Enhanced light extraction efficiency for the inclined-sidewall-shaped AlGaN-based DUV LED by using an omni-directional reflector with a thin hybrid dielectric layer.

In this Letter, an omni-directional reflector (ODR) with a thin hybrid dielectric layer (hybrid-ODR) is proposed to enhance the light extraction efficiency (LEE) for inclined-sidewall-shaped AlGaN-based deep ultraviolet light-emitting diode (DUV LED) by inserting a thin diamond with high refraction index into a conventional Al/Al2O3-based ODR. The three-dimensional finite-difference time-domain (3D FDTD) simulation results show that the LEE of TM-polarized light for the DUV LED with hybrid-ODR is enhanced by 18.5% compared with Al/Al2O3-based ODR. It is because the diamond can transform the evanescent wave in Al2O3 into the propagating light wave in diamond, thereby preventing effective excitation of the surface plasmon polariton (SPP) on the surface of the metal Al. Moreover, the Brewster's angle effect causes the TM-polarized light in diamond to propagate effectively into AlGaN. Furthermore, decreasing the total thickness of the dielectric layer also improves the scattering effect of the inclined sidewall. However, the utilization of hybrid-ODR results in a slight reduction in the LEE for transverse electric (TE) polarized light because the light is confined to the diamond layer and eventually absorbed by the metal Al.

Enhancing light extraction efficiency of the inclined-sidewall-shaped DUV micro-LED array by hybridizing a nanopatterned sapphire substrate and an air-cavity reflector.

In this work, we hybridize an air cavity reflector and a nanopatterned sapphire substrate (NPSS) for making an inclined-sidewall-shaped deep ultraviolet micro light-emitting diode (DUV micro-LED) array to enhance the light extraction efficiency (LEE). A cost-effective hybrid photolithography process involving positive and negative photoresist (PR) is explored to fabricate air-cavity reflectors. The experimental results demonstrate a 9.88% increase in the optical power for the DUV micro-LED array with a bottom air-cavity reflector when compared with the conventional DUV micro-LED array with only a sidewall metal reflector. The bottom air-cavity reflector significantly contributes to the reduction of the light absorption and provides more escape paths for light, which in turn increases the LEE. Our investigations also report that such a designed air-cavity reflector exhibits a more pronounced impact on small-size micro-LED arrays, because more photons can propagate into escape cones by experiencing fewer scattering events from the air-cavity structure. Furthermore, the NPSS can enlarge the escape cone and serve as scattering centers to eliminate the waveguiding effect, which further enables the improved LEE for the DUV micro-LED array with an air-cavity reflector.

On the origin of the enhanced light extraction efficiency of DUV LED by using inclined sidewalls.

It is known that light extraction efficiency (LEE) for AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) can be enhanced by using an inclined sidewall of mesa. However, the reported optimal inclined angles are different. In this work, to explore the origin for enhancing the LEE of DUV LED by using inclined sidewalls, we investigate the effect of an inclined sidewall angle on the LEE for AlGaN-based DUV LEDs with different mesa diameters by using ray tracing. It is found that when compared to large-size DUV LEDs with inclined sidewall, the LEE of small-size DUV LEDs with inclined sidewall is enhanced from both the bottom and side surfaces due to the reduced scattering length and material absorption. Additionally, the optimal inclined sidewall angle is recommended within the range of 25°-65°, and the optimal angle for DUV LEDs decreases as the chip size increases. It can be attributed to the fact that there are two scattering mechanisms for the inclined sidewall. For smaller chip sizes, most of the light is directly scattered into escape cones by the inclined sidewall, resulting in a larger optimal angle. For larger chip sizes, the light firstly experiences total internal reflections by the out-light plane and then is scattered into escape cones by the inclined sidewalls, leading to a smaller optimal angle.

Continuous ultrasonic ozone coupling technology-assisted control of ceramic membrane fouling coupled enhanced multiphase mixing to treat dye wastewater and CFD flow field simulation.

