Search results for: refractive surgery

Authors: Arun C. Gulani, Aaishwariya A. Gulani, Amanda Southall

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Background: Laser Corneoplastique™ as a least interventional, visually promising technique for patients with vision disability from corneal scars of varied causes has been retrospectively reviewed and proves to cause a paradigm shift in mindset and approach towards corneal scars as a Refractive surgery aiming for emmetropic, unaided vision of 20;/20 in most cases. Three decades of work on this technique has been compiled in this 15-year study. Subject and Methods: The objective of this study was to determine the success of Laser Corneoplastique™ surgery as a treatment of corneal scar cases. A survey of corneal scar cases caused by various medical histories that had undergone Laser Corneoplastique™ surgery over the past twenty years by a single surgeon Arun C. Gulani, M.D. were retrospectively reviewed. The details of each of the cases were retrieved from their medical records and analyzed. Each patient had been examined thoroughly at their preoperative appointments for stability of refraction and vision, depth of scar, pachymetry, topography, pattern of the scar and uncorrected and best corrected vision potential, which were all taken into account in the patients' treatment plans. Results: 64 eyes of 53 patients were investigated for scar etiology, keratometry, visual acuity, and complications. There were 25 different etiologies seen, with the most common being a Herpetic scar. The average visual acuity post-op was, on average, 20/23.55 (±7.05). Laser parameters used were depth and pulses. Overall, the mean Laser ablation depth was 30.67 (±19.05), ranging from 2 to 73 µm. Number of Laser pulses averaged 191.85 (±112.02). Conclusion: Refractive Laser Corneoplastique™ surgery, when practiced as an art, can address all levels of ametropia while reversing complex corneas and scars from refractive surgery complications back to 20/20 vision.

Keywords: corneal scar, refractive surgery, corneal transplant, laser corneoplastique

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Authors: Wasse Uddin Ahmed Saleh, Nawreenbinte Anwar

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A well-written operating note is crucial as a teaching tool for providing patients with high-quality medical care and fending off medico-legal claims. In this review article, some adjustments have been advised to the operative note guidelines by the Royal College of Surgeons (RCS) for different methods of ocular anesthesia and ophthalmic procedures like cataract surgeries, kerato-refractive surgeries, glaucoma surgeries, oculoplastic surgeries, etc. Some modifications of the WHO Surgical Safety Checklist have also been mentioned, including pre-operative responsibilities of the nurses, operative assistants and operating ophthalmologists. It has become essential to assemble globally accepted structured operative note guidelines modified for each ocular surgery.

Keywords: ocular surgeries, operation notes, cataract surgery, kerato-refractive surgery, Oculoplastic surgeries, guidelines

Procedia PDF Downloads 134

Authors: A. Belay, B. Kebede

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The concentration- and temperature-dependent refractive indices of solutions extracted from defective and non-defective coffee beans have been investigated using a He–Ne laser. The refractive index has a linear relationship with the presumed concentration of the coffee solutions in the range of 0.5–3%. Higher and lower values of refractive index were obtained for immature and non-defective coffee beans, respectively. The Refractive index of bean extracts can be successfully used to separate defective from non-defective beans.

Keywords: coffee extract, refractive index, temperature dependence

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Authors: Maryum Nawaz

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Purpose: To determine the frequency of refractive errors in squinting eyes of children from 4 to 16 years presenting at tertiary care hospital. Study Design: A descriptive cross-sectional study was done. Place and Duration: The study was conducted in Pediatric Ophthalmology, Hayatabad Medical Complex, Peshawar. Materials and Methods: The sample size was 146 keeping 41.45%5 proportion of refractive errors in children with squinting eyes, 95% confidence interval and 8% margin of error under WHO sample size calculations. Non-probability consecutive sampling was done. Result: Mean age was 8.57±2.66 years. Male were 89 (61.0%) and female were 57 (39.0%). Refractive error was present in 56 (38.4%) and was not present in 90 (61.6%) of patients. There was no association of gender, age, parent refractive errors, or early usage of electric equipment with the refractive errors. Conclusion: There is a high prevalence of refractive errors in a patient with strabismus. There is no association of age, gender, parent refractive errors, or early usage of electric equipment in the occurrence of refractive errors. Further studies are recommended for confirmation of these.

