Capillary Length Research Articles

Gravitational Effect on the Advancing and Receding Angles of a Two-Dimensional Cassie-Baxter Droplet on a Textured Surface.

Advancing and receding angles are physical quantities frequently measured to characterize the wetting properties of a rough surface. Thermodynamically, the advancing and receding angles are often interpreted as the maximum and minimum contact angles that can be formed by a droplet without losing its stability. Despite intensive research on wetting of rough surfaces, the gravitational effect on these angles has been overlooked because most studies have considered droplets smaller than the capillary length. In this study, however, by combining theoretical and numerical modeling, we show that the shape of a droplet smaller than the capillary length can be substantially modified by gravity under advancing and receding conditions. First, based on the Laplace pressure equation, we predict the shape of a two-dimensional Cassie-Baxter droplet on a textured surface with gravity at each pinning point. Then, the stability of the droplet is tested by examining the interference between the liquid surface and neighboring pillars and analyzing the free energy change upon depinning. Interestingly, it turns out that the apparent contact angles under advancing and receding conditions are not affected by gravity, while the overall shape of a droplet and the position of the pinning point are affected by gravity. In addition, the advancing and receding of the droplet with continuously increasing or decreasing volume are analyzed, and it is shown that the gravitational effect plays a key role in the movement of the droplet tip. Also, the gravitational effect on the degree of the stability of the droplet upon the external effect such as vibration is discussed. Finally, the theoretical predictions were validated against line tension-based front tracking modeling (LTM) that seamlessly captures the attachment and detachment between the liquid surface and the solid substrate. Our findings provide a deeper understanding on the advancing and receding phenomena of a droplet and essential insight into designing devices that utilize the wettability of rough surfaces.

High-Speed Capillary Electrophoresis Using a Thin-Wall Fused-Silica Capillary Combined with Backscatter Interferometry.

High-speed capillary electrophoresis (HSCE) is implemented using a 10 cm total length fused-silica capillary (50 μm i.d., 80 μm o.d.) combined with refractive index (RI) detection using backscatter interferometry (BSI). The short capillary length reduces analysis time while the ultrathin wall (15 μm) efficiently dissipates heat from the separation channel, mitigating the deleterious effects of Joule heating. The separation capillary is mounted on a temperature-controlled heat sink that stabilizes the temperature to ±0.004 °C. This temperature stabilization improves separation efficiency and enhances RI detection. Ohm's Law plots confirm the superior heat dissipation of the HSCE capillary compared to a similarly prepared conventional CE capillary (50 μm i.d., 363 μm o.d.). The speed and efficiency of HSCE combined with universal RI detection is illustrated through the separation of K+, Ba2+, Mg2+, Na+, Li+, and Tris+ in approximately 30 s, with efficiencies greater than 500 000 plates/m. Run-to-run repeatability is explored using nine consecutive electrokinetic injections of a K+, Na+, and Li+ mixture. The average migration times and %RSD for K+, Na+, and Li+ were measured to be 22.04 s (1.59%), 26.81 s (1.38%), and 29.80 s (2.21%), respectively. Finally, we show that the BSI signal is sensitive to the separation voltage through the Kerr mechanism. This leads to peaks in the electropherogram from the injection process that are useful for precisely defining the start of each separation and quantifying the amount of sample injected onto the capillary.

Evaluation of Die Swell Behavior During Capillary Extrusion of Poly(lactic acid)/ High density polyethylene Blend Melts

Poly lactic acid (PLA) and High density polyethylene (HDPE) have been blended in a Brabender plastograph in the molten state. The melt die swell of the blends has been studied by using a capillary rheometer. Effects of the capillary dimensions, shear stress, shear rate, temperature and blending ratio on die swell of PLA/HDPE blend melts were investigated. The results showed that die swell ratio decreased with increasing of capillary length and temperature while it increased with increasing of shear stress, shear rate and capillary diameter. It was also found that the plots of die swell versus blending ratio go through a maximum for blending ratio PLA/HDPE (60/40).
 

Attributes, Fabrication, and Applications of Gallium-Based Liquid Metal Particles.