In this study, ozone catalysts (hydrogenation-modified red mud, HM-RM) successfully prepared by hydrogenation-modification of industrial hazardous solid waste red mud (RM) as a raw material in accordance with the viewpoint of treating waste with waste and using waste. Meanwhile, as for the common phenomenon of membrane fouling, uneven distribution of multiphase solid catalysts and ozone in liquids, the addition of ultrasound can not only disperse materials, but also play a role in online cleaning of ceramic membranes and catalysts. The optimum treatment conditions for Rhodamine B (RhB) solution with volume of 2 L and concentration of 40 mg/L were catalyst concentration of 0.4 mg/L, reaction temperature of 45 °C, ultrasonic time of 1 h, ultrasonic intensity of 600 W, removal rate of RhB was up to 90 %. In addition, the computational fluid dynamics (CFD) simulation method was used to investigate the fluid flow between the two gas-liquid phases and the effect of the negative pressure of the membrane pump on the fluid by the analysis of flow, pressure and ozone flux of the ceramic membrane(CM) reaction apparatus. The CFD simulation results showed that at the inlet gas-liquid flow rate of 3 m/s and the negative pressure of 20,000 Pa, the maximum flow rates of CM-1 were 3 m/s, 0.752 m/s for CM-2, and 0.228 m/s for CM-3, respectively. Vortices, which are beneficial to solid-liquid mixing and gas-liquid mass transfer, formed between the suction port CM-1 of CM-1 and the inlets of CM-2 and CM-3. This discovery is consistent with relevant experimental research results. Significantly higher concentrations of both •OH and dissolved ozone were observed in the US/HM-RM/O3 system compared to other systems, indicating the significant improvement in ozone utilization rate through the application of ultrasound. The superiority of the US/HM-RM/O3 device was demonstrated. The real dye effluent was tested under optimum operating conditions and the results showed that COD and TOC were reduced by 81.34 % and 60.23 % respectively after 180 min of treatment. The above research can provide technical support for the treatment of dye wastewater using Ultrasound-enhanced ozone oxidation ceramic membranes.

Simultaneous removing algal and its extracellular organic matters by Mg/Al-layered double hydroxide /La-montmorillonite.

Rapid and effective simultaneous removal of algal and extracellular organic matter (EOM) is essential for algal blooms water emergency treatment. In this study, a composite material was prepared by physical and chemical interaction between La-montmorillonite (La-MMT) and Mg/Al-layered double hydroxide (LDHs), and its removal effect of algal and extracellular organic matters (EOM) was investigated. The results showed that the removal rate of chlorophyll a (chl-a) was 96.8% within 2 h when the LDHs/La-MMT2:1 dosage was 1.0 g/L. Three-dimensional fluorescence characteristic spectra and parallel factor analysis showed that the removal of EOM by composite material mainly reflected in the removal of humus-like substances. The reaction heat of composite material for the algal solution was -32.7 J/g. Zeta potential changed from -25.7 mV to -16.9 mV, the main treatment mechanisms of composite material were surface adsorption, complexation precipitation, charge neutralisation, and ion exchange. These findings herein proposed that composite material was a potential and proper treating agent for removing algal cells and EOM from algal blooms water.

Research progress of lens zonules.

Background: The lens zonule, a circumferential system of fibres connecting the ciliary body to the lens, is responsible for centration of the lens. The structural, functional, and positional abnormalities of the zonular apparatus can lead to the abnormality of the intraocular structure, presenting a significant challenge to cataract surgery. Main text: The lens zonule is the elaborate system of extracellular fibers, which not only centers the lens in the eye but also plays an important role in accommodation and lens immunity, maintains the shape of the lens, and corrects spherical aberration. The zonules may directly participate in the formation of cataract via the immune mechanism. Abnormal zonular fibers that affect the position and shape of the lens may play an important role in the pathogenesis of angle closure disease and increase the complexity of the surgery. Capsular tension rings and related endocapsular devices are used to provide sufficient capsular bag stabilization and ensure the safety of cataract surgery procedures. Better preoperative and intraoperative evaluation methods for zonules are needed for clinicians. Conclusions: The microstructure, biomechanical properties, and physiological functions of the lens zonules help us to better understand the pathogenesis of cataract and glaucoma, facilitating the development of safer surgical procedures for cataract. Further studies are needed to carefully analyze the structure-function relationship of the zonular apparatus to explore new treatment strategies for cataract and glaucoma.

Bioimaging and detecting endogenous and exogenous cyanide in foods, living cells and mice based on a turn-on mitochondria-targeted fluorescent probe.