Keywords: strabismus, refractive error, myopia, hypermetropia, astigmatism

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Authors: Ranitha Guna Selvi D, Ramakrishnan R, Mohideen Abdul Kader

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Purpose: To study the role of Vision centers in managing preventable blindness through refractive error correction in Rural South India. Methods: A retrospective analysis of patients attending 15 Vision centers in Rural South India from a period of January 2021 to December 2021 was done. Medical records of 10,85,81 patients both new and reviewed, 79,562 newly registered patients and 29,019 review patient’s from15 Vision centers were included for data analysis. All the patients registered at the vision center underwent basic eye examination, including visual acuity, IOP measurement, Slit-lamp examination, retinoscopy, Fundus examination etc. Results: A total of 1,08,581 patients were included in the study. Of the total 1,08,581 patients, 79,562 were newly registered patients at Vision center and 29,019 were review patients. Males were 52,201(48.1%) and Females were 56,308(51.9) among them. The mean age of all examined patients was 41.03 ± 20.9 years (Standard deviation) and ranged from 01 – 113 years. Presenting mean visual acuity was 0.31 ± 0.5 in the right eye and 0.31 ± 0.4 in the left eye. Of the 1,08,581 patients 22,770 patients had refractive error in right eye and 22,721 patients had uncorrected refractive error in left eye. Glass prescription was given to 17,178 (15.8%) patients. 8,109 (7.5%) patients were referred to the base hospital for specialty clinic expert opinion or for cataract surgery. Conclusion: Vision center utilizing teleconsultation for comprehensive eye screening unit is a very effective tool in reducing the avoidable visual impairment caused due to uncorrected refractive error. Vision Centre model is believed to be efficient as it facilitates early detection and management of uncorrected refractive errors.

Keywords: refractive error, uncorrected refractive error, vision center, vision technician, teleconsultation

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Authors: F. B. Masok, S. S Songdeg, R. R. Dawam

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Vision is an important process for learning and communication as man depends greatly on vision to sense his environment. Prevalence and variation of refractive errors conducted between December 2010 and May 2011 in Jos, revealed that 735 (77.50%) out 950 subjects examined for refractive error had various refractive errors. Myopia was observed in 373 (49.79%) of the subjects, the error in the right eyes was 263 (55.60%) while the error in the left was 210(44.39%). The mean myopic error was found to be -1.54± 3.32. Hyperopia was observed in 385 (40.53%) of the sampled population comprising 203(52.73%) of the right eyes and 182(47.27%). The mean hyperopic error was found to be +1.74± 3.13. Astigmatism accounted for 359 (38.84%) of the subjects, out of which 193(53.76%) were in the right eyes while 168(46.79%) were in the left eyes. Presbyopia was found in 404(42.53%) of the subjects, of this figure, 164(40.59%) were in the right eyes while 240(59.41%) were in left eyes. The number of right eyes and left eyes with refractive errors was observed in some age groups to increase with age and later had its peak within 60 – 69 age groups. This pattern of refractive errors could be attributed to exposure to various forms of light particularly the ultraviolet rays (e.g rays from television and computer screen). There was no remarkable differences between the mean Myopic error and mean Hyperopic error in the right eyes and in the left eyes which suggest the right eye and the left eye are similar.

Keywords: left eye, refractive errors, right eye, variation

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Authors: Yuliya Markava

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The laser in situ keratomileusis (LASIK) is widely common surgical procedure, which has become an alternative for patients who are not satisfied with the performance of other correction methods. A high level of patient satisfaction functional outcomes after refractive surgery confirms the high reliability and safety of LASIK and provides a significant improvement in the quality of life and social adaptation. Purpose: To perform clinical analysis of the results of correction made to the excimer laser system SCHWIND AMARIS 500E in patients with different types of refractive anomalies. Materials and Methods: This was a retrospective analysis of 1581 operations (812 patients): 413 males (50.86%) and 399 females (49.14%) at the age from 18 to 47 years with different types of ametropia. All operations were performed on excimer laser SCHWIND AMARIS 500E in the LASIK procedure. Formation of the corneal flap was made by mechanical microkeratome SCHWIND. Results: Analyzing the structure of refractive anomalies: The largest number of interventions accounted for myopia: 1505 eyes (95.2%), of which about a low myopia: 706 eyes (44.7%), moderate myopia: 562 eyes (35.5 %), high myopia: eyes 217 (13.7%) and supermyopia: 20 eyes (1.3%). Hyperopia was 0.7% (11 eyes), mixed astigmatism: 4.1% (65 eyes). The efficiency was 80% (in patients with supermyopia) to 91.6% and 95.4% (in groups with myopia low and moderate, respectively). Uncorrected visual acuity average values before and after laser operation was in groups: a low myopia 0.18 (up 0.05 to 0.31) and 0.80 (up 0.60 to 1.0); moderate myopia 0.08 (up 0.03 to 0.13) and 0.87 ( up 0.74 to 1.0); high myopia 0.05 (up 0.02 to 0.08) and 0.83 (up 0.66 to 1.0); supermyopia 0.03 (up 0.02 to 0.04) and 0.59 ( up 0.34 to 0.84); hyperopia 0.27 (up 0.16 to 0.38) and 0.57 (up 0.27 to 0.87); mixed astigmatism of 0.35 (up 0.19 to 0.51) and 0.69 (up 0.44 to 0.94). In all cases, after LASIK indicators uncorrected visual acuity significantly increased. Reoperation was 4.43%. Significance: Clinical results of refractive surgery at the excimer laser system SCHWIND AMARIS 500E in different ametropia correction is characterized by high efficiency.

