An international collaborative evaluation of central serous chorioretinopathy: different therapeutic approaches and review of literature. The European Vitreoretinal Society central serous chorioretinopathy study

Purpose: To study and compare the efficacy of different therapeutic options for the treatment of central serous chorioretinopathy (CSCR). Methods: This is a nonrandomized, international multicentre study on 1719 patients (1861 eyes) diagnosed with CSCR, from 63 centres (24 countries). Reported data included different methods of treatment and both results of diagnostic examinations [fluorescein angiography and/or optical coherent tomography (OCT)] and best-corrected visual acuity (BCVA) before and after therapy. The duration of observation had a mean of 11 months but was extended in a minority of cases up to 7 years. The aim of this study is to evaluate the efficacy of the different therapeutic options of CSCR in terms of both visual (BCVA) and anatomic (OCT) improvement. Results: One thousand seven hundred nineteen patients (1861 eyes) diagnosed with CSCR were included. Treatments performed were nonsteroidal anti-inflammatory eye drops, laser photocoagulation, micropulse diode laser photocoagulation, photodynamic therapy (PDT; Standard PDT, Reduced-dose PDT, Reduced-fluence PDT), intravitreal (IVT) antivascular endothelial growth factor injection (VEGF), observation and other treatments. The list of the OTHERS included both combinations of the main proposed treatments or a variety of other treatments such as eplerenone, spironolactone, acetazolamide, beta-blockers, anti-anxiety drugs, aspirin, folic acid, methotrexate, statins, vitis vinifera extract medication and pars plana vitrectomy. The majority of the patients were men with a prevalence of 77%. The odds ratio (OR) showed a partial or complete resolution of fluid on OCT with any treatment as compared with observation. In univariate analysis, the anatomical result (improvement in subretinal fluid using OCT at 1 month) was favoured by age <60 years (p < 0.005), no previous observation (p < 0.0002), duration less than 3 months (p < 0.0001), absence of CSCR in the fellow eye (p = 0.04), leakage outside of the arcade (p = 0.05) and fluid height >500 \u3bcm (p = 0.03). The OR for obtaining partial or complete resolution showed that anti-VEGF and eyedrops were not statistically significant; whereas PDT (8.5), thermal laser (11.3) and micropulse laser (8.9) lead to better anatomical results with less variability. In univariate analysis, the functional result at 1 month was favoured by first episode (p = 0.04), height of subretinal fluid >500 \u3bcm (p < 0.0001) and short duration of observation (p = 0.02). Finally, there was no statistically significant difference among the treatments at 12 months. Conclusion: Spontaneous resolution has been described in a high percentage of patients. Laser (micropulse and thermal) and PDT seem to lead to significant early anatomical improvement; however, there is little change beyond the first month of treatment. The real visual benefit needs further clarification

Prediction of Single Disc Seeding System Forces, Using a Semi-Analytical and Discrete Element Method (DEM)

There is a rising interest amongst Australian farmers to use disc seeders due to their ability to operate in high residue conditions and at higher speeds, commonly in the range of 12 to 15 km h−1. This paper reports on developing an analytical and discrete element method (DEM) force prediction model suited to a rotating flat disc blade operating at different sweep and tilt angles. To validate the models, field experiments were carried out with a flat disc blade at two tilt angles of 0 and 20° and four sweep angles of 6, 26, 45 and 90° in sandy soil. An analytical approach was developed following an experimental investigation that showed that only the forward portion of the disc blade is actively involved in generating soil failure, while the magnitude of this active portion of the soil-disc interface varied with sweep angle. The predicted active proportions correlated well with the experimental observations. As applying different sweep angles affects the direction of soil movement relative to the disc face, the directions of the friction and resultant forces at different sweep and tilt angles were determined. The equation of soil acceleration force was adapted to account for different sweep angles. Results showed that the predicted force fits relatively well with the measured data at 90, 45 and 26° sweep angle, while the low correlation between predicted and measured force at 6° sweep angle was due to the scrubbing reaction force not accounted for in the model. Results also showed that a better coefficient of determination (R2 = 0.93) was obtained between DEM vs. test results compared to the analytical model predictions (R2 = 0.86), particularly for predicting side forces. It was found from the study that both the developed analytical approach and DEM model enabled the prediction of soil forces at different sweep and tilt angles acting on a flat disc blade, which can assist in optimising disc design to lower the specific resistance

Prediction of Single Disc Seeding System Forces, Using a Semi-Analytical and Discrete Element Method (DEM) Considering Rotation Effects

Disc seeders are commonly used in no-till farming systems, and their performance evaluation generally rely on expensive and time-consuming field experiments. Mathematical models can help speed up force-related evaluations and improve the understanding of soil-disc interactions, to assist the performance optimisation processes. Previous analytical force prediction models of disc blades have not accounted for the free rotation aspect of the disc blade. This paper develops an analytical force prediction model from the wide blade failure theory adapted to suit rotating flat disc blades operating at different sweep and tilt angles and compares predictions with Discrete Element Method (DEM) simulations. To validate the two models, experiments were performed on a remoulded sandy soil condition using a rotating flat disc set at two tilt angles of 0° and 20°, and four sweep angles of 6, 26, 45 and 90° the 3-dimensional force components of draught, vertical and side forces were measured. Results showed a higher coefficient of determination (R2 = 0.95) was obtained with analytical model predictions compared to DEM predictions (R2 = 0.85) for their agreement with the test results. It was found that both the developed analytical approach and the DEM model can be used to predict tillage forces at different sweep and tilt angles acting on a rotating flat disc blade

Determination of discrete element model parameters for a cohesive soil and validation through narrow point opener performance analysis