This work discusses the attributes, fabrication methods, and applications of gallium‐based liquid metal particles. Gallium‐based liquid metals combine metallic and fluidic properties at room temperature. Unlike mercury, which is toxic and has a finite vapor pressure, gallium possesses low toxicity and effectively zero vapor pressure at room temperature, which makes it amenable to many applications. A variety of fabrication methods produce liquid metal particles with variable sizes, ranging from nm to mm (which is the upper limit set by the capillary length). The liquid nature of gallium enables fabrication methods—such as microfluidics and sonication—that are not possible with solid materials. Gallium‐based liquid metal particles possess several notable attributes, including a metal–metal oxide (liquid–solid) core–shell structure as well as the ability to self‐heal, merge, and change shape. They also have unusual phase behavior that depends on the size of the particles. The particles have no known commercial applications, but they show promise for drug delivery, soft electronics, microfluidics, catalysis, batteries, energy harvesting, and composites. Existing challenges and future opportunities are discussed herein.

Experimental and numerical investigation on the flow of mixed refrigerants through capillary tubes at cryogenic temperatures

Capillary tubes are the simplest form of expansion devices used in J-T refrigerators. Numerous researchers have worked on the flow of refrigerant through capillary tubes; however, only a few researchers have reported on flow through capillary tubes at cryogenic temperatures. This study focusses on the flow of refrigerant mixtures at cryogenic temperature through the capillary tube of a Mixed Refrigerant Joule-Thompson (MRJT) cryocooler. In order to design a capillary tube for such mixtures, a numerical model, which predicts pressure drop across the capillary tube, is developed in the present work. As the flow through the capillary is in two-phase region, the homogeneous flow model is employed in this analysis and various two-phase viscosity models are investigated. An algorithm to predict the design length of the capillary tube using the homogeneous flow model is developed. Experimentation is carried out to compare the same with the theoretical predictions. The model predicts capillary tube length with an accuracy of 20%.

Effect of gamma irradiation on the critical heat flux of nano-coated surfaces

An anodic electrophoretic deposition (EPD) technique is used to create a uniform TiO2 thin film coating on boiling thin steel plates (1.1 mm by 90 mm). All of the effective parameters except time of the EPD method are kept constant. To investigate the effect of gamma irradiation on the critical heat flux (CHF), the test specimens were irradiated in a gamma cell to different doses ranging from 100 to 300 kGy, and then SEM and BET analysis were performed. For each coated specimen, the contact angle and capillary length were measured. The specimens were then tested in a boiling pool for CHF and boiling heat transfer coefficient. It was observed that irradiation significantly decreases the maximum pore diameter while it increases the porosity, pore surface area and pore volume. These surface modifications due to gamma irradiation increased the CHF of the nano-coated surfaces compared to that of the unirradiated surfaces. The heat transfer coefficient (HTC) of the nano-coated surfaces irradiated at 300 kGy increased from 83 to 160 kW/(m2 K) at 885 kW/m2 wall heat flux by 100%. The CHF of the irradiated (300 kGy) and unirradiated surfaces are 2035 kW/m2 and 1583 kW/m2, respectively, an increase of nearly 31%.

Investigation into geometric effect in capillary discharge plasma generator using an improved ablation model

The wall material and the electrode material together determine the composition of the capillary discharge plasma. In this paper, an improved ablation model considering polyethylene (PE) and copper ablation and deposition was developed. Generators with different geometric sizes were calculated and tested. The results show that the concentration distributions of copper and PE in the generator were the pair-wise opposite, and the aspect ratio (AR) had a threshold (AR = 8.67). The copper mass density distribution varied from uniform to inhomogeneous with the increase in AR, which was similar to that of its concentration distribution. The maximum copper mass density increased with the increase in AR, and the AR threshold was also 8.67. The relationship between the copper or PE ablated mass and capillary length or diameter approximately followed a power law, and the relationship between the copper or PE ablated mass and AR approximately followed a proportional law. The PE mass density distribution was not similar to that of its concentration for AR ≥ 8.67. The PE ablated mass increased with the increase in AR, and its variation was similar to that of the maximum PE mass density. When the AR(AR > 5.2) was large enough, the PE mass density distribution determined the total mass density distribution. Otherwise, the total mass density distribution was determined by the mass density distribution of PE and copper. Overall, the simulation results were in good agreement with the experiments. These can be used to select the size and material of the capillary in simulating high heat flux plasma or electrothermal chemical gun ignition.

Imatinib Sets Pericyte Mosaic in the Retina.