Keywords: effectiveness of laser correction, LASIK, refractive anomalies, surgical treatment

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Authors: Ghandehari Motlagh, Mohammad

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Purpose: We tried to find the most common etiologies for anisometropia in pre-op cataract cases: axial or refractive. Methods: In this cross-sectional study ,41 pre-op cataract eyes with more than 0.33 difference between axial lengths of 2 eyes were enrolled.Considered for each 1mm difference between axial lengths in long eyes( AXL more than 25):1.75-2.00 D of anisometropia, for normal eyes(AXL: 22- 25):2.50D and for short eyes (AXL less than 22):3.50-3.75 D as axial anisometropia. If there are more or lesser anisometropia, we recorded as refractive anisometropia. Results: Average of anisometropia :4.24 D, prevalence of PK or LK :1 (2.38%), kc:1(2.38%), glaucoma surgery: 1(2.38%), and pseudophakic status of the opposite eye 8(19.04%). Prevalence of axial anisometropia:21 (52.4%) and refractive anisometropia 20(47.6%).Then on basis of this study we can rely on the patient’s refraction exactly before phaco for evaluation of axial length differences between the 2 eyes, because most of the anisometropias are axial. Conclusion: In most cases, cataract does not induce significant change in refractive error (secondary myopia) and AXL difference between the 2 eyes are correlated with anisometropia.so it can be used for cataract patient’s ocular biometry evaluation. Pre-cataract refraction is a valuable variable should be measured and recorded in routin eye examination.

Keywords: ocular axial length, anisometropia, cataract, ophthalmology and optometry

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Authors: Ti-An Tsai, Chun-Chih Wang, Hung-Wen Wang, I-Ling Chang, Lien-Wen Chen

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In this study, we demonstrate a high-resolution refractive index sensor based on a magnetic photonic crystal (MPC) composed of a triangular lattice array of air holes embedded in Si matrix. A microcavity is created by changing the radius of an air hole in the middle of the photonic crystal. The cavity filled with gyrotropic materials can serve as a refractive index sensor. The shift of the resonant frequency of the sensor is obtained numerically using finite difference time domain method under different ambient conditions having refractive index from n = 1.0 to n = 1.1. The numerical results show that a tiny change in refractive index of Δn = 0.0001 is distinguishable. In addition, the spectral response of the MPC sensor is studied while an external magnetic field is present. The results show that the MPC sensor exhibits a dramatic improvement in resolution.

Keywords: magnetic photonic crystal, refractive index sensor, sensitivity, high-resolution

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Authors: Lingmao Xu, Hui Zhou

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Ge film is widely used in infrared optical systems. Because of the special requirements of space application, it is usually used in low temperature. The refractive index of Ge film is always changed with the temperature which has a great effect on the manufacture of high precision infrared optical film. Specimens of Ge single film were deposited at ZnSe substrates by EB-PVD method. During temperature range 80K ~ 300K, the transmittance of Ge single film within 2 ~ 15 μm were measured every 20K by PerkinElmer FTIR cryogenic testing system. By the full spectrum inversion method fitting, the relationship between refractive index and wavelength within 2 ~ 12μm at different temperatures was received. It can be seen the relationship consistent with the formula Cauchy, which can be fitted. Then the relationship between refractive index of the Ge film and temperature/wavelength was obtained by fitting method based on formula Cauchy. Finally, the designed value obtained by the formula and the measured spectrum were compared to verify the accuracy of the formula.

Keywords: infrared optical film, low temperature, thermal refractive coefficient, Ge film

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Authors: Nissar Mohammad Karim, Norhayati Soin

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To ensure fast switching in high-K incorporated Complementary Metal Oxide Semiconductor (CMOS) transistors, the results on the basis of d (NBTI) by incorporating SiO2 dielectric with aged samples of CuO sol-gels have been reported. Precursor ageing has been carried out for 4 days. The minimum obtained refractive index is 1.0099 which was found after 3 hours of adhesive UV curing. Obtaining a low refractive index exhibits a low dielectric constant and hence a faster system.

