Smaller Hole Size Research Articles

Consequence analysis of vapour cloud explosion from the release of high-pressure hydrogen storage

Gaseous hydrogen is commonly stored under high pressures due to its low volumetric storage density. The safety concerns about its release and potential accidents, such as vapour cloud explosions, were of the highest importance in industries. This research work established a methodology for consequence analysis of compressed hydrogen releases, considering various stages of event escalation, including high-pressure gas release, gas jet dispersion, and overpressure evaluations. Specifically, compressed hydrogen release was defined as an under-expanded flow, characterised by a transition from sonic to supersonic velocities. The notional nozzle theory was employed to tackle the flow regime transition and provide revised nozzle size and gas velocity as inputs to the CFD model for gas jet dispersion. The model was validated against experimental results, exhibiting a good agreement with a deviation of less than 20%. The flammable gas mass in the cloud was determined using the dispersion model and then used for overpressure predictions. This approach proved to be more realistic than relying solely on the total hydrogen release amount. In a case study, release parameters such as release direction, wind speed and release hole size were investigated. It was observed that a downward release resulted in less gas dissipation, leading to larger overpressures compared to other release directions. Wind speed had a relatively lower impact compared to other parameters. The release hole size had the most significant influence on explosion overpressure, with the case of a larger release size (e.g., 50.8 mm) exhibiting a few hundred times higher of hazardous area compared to a small hole size (e.g., 3 mm).

Eco‐friendly glass wet etching for MEMS application: A review

AbstractGlass is one of the most essential materials in various industrial fields. A representative application is as interposers in the semiconductor and display industries and microfluidic devices in the bio‐industry. Due to technological advancements, electric devices and various products are becoming lighter and smaller. Consequently, precision processing of the substrate is becoming increasingly important. One significant leading technology among these is through glass via (TGV) technology, which is attracting attention as a future alternative to through silicon via. In particular, TGV should be capable of microfabrication with a large aspect ratio and a consistent small hole size. TGV is typically fabricated using a wet etching process, so wet etching technology is a prominent focus in microfabrication. However, glass has isotropic properties, making achieving a high aspect ratio difficult. Traditionally, research on the wet etching method using hydrofluoric acid (HF) has been conducted. Nevertheless, HF etching has several disadvantages, including air pollution and human harm. Additional studies have been performed to address these issues. This review paper will cover the conventional HF‐based wet etching method and alternative HF etching processes (eco‐friendly materials). This technology would significantly help overcome the traditional problems associated with HF etching and fabricating precision‐processed glass in the semiconductor, display, and bio‐device industries.

Machinability of submillimeter holes in ceramic matrix composites by high-frequency ultrasonic vibration-assisted drilling

Ceramic matrix composites (CMCs) are highly promising for the hot components of the high thrust-to-weight ratio aeroengines because of their excellent high-temperature resistance and lightweight. Submillimeter cooling holes are necessary cooling structures for the extremely high working temperature of a CMCs hot component. However, CMCs are hard, brittle, and poorly conductive. Current machining is trapped in severe tool wear, poor hole quality, and low efficiency in machining such small size holes. This paper proposes high-frequency ultrasonic vibration-assisted drilling (UAD) to machine submillimeter holes of CMCs. It reveals that increasing vibration frequency during machining can enlarge the cutting edge's effective rake angle and reduce drilling forces. Correspondingly, the tool life and hole quality are improved. The machinability of high-frequency UAD is rationalized by both theoretical analysis and experiments. Results show that compared with low-frequency UAD and Conventional drilling (CD), the drilling force in high-frequency UAD is reduced by 47 % and 81 %, the tool life is more than three times, and the hole quality is improved by 12 % and 35 %, respectively. Therefore, the study paved the way for the machining of submillimeter cooling holes in CMCs, which is important to the industrial application of CMCs.

EXPERIMENTAL ASSESSMENTS ON THE STRAIN CONCENTRATION AROUND SMALL HOLES IN PMMA

A series of tensile tests of polymethyl methacrylate (PMMA) open-hole specimens with holes of various diameters was carried out. Digital image correlation (DIC) analysis for the strain field distribution around the holes is performed. It is found that the evaluated strain concentration around relatively large holes (with diameter of several millimeters) is in good agreement with the classical elasticity solution; however, it tends to reduce in the samples containing smaller holes. Around the holes of diameter less than 500 <i>μ</i>m, maximum values of strain (hoop strain) are found to be 1.5-2 times lower than the classical elasticity solution, with extrapolated tendency to decrease down to unit value of strain concentration around the micro/nano-sized holes. Statistical analysis of the deviations between experimental and theoretical data is performed and discussed together with assessments on the accuracy of the obtained DIC results.

