Values Of Layer Thickness Research Articles

Behaviour of 32 CrMoV12-10 Steel Towards Boronizing Variables

During the shooting in gun barrels; there are many forces that affect each other such as external swelling caused by the explosion, excessive wear caused by the bullet core rubbing inside the barrel, high temperature caused by friction and gunpowder temperature, thermal expansion caused by temperature, chemical corrosion caused by gunpowder gases. It is expected that the barrel steel will show optimum resistance against all these effects. The most harmful of these is the wear force. The barrel, whose inner diameter expands due to wear, becomes unusable after a certain number of shots. In order to increase the effective number of shots, different hardening applications are made to the inner surfaces of the barrels of very different steel qualities. One of the commonly used barrel steels is 32CrMoV12-10 steel and hard chrome plating of the inner surface of the barrel. In this study, the boronizing behavior of 32CrMoV12-10 steel was investigated as an alternative coating technique. The changes in the type, layer thickness and hardness values ​​of boron compounds formed on the surface as a function of temperature and time were investigated. Boriding processes were carried out with a holding time of 2, 4 and 6 hours by setting the boriding temperature to 900oC. Typical columnar structures were observed at depths of 73, 100 and 133 μm in SEM microscope images. XRD (X-Ray Diffraction) analysis revealed that these were FeB, Fe2B, MnB and CrB compounds and that boride depth and hardness increased as the holding time increased. In microhardness tests conducted in this area, hardness values ​​up to 2500 HV were obtained.

The mechanical properties of aged PA-12 FS3300PA powder: influence of layer thickness, sintering orientations, and laser power

Abstract This research investigates the influence of layer thickness, laser power, and sintering orientation on the mechanical properties of aged Polyamide-12 (PA-12) FS3300PA using the Selective Laser Sintering (SLS) 3D printing method. Specimens were sintered with three different layer thicknesses, laser powers, and sintering orientations using SLS. The study also aimed to examine the resulting powder morphology, mechanical properties, and tensile fracture behaviors of the aged (more than eight continuously sintering cycles) and virgin FS3300PA powders. The specimens divided into ten groups: nine groups of aged powder and one group of virgin powder as a benchmark. The nine groups of aged powder were sintered with three different layer thicknesses (0.07 mm, 0.12 mm, and 0.15 mm), laser powers (65 W, 70 W, and 75 W), and orientations (YZY 0°, YZY 90°, and XYY 0°). The selections of these laser power and layer thickness values for the sintering setting are due to machine and material parameter limitation. The results from these parameters then compared with those of the virgin powder, which sintered using the parameters provided by the manufacturer, in terms of powder morphology, mechanical properties, and tensile fracture behaviours. Observation made using scanning electron microscope (SEM) revealed that there were not many changes in shape, size, and distribution between the virgin and aged powder, but slightly larger sizes and the presence of cracks found in the aged powder. The tensile strength, elongation at break value, and Young’s modulus all shared a similar trend, increasing with higher laser power but decreasing with increased layer thickness. Regarding the fracture morphologies, the number of pores and dimples decreased with increased laser power but increased with thicker layer thickness. There was also the occurrence of un-molten powder, especially in specimens sintered at the YZY 90° orientation with lower laser power and thicker layer thickness.

Effects of Anatomical Variation on Ganglion Cell and Nerve Fibre Layer Evaluation by Optical Coherence Tomography.