A novel fluorescent probe, with advanced features including "turn-on" fluorescence response, high sensitivity, good compatibility, and mitochondria-targeting function, has been synthesized based on structural design for detecting and visualizing cyanide in foods and biological systems. An electron-donating triphenylamine group (TPA) was employed as the fluorescent and an electron-accepting 4-methyl-N-methyl-pyridinium iodide (Py) moiety was used as a mitochondria-targeted localization unit, which formed intramolecular charge transfer (ICT) system. The "turn-on" fluorescence response of the probe (TPA-BTD-Py, TBP) toward cyanide is attributed two reasons, one is the insertion of an electron-deficient benzothiadiazole (BTD) group into the conjugated system between TPA and Py, and the other is the inhibition of ICT induced by the nucleophilic addition of CN-. Two active sites for reacting with CN- were involved in TBP molecule and high response sensitivity were observed in tetrahydrofuran solvent containing 3 % H2O. The response time could be reduced to 150 s, the linear range was 0.25-50 µM, and the limit of detection was 0.046 µM for CN- analysis. The TBP probe was successfully applied to the detection of cyanide in food samples prepared in aqueous solution, including the sprouting potato, bitter almond, cassava, and apple seeds. Furthermore, TBP exhibited low cytotoxicity, clear mitochondria-localizing capability in HeLa cells and excellent fluorescence imaging of exogenous and endogenous CN- in living PC12 cells. Moreover, exogenous CN- with intraperitoneal injection in nude mice could be well monitored visually by the "turn-on" fluorescence. Therefore, the strategy based on structural design provided good prospects for optimizing fluorescent probes.

Low-dose topiramate and hydrochlorothiazide-associated early acute myopia and angle narrowing: A case report.

Purpose: To report a unique case of topiramate and hydrochlorothiazide associated with acute myopia and angle narrowing. Patients and methods: A 34-year-old Asian woman presented with prominent binocular visual acuity decrease 6 h after taking only one dose of 25 mg topiramate, 25 mg hydrochlorothiazide, and 22.4 mg fluoxetine to lose weight. She was subsequently diagnosed with acute bilateral myopia and angle narrowing and was started on topical therapy. Results: Initial examination revealed a decreased visual acuity of 20/100 bilaterally, an elevated intraocular pressure of 23 mmHg in the right eye and 24 mmHg in the left eye, suprachoroidal effusions, and angle narrowing. After the discontinuation of these drugs and the use of IOP-lowering medication, the patient made full recovery. Conclusion: We speculate that there is a drug-drug interaction between topiramate and hydrochlorothiazide that may lead to the angle narrowing in a short time and at a low dose. Timely discontinuation of the drug usually leads to complete recovery within days to weeks.

Intermolecular and Intramolecular Priming Co-directed Synergistic Multi-strand Displacement Amplification Empowers Ultrasensitive Determination of microRNAs.

The construction of isothermal nucleic acid amplification systems with extremely high signal amplification abilities is of great importance for biomarker detection and disease diagnosis. Herein, for the first time, we proposed an intermolecular and intramolecular priming co-directed synergistic multi-strand displacement amplification (SM-SDA) system for microRNA (miRNA) detection. Strategically, the SM-SDA system is made of a single multi-functionalized hairpin probe (MF-HP) that is engineered with a long stem and endowed with target complementation, configuration transformation, enzyme recognition, and signal reporting abilities. The presence of a specific target, the model of miRNA-21, to react with MF-HP would cause an intermolecular priming-directed strand replication in parallel with an intramolecular priming-directed strand replication. The co-directed priming pattern results in the occurrence of SM-SDA containing a target-induced cyclical strand displacement amplification (T-CSDA), a target analogue primer (TAP)-induced CSDA (TAP-CSDA), and a nicked trigger primer (NTP)-induced CSDA (NTP-CSDA). The resulting multiple circuits with a synergetic signal amplification capacity remarkably enhance the target miRNA response, which has not only improved the sensitivity for qualitative and quantitative detection of miRNA but also realized the analysis of target miRNA from real clinical samples. As a proof-of-concept study, this simple but attractive isothermal signal amplification system holds a great potential for molecular diagnosis of diseases and will stimulate interest, new ideas, and discoveries in this fascinating field.