Vitreoretinal Abnormalities during Macular Hole Repair in Alport Syndrome.

To describe abnormal vitreoretinal findings during macular hole repair in Alport syndrome (AS). Case report of preoperative, intraoperative, and postoperative findings related to macular hole surgery in a patient with AS. A 50-year-old woman with Alport syndrome was found to have bilateral full-thickness macular holes. Surgery was recommended for her left eye given recent onset of vision loss and smaller hole size (313 um). Intraoperatively, the vitreous was found to have fine fibrillar strands and to be abnormally adherent to the retinal surface. There was little to no internal limiting membrane (ILM) present. Vitrectomy was performed with posterior cortical hyaloid peeling and 15% C3F8 gas tamponade. Two months after surgery, the macular hole was successfully closed. Abnormal vitreous composition and adherence to the retinal surface may contribute to macular hole formation in AS patients. Standard surgical approaches including ILM peeling may not be feasible, though thorough removal of the posterior cortical hyaloid may be sufficient to achieve macular hole closure.

Long-term outcomes of arthroscopic synovectomy and core decompression through multiple small bone holes for early-stage avascular necrosis of the femoral head

ObjectiveThis study described a minimally invasive approach for the management of early-stage avascular necrosis of the femoral head, which integrated arthroscopic intra-articular decompression and core decompression by drilling multiple small holes.MethodA total of 126 patients with 185 hip avascular necrosis were included between March 2005 and January 2008, and the hips were classified, based on the Association Research Circulation Osseous staging system, into stage I (n = 43), stage II (n = 114), and stage III (n = 28). Arthroscopic intra-articular inspection and debridement, along with drilling of multiple small holes for core decompression, were performed. The Modified Harris hip score system and radiographs were used to assess the pre- and post-surgery outcomes.ResultsOne hundred and three patients (involving 153 hips) were followed up successfully for an average of 10.7 ± 3.4 years (range: 9–12 years). After surgery, the overall survival rate was 51.6% (79 hips), and the clinical survival rates were 79%, 72%, 52%, 32%, and 10% for patients with stage I, IIa, IIb, IIc, and III, respectively. The outcomes of patients with Association Research Circulation Osseous Stages I or IIA were better than those of other stages, while hips with a large necrotic area had poor results. This approach preserved the original biomechanical strength of the femoral head after core decompression and eliminated arthritis factors in the hip joint.ConclusionThe core decompression with multiple small-size holes is an effective method for treating early-stage avascular necrosis of the femoral head, particularly in those with pathological changes in the hip joint.Level of evidenceTherapeutic study, Level IV.

Calculation of Thermal Fields when Drilling Small-Sized Holes in Carbon Fiber Reinforced Plastic

The Purpose of the paper. The study of thermal physics of the process of drilling polymer composite materials based on the capabilities of the engineering package Comsol Multiphysics. Determination of the values of temperatures arising in the cutting zone when drilling with a cutting tool in polymer composite materials, namely, in carbon fiber. Establishment of the depth of heat propagation inside the workpiece from the edge of the formed hole of the polymer composite material. In this work, the Fourier heat equations are used. Numerical simulation of the drilling process wascarried out in the engineering package COMSOL Multiphysics. A technique for modeling thermal effects during drilling of carbon fiber reinforced plastics in the Comsol Multiphysics environment has been developed. As a result of computer calculation, temperature fields were obtained at the edge of the carbon fiber reinforced plastic hole. The study of the thermal state of carbon plastics has been carried out. On the basis of the conducted research, it was revealed that the temperature during drilling of carbon fiber reaches 650 K. The distance over which heat spreads from the edges of the hole into the workpiece for carbon fiber is 3 mm. The developed technique for modeling the thermal impact of cutting polymer composite materials in the COMSOL Multiphysics environment can significantly simplify complex analytical calculations, help to avoid overheating of the part during drilling, which improves the quality of processing.

