Search Results (7)

Objectives: This study aims to compare the imaging performance of spectral-domain optical coherence tomography (SD-OCT) and swept-source OCT (SS-OCT) in the early postoperative assessment of patients undergoing vitreoretinal surgery with intraocular gas or air tamponade. Methods: Seventeen eyes of 17 patients who underwent pars plana vitrectomy with either sulfur hexafluoride (SF₆, 20%) or air tamponade were prospectively enrolled. All patients underwent OCT imaging on postoperative day 1 using both the SD-OCT system and the SS-OCT platform, without pharmacological mydriasis. Images were independently evaluated by two experienced ophthalmologists based on the ability to delineate four prespecified anatomical layers: inner retinal layers, ellipsoid zone (EZ), retinal pigment epithelium (RPE) and choroid. Images were classified as adequate quality if two or more of these structures were identifiable. Results: SS-OCT provided adequate-quality images in all 17 eyes (100%), with complete visualization of the inner retinal layers, EZ, RPE, and choroid in 15 eyes (88.2%). In contrast, SD-OCT yielded adequate-quality images in only three of 17 eyes (17.6%), demonstrating marked signal attenuation, interface artifacts, and inability to resolve deeper retinal structures in most cases. No difference in imaging performance was observed between SF₆ and air tamponade subgroups. Conclusions: SS-OCT demonstrates markedly superior imaging performance in gas-filled eyes on postoperative day 1 compared to SD-OCT, primarily attributable to its longer wavelength, reduced sensitivity roll-off, and superior penetration through optically challenging media. These findings suggest that SS-OCT may offer meaningful advantages for early postoperative monitoring following vitreoretinal surgery with tamponade; confirmation in larger prospective cohorts with clinical-outcome correlation is warranted before it can be recommended as the preferred modality. Full article

Background: Descemet membrane endothelial keratoplasty (DMEK) is the most frequently performed keratoplasty procedure in many countries. One of the most common early complications is an elevation of intraocular pressure (IOP). The aim of this study was to characterize early postoperative IOP behavior following DMEK performed with 10% sulfur hexafluoride (SF₆) tamponade and to determine the frequency and timing of required IOP-lowering interventions within the first 48 h. Methods: We retrospectively reviewed postoperative outcomes of 116 consecutive DMEK procedures between May and December 2024 at the University Medical Center in Mainz, Germany. No specific exclusion criteria were applied. All surgeries included a surgical iridectomy at the 6 o’clock position, 10% (SF₆) tamponade, and maintaining a mid-normal IOP at the end of surgery. Postoperative assessments included IOP measured using Goldmann applanation tonometry, the percentage of gas fill in the anterior chamber evaluated at the slit lamp, and the need for IOP-lowering interventions as determined by the on-call resident at 3, 24, and 48 h after surgery. IOP-lowering interventions consisted of venting in cases of elevated IOP, gas fill > 90%, and/or suspected angle closure or pupillary block, as well as intravenous or oral acetazolamide in cases of moderate IOP elevation with a lower gas fill and a patent iridectomy. If a single intervention was insufficient, a combined approach was used. Results: A total of 116 eyes from 98 patients (62 female, mean age 73.0 ± 9.8 years) were analyzed. DMEK was combined with cataract surgery in 41 eyes, and 4 eyes underwent phakic DMEK. Postoperatively, all iridectomies remained patent, and no cases of pupillary block occurred. Mean IOP and gas fill were within normal limits and declined steadily during the first 48 h. IOP-lowering procedures were performed in 11 eyes (9.5%), including venting (n = 3), acetazolamide administration (n = 7), and a combination of both (n = 1). There was no difference between DMEK and triple-DMEK regarding postoperative gas fill, IOP, or the need for IOP-lowering interventions. Mean postoperative IOP was significantly higher, and IOP-lowering interventions were more frequent in glaucoma vs. non-glaucoma patients. Re-bubbling was performed in 12 eyes (10.3%). Two cases of primary graft failure (1.7%) were recorded. Conclusions: In our patient cohort, a standardized surgical approach incorporating a surgical iridectomy at the 6 o’clock position, 10% SF₆ tamponade, and maintaining a mid-normal IOP at the end of surgery effectively prevented pupillary block. We recommend early postoperative assessment of IOP and percent gas fill to promptly identify and manage impending IOP elevation, which is particularly important in patients with glaucoma. Full article

Falling within the safe bands for human eyes, 1550 nm semiconductor lasers have a wide range of applications in the fields of LIDAR, fast-ranging long-distance optical communication, and gas sensing. The 1550 nm human eye-safe high-power tunnel junction quantum well laser developed in this paper uses three quantum well structures connected by two tunnel junctions as the active region; photolithography and etching were performed to form two trenches perpendicular to the direction of the epitaxial layer growth with a depth exceeding the tunnel junction, and the trenches were finally filled with oxides to reduce the extension current. Finally, a 1550 nm InGaAlAs quantum well laser with a pulsed peak power of 31 W at 30 A (10 KHz, 100 ns) was realized for a single-emitter laser device with an injection strip width of 190 μm, a ridge width of 300 μm, and a cavity length of 2 mm, with a final slope efficiency of 1.03 W/A, and with a horizontal divergence angle of about 13° and a vertical divergence angle of no more than 30°. The device has good slope efficiency, and this 100 ns pulse width can be effectively applied in the fields of fog-transparent imaging sensors and fast headroom ranging radar areas. Full article