Targeting the entrance channel of NNIBP: Discovery of diarylnicotinamide 1,4-disubstituted 1,2,3-triazoles as novel HIV-1 NNRTIs with high potency against wild-type and E138K mutant virus.

Inspired by our previous efforts on the modifications of diarylpyrimidines as HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTI) and reported crystallography study, novel diarylnicotinamide derivatives were designed with a "triazole tail" occupying the entrance channel in the NNRTI binding pocket of the reverse transcriptase to afford additional interactions. The newly designed compounds were then synthesized and evaluated for their anti-HIV activities in MT-4 cells. All the compounds showed excellent to good activity against wild-type HIV-1 strain with EC50 of 0.02-1.77 µM. Evaluations of selected compounds against more drug-resistant strains showed these compounds had advantage of inhibiting E138K mutant virus which is a key drug-resistant mutant to the new generation of NNRTIs. Among this series, propionitrile (3b2, EC50(IIIB) = 0.020 µM, EC50(E138K) = 0.015 µM, CC50 = 40.15 µM), pyrrolidin-1-ylmethanone (3b8, EC50(IIIB) = 0.020 µM, EC50(E138K) = 0.014 µM, CC50 = 58.09 µM) and morpholinomethanone (3b9, EC50(IIIB) = 0.020 µM, EC50(E138K) = 0.027 µM, CC50 = 180.90 µM) derivatives are the three most promising compounds which are equally potent to the marketed drug Etravirine against E138K mutant strain but with much lower cytotoxicity. Furthermore, detailed SAR, inhibitory activity against RT and docking study of the representative compounds are also discussed.

Ginsenoside-Rb1-Mediated Anti-angiogenesis via Regulating PEDF and miR-33a through the Activation of PPAR-γ Pathway.

Angiogenesis is the formation of new blood vessels from the existing vasculature, which is involved in multiple biological processes, including atherosclerosis, ischemic heart disease, and cancer. Ginsenoside-Rb1 (Rb1), the most abundant ginsenoside isolated form Panax ginseng, has been identified as a promising anti-angiogenic agent via the up-regulation of PEDF. However, the underlying molecular mechanisms still unknown. In the present study, human umbilical vein endothelial cells (HUVECs) were selected to perform in vitro assays. Rb1 (0-20 nM) treatment induced pigment epithelial-derived factor (PEDF) protein expression in concentration and time-dependent manners. Interestingly, it was also demonstrated that the exposure of Rb1 (10 nM) could increase PEDF protein expression without any alteration on mRNA level, suggesting the involvement of posttranscriptional regulation. Furthermore, bioinformatics predictions indicated the regulation of miR-33a on PEDF mRNA 3'-UTR, which was further confirmed by luciferase reporter gene assay and real-time PCR. Over-expression of pre-miR-33a was found to regress partly Rb1-mediated PEDF increment and anti-angiogenic effect in HUVECs. Additionally, Rb1-reduced miR-33a and increased PEDF expression was prevented by pre-incubation with peroxisome proliferator-activated receptor-γ (PPAR-γ) antagonist (GW9662) or transfection with PPAR-γ siRNA in HUVECs. Taken together, our findings demonstrated that Rb1 exerted anti-angiogenic effects through PPAR-γ signaling pathway via modulating miR-33a and PEDF expressions. Thus, Rb1 may have the potential of being developed as an anti-angiogenic agent, however, further appropriate studies are warranted to evaluate the effect in vivo.

Design, synthesis and anti-HIV evaluation of novel diarylpyridine derivatives as potent HIV-1 NNRTIs.

As a continuation of our efforts to discover and develop "me-better" drugs of DAPYs, novel diarylpyridine derivatives were designed, synthesized and evaluated for their anti-HIV activities in MT-4 cells. The majority of these compounds showed high activity against wild-type HIV-1 strain (IIIB) with EC50 values in the range of 0.04-4.41 µM. Among them, compound 5b2 (EC50 = 0.04 µM, SI = 3963) was the most potent. This compound showed anti-HIV-1IIIB activity superior than of Nevirapine but still inferior than of Etravirine. Selected compounds were also evaluated for the activity against reverse transcriptase (RT), and most of the compounds exhibited submicromolar IC50 values indicating they are specific RT inhibitors. Preliminary structure-activity relationships and modeling studies of these new analogues provide valuable avenues for future molecular optimization.