Nanometer precision height gauge for small holes with high aspect ratio

The demand for measuring the feature size of small holes is increasing. In this study, a nanometer precision height gauge for small holes with a high aspect ratio was developed. The height gauge comprises a Michelson interferometer, a moving and weight balance system, a tactile probing system, and a positioning control system. The errors due to the angular deflection of the moving stage were analyzed, and a corner-cube-based interferometer was designed. The structural design of the moving and weight balance systems was explored. A tactile micro/nano-probing system was developed and used. The signal processing, positioning control and measurement strategy, and software were developed. The system was calibrated and verified by testing the reference ring gauge. The experimental results show that the height gauge can achieve a resolution of 5 nm, a measurement uncertainty of 90 nm (k = 2), and a measuring range of 30 mm. The prototype can be used to measure the depth of small holes with a high aspect ratio.

Drilling parameter optimization of cenosphere/HDPE syntactic foam using CO2 laser

High-density polyethylene is a high-strength, and low-weight material system. Besides numerous applications in a variety of fields and products, its machining for generation of holes is rather difficult with traditional methods such as drilling as the process is not very conducive for composites due to associated damage. Hence, a non-contact material removal process such as laser machining provides an appealing, cost-effective, accurate, and fast alternative. For this study, the effect of the laser process controls key parameters such as laser power and laser speed on the cut surface integrity defined by surface roughness, kerf taper angle, and heat-affected zone of neat HDPE and HDPE with 60 wt% cenosphere was investigated and optimized using response surface methodology. Also, the machining operation was visualized using a Photron FASTCAM SA 1.1 high-speed camera to observe the effects of the high-intensity laser beam on specimens and to investigate the mechanism of laser machining. The optimum values for a defect-free cut surface (minimum surface roughness and low kerf taper angle) in neat HDPE comes out to be as laser power of 97.5 W and laser speed of 5 mm/s, with corresponding surface roughness and kerf taper angle of 54.304 μm and 0.152 degrees respectively and the optimum input values for HDPE with 60 wt% cenosphere are 102.126 W laser power and 5 mm/s laser speed, with corresponding surface roughness and kerf taper angle of 26.574 μm and 0.253 degrees. This study finds importance for the industrial and medical application to creates small size holes for mechanical joints such as rivets, bolts, and screws in assembly as low surface roughness and kerf width are always preferred as quality parameters in creating holes for industrial applications.

Unclogged Janus Mesh for Fog Harvesting.

Janus membranes with asymmetric surface wettability have been extensively utilized in various fields, including fog harvesting, because of their novel liquid transport properties. However, Janus membranes have an inherent disadvantage in terms of aerodynamic efficiency in harvesting fog because of the clogged water bridges caused by the small pore size. In the present work, we applied Janus wettability to mesh geometry with systematically varying hole sizes. For a clogged mesh with a small hole size, capillary water transport to the mesh back via the wettability gradient in the direction of fog flow helps harvest more fog by enhancing water drainage, similarly to the Janus membrane. The advantage of the capillary water transport extends to a clog-free mesh with larger hole sizes but more preferably to a Janus mesh with a superhydrophilic back, which presents the highest level of fog-harvesting yield because of the fast shedding frequency and short onset time. In contrast, a Janus mesh with a superhydrophobic front, which also has a wettability gradient along the fog flow, produces a lower fog-harvesting performance, particularly at slow fog speeds, because of the dropwise deposition of large water drops that locally disturb fog flow around a protruding water surface. On the other hand, the other type of Janus mesh with a superhydrophilic front is observed to minimize this disadvantage in the local fog flow by virtue of the filmwise deposition. It is also found that some Janus treatments can help protect mesh holes from clogging up by either forming a thin water meniscus or resisting water transport through the mesh holes.

