Dispersion of a solute in a Herschel–Bulkley fluid flowing in a conduit

The dispersion of a solute in a Herschel-Bulkley fluid is studied by using the generalized dispersion model in both pipe and channel. With this method the entire dispersion process is described as a simple diffusion process with the effective diffusion coefficient as a function of time. The results for Newtonian fluid, power law fluid and Bingham fluid are obtained as special cases by giving appropriate values to the power law index and yield stress. The effects of power law index, yield stress on the dispersion coefficient and mean concentration have been discussed computationally and graphically. The effect of power law index and yield stress is found to reduce the dispersion coefficient. It is observed that the critical time for dispersion coefficient to reach the steady state is varying with the yield stress and power law index. It is noticed that time to assume the critical value in Newtonian case is 0.5 and in the channel case the corresponding value of time is 0.55 which are in agreement with the existed results. It is also observed that in the non- Newtonian fluids this time is less than that of Newtonian fluid case and in Bingham fluid the critical value of time in pipe flow analysis (channel flow analysis) is attained at 0.45 (0.52) while in power law fluid it is at 0.43(0.48) and in the case of Herschel-Bulkley fluid it is 0.41 (0.45)

Retinal Microvascular Alterations in Patients with Quiescent Posterior and Panuveitis Using Optical Coherence Tomography Angiography

Purpose: To quantify retinochoroidal vascular parameters using swept-source optical coherence tomography (SS-OCTA) in quiescent posterior and panuveitis. Methods: In this cross-sectional study, subjects with quiescent posterior and panuveitis underwent fundus imaging using SS-OCTA (DRI Triton®, Topcon, Japan). The metrics calculated were fractal dimension (FD), foveal avascular zone (FAZ) area, retinal vascularity index (capillary density index-CDI), and choroidal vascularity index (CVI). Results: We included 38 eyes of 20 patients, 9 males aged 34.7 ± 10.5 years, 30 eyes of 30 age- and gender-matched healthy controls, 10 females aged 33.6 ± 8.5 years. Comparing patients with controls, we found a lower FD (p  .001), lower CDI in the superficial plexus (p = .019), and lower CVI (p < .001). We also found lower retinal and choroidal and thicknesses (p < .001 and p = .025, respectively). Conclusions: Patients with quiescent posterior and panuveitis have a significantly reduced retinochoroidal vascular density compared to healthy control subjects

The use of optical coherence tomography angiography in comparing choriocapillaris recovery between two treatment strategies for multifocal choroiditis: a pilot clinical trial

PURPOSE: To compare differences in choriocapillaris flow deficit (CC FD) in multifocal choroiditis (MFC) between two treatment arms using optical coherence tomography angiography (OCTA). METHODS: In this prospective randomized clinical trial, patients were randomized to either Group 1 which received standard tapering dose of oral corticosteroids, or Group 2 which received additional dexamethasone implant (or intravitreal methotrexate). The patients were followed-up until 12 weeks using OCTA and other imaging tools. CC FD and visual acuity between the two groups were compared at each visit. RESULTS: Twenty-five subjects (17 males; 25 eyes) were studied (11 eyes in Group 1). There were no differences between the visual acuity or CC FD (1.12 versus 1.08 mm 2; p = 0.86) at baseline between the groups. However, patients in Group 2 achieved better visual acuity (0.32 ± 0.23 versus 0.15 ± 0.11; p = 0.025) and CC FD (0.54 versus 0.15 mm 2; p = 0.008) at 12 weeks. CONCLUSIONS: OCTA is a useful tool in monitoring the CC FD recovery after treatment in MFC. Patients receiving intravitreal corticosteroid/methotrexate in addition to systemic corticosteroid showed greater resolution of CC FD on OCTA compared to those receiving only oral corticosteroids

Retinal Microvascular Alterations in Patients with Quiescent Posterior and Panuveitis Using Optical Coherence Tomography Angiography

Purpose To quantify retinochoroidal vascular parameters using swept-source optical coherence tomography (SS-OCTA) in quiescent posterior and panuveitis. Methods In this cross-sectional study, subjects with quiescent posterior and panuveitis underwent fundus imaging using SS-OCTA (DRI Triton (R), Topcon, Japan). The metrics calculated were fractal dimension (FD), foveal avascular zone (FAZ) area, retinal vascularity index (capillary density index-CDI), and choroidal vascularity index (CVI). Results We included 38 eyes of 20 patients, 9 males aged 34.7 +/- 10.5 years, 30 eyes of 30 age- and gender-matched healthy controls, 10 females aged 33.6 +/- 8.5 years. Comparing patients with controls, we found a lower FD (p .001), lower CDI in the superficial plexus (p = .019), and lower CVI (p < .001). We also found lower retinal and choroidal and thicknesses (p p = .025, respectively). Conclusions Patients with quiescent posterior and panuveitis have a significantly reduced retinochoroidal vascular density compared to healthy control subjects

The use of optical coherence tomography angiography in comparing choriocapillaris recovery between two treatment strategies for multifocal choroiditis:a pilot clinical trial

PURPOSE: To compare differences in choriocapillaris flow deficit (CC FD) in multifocal choroiditis (MFC) between two treatment arms using optical coherence tomography angiography (OCTA). METHODS: In this prospective randomized clinical trial, patients were randomized to either Group 1 which received standard tapering dose of oral corticosteroids, or Group 2 which received additional dexamethasone implant (or intravitreal methotrexate). The patients were followed-up until 12 weeks using OCTA and other imaging tools. CC FD and visual acuity between the two groups were compared at each visit. RESULTS: Twenty-five subjects (17 males; 25 eyes) were studied (11 eyes in Group 1). There were no differences between the visual acuity or CC FD (1.12 versus 1.08 mm(2); p = 0.86) at baseline between the groups. However, patients in Group 2 achieved better visual acuity (0.32 ± 0.23 versus 0.15 ± 0.11; p = 0.025) and CC FD (0.54 versus 0.15 mm(2); p = 0.008) at 12 weeks. CONCLUSIONS: OCTA is a useful tool in monitoring the CC FD recovery after treatment in MFC. Patients receiving intravitreal corticosteroid/methotrexate in addition to systemic corticosteroid showed greater resolution of CC FD on OCTA compared to those receiving only oral corticosteroids

Optical Coherence Tomography Findings of Underlying Choroidal Neovascularization in Punctate Inner Choroidopathy

Purpose: To analyze findings on optical coherence tomography (OCT) suggestive of choroidal neovascularization (CNV) in lesions of punctate inner choroidopathy (PIC). Methods: In this multi-center retrospective study, clinical data of patients with PIC were retrospectively analyzed. Quantitative data (height, width, and volume of PIC lesions), and qualitative data (disruption of ellipsoid zone (EZ)/Bruch's membrane (BM), outer retinal fuzziness, and choroidal back-shadowing) were compared between CNV+ and CNV– groups using Mann–Whitney U-test and Fischer's exact test. Results: In total, 35 eyes (29 patients; 21 women; mean age: 33.3 ± 6.5 years) were selected for analysis. Of the 35 PIC lesions studied, 17 had underlying CNV. Lesions with CNV+ had larger height, width, and volume (p < 0.001) and several distinctive features, such as disruption of EZ and BM, outer retinal fuzziness, and hypo-reflective back-shadowing (p < 0.001) compared with CNV—lesions. Conclusions: Quantitative and qualitative OCT analysis can aid in the prediction of an underlying CNV in the eyes with PIC