respectively.
CONCLUSION
MB2 rate was higher in the first molar (61.68%), and the isthmus rate was higher in the second molar (44.11%). DZ and SZ were thinner in MB2 than in MB1 at the maxillary molars with two mesial canals. The results indicated that more conservative preparation must be applied to the MB2 canal in the maxillary molars.
PubMed: 35382485
DOI: 10.15644/asc56/1/6 -
Clinical and Experimental Dental... Dec 2020Creating a tooth-like appearance by use of dental ceramics is still a challenge. Opalescence is a unique property of dental enamel, attempted to be mimicked by dental...
OBJECTIVES
Creating a tooth-like appearance by use of dental ceramics is still a challenge. Opalescence is a unique property of dental enamel, attempted to be mimicked by dental restorative materials. This study aimed to assess the effect of ceramic thickness on opalescence.
MATERIALS AND METHODS
Twenty-four discs were fabricated of feldspathic ceramic, IPS e.max, zirconia and Enamic ceramics with 10 mm diameter and 0.5 and 1 mm thicknesses (n = 12). The opalescence of ceramic specimens was calculated by measuring the difference in yellow-blue axis (CIE ∆b*) and red-green axis (CIE ∆a*) between the transmitted and reflected spectra. One-way ANOVA was applied to compare the opalescence of different ceramic specimens with variable thicknesses at .05 level of significance.
RESULTS
The opalescence of feldspathic, IPS e.max, zirconia and Enamic ceramic specimens with 0.5 mm thickness was 1.06 ± 0.15, 3.39 ± 0.15, 1.98 ± 0.15 and 1.44 ± 0.15, respectively. By increasing the thickness to 1 mm, the opalescence of feldspathic, IPS e.max, zirconia and Enamic ceramics changed to 1.12 ± 0.15, 1.47 ± 0.15, 3.85 ± 0.15 and 2.00 ± 0.15, respectively. In all groups except for IPS e.max, the mean opalescence of 1-mm-thick specimens was higher than that of 0.5-mm-thick specimens.
CONCLUSION
Type and thickness of ceramic affect its opalescence. The opalescence of all ceramic specimens tested in this study with 0.5 and 1 mm thicknesses was lower than that of the enamel.
Topics: Ceramics; Dental Enamel; Dental Porcelain; Dental Restoration, Permanent; Humans; Iridescence; Materials Testing; Surface Properties; Zirconium
PubMed: 32902165
DOI: 10.1002/cre2.325 -
Polymers Apr 2023This paper aimed to experimentally clarify the crushing mechanism and performance of expanded polypropylene foam (EPP) and analyze the influence of density and thickness...
This paper aimed to experimentally clarify the crushing mechanism and performance of expanded polypropylene foam (EPP) and analyze the influence of density and thickness on its mechanical behavior and energy absorption properties under static crushing loadings. Hence, a series of compression tests were carried out on EPP foams with different densities and thicknesses. For foam with a density of 60 kg/m, the mean crushing strength, energy absorption (E, energy absorption efficiency (E), specific energy absorption (SEA), and energy absorption per unit volume (w) increased by 245.3%, 187.2%, 42.3%, 54.3%, and 242.8%, respectively, compared to foam with a density of 20 kg/m. Meanwhile, compared to foam with a thickness of 30 mm, the mean crushing strength, energy absorption (), energy absorption efficiency (), SEA, and energy absorption per unit volume () for foam with a thickness of 75 mm increased by 53.3%, 25.2%, -10.8%, -4.7%, and -10.6%, respectively. The results show that foam density has a significantly greater influence on static compressive performance than foam thickness. The microstructures of the EPP foam before and after static compression were compared by observing with a scanning electron microscope (SEM), and the failure mechanism was analyzed. Results showed that the load and energy as well as the deformation and instability processes of its cells were transferred layer by layer. The influence of density on the degree of destruction of the internal cells was obvious. Due to its larger mass and larger internal damping, thicker foams were less damaged, and less deformation was produced. Additionally, the EPP foam exhibited a considerable ability to recover after compression.
PubMed: 37177205
DOI: 10.3390/polym15092059 -
Proceedings of the National Academy of... Dec 2021The relationship between sample thickness and quality of data obtained is investigated by microcrystal electron diffraction (MicroED). Several electron microscopy (EM)...
The relationship between sample thickness and quality of data obtained is investigated by microcrystal electron diffraction (MicroED). Several electron microscopy (EM) grids containing proteinase K microcrystals of similar sizes from the same crystallization batch were prepared. Each grid was transferred into a focused ion beam and a scanning electron microscope in which the crystals were then systematically thinned into lamellae between 95- and 1,650-nm thick. MicroED data were collected at either 120-, 200-, or 300-kV accelerating voltages. Lamellae thicknesses were expressed in multiples of the corresponding inelastic mean free path to allow the results from different acceleration voltages to be compared. The quality of the data and subsequently determined structures were assessed using standard crystallographic measures. Structures were reliably determined with similar quality from crystalline lamellae up to twice the inelastic mean free path. Lower resolution diffraction was observed at three times the mean free path for all three accelerating voltages, but the data quality was insufficient to yield structures. Finally, no coherent diffraction was observed from lamellae thicker than four times the calculated inelastic mean free path. This study benchmarks the ideal specimen thickness with implications for all cryo-EM methods.