PEDF improves atherosclerotic plaque stability by inhibiting macrophage inflammation response.

BACKGROUND: Atherosclerosis is a vascular disease with plaque formation and growth. Instable plaque with chronic inflammation is closely related to adverse cardiac outcomes. Pigment epithelium-derived factor (PEDF) is an endogenous multifunctional cytokine that possesses the ability of anti-inflammation. The aim of this study is to detect whether PEDF has protective effect on the stability of atherosclerotic plaque and to explore whether the effect of anti-inflammation involved. METHODS AND RESULTS: ApoE-/- mice fed with high fat diet and RAW264.7 cells were used to evaluate anti-inflammatory activities of PEDF both in vivo and in vitro. PEDF overexpression improved atherosclerotic plaque stability in ApoE-/- mice. The expression of inflammatory factors (interleukin-1ß [IL-1ß], interleukin-6 [IL-6], tumor necrosis factor-α [TNF-α], monocyte chemotactic protein-1 [MCP-1] and matrix metalloproteinase [MMP-9]) was significantly decreased with PEDF overexpression in vivo and in vitro. The anti-inflammation effect of PEDF was attenuated by PPAR-γ specific antagonist GW9662. In addition, PEDF significantly decreased the expression of phosphorylated ERK-MAPK, p38-MAPK and JNK-MAPK. GW9662 partly reversed the PEDF-mediated depression of phosphorylated ERK- and p38-MAPK but has no significant effect on JNK-MAPK. CONCLUSIONS: PEDF has protective effect on increasing AS plaque stability through ameliorating macrophage inflammation. PPAR-γ and downstream MAPKs were involved in the mechanism.

Design, synthesis and anti-HIV evaluation of novel diarylpyridine derivatives targeting the entrance channel of NNRTI binding pocket.

The development of novel NNRTIs with activity against variants of HIV-1RT is crucial for overcoming treatment failure. In the present study, a series of novel 6-substituted diarylpyridine derivatives targeting the entrance channel of the NNIBP of RT were designed through a molecular hybridization strategy. Encouragingly, these new diarylpyridine derivatives were found to be active against wild-type (WT) HIV-1 with an EC50 values ranging from 0.035 µM to 1.99 µM. Nearly half of them exhibited more potent inhibitory activities in cellular assays than the control drug nevirapine (NVP). Notably, three most promising compounds If (EC50 = 35 nM), Ia (EC50 = 43 nM) and IIa (EC50 = 41 nM) showed high potency against WT and were comparable to the reference drug delavirdine (DLV) (EC50 = 33 nM). Moreover, compounds Ib, IIb and IIh displayed effective activity against the most common clinically observed single and double-mutated HIV-1 strains in micromolar concentrations. In particular, the inhibition of IIb against the K103N mutation (EC50 = 49 nM), which confers resistance to a wide variety of NNRTIs, was about 140 times more effective than NVP (EC50 = 6.78 µM), 50 times more than DLV (EC50 = 2.48 µM) and about 3 times more than EFV (EC50 = 0.12 µM), indicating that the newly designed compounds have great potential to be further developed as new anti-HIV-1 agents. Preliminary structure-activity relationships (SARs) and molecular modeling of the new diarylpyridine derivatives were discussed in detail.

Design, synthesis and anti-HIV evaluation of novel diarylnicotinamide derivatives (DANAs) targeting the entrance channel of the NNRTI binding pocket through structure-guided molecular hybridization.

Through a structure-based molecular hybridization approach, a novel series of diarylnicotinamide derivatives (DANAs) targeting the entrance channel of HIV-1 NNRTIs binding pocket (NNIBP) were rationally designed, synthesized and evaluated for their anti-HIV activities in MT-4 cells together with the inhibition against the reverse transcriptase (RT) in an enzymatic assay. Encouragingly, most of the new DANAs were found to be active against wild-type HIV-1 with an EC50 in the range of 0.027-4.54 µM. Among them, compound 6b11 (EC50 = 0.027 µM, SI > 12518) and 6b5 (EC50 = 0.029 µM, SI = 2471) were identified as the most potent inhibitors, which were more potent than the reference drugs nevirapine (EC50 = 0.31 µM) and delavirdine (EC50 = 0.66 µM). Some DANAs were also active at micromolar concentrations against the K103N + Y181C resistant mutant. Compound 6b11 exhibited the highest enzymatic inhibition activity (IC50 = 20 nM), which is equal to that of efavirenz (EC50 = 20 nM) and 31 times higher than that of nevirapine (EC50 = 0.62 µM). Preliminary structure-activity relationships (SARs) and molecular modeling of these new DANAs have been discussed.