Keywords: refractive index, Sol-Gel, precursor aging, aging

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Authors: Nissar Mohammad Karim, Norhayati Soin

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To ensure fast switching in high-K incorporated Complementary Metal Oxide Semiconductor (CMOS) transistors, the results on the basis of d (NBTI) by incorporating SiO2 dielectric with aged samples of CuO sol-gels have been reported. Precursor ageing has been carried out for 4 days. The minimum obtained refractive index is 1.0099 which was found after 3 hours of adhesive UV curing. Obtaining a low refractive index exhibits a low dielectric constant and hence a faster system.

Keywords: refractive index, sol-gel, precursor ageing, metallurgical and materials engineering

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Authors: Husain Rajib, K. S. Kishor, D. G. Jewel

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Background: Uncorrected refractive error is a common cause of preventable visual impairment in pediatric age group which can be lead to blindness but early detection of visual impairment can reduce the problem that will have good effective in education and more involve in social activities. Glasses are the cheapest and commonest form of correction of refractive errors. To achieve this, patient must exhibit good compliance to spectacle wear. Patient’s attitude and perception of glasses and eye health could affect compliance. Material and method: A Prospective community based cross sectional study was designed in order to evaluate the knowledge, attitude and practices about refractive errors and eye health amongst the primary school going children. Result: Among 140 respondents, 72 were males and 68 were females. We found 50 children were myopic and out of them 26 were male and 24 were female, 27 children were hyperopic and out of them 14 were male and 13 were female. About 63 children were astigmatic and out of them 32 were male and 31 were female. The level of knowledge, attitude was satisfactory. The attitude of the students, teachers and parents was cooperative which helps to do cycloplegic refraction. Practice was not satisfactory due to social stigma and information gap. Conclusion: Knowledge of refractive error and acceptance of glasses for the correction of uncorrected refractive error. Public awareness program such as vision screening program, eye camp, and teachers training program are more beneficial for wearing and prescribing spectacle.

Keywords: refractive error, stigma, knowledge, attitude, practice

Procedia PDF Downloads 259

Authors: Marziehossadat Moezzi

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In this paper, electromagnetically induced transparency (EIT) is investigated in a cylindrical quantum dot (QD) with a parabolic confinement potential. We study the effect of control lasers polarization on absorption coefficient, refractive index and also on the generation of the double transparency windows in this system. Considering an effective mass method, the time-independent Schrödinger equation is solved to obtain the energy structure of the QD. Also, we study the effect of structural characteristics of the QD on refraction and absorption of the QD in the presence of EIT.

Keywords: electromagnetically induced transparency, cylindrical quantum dot, absorption coefficient, refractive index

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Authors: Durga Prasad Sapkota, Madhu Sudan Kayastha, Koichi Wakita

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In this paper, we have compared and analyzed the electron absorption properties between with and without excitonic effect bulk in high purity GaAs spatial light modulator for an optical fiber communication network. The electroabsorption properties such as absorption spectra, change in absorption spectra, change in refractive index and extinction ratio have been calculated. We have also compared the result of absorption spectra and change in absorption spectra with the experimental results and found close agreement with experimental results.

Keywords: exciton, refractive index change, extinction ratio, GaAs

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Authors: Mehmet Ali Kisaçam, P. Sema Temizer Ozan, Ayşe Doğan, Gonca Ozan, F. Sarper Türker

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Cardiovascular disease which is one of the most common health problems worldwide has crucial importance because of its’ morbidity and mortality rates. Nitric oxide synthase and arginase use L-arginine as a substrate and produce nitric oxide (NO), citrulline and urea, ornithine respectively. Endothelial dysfunction is characterized by reduced bioavailability of vasodilator and anti-inflammatory molecule NO. The purpose of the study to assess endothelial function via arginase activity and NO levels in patients undergoing coronary artery bypass grafting (CABG) surgery. The study was conducted on 26 patients (14 male, 12 female) undergoing CABG surgery. Blood samples were collected from the subjects before surgery, after the termination and after 24 hours of the surgery. Arginase activity and NO levels measured in collected samples spectrophotometrically. Arginase activity decreased significantly in subjects after the termination of the surgery compared to before surgery data. 24 hours after the surgery there wasn’t any significance in arginase activity as it compared to before surgery and after the termination of the surgery. On the other hand, NO levels increased significantly in the subject after the termination of the surgery. However there was no significant increase in NO levels after 24 hours of the surgery, but there was an insignificant increase compared to before surgery data. The results indicate that after the termination of the surgery vascular and endothelial function improved and after 24 hours of the surgery arginase activity and NO levels returned to normal.