Background/Objectives: The automated analyses of optical coherence tomography (OCT) scans of the retina occasionally suggest the presence of tissue deficits when no visual field defects can be detected. This study was made to find the sources of such alerts. Methods: Data from a population-based cohort of 360 participants aged 30-80 years was analysed for the anatomical sources of alerts after the extensive exclusion of participants where any suspicion of abnormality could be raised. An analysis was made of 12 × 9 mm volume scans centred between the disc and the fovea. The exclusions comprised 107 eyes with definite or borderline abnormal visual fields or other potentially confounding characteristics. A statistical analysis of the thickness patterns was made using the manufacturer's proprietary algorithm. The analysis comprised alerts corresponding to local layer thickness values in the lower 5th percentile of an independent reference population. Results: Of the 613 eligible healthy eyes, thickness deficit alerts were seen in 391. They were related to the angle between the temporal nerve fibre ridges being wider, narrower, or rotated compared to the reference template in 174 eyes and to the variations in the size of the macula in 207 eyes. The source was unidentifiable in 28 eyes. The common sources were a thin papillomacular nerve fibre layer accompanied by arcuate nerve fibre ridges spaced far apart and a thinly, but wider than the normal macular ganglion cell layer. Conclusions: Anatomical variation in the retinal nerve fibre and ganglion cell layers was the source of more than 90% of the thickness deficit alerts in the eyes with normal visual fields.

Novel Mixed-Matrix Pervaporation Membrane Based on Polyether Block Amide Modified with Ho-Based Metal-Organic Framework.

Segmented polymers, such as polyether block amide (PEBA), exhibit unique properties due to the combination of different segments. PEBA consists of soft polyester and rigid polyamide blocks, enabling its use in various industrial applications, including membrane technologies. In this study, PEBA membranes modified with a holmium-based metal-organic framework (Ho-1,3,5-H3btc) were developed for enhanced pervaporation separation of water/isopropanol and water/phenol mixtures. The effect of 1-7 wt.% Ho-1,3,5-H3btc content variation and the selection of a porous substrate (commercial from fluoroplast F42L (MFFC) and developed membranes from polyvinylidene fluoride without (PVDF) and with a non-woven polyester support (PVDF-s)) on dense and/or supported membrane properties, respectively, was investigated. The dense and supported PEBA/Ho-1,3,5-H3btc membranes were studied by use of Fourier transform infrared spectroscopy, scanning electron and atomic force microscopies, swelling measurements, and pervaporation experiments. The supported membrane from PEBA with 5 wt.% Ho-1,3,5-H3btc applied onto the PVDF-s substrate exhibited optimal pervaporation performance: a 1040 g/(m2h) permeation flux and a 5.2 separation factor in water/phenol (1 wt.%) mixture separation at 50 °C due to optimal values of roughness, swelling degree, and selective layer thickness. This finding highlights the potential of incorporating Ho-1,3,5-H3btc into PEBA for developing high-performance pervaporation membranes.

Ferrofluid Droplet Chains in Thermotropic Nematic Liquid Crystals.

Dispersing ferrofluids in liquid crystals (LCs) produces unique systems which possess magnetic functionality and novel phenomena such as droplet chaining. This work reports the formation of ferrofluid droplet chains facilitated by the topological defects within the LC director field, induced by the dispersed ferrofluid. The translational and rotational motion of these chains could be controlled via application of external magnetic fields. The process of the droplet chain formation in LCs can be stabilized by the addition of surfactants. The magnetic colloidal particles in the ferrofluid located at the interface between the ferrofluid and the LC are arranged so that a boundary layer was formed. The velocities and boundary layer thickness values of ferrofluid droplet chains in nematic 5CB (4-Cyano-4'-pentylbiphenyl) were investigated for varying average droplet sizes and number of droplets in a chain. The creation and behaviour of ferrofluid droplet chains in 5CB with the addition of the surfactant polysorbate 60 (Tween-60) and without, was comparatively investigated. The integration of liquid crystals and ferrofluids along with the incorporation of functional materials facilitates the innovative development of advanced materials for future applications.

2D Titanium Carbide MXene and Single-Molecule Fluorescence: Distance-Dependent Nonradiative Energy Transfer and Leaflet-Resolved Dye Sensing in Lipid Bilayers.

