Intraocular pressure variation from ocular compression in low and high myopia.

CLINICAL RELEVANCE: Change in intraocular pressure during acute ocular compression is related to aqueous humour dynamics. Monitoring intraocular pressure (IOP) change throughout ocular compression has potential to evaluate aqueous outflow facilities. BACKGROUND: Recent studies have monitored lamina cribrosa deformation using optical coherence tomography during ocular compression. IOP was measured only once immediately after ocular compression. This study aimed to evaluate IOP changes during and after ocular compression and compare the differences between low and high myopia. METHODS: Two groups of young, healthy adults were age-matched and underwent ocular compression. IOP was measured at baseline and monitored during a 2-min ocular compression followed by a 10-min recovery phase. Rebound tonometry was used and applied at 30-s intervals. RESULTS: Thirty low and 30 high myopes (60 right eyes) were included in the study. They had similar baseline IOP at 14.9 mmHg. IOP was elevated to 21.7 ± 3.8 mmHg and 22.3 ± 4.2 mmHg for the low and high myopic group, respectively (p = 0.877). Low myopes had faster IOP decay during ocular compression at -3.24 mmHg/min than high myopes at -2.58 mmHg/min (p = 0.0528). The IOP dropped below the baseline level after the release of the compressive force. Low myopes had IOP that returned to baseline levels faster (at 360 s) than high myopes (at 510 s). CONCLUSION: Measuring IOP once immediately after ocular compression could under-estimate the effect of IOP elevation during ocular compression. Further studies are required regarding IOP changes from ocular compression in aqueous humour dynamics.

Quantitative evaluation on thermal seeing induced 2m ring solar telescope.

Thermal seeing is one of the factors that affect solar telescope observations. A comprehensive analysis method is developed to quantify the thermal seeing effects. A three-dimensional Large Eddy Simulation (LES) turbulence model is used to obtain the transient flow fields around the primary mirror, the secondary mirror and the heat-stop. The thermal seeing is calculated based on the stochastic dynamic influence of turbulence on the light rays. The key parameters of the simulation were calibrated by experiments, and the simulation results were validated by empirical formulas. This method has been applied to evaluate the thermal seeing of the 2m Ring Solar Telescope (2m-RST). Error allocation is performed based on the research results to ensure the Observation effect of 2m-RST.

Research on piston error sensing for segmented mirrors under atmospheric turbulence.

Large aperture ground-based segmented telescopes typically use electrical edge sensors to detect co-phase errors. However, complex observing environments can lead to zero-point drift of the edge sensors, making it challenging to maintain the long-term co-phase of the segmented primary mirror using only edge sensors. Therefore, employing optical piston error detection methods for short-term calibration of edge sensors can address the issue of zero-point drift in the sensors. However, atmospheric turbulence can affect calibration accuracy based on the observational target. To achieve high-precision calibration of electrical edge sensors, this study investigates the impact of atmospheric turbulence on optical piston error detection. Based on simulated results, it is found that the actual measured piston error in the presence of atmospheric turbulence is the difference between the average phases of the two segments. Subsequently, optical piston error detection experiments were conducted in a segmented mirror system under simulated turbulent conditions with varying turbulence intensities. Experimental studies have shown that the detection accuracy of the optical method is almost the same as without turbulence when using a detection aperture size that is 0.82 times the atmospheric coherence length and an exposure time of at least 40 ms. The root mean square of the cross-calibration is better than 3 nm. These experimental results indicate that under conditions of good atmospheric seeing, the optical piston error detection method can meet the short-term calibration requirements of edge sensors by setting reasonable detection area size and exposure time. It may even be possible to directly use optical detection methods to replace edge sensors for real-time detection of piston errors.

Research on accurate non-contact temperature measurement method for telescope mirror.

Non-contact temperature measurement for a solar telescope mirror is critical for improving the mirror seeing and thermal deformation of solar telescopes, a long-standing challenge in astronomy. This challenge arises from the telescope mirror's inherent weak thermal radiation, often overwhelmed by reflected background radiations due to its high reflectivity. In this work, an infrared mirror thermometer (IMT) is equipped with a thermally-modulated reflector, and a measurement method based on an equation for extracting mirror radiation (EEMR) has been developed for probing the accurate radiation and temperature of the telescope mirror. Using this approach, we can extract the mirror radiation from the instrumental background radiation via the EEMR. This reflector has been designed to amplify the mirror radiation signal incident on the infrared sensor of IMT, while inhibiting the radiation noise from the ambient environment. In addition, we also propose a set of evaluation methods for IMT performance based on EEMR. The results reveal that the temperature measurement accuracy of IMT to the solar telescope mirror using this measurement method can be achieved better than ±0.15°C.