Keywords: arginase, bypass, cordiopulmonary, nitric oxide

Procedia PDF Downloads 204

Authors: T. Srinivasa Krishna, K. Narendra, K. Thomas, S. S. Raju, B. Munibhadrayya

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The densities, speeds of sound and refractive index of the binary mixture of ionic liquid (IL) 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Imide]) and Pyrrolidin-2-one(PY) was measured at atmospheric pressure, and over the range of temperatures T= (298.15 -323.15)K. The excess molar volume, excess isentropic compressibility, excess speed of sound, partial molar volumes, and isentropic partial molar compressibility were calculated from the values of the experimental density and speed of sound. From the experimental data excess thermal expansion coefficients and isothermal pressure coefficient of excess molar enthalpy at 298.15K were calculated. The results were analyzed and were discussed from the point of view of structural changes. Excess properties were calculated and correlated by the Redlich–Kister and the Legendre polynomial equation and binary coefficients were obtained. Values of excess partial volumes at infinite dilution for the binary system at different temperatures were calculated from the adjustable parameters obtained from Legendre polynomial and Redlich–Kister smoothing equation. Deviation in refractive indices ΔnD and deviation in molar refraction, ΔRm were calculated from the measured refractive index values. Equations of state and several mixing rules were used to predict refractive indices of the binary mixtures and compared with the experimental values by means of the standard deviation and found to be in excellent agreement. By using Prigogine–Flory–Patterson (PFP) theory, the above thermodynamic mixing functions have been calculated and the results obtained from this theory were compared with experimental results.

Keywords: density, refractive index, speeds of sound, Prigogine-Flory-Patterson theory

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Authors: S. Sadegzadeh, A. Mousavi

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Temperature-dependent tunable photonic crystals have attracted widespread interest in recent years. In this research, transmission characteristics of a one-dimensional photonic crystal structure with a single defect have been studied. Here, we assume two different defect layers: InSb as a semiconducting layer and HgBa₂Ca₂Cu₃O₁₀ as a high-temperature superconducting layer. Both the defect layers have temperature-dependent refractive indexes. Two different types of dielectric materials (Si as a high-refractive index dielectric and MgF₂ as a low-refractive index dielectric) are used to construct the asymmetric structures (Si/MgF₂)^NInSb(Si/MgF₂)^N named S.I, and (Si/MgF₂)^NHgBa₂Ca₂Cu₃O₁₀(Si/MgF₂)^N named S.II. It is found that in response to the temperature changes, transmission peaks within the photonic band gap of the S.II structure, in contrast to S.I, show a small wavelength shift. Furthermore, the results show that under the same conditions, S.I structure generates an extra defect mode in the transmission spectra. Besides high efficiency transmission property of S.II structure, it can be concluded that the semiconductor-dielectric photonic crystals are more sensitive to temperature variation than superconductor types.

Keywords: defect modes, photonic crystals, semiconductor, superconductor, transmission

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Authors: Nagaraju Pendam, C. P. Vardhani

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A simple technology–compatible design of silicon-on-insulator based 1×2 optical power splitter is proposed. For developing large area Opto-electronic Silicon-on-Insulator (SOI) devices, the power splitter is a key passive device. The SOI rib- waveguide dimensions (height, width, and etching depth, refractive indices, length of waveguide) leading simultaneously to single mode propagation. In this paper a low loss optical power splitter is designed by using R Soft cad tool and simulated by Beam propagation method, here s-bend waveguides proposed. We concentrate changing the refractive index difference, branching angle, width of the waveguide, free space wavelength of the waveguide and observing transmitted power, effective refractive index in the designed waveguide, and choosing the best simulated results to be fabricated on silicon-on insulator platform. In this design 1550 nm free spacing are used.

Keywords: beam propagation method, insertion loss, optical power splitter, rib waveguide, transmitted power

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Authors: Mohamed Salah El-Din Mahmoud, Heba Radi Atta Allah

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Background: Our study assesses the safety profile and efficacy of toric Implantable Collamer Lens (T-ICL) and toric implantable phakic contact lens (IPCL) for the correction of high myopia with astigmatism. Methods: A prospective interventional randomized comparative study included 60 myopic eyes divided into 2 groups, group A including 30 eyes that were implanted with T-ICL, and group B including 30 eyes that were implanted with toric IPCL. The refractive results, visual acuity, corneal endothelial cell count, and intraocular pressure (IOP) were evaluated at baseline and at 1, 6, and 9 months post-surgery. Any complications either during or after surgery were assessed. Results: A significant reduction in both spherical and cylindrical refractive errors with good predictability was reported in both groups compared with preoperative values. Regarding the predictability, In T-ICL group (A), the median spherical and cylindrical errors were significantly improved from (-10 D & -4.5 D) pre-operatively to (-0.25 D & - 0.3 D) at the end of 9 months follow up period. Similarly, in the toric IPCL group (B), the median spherical and cylindrical errors were significantly improved from (-11 D & -4.5 D) pre-operatively to (-0.25 D & - 0.3 D) at the end of 9 months follow up period. A statistically significant improvement of UCDVA at 9 months postoperatively was found in both groups, as median preoperative Log Mar UCDVA was 1.1 and 1.3 in groups A and B respectively, which was significantly improved to 0.2 in both groups at the end of follow-up period. Regarding IOP, no significant difference was found between both groups, either pre-operatively or during the postoperative period. Regarding the endothelial count, no significant differences were found during the pre-operative and postoperative follow-up periods between the two groups. Fortunately, no intra or postoperative complications as cataract, keratitis or lens decentration had occurred. Conclusions: Toric IPCL is a suitable alternative to T-ICL for the management of high myopia with astigmatism, especially in developing countries, as it is cheaper and easier for implantation than T-ICL. However, data over longer follow-up periods are needed to confirm its safety and stability.