Despite their growing popularity, many fundamental properties and applications of MXene materials remain underexplored. Here, the nonradiative energy transfer properties of 2D titanium carbide MXene are investigatedand their application in single-molecule biosensing is explored for the first time. DNA origami positioners are used for single dye placement immobilized by a specific chemistry based on glycine-MXene interactions, allowing precise control of their orientation on the surface. Each DNA origami structure carries a single dye molecule at predetermined heights. Single-molecule fluorescence confocal microscopy reveals that energy transfer of an organic emitter (ATTO 542) on transparent thin films made of spincast Ti3C2Tx flakes follows a cubic distance dependence, where 50% of energy transfer efficiency is reached at 2.7nm (d0). MXenes are applied as short-distance spectroscopic nanorulers, determining z distances of dye-labeled supported lipid bilayers fused on MXene's hydrophilic surface. Hydration layer (2.1nm) and lipid bilayer thickness (4.5nm) values that agree with the literature are obtained. These results highlight titanium carbide MXenes as promising substrates for single-molecule biosensing of ultrathin assemblies, owing to their sensitivity near the interface, a distance regime that is typically inaccessible to other energy transfer tools.

Determination of Lubrication Layer Thickness and Its Effect on Concrete Pumping Pressure.

The flow of six kinds of fresh concrete under different flow rates and lubrication layer thickness (TLL) values in the horizontal pipe was numerically simulated. The influence of the TLL on the pressure per unit length (PL) was analyzed. It was determined that the formation of the lubrication layer (LL) significantly reduces the PL in concrete pumping. As the TLL increased, the PL decreased. However, the degree of reduction in the PL gradually decreased as the TLL increased. Relating the simulated PL with the experimental PL, the size of the TLL was obtained, which was between 1 and 3 mm. The minimum and maximum were 1.23 and 2.58 mm, respectively, and the average value was 1.97 mm. The strength (S24, S50), the size of the aggregate (A10, A20, A25), and the flow rate of pumping all affected the TLL. The type of fresh concrete and the flow rate of pumping significantly affected the PL, which impacted the TLL. However, the TLL also impacted the PL. Finally, this made the TLL change within a certain range. When PL > 14,000 Pa/m, 2 mm < TLL< 3 mm; on the other hand, 1 mm < TLL< 2 mm. Therefore, we can use CFD to simulate the flow of all types of concrete in the actual pumping pipeline with a TLL of 2 mm to obtain their pumping pressure and guide the actual construction.

Pengaruh Tekanan Gas pada Proses Thermal Spray Aluminium (TSA) terhadap Keausan dan Morfologi Pada Baja ST 60

The use of steel in industry continues to increase until now making it the material most often used in transportation equipment such as cars, ships and trains. Steel is used in the transportation construction industry, steel materials are often used for railway axle construction. Hardness values ​​were taken using the Vickers micro test, and wear using a taber abrasive tool. Based on this background, research will be carried out "The Effect of Gas Pressure in the Thermal Spray Aluminum (TSA) Process on the Hardness and Wear Resistance of ST-60 Steel". This research uses medium carbon steel material with a coating process via TSA. The resulting layer is expected to have better hardness and wear values. The research method used in this research is the experimental method. The experimental method is a method used to test the effect of a treatment on the object under study by comparing when treatment is carried out and without treatment. This research carried out tests on 15 test objects. The substrate material used is ST 60 steel. In the thermal spray process three variations of gas pressure are used, namely 3 Bar, 6 Bar, and 9 Bar. Hardness values ​​were taken using the Vickers micro test, and wear using a taber abrasive tool. The highest average value of layer wear occurred at a pressure variation of 4 Bar with a layer thickness of 0.00859 mm2/kg. The lowest average layer wear value occurred at a pressure variation of 3 Bar with a wear value of 0.00729 mm2/kg. Meanwhile, based on coating layer thickness testing, the highest average layer thickness value occurred at a pressure variation of 4 Bar with a layer thickness of 423.854 µm. The lowest average layer thickness value occurred at a pressure variation of 3 Bar with a layer thickness of 241.505 µm.