Study of transient behaviors of wavefront error caused by natural convection for improving mirror seeing.

Astronomical seeing parameters calculated based on the Kolmogorov turbulence model cannot fully evaluate the effect of the natural convection (NC) above a solar telescope mirror on the image quality, as the convective air motions and temperature variations of the NC are significantly different from the Kolmogorov turbulence. In this work, a new method based on the transient behaviors and frequency characteristics of NC-related wavefront error (WFE) are investigated in detail and used to evaluate the image quality degradation caused by a heated telescope mirror, aiming to make up for the deficiency of astronomical seeing parameters with the conventional method in evaluating the image quality degradation. Transient computational fluid dynamics (CFD) simulations and WFE calculations based on discrete sampling and ray segmentation are performed to quantitatively evaluate the transient behaviors of the NC-related WFE. It clearly exhibits apparent oscillatory characteristics, which are coupled by main oscillation with low frequencies and minor oscillation with high frequencies. Moreover, the generation mechanisms of two types of oscillations are studied. The conspicuous oscillation frequencies of the main oscillation caused by heated telescope mirrors with varying dimensions are primarily lower than 1 Hz, suggesting that active optics may be adopted to correct the main oscillation of NC-related WFE while the adaptive optics may correct the minor oscillation. Furthermore, a mathematical relationship between WFE, temperature rise, and mirror diameter is derived, revealing a significant correlation between WFE and mirror diameter. Our work suggests the transient NC-related WFE should be considered as one of the critical supplements to the mirror seeing evaluation.

Active maintenance of a segmented mirror based on edge and tip sensing.

An 8 m ring aperture segmented telescope is one of the important elements of the Chinese Giant Solar Telescope (CGST) project. In addition, active control of the primary mirror has become a key technology of the 8 wm ring solar telescope (8 m RST). Due to the particularity of the ring aperture, the active maintenance of the segmented RST faces the following problem: edge detection cannot provide enough information to fulfil the closed-loop control. A scheme of using edge and tip detection to complete the active maintenance of an 8 m RST has been proposed. To study the feasibility and performance of edge detection combined with tip detection, we built a workbench of a two-segmented mirror and carried out an active maintenance analysis and experiment. Two capacitive sensors were used to detect the edge height change between the segments, and a Shack-Hartmann sensor was used to detect the tip and tilt change of the segment. A stable mirror figure was achieved during 100 min, and the mirror figure error was maintained at 18.94 nm. This work will provide reference for the implementation of the active control for a segmented ring telescope and also give evidence for the choice of the primary mirror of the CGST.

A combination of portal vein stent insertion and endovascular iodine-125 seed-strip implantation, followed by transcatheter arterial chemoembolization with sorafenib for treatment of hepatocellular carcinoma-associated portal vein tumor thrombus.

PURPOSE: This study aimed to assess efficacy of portal vein stent (PVS) insertion and endovascular iodine-125 (125I) seed-strip implantation, followed by transcatheter arterial chemoembolization (TACE) with sorafenib (PVS-125I TACE-S) in patients with hepatocellular carcinoma (HCC)-associated type II or type III portal vein tumor thrombus (PVTT). MATERIAL AND METHODS: A retrospective study was performed on 53 consecutive patients with HCC and type II or type III PVTT, from May 2014 to July 2018. Patients were divided into 2 groups, including group A with 28 patients treated with PVS-125I TACE-S, and group B with 25 patients treated with TACE-S. Primary end-point was overall survival (OS), while secondary endpoints were hepatic function and disease control rate (DCR). Albumin-bilirubin (ALBI) score approach was used for evaluating liver function. Cox regression analysis was applied to identify factors associated with treatment outcomes. RESULTS: No pre-operative differences were found in ALBI scores between group A and group B (-2.57 ±0.42 vs. -2.61 ±0.38, p = 0.724), or in these scores at 1 month post-operatively (-2.62 ±0.46 vs. -2.20 ±0.59, p = 0.666). However, these scores were significantly different at 3 (-2.17 ±0.59 vs. -1.69 ±0.48, p = 0.007) and 6 (-2.28 ±1.23 vs. -1.47 ±0.31, p = 0.044) months post-operatively. In addition, group A exhibited higher DCR (71.4% vs. 44.0%, p = 0.043) after 6 months of treatment and extended OS duration (11.4 vs. 7.7 months, p = 0.007). A stratified analysis revealed that OS in patients with type II PVTT did not differ significantly (10.4 vs. 10.7 months, p = 0.689), but OS with type III varied significantly (11.5 vs. 7.5 months, p = 0.002). Multivariate analysis revealed that tumor size > 10 cm (p = 0.002) and multiple tumors (p = 0.022) were independent predictors for poor prognosis, whereas PVS-125I TACE-S was predictor for favorable patient's prognosis (p = 0.040). CONCLUSIONS: PVS-125I TACE-S represents a potentially viable strategy for improving hepatic functionality, DCR, and OS in HCC with type III PVTT compared with TACE-S alone.