Keywords: T-ICL, Toric IPCL, IOP, corneal endothelium

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Authors: Anton V. Bourdine, Vladimir A. Burdin, Oleg R. Delmukhametov

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This work presents a fast and simple method for the design of large core silica optical fibers with differential mode delay (DMD) management. Some results are reported concerned with refractive index profile optimization for 42 µm core 16-LP-mode optical fiber for next-generation optical networks. Here special refractive index profile form provides total DMD reducing over all mode staff under desired enhanced mode effective area. Method for the simulation of 'real manufactured' few-mode optical fiber (FMF) core geometry differing from the desired optimized structure by core non-symmetrical ellipticity and refractive index profile deviation including local fluctuations is proposed. Results of the following analysis of optimized FMF with inserted geometry distortions performed by earlier on developed modification of rigorous mixed finite-element method showed strong DMD degradation that requires additional higher-order mode management. In addition, this work also presents a method for design mode division multiplexer channel precision spatial positioning scheme at FMF core end that provides one of the potentiality solutions of described DMD degradation problem concerned with 'distorted' core geometry due to features of optical fiber manufacturing techniques.

Keywords: differential mode delay, few-mode optical fibers, nonlinear Shannon limit, optical fiber non-circularity, ‘real manufactured’ optical fiber core geometry simulation, refractive index profile optimization

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Authors: Juntao Li

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The metasurfaces for beam deflecting with gradient silicon posts in the square lattices were fabricated on the thin film crystal silicon with quartz substrate. By using the crystals silicon with high refractive index and high transmission to control the phase over 2π coverage, we demonstrated the polarization independent beam deflecting at wavelength of 532nm with 45% transmission in experiment and 70% in simulation into the desired angle. This simulation efficiency is almost close to the TiO2 metasurfaces but has higher refractive index and lower aspect ratio to reduce fabrication complexity. The result can extend the application of silicon metalsurfaces from 700 nm to 500 nm hence open a new way to use metasurfaces efficiently in visible light regime.

Keywords: metasurfaces, crystal silicon, light deflection, visible light

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Authors: Babak Masoomian, Masoud Khorrami Nejad, Hamid Riazi Esfahani

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Purpose: To report the result of strabismus surgery in eye-salvaged retinoblastoma (Rb) patients. Methods: A retrospective case series including 18 patients with Rb and strabismus who underwent strabismus surgery after completing tumor treatment by a single pediatric ophthalmologist. Results: A total of 18 patients (10 females and 8 males) were included with a mean age of 13.3 ± 3.0 (range, 2-39) months at the time tumor presentation and 6.0 ± 1.5 (range, 4-9) years at the time of strabismus surgery. Ten (56%) patients had unilateral, and 8(44%) had bilateral involvement, and the most common worse eye tumor’s group was D (n=11), C (n=4), B (n=2) and E (n=1). Macula was involved by the tumors in 12 (67%) patients. The tumors were managed by intravenous chemotherapy (n=8, 47%), intra-arterial chemotherapy (n=7, 41%) and both (n=3, 17%). After complete treatment, the average time to strabismus surgery was 29.9 ± 20.5 (range, 12-84) months. Except for one, visual acuity was equal or less than 1.0 logMAR (≤ 20/200) in the affected eye. Seven (39%) patients had exotropia, 11(61%) had esotropia (P=0.346) and vertical deviation was found in 8 (48%) cases. The angle of deviation was 42.0 ± 10.4 (range, 30-60) prism diopter (PD) for esotropic and 35.7± 7.9 (range, 25-50) PD for exotropic patients (P=0.32) that after surgery significantly decreased to 8.5 ± 5.3 PD in esotropic cases and 5.9±6.7 PD in exotropic cases (P<0.001). The mean follow-up after surgery was 15.2 ± 2.0 (range, 10-24) months, in which 3 (17%) patients needed a second surgery. Conclusion: Strabismus surgery in treated Rb is safe, and results of the surgeries are acceptable and close to the general population. There was not associated with tumor recurrence or metastasis.