The nervous system demands an adequate oxygen and metabolite exchange, making pericytes (PCs), the only vasoactive cells on the capillaries, essential to neural function. Loss of PCs is a hallmark of multiple diseases, including diabetes, Alzheimer’s, amyotrophic lateral sclerosis (ALS) and Parkinson’s. Platelet-derived growth factor receptors (PDGFRs) have been shown to be critical to PC function and survival. However, how PDGFR-mediated PC activity affects vascular homeostasis is not fully understood. Here, we tested the hypothesis that imatinib, a chemotherapeutic agent and a potent PDGFR inhibitor, alters PC distribution and thus induces vascular atrophy. We performed a morphometric analysis of the vascular elements in sham control and imatinib-treated NG2-DsRed mice. Vascular morphology and the integrity of the blood–retina barrier (BRB) were evaluated using blood albumin labeling. We found that imatinib decreased the number of PCs and blood vessel (BV) coverage in all retinal vascular layers; this was accompanied by a shrinkage of BV diameters. Surprisingly, the total length of capillaries was not altered, suggesting a preferential effect of imatinib on PCs. Furthermore, blood–retina barrier disruption was not evident. In conclusion, our data suggest that imatinib could help in treating neurovascular diseases and serve as a model for PC loss, without BRB disruption.

Physical Constraints for Improved Soil Hydraulic Parameter Estimation by Pedotransfer Functions

AbstractGlobal land surface models use spatially distributed soil information for the parameterization of soil hydraulic properties (SHP). Parameters of measured SHP are correlated with easy‐to‐measure soil properties to construct general pedotransfer functions (PTFs) used to predict SHP from spatial soil information. Global PTFs are based on a limited number of samples yielding highly variable and poorly constrained SHP. The study implements a physical constraint, soil‐specific capillary length, to reduce unphysical combinations of SHP. The procedure fits concurrently soil water retention and capillary length using the same parameters. Results suggest that meeting the capillary length constraint has minor effects on the goodness of fit to soil water retention data. Constrained SHP were applied to represent 4 years of lysimeter fluxes yielding evapotranspiration values in close agreement with measurements relative to slight overestimation by unconstrained SHP. The procedure was applied for testing constraint SHP at a regional scale in New Zealand using the surface evaporation capacitance model and Noah‐MP for detailed simulations of land surface processes. The use of constrained SHP in both models yields higher surface runoff in agreement with observations (unconstrained SHP severely underestimated runoff generation). The concept of constrained SHP could be extended to include other physical constraints to improve PTFs, for example, by consideration of vegetation cover and soil structure effects on infiltration.

Role of the renin-angiotensin system in kidney development and programming of adult blood pressure.

Adverse events during fetal life such as insufficient protein intake or elevated transfer of glucocorticoid to the fetus may impact cardiovascular and metabolic health later in adult life and are associated with increased incidence of type 2 diabetes, ischemic heart disease and hypertension. Several adverse factors converge and suppress the fetal renin-angiotensin-aldosterone system (RAAS). The aim of this review is to summarize data on the significance of RAAS for kidney development and adult hypertension. Genetic inactivation of RAAS in rodents at any step from angiotensinogen to angiotensin II (ANGII) type 1 receptor (AT1) receptors or pharmacologic inhibition leads to complex developmental injury to the kidneys that has also been observed in human case reports. Deletion of the 'protective' arm of RAAS, angiotensin converting enzyme (ACE) 2 (ACE-2) and G-protein coupled receptor for Angiotensin 1-7 (Mas) receptor does not reproduce the AT1 phenotype. The changes comprise fewer glomeruli, thinner cortex, dilated tubules, thicker arterioles and arteries, lack of vascular bundles, papillary atrophy, shorter capillary length and volume in cortex and medulla. Altered activity of systemic and local regulators of fetal-perinatal RAAS such as vitamin D and cyclooxygenase (COX)/prostaglandins are associated with similar injuries. ANGII-AT1 interaction drives podocyte and epithelial cell formation of vascular growth factors, notably vascular endothelial growth factor (VEGF) and angiopoietins (Angpts), which support late stages of glomerular and cortical capillary growth and medullary vascular bundle formation and patterning. RAAS-induced injury is associated with lower glomerular filtration rate (GFR), lower renal plasma flow, kidney fibrosis, up-regulation of sodium transporters, impaired sodium excretion and salt-sensitive hypertension. The renal component and salt sensitivity of programmed hypertension may impact dietary counseling and choice of pharmacological intervention to treat hypertension.