A comprehensive modeling, analysis, and optimization of two phase, non–isobaric, and non–isothermal PEM fuel cell

A comprehensive modeling, analysis, and optimization of two phase, non–isobaric, and non–isothermal PEM fuel cell

Analysis of the influence of printing parameters on the compression resistance of PLA in the FDM process

PurposeThe rapid growth of 3D printing has transformed the cost-effective production of prototypes and functional items, primarily using extrusion technology with thermoplastics. This study aims to focus on optimizing mechanical properties, precisely highlighting the crucial role of mechanical compressive strength in ensuring the functionality and durability of 3D-printed components, especially in industrial and engineering applications.Design/methodology/approachUsing the Box−Behnken experimental design, the research investigated the influence of layer thickness, wall perimeter and infill level on mechanical resistance through compression. Parameters such as maximum force, printing time and mass utilization are considered for assessing and enhancing mechanical properties.FindingsThe layer thickness was identified as the most influential parameter over the compression time, followed by the degree of infill. The number of surface layers significantly influences both maximum strength and total mass. Optimization strategies suggest reducing infill percentage while maintaining moderate to high values for surface layers and layer thickness, enabling the production of lightweight components with adequate mechanical strength and reduced printing time. Experimental validation confirms the effectiveness of these strategies, with generated regression equations serving as a valuable predictive tool for similar parameters.Practical implicationsThis research offers valuable insights for industries using 3D printing in creating prototypes and functional parts. By identifying optimal parameters such as layer thickness, surface layers and infill levels, the study helps manufacturers achieve stronger, lighter and more cost-efficient components. For industrial and engineering applications, adopting the outlined optimization strategies can result in components with enhanced mechanical strength and durability, while also reducing material costs and printing times. Practitioners can use the developed regression equations as predictive tools to fine-tune their production processes and achieve desired mechanical properties more effectively.Originality/valueThis research contributes to the ongoing evolution of additive manufacturing, providing insights into optimizing structural rigidity through polylactic acid (PLA) selection, Box−Behnken design and overall process optimization. These findings advance the understanding of fused deposition modeling (FDM) technology and offer practical implications for more efficient and economical 3D printing processes in industrial and engineering applications.

Study of Gd/Co Multilayers with Different Cobalt Layer Thickness Values

Study of Gd/Co Multilayers with Different Cobalt Layer Thickness Values

Correlation between Photoluminescence Features and Enhanced Performance in Formamidinium Lead Triiodide Quantum Dot Solar Cells by Replacement of Octadecene

In this study, an innovative approach is developed for fabricating formamidinium lead triiodide (FAPbI3) quantum dots (QDs) by substitution of octadecene (ODE). The results showcase the formation of superior‐quality FAPbI3 QD films, boasting enhanced photoluminescence (PL) and transport properties. Specifically, ODE has been replaced with octene (OCE), a shorter linear alpha olefin. Comparisons are drawn between the novel synthesis method and the conventional ODE‐based QD films, scrutinizing their optical properties and applicability in QD solar cells. The outcomes highlight distinctions in temperature‐dependent PL emission characteristics, revealing an unprecedented absolute PL QY of up to 84%, a notable improvement from the 70% achieved with ODE, along with enhanced transport properties. Furthermore, the performance of both systems in QD solar cells is evaluated for two values of layer thickness, 100 and 200 nm, to investigate the transport properties at the device level. The results exhibit a remarkable improvement from 200% to 150% in average power conversion efficiency (PCE) and consistently higher values for open‐circuit voltage and short‐circuit current density for the OCE‐based solar cell compared to an ODE‐based counterpart for both thickness values, reaching a striking 6.7% PCE for the best‐performing device despite the nonideal conditions.