The discrete element method (DEM) is a powerful tool that can be used to predict soil disturbance and soil cutting forces to assist design optimisation of soil cutting tools. In this study, DEM input parameters were calibrated to model a cohesive soil (Black Vertosol of southern Queensland, Australia) using the hysteretic spring contact model, coupled with linear cohesion model, and nominal particle radius of 5 mm. DEM simulations were validated using experimental results for the effects of opener rake angle and cutting edge chamfer, and bentleg opener shank offset on no-tillage narrow point opener performance. Overall, DEM results closely agreed with experimental results and exhibited similar trends. By using particle displacement analysis to predict loosened furrow boundary, most predictions of furrow parameters namely furrow cross-sectional area, furrow width, and critical depth had relative errors ranging from 1 % to 19 %. Lateral soil throw was predicted with relative errors of 0.2 %–9 %, except for the straight opener with 45° rake angle (-32 %). Ridge height was over predicted in all cases due to larger DEM particles than actual soil particles used. Relative errors of 20 %, 22 %, -31 %, and -5 % in draught were recorded for the straight openers with 90° (blunt), 90° (chamfered), and 45° rake angles, and the bentleg opener, respectively. These results show that DEM and the input parameters determined to model the cohesive soil of this study can be used to reliably assess furrow opener performance

Evaluation of bentleg and straight narrow point openers in cohesive soil

The bentleg opener was developed to overcome the high soil disturbance caused by straight narrow point openers, with the original evaluation conducted on sandy soils. A bentleg furrow opener was compared to narrow point openers with varying rake angles (45° and 90°) and cutting edge cross-sections (blunt, and single- and double-side chamfers) for soil disturbance, tillage forces, and soil aggregate break down in Black Vertosol (Vertisol in the USDA Soil Taxonomy), a highly cohesive soil relative to sandy soils used previously. Whereas the 45° rake angle caused greater soil disturbance, produced larger soil aggregates, and reduced draught and vertical force requirements, all openers with 90° rake angle (blunt and chamfered openers) had a shallow critical depth (44–46 mm) and caused smearing. Contrary to previous findings in sandy soil, both single and double side chamfering of opener cutting edge had no significant effect on soil movement, furrow width, and furrow cross-sectional area. However, greater soil movement was observed on the chamfered side of the single-side chamfered opener than the non-chamfered side. The chamfers significantly reduced draught and vertical forces and produced smaller soil aggregates. The bentleg opener loosened soil to the furrow bottom but caused the least soil movement out of the furrow and formed a ridge in the middle of the furrow, which resulted in the highest furrow backfill. It also encountered a downward vertical force which assisted penetration and had a greater proportion of aggregates within the optimum range (1.18 and 9.5 mm). The bentleg opener, thus, shows potential for improved seed covering and satisfactory performance at operating speeds above 8 km h−1

No-tillage furrow opener performance: a review of tool geometry, settings and interactions with soil and crop residue

The primary features of an effective and efficient furrow opener include controlled soil disturbance and low draught and vertical force requirements. When integrated in a no-tillage seeding system, furrow openers should also have the ability to assist, and not hinder, the functions of seeding system components – such as maintaining adequate surface residue distribution, accurate and uniform placement of seeds and fertiliser, and regular inter-plant spacing. This review highlights how these goals are affected by opener type, geometry and settings, and soil and residue conditions. Typically, tine openers cause greater soil disturbance than disc openers whereas disc openers are likely to cause residue hairpinning. Winged tine openers reduce residue interference with seed placement and support greater lateral seed spread. Inverted-T openers can achieve subsurface soil shattering, which helps conserve moisture and provides good seed–soil contact. A tine opener with concave cutting edge reduces soil disturbance relative to straight and convex cutting edges. Increasing rake angle, tine width and operating depth increase degree of soil disturbance and draught requirement. Increasing forward speed reduces residue interference with sowing but might decrease the accuracy and uniformity of depth and separation of seed and fertiliser placement. Relative to common openers, bentleg openers have lower draught and penetration force requirements while combining minimal lateral soil throw with high furrow backfill, even at speeds of up to 16 km h–1. The performance of bentleg openers need to be evaluated under residue conditions and in cohesive and adhesive soils. Recommendations for future research are presented

Analysis of effects of operating speed and depth on bentleg opener performance in cohesive soil using the discrete element method

High operating speeds are desirable, different seeding depths are required, and low soil disturbance is necessary for sowing in no-tillage farming. The effects of operating speed (8–16 km h−1) and depth (60–120 mm) on bentleg opener (four variations) performance were analysed in comparison to straight openers in a virtual soil bin using the discrete element method (DEM). Generally, increasing operating depth and speed resulted in increased soil disturbance and reaction forces. However, the bentleg openers loosened furrows down to the furrow bottom and caused less lateral soil throw at all operating depths and speeds. Bentleg openers, particularly without foot, increased furrow width by lower magnitudes compared with straight openers as operating speed was increased. The greatest lateral soil throw beyond furrow banks recorded for the bentleg openers at operating speed and depth of 16 km h−1 and 60 mm were less than the least for the straight openers, except for the footless bentleg with forward raked side leg. Backward raked side leg had the lowest impact on lateral soil throw and spill over distance with increasing operating speed. Increasing operating speed shifted the main ridge created by the bentleg openers above the furrow’s centre outward to the left. Furrow backfill of 97–100% was achieved with the bentleg openers. Bentleg openers with 45° foot rake angle required the lowest draught and vertical forces. Backward raked side leg resulted in the highest draught force among the bentleg openers and the greatest vertical (penetration) force among all the opener