Assessing Water Infiltration and Soil Water Repellency in Brazilian Atlantic Forest Soils

This study presents the results of the soil hydraulic characterization performed under three land covers, namely pasture, 9-year-old restored forest, and remnant forest, in the Brazilian Atlantic Forest. Two types of infiltration tests were performed, namely tension (Mini-Disk Infiltrometer, MDI) and ponding (Beerkan) tests. MDI and Beerkan tests provided complementary information, highlighting a clear increase of the hydraulic conductivity, especially at the remnant forest plots, when moving from near-saturated to saturated conditions. In addition, measuring the unsaturated soil hydraulic conductivity with different water pressure heads allowed the estimation of the macroscopic capillary length in the field. This approach, in conjunction with Beerkan measurements, allowed the design better estimates of the saturated soil hydraulic conductivity under challenging field conditions, such as soil water repellency (SWR). This research also reports, for the first time, evidence of SWR in the Atlantic Forest, which affected the early stage of the infiltration process with more frequency in the remnant forest.

Capillary imbibition of confined water in nanopores

The spontaneous capillary imbibition of confined nanopores is investigated using an analytical model that includes the slip effect, wettability and effective viscosity at the water surface interface. The results show that the effective viscosity of confined water is larger than that of bulk water and decreases with diameter and wettability. The effective slip length is negative for a contact angle of 0◦, and the effective slip length is positive and increases with diameter. The results of the presented model show that the capillary imbibition length for nanoconfined water can vary up to 0.389-1.033 times that determined by the Lucas-Washburn equation with no-slip boundary conditions for nanopores due to the effective viscosity and slippage with various dimensions and contact angles. The enhancement increases with diameter and contact angle. These results elucidate the confined movement through nanopores, which can be used to understand fracturing-fluid flow in the nanopores of shale reservoir formations. Cited as : Zeng, F., Zhang, Q., Guo, J., Meng, Y., Shao, X., Zheng, Y. Capillary imbibition of confined water in nanopores. Capillarity, 2020, 3(1): 8-15, doi: 10.26804/capi.2020.01.02

Prenatal dexamethasone exposure exerts sex-specific effect on placental oxygen and nutrient transport ascribed to the differential expression of IGF2.

BackgroundClinical studies have showed that dexamethasone exposure during pregnancy could cause fetal growth retardation, but the mechanism by which prenatal dexamethasone exposure influences placental nutrient transport is still unclear. This study investigated the impacts of prenatal dexamethasone on the placental oxygen and nutrient transport.MethodsPregnant Wistar rats were subcutaneously administered with dexamethasone from day 9 to day 20 of gestation at 0.2 or 0.8 mg/kg·d. Pregnant rats were sacrificed on gestational day 20. The placental tissue was collected for analysis.ResultsPrenatal dexamethasone exposure (PDE) declined the fetal weight and increased the intrauterine growth retardation (IUGR) rate in a dose-dependent manner. The total placental volume and the length, density and surface area of fetal capillaries in the labyrinth zone reduced in a dose-dependent manner. In addition, the thickness of syncytial membrane dose-dependently increased, resulting in a dose-dependent decrease in oxygen diffusion capacity. Furthermore, after PDE, the nutrient transport area and oxygen diffusion capacity of male placenta were lower than that of female placenta. The mRNA and protein expression of placental nutrient transporters including glucose transporter 1 (GLUT1), glucose transporter 3 (GLUT3), L-type amino acid transporter 1 (LAT1), lipoprotein lipase (LPL) and scavenger receptor class B type 1 (SRB1) increased in female placenta. However, in male placenta, the expression of LAT1, LPL and SRB1 was significantly decreased and GLUT1 and GLUT3 have a decrease trend. We further investigated the expression of insulin-like growth factor 1 (IGF1) and insulin-like growth factor 2 (IGF2) related to placental and fetal growth and development. Our study showed that the expression of IGF1 was significantly decreased both in male and female placentas after PDE. But the expression of IGF2 was significantly increased in female placentas while significantly decreased in male placentas.ConclusionsOur study shows prenatal dexamethasone exposure exerts sex-specific influence on the placental oxygen and nutrient transport. This might be ascribed to the differential expression of IGF2 after PDE. These findings provide evidence on the dexamethasone-induced toxicity to the placenta and fetal development.