Keywords: retinoblastoma, strabismus, chemotherapy, surgery

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Authors: N. Bendimerad, M. Lemerini, A. Guen

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In this work, we propose to determine the density of neutral particles of an electric discharge peak - Plan types performed in air at atmospheric pressure by applying a technique based on laser interferometry. The experimental methods used so far as the shadowgraph or stereoscopy, give rather qualitative results with regard to the determination of the neutral density. The neutral rotational temperature has been subject of several studies but direct measurements of kinetic temperature are rare. The aim of our work is to determine quantitatively and experimentally depopulation with a Mach-Zehnder type interferometer. This purely optical appearance of the discharge is important when looking to know the refractive index of any gas for any physicochemical applications.

Keywords: laser source, Mach-Zehnder interferometer, refractive index, corona discharge

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Authors: Minna Salim, James Brady

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Postoperative nausea and pain (PONV) are adverse effects following surgical procedures. It is especially pronounced in patients undergoing orthognathic surgery, as their mouth is closed postoperatively using wires or rubber bands. Postoperative mouth closure increases the discomfort and risk of complications associated with nausea and vomiting. Many surgeons and institutions apply gastric decompression in hopes of aspirating stomach contents and, therefore, decreasing PONV incidence. This review observed that PONV incidence was not affected by gastric decompression overall. However, the effect of gastric decompression on PONV in orthognathic surgery was variable. This paper aims to summarize the findings of gastric decompression on PONV and to determine the need for it in orthognathic surgery.

Keywords: gastric decompression, nasogastric tube, orthognathic surgery, postoperative nausea, vomiting

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Authors: Beddiaf Abdelaziz

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The optical characteristics of thin films of silicon oxynitride SiOₓNy prepared by the Low-Pressure Chemical Vapor Deposition (LPCVD) technique have been studied. The films are elaborated from the SiH₂Cl₂, N₂O and NH₃ gaseous mixtures. The flows of SiH₂Cl₂ and (N₂O+NH₃) are 200 sccm and 160 sccm respectively. The deposited films have been characterized by ellipsometry, to model our silicon oxynitride SiOₓNy films. We have suggested two theoretical models (Maxwell Garnett and Bruggeman effective medium approximation (BEMA)). These models have been applied on silicon oxynitride considering the material as a heterogeneous medium formed by silicon oxide and silicon nitride. The model's validation was justified by the confrontation of theoretical spectra and those measured by ellipsometry. This result permits us to obtain the optical refractive coefficient of these films and their thickness. Ellipsometry analysis of the optical properties of the SiOₓNy films shows that the SiO₂ fraction decreases when the gaseous ratio NH₃/N₂O increases. Whereas the increase of this ratio leads to an increase of the silicon nitride Si3N4 fraction. The study also shows that the increasing gaseous ratio leads to a strong incorporation of nitrogen atoms in films. Also, the increasing of the SiOₓNy refractive coefficient until the SiO₂ value shows that this insulating material has good dielectric quality.

Keywords: ellipsometry, silicon oxynitrde, model, refractive coefficient, effective medium

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Authors: Martin C. Eze, Gao Min

Abstract:

Lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) dopant is beneficial in improving the properties of 2,2′,7,7′-Tetrakis (N, N-di-p-methoxyphenylamino)-9,9′-spiro-bifluorene (Spiro-OMETAD) transport layer used in perovskite solar cells (PSCs). Properties such as electrical conductivity, band energy mismatch, and refractive index of Spiro-OMETAD layers are believed to play key roles in PSCs performance but only the dependence of electrical conductivity on Li-TFSI doping has been extensively studied. In this work, the effect of Li-TFSI doping level on highest occupied molecular orbital (HOMO) energy, electrical conductivity, and refractive index of Spiro-OMETAD film and PSC performance was demonstrated. The Spiro-OMETAD films were spin-coated at 4000 rpm for 30 seconds from solutions containing 73.4 mM of Spiro-OMeTAD, 23.6 mM of 4-tert-butylpyridine, 7.6 mM of tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine) cobalt(III) tri[bis(trifluoromethane) sulfonimide] (FK209) dopant and Li-TFSI dopant varying from 37 to 62 mM in 1 ml of chlorobenzene. From ultraviolet photoelectron spectroscopy (UPS), ellipsometry, and 4-probe studies, the results show that films deposition from Spiro-OMETAD solution doped with 40 mM of Li-TFSI shows the highest electrical conductivity of 6.35×10-6 S/cm, the refractive index of 1.87 at 632.32 nm, HOMO energy of -5.22 eV and the lowest HOMO energy mismatch of 0.21 eV compared to HOMO energy of perovskite layer. The PSCs fabricated show the best power conversion efficiency, open-circuit voltage, and fill factor of 17.10 %, 1.1 V, and 70.12%, respectively, for devices based on Spiro-OMETAD solution doped with 40 mM of Li-TFSI. This study demonstrates that the optimum Spiro-OMETAD/ Li-TFSI doping ratio of 1.84 is the optimum doping level for Spiro-OMETAD layer preparation.