We evaluated the closure of full-thickness macular holes (MHs) the day after surgery in minimizing the burden and maximizing patient outcomes. Herein, 25-gauge pars plana vitrectomy, internal limiting membrane peeling, and fluid–gas (20% sulfur hexafluoride) were performed for the treatment. Patients were instructed to remain in the facedown position until the confirmation of MH closure, and the position was discontinued in cases where the closure was confirmed. In total, 43 eyes of 43 patients, whose average age was 69.7 ± 8.6 years, were enrolled in this study. We used swept source (SS)-optical coherence tomography (OCT) for the confirmation of MH closure for gas-filled eyes and used spectral domain (SD)-OCT for the reconfirmation of MH closure after the gas volume was reduced to less than half of the vitreous cavity. MH closure was confirmed in 40 eyes (93%, the closure group) on the next day after surgery. The time from surgery to SS-OCT imaging was 24.7 h. Although facedown positioning was terminated in cases where MH closure was confirmed, there were no cases in which the MH was re-opened afterward. The basal and minimum MH size was significantly larger in the non-closure group than that in the closure group (p = 0.027, p = 0.043, respectively). Therefore, checking with SS-OCT the day after surgery and terminating facedown positioning in cases where MH closure was confirmed would be a useful method, removing a great burden for the elderly without sacrificing the MH closure rate. Full article

Torrefaction is an effective technology to overcome the defects of biomass which are adverse to its utilization as solid fuels. For assessing the torrefaction process, it is essential to characterize the properties of torrefied biomass. However, the preparation and characterization of torrefied biomass often consume a lot of time, costs, and manpower. Developing a reliable method to predict the fuel properties of torrefied biomass while avoiding various experiments and tests is of great value. In this study, a machine learning (ML) model of back propagation neural network (BPNN) hybridized with genetic algorithm (GA) optimization was developed to predict the important properties of torrefied biomass for the fuel purpose involving fuel ratio (FR), H/C and O/C ratios, high heating value (HHV) and the mass and energy yields (MY and EY) based on the proximate analysis results of raw biomass and torrefaction conditions. R² and RMSE were examined to evaluate the prediction precision of the model. The results showed that the GA-BPNN model exhibited excellent accuracy in predicting all properties with the values of R² higher than 0.91 and RMSE less than 1.1879. Notably, the GA-BPNN model is applicable to any type of biomass feedstock, whether it was dried or not before torrefaction. This study filled the gap of ML application in predicting the multiple fuel properties of torrefied biomass. The results could provide reference to torrefaction technology as well as the design of torrefaction facilities. Full article

Purpose: To investigate clinical and surgical factors influencing the outcome after primary rhegmatogenous retinal detachment surgery. Methods: A retrospective, single-centre, case-control study of 1017 eyes of 1017 consecutive patients with primary rhegmatogenous retinal detachment (RRD) who underwent pars plana vitrectomy (PPV), were included in the study. Analysed surgical factors were: combined procedure with phacoemulsification, type of retinopexy (cryocoagulation, endolaser, combined), type of tamponade (gas, silicone oil), and anatomical factors: primary proliferative vitreoretinopathy (PVR) and macular detachment at the time of surgery. Results: Overall retinal re-detachment rate was 10.1%. The main reason for re-detachment was an insufficient retinopexy in 53.6%, followed by PVR (37.3%), and retinal detachment occurred at a different location caused by another break in 9.1%. No significant difference in the rate of re-detachment was found if a phacoemulsification with simultaneous IOL implantation was performed (p = 0.641). No significant difference between the various retinopexy techniques was found (p = 0.309). Risk factors re-detachment were primary PVR (p = 0.0003), silicone oil as initial tamponade (p = 0.0001) as well as macula off detachments (p = 0.034). Conclusions: The present study showed no significant difference between the types of retinopexy and if additional phacoemulsification was performed or not. Factors associated with a higher risk for re-detachment were detached macula at surgery, primary PVR and primary oil-filling. Full article

Molten steel is alloyed during tapping from the melting furnace to the argon-bottom stirred ladle. The metallic additions thrown to the ladle during the ladle filling time are at room temperature. The melting rates or kinetics of sinking-metals, like nickel, are simulated through a multiphase Euler–Lagrangian mathematical model during this operation. The melting rate of a metallic particle depends on its trajectory within regions of the melt with high or low turbulence levels, delaying or speeding up their melting process. At low steel levels in the ladle, the melting rates are higher on the opposite side of the plume zone induced by the bottom gas stirring. This effect is due to its deviation after the impact of the impinging jet on the ladle bottom. The higher melting kinetics are located on both sides at high steel levels due to the more extensive recirculation flows formed in taller baths. Making the additions above the eye of the argon plume spout increases the melting rate of nickel particles. The increase of the superheat makes the heat flux more significant from the melt to the particle, increasing its melting rate. At higher superheats, the melting kinetics become less dependent on the fluid dynamics of the melt. Full article