Ginsenoside-Rg1 enhances angiogenesis and ameliorates ventricular remodeling in a rat model of myocardial infarction.

Ginsenoside-Rg1 (Rg1) has been used in the traditional Chinese medicine for over 2,000 years. The present study was performed to test our hypothesis that Rg1 provides pro-angiogenic and anti-fibrotic benefits in the ischemic myocardium in a rat model of myocardial infarction. The expression of vascular endothelial growth factor (VEGF) and phosphorylation/activation of PI3K, Akt, and p38 MAPK signaling pathways were examined in human umbilical vein endothelial cells and in the myocardial samples of rats. In addition, the expression levels of TNF-α and collagen I level, the number of newly formed blood vessels, the extent of myocardial fibrosis, and left ventricular function were measured in vivo. Our results demonstrated that administration of Rg1 increased VEGF expression levels, activated PI3K/Akt, and inhibited p38 MAPK in vitro and in vivo. Furthermore, Rg1 increased the density of newly formed vessels, decreased TNF-α and collagen I expression levels and area of myocardial fibrosis, and improved left ventricle function in vivo. PI3K inhibitor LY294002 significantly attenuated Rg1-enhanced VEGF expression and capillary density. As well, inhibition of p38 MAPK slightly increased VEGF expression in vitro and in vivo, increased capillary density, and decreased TNF-α and collagen I expression levels and area of myocardial fibrosis in vivo. Rg1-induced activation of PI3K/Akt also contributed to the downregulation of p38 MAPK. Thus, Rg1 is effective in promoting angiogenesis and attenuating myocardial fibrosis, resulting in ameliorated left ventricular function. The possible mechanisms may involve activation of PI3K/Akt, inhibition of p38 MAPK, and cross talk between the two signaling pathways.

Seven-year follow-up of LASIK for moderate to severe myopia.

PURPOSE: To evaluate long-term refractive outcomes of LASIK for correcting moderate to severe myopia. METHODS: A long-term (7-year) prospective follow-up study of visual and refractive outcomes in patients who underwent myopic LASIK surgery in 1998 and 1999. Fifty-nine patients (104 eyes) of the original cohort of 75 patients underwent detailed clinical assessment at 1 and 7 years postoperatively. The main outcome measures were predictability, efficacy, safety, and stability. Topography, corneal thickness, and postoperative complications were recorded at 7 years. All patients completed a questionnaire assessing their satisfaction with the procedure. RESULTS: At 7 years postoperatively, 89.4% of eyes were within 0.50 diopters (D) of attempted correction, and 90.4% were within 1.00 D. All eyes had 20/40 or better vision and 94.2% had 20/20 or better. Best spectacle-corrected visual acuity was unchanged or improved in 80.8% of eyes. Eyes did not regress in refraction between 1 and 7 years postoperatively. Complications were rare and patient satisfaction with the surgery was high. CONCLUSIONS: LASIK surgery has predictable and stable results in refractive and visual outcomes in correcting moderate to high myopia on long-term follow-up. Refractive stability is maintained over 7 years, with no evidence of progressive late-onset complications.

Long-term prospective follow-up study of myopic photorefractive keratectomy.

The aim of this study was to evaluate the long-term outcome of excimer laser myopic photorefractive keratectomy (PRK). We undertook an 11-year prospective follow-up study of visual and refractive outcomes in 46 patients (85 eyes). The main outcome measures were predictability, efficacy, stability and safety of PRK. At 11 years after the operation, 56.5% of eyes were within +/-0.5 D of attempted correction and 81.2% were within +/-1.0 D; 87% had vision of 20/40 or better, and 52% had 20/20 or better. The best spectacle-corrected visual acuity was unchanged or improved in 91% of eyes at 11 years. Eyes with moderate and severe myopia showed a significant change between 3 and 11 years. PRK surgery for myopia shows predictable and stable results in the long term, with a slight regression in refraction, mainly for patients with severe myopia.