Different Types Of Lenses Research Articles

Optics of spectacle lenses intended to treat myopia progression.

This is a review of the optics of various spectacle lenses that have been used in myopia control over the last 60 years, with emphasis on approximately the last 15 years.Myopia has become an increasing health problem worldwide, particularly in some East Asian countries. This has led to many attempts to slow its progression in children and reduce its endpoint value. This review is concerned with the optics of spectacle lenses for use in myopia control, from bifocal lenses to multisegment and diffusion optics lenses. Treatments are based on theories of the onset or progression of myopia. These include the hypotheses that eye growth and myopia in susceptible children may be stimulated by (1) poor accommodation response and the consequent hyperopic defocus with near vision tasks, (2) relative hyperopic peripheral refraction, and (3) high retinal image contrast as occurs in urban environments. Using spectacle lenses to slow myopia progression has a history of about 60 years. The review is laid out in approximately the order in which different types of lenses have been introduced: bifocals, conventional progressive addition lenses, undercorrection with single-vision lenses, specialized progressive addition lenses, defocus-incorporated multiple segments, diffusion optics, and concentric bifocals. In the review, some of the lenses are combined with an eye model to determine refractive errors for peripheral vision for the stationary eye and for foveal vision for the rotating eye. Numbers are provided for the reported success of particular designs in retarding myopia progression, but this is not an epidemiological paper, and there is no critical review of the findings. Some of the recent treatments, such as multiple segments, appear to reduce the eye growth and myopia progression by better than 50% over periods of up to 2 years.

Disentangling the Black Hole Mass Spectrum with Photometric Microlensing Surveys

From the formation mechanisms of stars and compact objects to nuclear physics, modern astronomy frequently leverages surveys to understand populations of objects to answer fundamental questions. The population of dark and isolated compact objects in the Galaxy contains critical information related to many of these topics, but is only practically accessible via gravitational microlensing. However, photometric microlensing observables are degenerate for different types of lenses, and one can seldom classify an event as involving either a compact object or stellar lens on its own. To address this difficulty, we apply a Bayesian framework that treats lens type probabilistically and jointly with a lens population model. This method allows lens population characteristics to be inferred despite intrinsic uncertainty in the lens class of any single event. We investigate this method’s effectiveness on a simulated ground-based photometric survey in the context of characterizing a hypothetical population of primordial black holes (PBHs) with an average mass of 30M ⊙. On simulated data, our method outperforms current black hole (BH) lens identification pipelines and characterizes different subpopulations of lenses while jointly constraining the PBH contribution to dark matter to ≈25%. Key to robust inference, our method can marginalize over population model uncertainty. We find the lower mass cutoff for stellar origin BHs, a key observable in understanding the BH mass gap, particularly difficult to infer in our simulations. This work lays the foundation for cutting-edge PBH abundance constraints to be extracted from current photometric microlensing surveys.

Evaporation and desalination using a solar concentrator in an agricultural complex

The purpose of the article is to study boiling and distilling water using solar concentrator, the actual application and profitability of using such a method of liquid evaporation. The use of various modern types of technologies makes it possible to purify water as efficiently as possible, while avoiding the decomposition of compounds. The different configurations of boiling by means of solar concentrator allow meeting different forms of application. Such configuration changes include different types of lenses, as well as different shapes and sizes of the solar concentrator itself, the use of mirror arrays that can be configured in such a way as to direct sunlight to one point to achieve high temperatures.