Effect of sieve plate packing on bubble size distribution in a cyclonic flotation column

The application of packed technology effectively reduces the height of flotation column and improves the treatment capacity. The effect of packed sieve plate on bubble size and velocity in flotation column affect the flotation recovery. Based on high-speed dynamic measurement and particle image velocimetry (PIV) measurement, the velocity and size of bubbles in open and packed flotation column were compared first and then the effect of different packing method was studied. With sieve plate packing, the peak tangential velocity of bubble decreased by 92%; the number of bubbles within the range of 1–2.5 mm increased from 62.79% to 83.34% and the mean bubble diameter decrease from 2.14 mm to 1.82 mm. Sieve plate packed weakens the influence of rotation flow, reduces the bubble size and makes the distribution is more uniform in flotation column, which is conducive to the collision and adhesion of particles and bubbles. The effect study of opening hole size, thickness and packed position of sieve plate on bubble size distribution shows that the small opening hole size of sieve plate has a strong segmentation effect on bubbles, and can reduce the bubble size; Thick sieve plate will increase bubble coalescence and increase bubble size; The bubbles have a good distribution with sieve plate packed at a height of 0.5 times the diameter of the column. This study can provide guidance for the design of packed method in flotation column.

Decompressive craniectomy in the treatment of supratentorial hypertensive intracerebral hematomas

The study objective is to evaluate feasibility and effectiveness of decompressive craniectomy (DC) for treatment оf supratentorial hypertensive intracerebral hematomas (ICH).Materials and methods. Between 1996 to 2019, 97 patients with supratentorial hypertensive ICHs underwent surgical treatment. DC was performed in 50 patients (primary - in 41, secondary - in 9). Putaminal hematomas were diagnosed in 30 patients, subcortical - in 20. The comparison group consisted of 47 patients, of which 20 had osteoplastic craniotomy (OPC) with microsurgical removal of ICH, and 27 had endoscopic aspiration (EA). The performed DCa were treated as unjustified (decreased brain dislocation without prolapse of the brain substance into the trepanation defect), ineffective (preservation of brain dislocation and absence of prolapse of the brain substance into the trepanation defect, as well as small size of the trepanation hole) and effective (prolapse of the brain substance into the trepanation defect and regression of transverse brain dislocation).Results. DC was effective only in 22 (44 %) patients (13 - primary, 9 - secondary). Among patients with subcortical ICH, mortality rate after DC was equal to that after OPC and EA. Among patients with putaminal ICH, the mortality rate after DC was significantly higher than after OPC and EA. Among the patients who underwent primary EA and delayed DC (due to recurrent ICH), postoperative mortality rate was significantly higher than among the patients who underwent repeated EA of recurrent ICH. However, there were no fatal outcomes among patients who underwent delayed DC due to increased edema and transverse dislocation of the brain without recurrent ICH.Conclusion. In the surgical treatment of supratentorial hypertensive ICH, decompressive effect of DC was achieved only in 44 % of patients. Open removal of putaminal hematomas in combination with DC was unjustified, mortality rate was 66 %. Primary DC with removal of ICH is indicated in patients with subcortical hematomas with a volume >50 cm3 , with transverse dislocation >7 mm, deep deafness or sopor. Delayed DC, regardless of the location of ICH, is recommended in case of increased edema and transverse dislocation of the brain in patients without recurrent hemorrhage.

Screw hole location for laptop based on improved RCF

The recent application of computer vision to disassembly and remanufacturing has pushed forward this field significantly. In disassembling the laptop, we find that the existing positioning screw methods such as hough transform and template matching were not suitable for black laptops, so we propose a new method to solve this problem. We use RCF network to locate the screw hole contour, and make two improvements according to the characteristics of small screw hole size: 1. A feature integration module is added to RCF network to increase multi-scale features.2. A modulating factor is added to the loss function to enhance the attention to the indistinguishable pixels. Our approach has shown good results on black laptops and has higher ODS and OIS than the original RCF network and the existing method.

Effect of different ionic liquids acting as plasticizers on the multi-scale structures and physical properties of hydroxypropyl methylcellulose/monosodium phosphate photophobic film

Different ionic liquid (IL)s were added to hydroxypropyl methylcellulose /monosodium phosphate (HPMC/MSP) photophobic film to improve its ductility, and their effects on its multi-scale structures and physical properties were studied. After adding these ILs, smoothness of the fractal structure, tensile strength, modulus of the film did not change obviously, while the crystallinity, the number of holes, and elongation increased, the hole size and Tg decreased. Compared to films with other ILs, the film with 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) showed the largest elongation and crystallinity, the smallest hole size, the least holes, and highest whiteness. The film with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) showed the largest water content and the lowest Tg. The increased elongation proved that all these ILs could improve the ductility of the film, among which, [EMIM]BF4 had the strongest plasticizing effect.