Integrated Experiment-Theory Framework for Studying Mass Transport Effects in Electrochemical CO2 Reduction on Copper

Electrochemical carbon dioxide reduction (eCO2R) has emerged as a promising approach to produce high-value fuels and chemicals using renewable energy sources. In particular, Cu catalysts can convert CO2 to a wide range of hydrocarbon and oxygenate products, including CO, formate, ethanol and ethylene. However, the activity and selectivity of eCO2R is highly dependent on mass transport and the corresponding reaction microenvironment present under operating conditions. In this talk, we present an integrated framework that combines experiments with computational fluid dynamics (CFD) and density functional theory (DFT) based microkinetic modeling to predict the effect of varying mass transport on eCO2R in a custom-designed flow cell. The flow cell is designed with multiple electrolyte jets impinging onto the electrocatalyst surface for rapid and homogeneous reactant transport. We first demonstrate the effect of mass transport in a flow cell architecture by controlling the flow rate of CO2-saturated 0.1 M KHCO3 to a Cu electrocatalyst. Significant increases in the production rates of formate and CO are observed with increasing flow rate, as well as an enhancement in multi-carbon products at high overpotentials. Increasing flow rate promotes hydrogen evolution at low overpotentials but has little effect at large overpotentials, suggesting a transition from HCO3 - to water as the dominant proton donor with increasing overpotential. CFD simulations are employed to model the distribution of boundary layer thicknesses within the flow cell, which subsequently set the boundary conditions for the coupled 1D transport-microkinetic model. The calculated boundary layer thickness values are corroborated by experimentally measured transport-limited currents. Our model successfully predicts experimentally observed trends in selectivity with mass transport, such as an increase in the production of ethylene and ethanol at high flow rates due to enhanced CO2 transport. The slight suppression of hydrogen reduction at higher flow rates due to an increase in *CO coverage is also predicted and supported by experimental results. This work demonstrates the importance of incorporating transport processes in the CFD-DFT coupled modeling of device performance for electrochemical CO2 reduction.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL release number: LLNL-ABS-857566.

Values of peripapillary retinal nerve fibre layer thickness are different in children and adults

ABSTRACT Clinical relevance The detection of abnormal values of peripapillary nerve fibre layer (pRNFL) thickness measured with optical coherence tomography (OCT) is important for detecting optic nerve disease in children. Background To evaluate the level of agreement between the adult reference database supplied with an OCT device and the present paediatric study database for the measurement of pRNFL thickness in children. This study also aimed to provide reference values for pRNFL thickness according to the spherical equivalent in the paediatric population. Methods This was a cross-sectional study. One hundred and twenty-six healthy children were included, who had undergone a full ophthalmological examination including cycloplegic refraction and examination of pRNFL thickness using the Topcon 3D OCT 2000 device (Topcon Corporation, Tokyo, Japan). Values equal to or below the fifth percentile (≤p5) and above the 95th percentile (>p95) were considered abnormal. Observed agreement and specific agreement were investigated between OCT measurements classified with paediatric and adult reference values for normality. Results Values ≤ p5 in the adult database were recorded for 2 of the 30 values (6.6%) of the pRNFL values by quadrants ≤p5 in the paediatric database and 17 of the 88 (19.3%) values by sectors ≤p5. For values >p95 in the adult database, 88% by quadrants and 72% by sectors would have been classified as being within the normal range using the paediatric database. Conclusion The use of adult reference values currently available in OCT devices can lead to classification errors concerning the normal range of pRNFL thickness in a large proportion of paediatric patients. The use of normative paediatric databases, such as the one discussed in this study, should be taken into consideration.

Microstructural and kinetics analysis of FeB–Fe2B layer grown by pulsed-DC powder-pack boriding on AISI 316 L steel

In this study, novel findings were obtained regarding the influence of a 10 A current intensity on the growth of an FeB–Fe2B layer during pulsed-DC powder-pack boriding. Boride layer formation was carried out on AISI 316 L steel at 1123–1223 K for different exposure times at each temperature, considering 10 s polarity inversion cycles. The boride layer was characterized by x-ray diffraction and high-speed Berkovich nanoindentation, the latter being used to determine the hardness and reduced Young’s modulus mappings along the depth of the layer-substrate system. Moreover, the growth kinetics of the FeB–Fe2B layer on the steel’s surface was modeled using the heat balance integral method (HBIM). This involved transforming Fick’s second law into ordinary differential equations over time, assuming a quadratic boron concentration profile in space to determine the B diffusion coefficients in FeB and Fe2B, respectively. From the Arrhenius relationship, the B activation energies in the boride layer were estimated considering the contribution of the electromigration effect; the results showed an approximately 30% reduction compared to the values obtained in the conventional powder-pack boriding for AISI 316 L steel. Finally, the theoretical layer thickness obtained by the HBIM demonstrated an error of no more than 5% against the experimental FeB and FeB + Fe2B layer thickness values.