Keywords: electrical conductivity, homo energy mismatch, lithium bis(trifluoromethanesulfonyl)imide, power conversion efficiency, refractive index

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Authors: Ayu Nabila Kusuma Pradana, Aprinaldi Jasa Mantau, Tomohiko Akahoshi

Abstract:

The incidence of Disseminated intravascular coagulation (DIC) following gastrointestinal surgery has a poor prognosis. Therefore, it is important to determine the factors that can predict the prognosis of DIC. This study will investigate the factors that may influence the outcome of DIC in patients after gastrointestinal surgery. Eighty-one patients were admitted to the intensive care unit after gastrointestinal surgery in Kyushu University Hospital from 2003 to 2021. Acute DIC scores were estimated using the new Japanese Association for Acute Medicine (JAAM) score from before and after surgery from day 1, day 3, and day 7. Acute DIC scores will be compared with The Sequential Organ Failure Assessment (SOFA) score, platelet count, lactate level, and a variety of biochemical parameters. This study applied machine learning algorithms to predict the prognosis of DIC after gastrointestinal surgery. The results of this study are expected to be used as an indicator for evaluating patient prognosis so that it can increase life expectancy and reduce mortality from cases of DIC patients after gastrointestinal surgery.

Keywords: the survival rate, gastrointestinal surgery, JAAM score, neural network, machine learning, disseminated intravascular coagulation (DIC)

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Authors: Gong Zhang, Hong Cai, Bin Dong, Jifang Tao, Aiqun Liu, Dim-Lee Kwong, Yuandong Gu

Abstract:

An on-chip refractive index sensor with high sensitivity and large measurement range is demonstrated in this paper. The sensing structures are based on Mach-Zehnder interferometer configuration, built on the SOI substrate. The wavelength sensitivity of the sensor is estimated to be 3129 nm/RIU. Meanwhile, according to the interference pattern period changes, the measured period sensitivities are 2.9 nm/RIU (TE mode) and 4.21 nm/RIU (TM mode), respectively. As such, the wavelength shift and the period shift can be used for fine index change detection and larger index change detection, respectively. Therefore, the sensor design provides an approach for large index change measurement with high sensitivity.

Keywords: Mach-Zehnder interferometer, nanotechnology, refractive index sensing, sensors

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Authors: S. S. Sree Sanker, K. N. Madhusoodanan

Abstract:

Optical biosensors are dominant alternative for traditional analytical methods, because of their small size, simple design and high sensitivity. Photonic sensing method is one of the recent advancing technology for biosensors. It measures the change in refractive index which is induced by the difference in molecular interactions due to the change in concentration of the analyte. Glucose is an aldosic monosaccharide, which is a metabolic source in many of the organisms. The terahertz waves occupies the space between infrared and microwaves in the electromagnetic spectrum. Terahertz waves are expected to be applied to various types of sensors for detecting harmful substances in blood, cancer cells in skin and micro bacteria in vegetables. We have designed glucose sensors using silicon based 1D and 2D photonic crystal pillar arrays in terahertz frequency range. 1D photonic crystal has rectangular pillars with height 100 µm, length 1600 µm and width 50 µm. The array period of the crystal is 500 µm. 2D photonic crystal has 5×5 cylindrical pillar array with an array period of 75 µm. Height and diameter of the pillar array are 160 µm and 100 µm respectively. Two samples considered in the work are blood and glucose solution, which are labelled as sample 1 and sample 2 respectively. The proposed sensor detects the concentration of glucose in the samples from 0 to 100 mg/dL. For this, the crystal was irradiated with 0.3 to 3 THz waves. By analyzing the obtained S parameter, the refractive index of the crystal corresponding to the particular concentration of glucose was measured using the parameter retrieval method. Refractive indices of the two crystals decreased gradually with the increase in concentration of glucose in the sample. For 1D photonic crystals, a gradual decrease in refractive index was observed at 1 THz. 2D photonic crystal showed this behavior at 2 THz. The proposed sensor was simulated using CST Microwave studio. This will enable us to develop a model which can be used to characterize a glucose sensor. The present study is expected to contribute to blood glucose monitoring.

Keywords: CST microwave studio, glucose sensor, photonic crystal, terahertz waves

Procedia PDF Downloads 280