Breathable Textile Rectangular Ring Microstrip Patch Antenna at 2.45 GHz for Wearable Applications.

A textile patch antenna is an attractive package for wearable applications as it offers flexibility, less weight, easy integration into the garment and better comfort to the wearer. When it comes to wearability, above all, comfort comes ahead of the rest of the properties. The air permeability and the water vapor permeability of textiles are linked to the thermophysiological comfort of the wearer as they help to improve the breathability of textiles. This paper includes the construction of a breathable textile rectangular ring microstrip patch antenna with improved water vapor permeability. A selection of high air permeable conductive fabrics and 3-dimensional knitted spacer dielectric substrates was made to ensure better water vapor permeability of the breathable textile rectangular ring microstrip patch antenna. To further improve the water vapor permeability of the breathable textile rectangular ring microstrip patch antenna, a novel approach of inserting a large number of small-sized holes of 1 mm diameter in the conductive layers (the patch and the ground plane) of the antenna was adopted. Besides this, the insertion of a large number of small-sized holes improved the flexibility of the rectangular ring microstrip patch antenna. The result was a breathable perforated (with small-sized holes) textile rectangular ring microstrip patch antenna with the water vapor permeability as high as 5296.70 g/m2 per day, an air permeability as high as 510 mm/s, and with radiation gains being 4.2 dBi and 5.4 dBi in the E-plane and H-plane, respectively. The antenna was designed to resonate for the Industrial, Scientific and Medical band at a specific 2.45 GHz frequency.

The performance and mechanism of recovering lithium on H4Ti5O12 adsorbents influenced by (1 1 0) and (1 1 1) facets exposed

The improved adsorption capacities by increasing specific surface area methods are merely reached about 50% of H4Ti5O12’s theoretical adsorption capacity, and the adsorption behavior and mechanism of lithium on special facets of H4Ti5O12 remain unclear. In this study, a flower-shaped Li4Ti5O12 and an octahedral Li4Ti5O12 were prepared with the specific surface areas of 176.23 and 83.02 m2/g, and the corresponding adsorption behaviors of the obtained adsorbents exposed with (110) and (111) facets were investigated by using experimental and computational methods. The maximum Li+ uptake values on H4Ti5O12 (110) and H4Ti5O12 (111) are 26.85 mg/g and 33.56 mg/g at 45 °C in 24 mM LiCl solutions, respectively. The fifth reuse ability of H4Ti5O12 (111) still remains 88.9% of the original’s, which is higher than H4Ti5O12 (110) (76.3%). Although with lower specific surface area, the octahedral H4Ti5O12 have higher ions selectivity, greater adsorption capacity, and better reuse ability than flower-shaped H4Ti5O12, which may due to the special (111) facet exposed. Firstly, H4Ti5O12 (111) owned small hole sizes can inhibit other ions diffusing into H4Ti5O12 and improve the ion selectivity. Secondly, the immigration paths by the First-principles calculations revealed that the Li+ migrate onto the Li4Ti5O12 (111) is easier to than Li4Ti5O12 (110) through 8a-16c-8a-16c sites. At last, [Li(H2O)4]+ can form the stable complexes and its adsorption energies on (111) are higher than on (110) facets, which may lead to larger adsorption capacity and better reuse ability. This work will help to understand the [Li(H2O)4]+ adsorption behavior and mechanism on different crystal facets by experiments and computations.

Twelve-month follow-up after posterior 25G vitrectomy due to idiopathic full-thickness macular hole treated with “inverted ILM flap” technique