Comparative analysis of changes in retinal layer thickness following femtosecond laser-assisted cataract surgery and conventional cataract surgery

BackgroundTo investigate the influence of femtosecond laser-assisted cataract surgery (FLACS) on macula by examining changes in retinal layers after FLACS and to compare these changes with those after conventional cataract surgery (CCS).MethodsThis study included 113 unrelated Korean patients with age-related cataract who underwent CCS or FLACS in Severance Hospital between September 2019 and July 2021. Optical coherence tomography was performed before and 1 month after surgery. The total retinal layer (TRL) was separated into the inner retinal layer (IRL) and outer retinal layer (ORL); moreover, the IRL was subdivided into the retinal nerve fiber layer, ganglion cell layer, inner plexiform layer, inner nuclear layer (INL), outer plexiform layer, and outer nuclear layer. We performed between-group comparisons of the postoperative thickness in each retinal layer and the postoperative differences in retinal thickness. The average retinal thickness of the four inner macular ring quadrants was used for comparative analysis.ResultsCompared with the CCS group, the FLACS group exhibited a thicker ORL (P = 0.004) and a thinner INL (P = 0.007) after surgery. All retinal layer thickness values showed significant postoperative changes regardless of the type of surgery (P < 0.05). The postoperative increase in TRL and IRL thickness was significantly smaller in the FLACS group than in the CCS group (P = 0.027, P = 0.012).ConclusionsThe 1-month postoperative retinal changes were less pronounced in the FLACS group than in the CCS group.

The Effect of Boriding Temperature and Time on the Structural and Mechanical Properties of M42 Steel

In this study, the effect of boriding temperature and time on the structural and mechanical properties of M42 high speed steel were investigated. Samples placed in Ekabor II powder were exposed to pack boriding treatment at 900°C and 1000°C for 4 hour and at 950°C for 2, 4 and 6 hours. Scanning electron microscope (SEM) images indicate that boron diffuses into the samples and a sawtooth-like cross-sectional morphology is formed. The presence of boron has also been proven by Energy Dispersive X-ray spectrometry (EDX). In addition, it was determined that boron layer thickness increased with increasing boriding temperature. When the microhardness values were examined, it was observed that the sample borided at the highest temperature had the highest hardness value and the hardness values decrease with the decreasing of boriding temperature. Similar results were also obtained regarding the boriding time. The highest microhardness and layer thickness values were obtained after 6 hours of boriding. Additionally, it was observed that the hardness values of borided samples decreased as they moved from the surface to the inner parts.

Evaluation of lamina cribrosa curvature index in different types of glaucoma.