Topics: Animals; Benchmarking; Cryoelectron Microscopy; Crystallization; Crystallography; Electrons; Humans; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Models, Molecular; Specimen Handling
PubMed: 34873060
DOI: 10.1073/pnas.2108884118 -
Clinical and Experimental Dental... Dec 2022Mechanical properties are cardinal for the long-term clinical success of laminate veneer restorations but the selection of new restorative materials should ideally be...
OBJECTIVES
Mechanical properties are cardinal for the long-term clinical success of laminate veneer restorations but the selection of new restorative materials should ideally be based on clinical evidence, therefore, in vitro testing of dental materials is a good alternative to evaluate their properties and understand their behavior so this study aimed to compare and evaluate the effect of two different thicknesses and yttria percentage on the fracture resistance of laminate veneer zirconia restorations.
MATERIALS AND METHODS
Forty laminate veneer restoration prepared from partial sintering zirconia of 3Y (yttria), 5Y (yttria), combined 3Y&5Y (yttria), and lithium disilicate. Specimens were assigned into four main groups according to their percentage of yttria content (n = 10) and subgrouped into two thicknesses (0.5 mm thickness and 0.3 mm thickness) (n = 5) as follows: Group I, II, III, and IV (Group I for lithium disilicate (control), Group II for 3Y zirconia, Group III for 5Y zirconia, and Group IV for combined 3Y&5Y zirconia), each of them subdivided according to their thickness into two subgroups (n = 5 for each one) and resistance to fracture for each restoration was evaluated using a universal testing machine. Data were analyzed using a one-way analysis of variance and Duncan's tests at a 5% level of significance.
RESULTS
The thickness of laminate veneer restoration significantly affects the fracture resistance value of all type of laminate veneers restorations (fracture resistance mean value was highest for 0.5 mm thickness and lower for 0.3 mm thickness restorations) and yttria percentage significantly affect fracture resistance value of zirconia laminate veneer restorations (fracture resistance mean value was highest for 0.5 mm thickness of 3Y zirconia [865 N] and combined 3Y&5Y zirconia [846 N]).
CONCLUSIONS
Reducing the thickness of laminate zirconia veneer restorations to 0.3 mm reduces its fracture resistance and increasing yttria percentage had an adverse effect on fracture resistance of zirconia laminate veneer restorations.
Topics: Dental Stress Analysis; Materials Testing; Zirconium
PubMed: 36099336
DOI: 10.1002/cre2.658 -
Journal of Clinical Neurology (Seoul,... Mar 2023We aimed to determine the effect of demographic factors on cortical thickness and brain glucose metabolism in healthy aging subjects.
BACKGROUND AND PURPOSE
We aimed to determine the effect of demographic factors on cortical thickness and brain glucose metabolism in healthy aging subjects.
METHODS
The following tests were performed on 71 subjects with normal cognition: neurological examination, 3-tesla magnetic resonance imaging, F-fluorodeoxyglucose positron-emission tomography, and neuropsychological tests. Cortical thickness and brain metabolism were measured using vertex- and voxelwise analyses, respectively. General linear models (GLMs) were used to determine the effects of age, sex, and education on cortical thickness and brain glucose metabolism. The effects of mean lobar cortical thickness and mean lobar metabolism on neuropsychological test scores were evaluated using GLMs after controlling for age, sex, and education. The intracranial volume (ICV) was further included as a predictor or covariate for the cortical thickness analyses.
RESULTS
Age was negatively correlated with the mean cortical thickness in all lobes (frontal and parietal lobes, =0.001; temporal and occipital lobes, <0.001) and with the mean temporal metabolism (=0.005). Education was not associated with cortical thickness or brain metabolism in any lobe. Male subjects had a lower mean parietal metabolism than did female subjects (<0.001), while their mean cortical thicknesses were comparable. ICV was positively correlated with mean cortical thickness in the frontal (=0.016), temporal (=0.009), and occipital (=0.007) lobes. The mean lobar cortical thickness was not associated with cognition scores, while the mean temporal metabolism was positively correlated with verbal memory test scores.
CONCLUSIONS
Age and sex affect cortical thickness and brain glucose metabolism in different ways. Demographic factors must therefore be considered in analyses of cortical thickness and brain metabolism.
PubMed: 36647225
DOI: 10.3988/jcn.2022.0021