Background: We conducted a prospective, follow-up study to analyze a long-term recovery process after posterior vitrectomy for idiopathic full-thickness macular hole. Material and methods: Sixty eyes were evaluated in 59 patients who underwent surgery for idiopathic fullthickness macular hole using posterior 25G vitrectomy with the “inverted ILM flap” technique from the beginning of 2013 to the end of 2014. In 55 eyes, posterior 25G phaco-vitrectomy with ILM peeling was performed using the “inverted ILM flap” technique with IOL implantation. In 5 pseudophakic eyes, posterior vitrectomy was performed with the technique as above. All patients were interviewed regarding the duration of the disease and pre- and postoperatively at intervals of 1, 3, 6, and 12 months. The following tests were performed: best-corrected visual acuity (BCVA), best-corrected near visual acuity (BCNVA), intraocular pressure (IOP) measurement, physical examination of the anterior and posterior segment of the eye, and spectral domain optical coherence tomography (SD-OCT). Results: The anatomical success in the study was 95%, and we achieved the improvement in visual acuity in 91.7% of the operated eyes. The visual acuity in the time interval before surgery and 12 months afterward improved from 0.1 to 0.29 and was statistically significant (p < 0.05). Shorter duration and smaller hole size were significant predictors of improved postoperative visual acuity. The U-type of the hole closure predisposed to the most significant improvement in visual acuity in patients. Conclusions: The obtained functional and anatomical results may confirm the effectiveness of posterior vitrectomy using the “inverted ILM flap” technique in treating idiopathic full-thickness macular holes. The observed sparce complications did not differ from the complication profile described by other authors.

Modelling and Assessment of Accidental Gas Release from Damaged Subsea Pipelines

Due to the high demand on hydrocarbon exploration nowadays and in future overall the world, the risk potential of Subsea gas and oil leakage increases and can lead to a catastrophic incidents such as explosion, fire or loss stability of subsea constructions. Therefore, the purpose of this paper is to assess and control the potential of hazards for the gas flows from subsea pipelines rupture to sea surface with varying of influence parameters on gas plume. 2D Computational Fluid Dynamics (CFD) simulations have been carried out. The influence parameters that contained in the present paper leakage hole sizes and water depths. The Rotvoll experiment data is used in order to validate numerical computational fluid dynamics model. The subsea gas diffusion behavior is investigated for the risk assessment aspect. The main parameters which included to assess the gas dispersion are rising time and fountain height. Observed from our sceneries results that the water depth has a major effect on gas rise time where the deeper water depth is about 3 times longer than the lower water depth to reach water surface whilst the hole size has a high effect on the fountain height where the larges hole size is approximately 2.1 times higher than the smaller hole size. So our objective is helping the petroleum companies to find a mitigation method by modelling and assessing the gas release in order to contain the subsea gas leakage.

Thermal conductance of structured silicon nanocrystals

We calculate the thermal conductance of a structured silicon nanocrystal with a hole of different sizes. The numerical study is based on non-equilibrium molecular dynamics simulations using two potential models for the interatomic interactions: (i) an empirical Tersoff–Brenner (Tersoff) potential; (ii) a semi-empirical tight binding (TB) potential. TB potential model predicts a similar thermal conductance for the nanocrystal with no hole and with a small size hole, which contrasts with the monotonic decrease predicted by Tersoff potential model. In addition, thermal conductance decreasing is higher for TB potential model when the surface-to-volume ratio increases. This points out that to study thermal properties of nanostructures with high surface-to-volume ratio is mandatory the use of potential models with high transferability to take adequately into account the relevant quantum physical effects due to boundaries and surfaces.

Factors affecting anatomical and visual outcome after macular hole surgery: findings from a large prospective UK cohort.

To reassess the definition of a large macular hole, factors predicting hole closure and post-surgery visual recovery. Database study of 1483 primary macular hole operations. Eligible operations were primary MH operations treated with a vitrectomy and a gas or air tamponade. Excluded were eyes with a history of retinal detachment, high myopia, previousvitrectomy or trauma. A higher proportion of operations were performed in eyes from females (71.1%) who were 'on average' younger (p < 0.001), with slightly larger holes (p < 0.001) than male patients. Sulfur hexafluoride gas was generally used for smaller holes (p < 0.001). From 1253 operations with a known surgical outcome, successful hole closure was achieved in 1199 (96%) and influenced by smaller holes and complete ILM peeling (p < 0.001), but not post-surgery positioning (p = 0.072). A minimum linear diameter of ~500 μm marked the threshold where the success rate started to decline. From the 1056 successfully closed operations eligible for visual outcome analysis, visual success (defined as visual acuity of 0.30 or better logMAR) was achieved in 488 (46.2%) eyes. At the multivariate level, the factors predicting visual success were better pre-operative VA, smaller hole size, shorter duration of symptoms and the absence of AMD. Females undergoing primary macular hole surgery tend to be younger and have larger holes than male patients. The definition of a large hole should be changed to around 500 μm, and patients should be operated on early to help achieve a good post-operative VA.