English

BACKGROUND Lens induced glaucomas are common in India. There were different types of lens induced glaucomas based on clinical features and morphological features. This study was undertaken to evaluate the various characteristics and presentations of glaucomas, to define the risk factors and to evaluate as to how they influence the post-operative visual acuity, intra ocular pressure, inflammation and optic disc changes. METHODS This longitudinal study included 90 cases of lens induced glaucoma admitted in the ophthalmic wards of the Great Eastern Medical School and Hospital, Srikakulam, during the period March 2018 to March 2020. All consecutive patients diagnosed as lens induced glaucoma on the basis of clinical symptoms and signs were included. At presentation, visual acuity, IOP, inflammation including corneal changes were recorded, which were repeated after institution of medical line of treatment and postoperatively patients were followed up regularly at 2, 4 and 6 weeks intervals and the same parameters were evaluated including optic disc changes. RESULTS Occurrence of lens induced glaucoma in the hospital during the study period was 1.72 %. The mean age of presentation of various types of glaucomas was 60.57 years and the female to male ratio was 2:1. The most frequent type of lens induced glaucoma was phacomorphic glaucoma (70 %). In 34.4 % patients best corrected visual acuity was found to be better than 6 / 18. In 14.4 % of cases, visual acuity was found be worse than 6 / 60. In patients who presented with symptoms of less than two weeks duration, better visual acuity of 6 / 12 or more was noted (76.2 %, P < 0.01). In 60 % patients who presented with IOP levels of less than 35 mmHg, better visual acuity of 6 / 12 or more was noted in 76.2 %. The mean IOP noted in patients with symptoms of 2 to 4 weeks duration was found to be 40.33 ± 9.36 mmHg. Inflammation was more severe in patients who were symptomatic for more than 2 weeks (37.50 %, P < 0.05) and also in cases with IOP more than 35 mmHg (40 %). Optic disc of the presented eye was found to be damaged in 35.5 % of cases and in patients presenting with symptoms of more than 2 weeks’ duration it was 62.5 % (P < 0.01). CONCLUSIONS Presentation with intraocular pressure value greater than 35 mm of Hg and with symptoms of more than two weeks would result in severe inflammation further affecting the cornea and causing optic nerve damage which would ultimately jeopardize vision. This can be prevented by early presentation and regular screening of people above 60 years of age. KEYWORDS Lens-Induced, Glaucoma, Cataract

Limbal Metabolic Support Reduces Peripheral Corneal Edema with Contact-Lens Wear.

PurposeTo assess the influence of limbal metabolic support on corneal edema during scleral-lens (SL) and soft-contact-lens (SCL) wear for healthy lens wearers.MethodsA two-dimensional (2D) model of the cornea and sclera was designed on Comsol Multiphysics 5.4 along with SL and SCL architectures to mimic lens-wear induced hypoxia. The cornea is suffused with oxygen and metabolites from the limbus and aqueous humor. Air oxygen is supplied from and carbon dioxide is expelled to the atmosphere. Lens-oxygen permeability (Dk) was adjusted to investigate lens-wear safety against edema in different wear conditions. The 2D concentrations of oxygen, carbon dioxide, bicarbonate, lactate, sodium, chloride, glucose, and pH are quantified. Central-to-peripheral swelling of the cornea is determined by the change in stromal hydration caused by changing metabolite concentrations at the endothelium during hypoxia.ResultsThe metabolic model assesses central-to-peripheral corneal swelling with different types of lenses, and oxygen Dks. Limbal metabolic support reduces edema from the periphery to approximately 1 mm away from the central cornea. Despite thicker lens designs, the peripheral cornea exhibits practically zero swelling due to limbal metabolic support.ConclusionsThe metabolic model accurately predicts central-to-peripheral corneal edema with various contact-lens designs, post-lens tear-film thicknesses, and lens oxygen Dk values. Despite the thicker periphery of most contact-lens designs, lactate and bicarbonate support from the limbus significantly reduces peripheral and mid-peripheral corneal edema, whereas oxygen has a lesser effect.Translational RelevanceBy utilizing metabolic kinetics, we provide a 2D computational tool to predict oxygenation safety across the entire cornea with various types and designs of contact lenses.

Bioprinting of Multiscaled Hepatic Lobules within a Highly Vascularized Construct.

Highly vascularized complex liver tissue is generally divided into lobes, lobules, hepatocytes, and sinusoids, which can be viewed under different types of lens from the micro- to macro-scale. To engineer multiscaled heterogeneous tissues, a sophisticated and rapid tissue engineering approach is required, such as advanced 3D bioprinting. In this study, a preset extrusion bioprinting technique, which can create heterogeneous, multicellular, and multimaterial structures simultaneously, is utilized for creating a hepatic lobule (≈1 mm) array. The fabricated hepatic lobules include hepatic cells, endothelial cells, and a lumen. The endothelial cells surround the hepatic cells, the exterior of the lobules, the lumen, and finally, become interconnected with each other. Compared to hepatic cell/endothelial cell mixtures, the fabricated hepatic lobule shows higher albumin secretion, urea production, and albumin, MRP2, and CD31 protein levels, as well as, cytochrome P450 enzyme activity. It is found that each cell type with spatial cell patterning in bioink accelerates cellular organization, which could preserve structural integrity and improve cellular functions. In conclusion, preset extruded hepatic lobules within a highly vascularized construct are successfully constructed, enabling both micro- and macro-scale tissue fabrication, which can support the creation of large 3D tissue constructs for multiscale tissue engineering.