The aim of this study was to evaluate the lamina cribrosa curvature index in different types of glaucoma in comparison with clinical findings and conventional measurement methods. Patients older than 18years who were followed up in Glaucoma Unit of Department of Ophthalmology at Fırat University Faculty of Medicine, whose disease had been under control at least for 1year, who had at least three reliable visual fields, whose refractive error was between - 6 and + 5 diopter and who did not have any disease other than glaucoma that would affect the visual field, were included in the study. Clinical and demographic characteristics, visual field, optical coherence tomography and lamina cribrosa curvature index (LCCI) results were evaluated. The study patients were divided into six groups: early-stage primary open-angle glaucoma (POAG) as group 1 and intermediate-advanced stage POAG as group 2, pseudo-exfoliation glaucoma (PEXG) as group 3, normal tension glaucoma (NTG) as group 4, ocular hypertension patients whom subsequently developed POAG as group 5 and healthy control as group 6. A total of 189 eyes of 101 patients were included in our study. Forty-seven patients were male (46.5%) and 54 were female (53.5%). The mean age was 62.43 ± 1.49years. LCCI, mean deviation (MD), visual field index (VFI), pattern standard deviation (PSD) and retinal nerve fiber layer thickness (RNFL) values were analyzed in all groups and Pearson correlation analysis showed statistically significant correlation between PSD and RNFL measurements with LCCI values in all groups. MD value was correlated with LCCI in groups 2, 3 and 4, while VFI value was correlated with LCCI in all groups except group 5. When the groups were compared with each other according to the Post-Hoc Tamhane test, LCCI measurement showed statistically significant results in accordance with MD, VFI, PSD and RNFL values. The LCCI assessment is mostly consistent with conventional tests. In this study, in which different types of glaucoma and healthy subjects were examined simultaneously, LCCI shows promise as a detailed and reliable assessment method.

Visual evoked potentials in patients with congenital color vision deficiency.

Congenital color vision deficiency (CCVD) is an eye disease characterized by abnormalities in the cone cells in the photoreceptor layer. Visual evoked potentials (VEPs) are electrophysiological tests that physiologically examine the optic nerve, other visual pathways, and the visual cortex. The aim of this research was to determine whether there are VEP abnormalities in CCVD patients. Patients with CCVD and healthy individuals were included in this prospective case-control study. Participants with eye disease or neurodegenerative disease were excluded from the study. Pattern reversal VEP (PVEP), flash VEP (FVEP), and optical coherence tomography were performed on all participants. Twenty healthy individuals (15 male) and 21 patients with CCVD (18 male) were included in the study. The mean ages of healthy individuals and patients with CCVD were 29.8 ± 9.6 and 31.1 ± 10.9years (p = 0.804). Retinal nerve fiber layer thickness and central macular thickness values did not differ between the two groups. In PVEP, Right P100, Left N75, P100, N135 values were delayed in CCVD patients compared to healthy individuals (p = 0.001, p = 0.032, p = 0.003, p = 0.032). At least one PVEP and FVEP abnormality was present in nine (42.9%) and six (28.6%) of the patients, respectively. PVEP or FVEP abnormalities were found in 13 (61.9%) of the patients. This study indicated that there may be PVEP and FVEP abnormalities in patients with CCVD.

Peripapillary Microvascular and Structural Parameters in Atrophic Nonarteritic Anterior Ischemic Optic Neuropathy, Unaffected Fellow Eyes and Controls in an Indian Population

ABSTRACT Nonarteritic ischemic optic neuropathy (NAION) is believed to be an ischemic insult to the optic nerve head and is one of the most common acute optic neuropathies of adulthood. Prevention of NAION in the fellow eye has not yet been accomplished. Optical coherence tomography angiography (OCTA) is a new and emerging non-invasive technology that provides microvascular information that complements the structural data. This prospective study is aimed to fill the lacunae in data that is available in the Indian population. We included 36 patients with NAION, their 36 fellow eyes and 37 healthy controls. The peripapillary perfusion index, peripapillary flux, peripapillary retinal nerve fibre layer (RNFL) thickness values and disc volumes of eyes were evaluated. The NAION eyes had lower peripapillary perfusion index, flux and RNFL thickness values in all sectors compared with both the fellow and the healthy control eyes (p = < .05). A statistically significant difference was found in disc volume between control eyes and fellow eyes, which included eyes with disc at risk configuration as well as normal disc configuration. Eyes with disc at risk configuration had a numerically lower disc volume than eyes with normal disc configuration. Fellow eyes overall had numerically lower perfusion index, higher RNFL thickness, and similar flux which was statistically non-significant compared with the healthy eyes. Correlation between the localization of visual field defects and the quadrants showing impairments of perfusion index and peripapillary RNFL were also assessed. These findings may indicate the potential vascular risk factors for the development of NAION in fellow eyes.