A Dual-Parameter Internally Calibrated Fabry-Perot Microcavity Sensor

We propose and experimentally demonstrate multi-parameter sensors based on the antiresonant (AR) reflecting guidance in a single-mode fiber (SMF)-capillary-SMF structure. The sensor is manufactured by simply fusion splicing a certain length of hollow silica capillary between two commercial SMFs. Two prototypes with different lengths of the sandwiched capillary are fabricated and tested. The first sensor works in a reflection mode, based on the combined mechanisms of Fabry-Perot (FP) interference and AR reflecting guidance. As the length of the silica capillary exceeds the critical length for the transition of FP and AR, a typical amplitude modulation (AM) signal can be observed in the reflection spectrum of the device, including the AR envelope and the FP interference signal. Both the FP interference signal and the AR envelope can be used for sensing applications so that multi-parameter measurements can be realized. Measurements of temperature and strain were investigated in the demonstration experiment. The second sensor works in a transmission fashion. Multiple lossy dips exist at the sensor’s transmission spectrum as the length of the sandwiched capillary increases due to the AR reflecting guidance in the capillary. The sensor was demonstrated for measuring bending and temperature. Due to macro-bending loss, the intensities of the lossy dips changed with bending; the wavelengths of the lossy dips shifted with temperature due to the temperature-induced changes in the resonance condition. The proposed SMF-capillary-SMF structure-based sensor and the multi-parameter codifying concept could find applications in the multi-parameter sensing field due to its compactness and simplicity.

Nucleate boiling heat transfer and critical heat flux (CHF) from micro-pit surfaces

This paper studies pool boiling enhancement on the micro-pit surfaces. Microscale pits fabricated on plain surface are able to reduce boiling incipience superheat, and improve both nucleate boiling heat transfer coefficient and critical heat flux (CHF). Boiling enhancement magnitudes have a weak dependence on the micro-pit diameter, but increase monotonously with decreasing the pit depth. There exists an optimum pit-to-pit spacing for the maximum boiling enhancements, which is virtually identical to bubble departure diameter, and estimated using the capillary length. The major mechanism behind is that this spacing is favorable for alleviating hydrodynamic instabilities induced by the counterflow between liquid inflow and vapor outflow. The highest heat transfer coefficient and CHF using water as fluid under the present conditions are 70.0 kW/m2K and 165.7 W/cm2, improved by 58.8% and 33.7% compared to the plain surface, respectively, at micro-pit diameter of 100 μm, depth of 100 μm and spacing of 2.5 mm. Finally, a correlation devised for predicting the nucleate boiling heat transfer coefficient on the micro-pit surfaces by incorporating dimensionless pit depth is proposed, with MAE of 8.3%.

Unified framework for mapping shape and stability of pendant drops including the effect of contact angle hysteresis

Solution of the Young-Laplace equation for fluid-fluid interface shapes is crucial in several applications related to colloids, capillarity, and surfaces. Despite significant progress in analysis and computation, the solution framework in literature is quite sparse with different norms for non-dimensionalisation and often limited to simplistic boundary conditions. These problems can be overcome and a unified solution framework can be developed if the relevant parameters are non-dimensionalised with respect to the capillary length, and collapsed onto a single graphical chart in the form of axes and contours. Here we use vector parameterized cubic splines to represent axisymmetric droplet profiles, which are then evolved quasi-statically to get to the equilibrium shapes using a novel thermodynamic free energy minimization-based algorithm. The generated dataset for a wide range of geometric and surface parameters is validated and then compiled in the form of a graphical chart. The chart traces the complete profile of axisymmetric pendant drops, predicts their evolution and stability on any surface, all without running any computer simulation. Most importantly, the contact angle contours on this chart offer the capability to incorporate the effect of contact angle hysteresis, a situation which is practically relevant, but has yet not been modelled.

A simulation study of a high-resolution fast neutron imaging detector based on liquid scintillator loaded capillaries

At present, the highest spatial resolution of a fast neutron imaging detector, mainly determined by the range of secondary particles generated by fast neutrons, is about hundreds of microns. In view of the above inherent spatial resolution limitation, a capillary-based scintillation detector that can improve the spatial resolution of fast neutron imaging by recording and reconstructing the recoil proton track was developed. The purpose of this paper is to develop a detector for recognizing recoil proton events, reconstructing particle track and improving the position resolution with track reconstruction method to reconstruct the position of interaction. The proposed detector consists of a 1000 × 1000 array of glass capillaries loaded with a high refractive index liquid scintillator. Each glass capillary was 10 μm in diameter and 5 cm in length. The recoil protons generated by the incident neutrons move within the detector and produce scintillation light within each capillary that they traverse. The light emitted from the capillary array can be recorded by employing an intensified CCD camera. We used Geant4 to simulate the detector performance and CERN ROOT analysis framework to record physical information of recoil proton, including position, energy deposition in each capillary and track length. Based on Hough transform, a rapid, computerized and efficient proton track reconstruction procedure was developed. The recoil proton events display a continuous extended structure. The track reconstruction algorithms can reconstruct individual track precisely, and when the counting rate was relatively low, the track reconstruction results were in good agreement with simulation data. Moreover, for intensive overlap conditions, this algorithm also reconstructs periphery tracks with high rate of accuracy.