The efficacy of the combination of percutaneous transhepatic biliary drainage and 125I stranded seeds for malignant bile duct obstruction treatment.

PURPOSE: To investigate the efficacy of percutaneous transhepatic biliary drainage (PTBD) combined with iodine-125 (125I) stranded seeds for the treatment of malignant bile duct obstruction (MBO). MATERIAL AND METHODS: A retrospective study was performed on 58 consecutive MBO patients. Twenty patients underwent PTBD combined with 125I stranded seeds (group A). Thirty-eight patients underwent percutaneous trans-hepatic biliary drainage (group B). Total bilirubin, direct bilirubin, and indirect bilirubin levels were compared preoperatively, 1-week, 1-month, and 3-months post-operatively. Carbohydrate antigen 19-9 (CA19-9), cancer antigen 125 (CA125), and carcino-embryonic antigen (CEA) levels were compared at preoperative and 3-month post-operative stages. The time free from biliary obstruction and survival times were compared. RESULTS: The differences in total bilirubin, direct bilirubin, and indirect bilirubin levels between the two groups were not significant preoperatively (p = 0.857, p = 0.719, and p = 0.870), and 1-week post-operatively (p = 0.259, p = 0.395, and p = 0.145). However, 1-month (p = 0.012, p = 0.005, and p = 0.049) and 3-months post-operatively (p < 0.001, p = 0.001, and p = 0.001), group A was lower than group B. Differences in CA19-9, CA125, and CEA levels between the two groups were not significant preoperatively (p = 0.229, p = 0.116, and p = 0.273) and 3-months post-operatively (p = 0.159, p = 0.342, and p = 0.306). The median biliary obstruction free time was 7.0 months for group A and 5.0 months for group B (p < 0.001). The median survival time was 9.0 months for group A and 6.0 months for group B (p = 0.001). CONCLUSIONS: PTBD combined with 125I stranded seeds seem to reduce bilirubin levels and prevents biliary obstruction, promoting survival.

Efficacy of 125I Versus Non-125I Combined with Transcatheter Arterial Chemoembolization for the Treatment of Unresectable Hepatocellular Carcinoma with Obstructive Jaundice.

PURPOSE: To compare the therapeutic effects of 125I versus non-125I combined with transcatheter arterial chemoembolization (TACE) for the treatment of unresectable hepatocellular carcinoma (HCC) with obstructive jaundice. METHODS: A retrospective analysis was conducted using the records of 54 consecutive patients who were initially diagnosed with HCC with obstructive jaundice between May 2009 and July 2016. Twenty-one cases (group A) were treated with percutaneous transhepatic biliary drainage (PTBD) followed by 125I radioactive seed strip implantation through the PTBD tube. After the total serum bilirubin level was reduced to normal and the liver function recovered to Child-Pugh class A or early B, TACE was conducted. In 33 cases (group B) PTBD was performed in combination with TACE without applying the 125I radioactive seeds. The duration of biliary patency and survival were analyzed. RESULTS: The technical success rate in both groups was 100%. The median biliary patency time was 6.000 ± 0.315 months (95% CI 5.382-6.618 months) in group A and 4.000 ± 0.572 months (95% CI 2.879-5.121 months) in group B; the two groups were significantly different (P = 0.001). The median survival was 11.000 ± 0.864 months (95% CI 9.306-12.694 months) in group A and 9.000 ± 0.528 months (95% CI 7.965-10.035 months) in group B; the two groups were significantly different (P = 0.022). CONCLUSIONS: The combination of 125I with TACE was more effective than TACE without the radioactive seeds for treating patients with unresectable HCC with obstructive jaundice. Future prospective trials with larger samples will be required to validate these results.