Nonexudative Macular Neovascularization Supporting Outer Retina in Age-Related Macular Degeneration: A Clinicopathologic Correlation

Type 1 macular neovascularization (MNV) secondary to age-related macular degeneration (AMD) may sustain hypoxic and micronutrient-insufficient outer retinal cells compensatorily. We explored this hypothesis via histologic analysis of an eye with a shallow irregular retinal pigment epithelial elevation (SIRE) on OCT and good vision. Case study and clinicopathologic correlation. A white woman with untreated nonexudative neovascular AMD and 20/30 visual acuity (left eye) and neovascular AMD (right eye), with 9 years' multimodal imaging before dying at 90 years of age. The left eye was preserved 6.25 hours after death and prepared for submicrometer epoxy resin sections and transmission electron microscopy aligned to clinical OCT B-scans. Inside and outside the MNV area, layer thicknesses, phenotypes, and vascular density of native choriocapillaris and neovessels were measured. Lengths of choriocapillaries and intervening gaps in the index eye and in early AMD eyes and healthy eyes with similar age (n= 19 each) from the Project MACULA (Maculopathy Unveiled by Laminar Analysis) online histopathologic resource (http://projectmacula.cis.uab.edu/) were measured with custom software (Caps and Gaps). Descriptive features, vascular density, histologic and OCT layer thicknesses, and distribution of choriocapillaries and intervening gaps. The SIRE correlated to a type 1 MNV that expanded slowly without evidence of exudation and with numerous choroidal vessels traversing Bruch's membrane defects, some visible on OCT. Tissue layers in and adjacent to the MNV area showed continuous RPE and characteristic AMD deposits. Capillary-like neovessels with fenestrations and caveolae resembling native choriocapillaris lined the retinal pigment epithelium (RPE) with a vascular density comparable with surrounding non-MNV areas. Relative to early AMD and healthy aged eyes, the index eye showed similar capillary lengths but larger gaps between vessels, indicating dropout. Outer nuclear layer thickness was preserved and showed less photoreceptor degeneration over areas of relative choriocapillaris health, including the type 1 MNV. Eyes with nonexudative type 1 MNV in AMD may progress to exudation, yet this stable MNV complex supported outer retinal structure for 9 years. Distinguishing features were numerous connecting vessels, high density of neovessels, continuous RPE, and slow growth. Maintaining beneficial type 1 MNV may be a therapeutic strategy.

A practical guide to the stereological assessment of glomerular number, size, and cellular composition.

The evaluation of a range of measures in the kidneys, such as developmental stage, rate and success, injury, and disease processes, relies on obtaining information on the three-dimensional structure of the renal corpuscles, and in particular the glomerular capillary tufts. To do this in the most accurate, comprehensive, and unbiased manner depends on a knowledge of stereological methods. In this article, we provide a practical guide for researchers on how to quantitate a number of structures in the kidneys, including the estimation of total glomerular number, glomerular capillary length and filtration surface area, and the cellular composition of individual glomeruli. Guidance is also provided on how to apply these methods to kidneys at different sizes and levels of maturity.

Widefield Swept Source OCTA in Retinitis Pigmentosa.

(1) Background: To evaluate superficial capillary plexus (SCP), deep capillary plexus (DCP), choriocapillaris (CC), perfusion density (PD), and vessel length density (VLD) in macular and near/mid periphery regions in patients with retinitis pigmentosa (RP) using widefield swept source optical coherence tomography angiography (WSS-OCTA). (2) Methods: Twelve RP patients (20 eyes) and 20 age-matched subjects (20 eyes) were imaged with the SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). Quantitative analysis was performed in the macular and peripheral regions. The main outcome measures were SCP, DCP, CC, PD, and VLD in central and peripheral areas. (3) Results: Mean visual acuity, central macular thickness, and microperimetry were significantly reduced in RP patients compared to normal subjects (p < 0.05). The perfusion density and VLD of SCP, DCP, and CC were significantly reduced in RP patients compared to normal controls both in the central and peripheral retina (p < 0.05). A significant direct correlation was found in RP patients between PD of the 1.5 mm central retina both in DCP and CC and microperimetry at 4° and 8°. (4) Conclusions: Widefield SS-OCTA shows an impairment of retinal and choroidal perfusion density and vessel length density in central and peripheral retina of RP patients. The reduction of flow features correlates with the macular function.