A CLINICAL STUDY ON LENS INDUCED GLAUCOMA AND ITS VISUAL OUTCOME IN PATIENTS ATTENDING GOVERNMENT GENERAL HOSPITAL, KADAPA.

Background: India being a developing country, causes of Blindness in India will be different than developed countries. There are 10million (37 million in world) blind people in India today in which 80 percent if taken care in time, completely preventable. AIM: To evaluate sex predominance, prevalence of different types of lens induced Glaucoma and its visual outcomes in patients attending government general hospital, kadapa. MATERIAL AND METHODS: This prospective study was conducted in Ophthalmology department of government general hospital, kadapa, Andhra Pradesh from January 2018 to June 2019. 32 Patients visiting the Hospital with classical symptoms of Lens induced Glaucoma were taken into study. RESULTS: A Total of 32 patients were taken into this study in which 12(37.50%) were male patients and 20(62.50%) were Female. Among different LIG patients maximum patients had Phacomorphic Glaucoma accounting 62.50% (20 patients) and Phacolytic Glaucoma 34.37% (11 patients).
 Keywords: Lens-induced glaucoma, Cataract, Phacomorphic glaucoma, Phacolytic glaucoma and Small incision cataract surgery (SICS)

Contact Lens Solutions and Contact Lens Discomfort: Examining the Correlations Between Solution Components, Keratitis, and Contact Lens Discomfort.

This article will examine the current literature, as it relates to contact lens discomfort (CLD) secondary to contact lens solutions. The reader will better understand the characteristics of contact lenses, as they uniquely interact with each type of contact lens solution and also gain a better comprehension of the components of contact lens solution such as preservatives, surfactants, and chelating agents, which may contribute to discomfort. By investigating corneal staining theory and the mechanisms that contribute to its presence, the reader will gain insight into this clinical finding, which relates to selection of contact lens solutions. The FDA standards for testing solutions and how this relates to contact lens keratitis will also be appraised in regards to current ISO recommendations. Finally, better selection of multipurpose contact lens solution (MPS) and hydrogen peroxide-based solutions for patients should be accessible to the clinician based on this review and preexisting clinical findings or diagnoses. A review of current published literature from peer reviewed journals and online journals was conducted to gain an understanding of contact lens solution's impact on contact lens discomfort. Many studies have been conducted comparing comfort between various types of contact lens solutions. It is challenging to decipher this information and apply it clinically when selecting solutions for patients. By comparing solution components, how contact lens solutions interact with different types of lenses, keratitis related to contact lenses, and preexisting ocular conditions, this review will improve a clinician's ability to eliminate CLD.

Contribution of the Imaging System Components in the Overall Error of the Two-Dimensional Digital Image Correlation Technique

Abstract Digital image correlation (DIC) is one of the most widely used non-invasive methods for measuring full-field surface strains in a wide variety of applications. The DIC method has been used by numerous researchers for measuring strains during the plastic range of deformation where the strains are relatively large. The estimation of the amount of background strain error in the measurements is of prime importance for determining the applicability of this method for measuring small strains (such as the elastic strains in metals, ceramics, bone samples, etc.). In this study, the strain errors in 2D-DIC measurements associated with different types of imaging systems were investigated. In-plane rigid-body-translation, experiments were used to estimate the overall amount of error in DIC displacement and strain measurements. Different types of cameras having different types of sensors and different spatial resolutions were used in the study. Also, for the same type of camera, different types of lenses were used. Results show that the DIC measurement accuracy depends on the magnitude of image displacement and that different error estimation parameters can be used for quantifying the accuracy of the measurements. Also, the effect of the lens on measurement accuracy is more pronounced than that of the camera. Furthermore, imaging conditions such as image sharpness and camera gain also affect the accuracy. Further still, the measurement accuracy was found to be influenced by the direction of translation. The results indicate that measurement error can be reduced by orienting the camera such that the major displacement direction is parallel to the width direction of the image. The experimental approach used in this study can be used for quantitatively assessing the quality of the different types of cameras and lenses and to determine their suitability for use in experimental techniques that depend on image analysis such as DIC and particle image velocimetry (PIV).

Multifunctional metasurface lens for imaging and Fourier transform.

A metasurface can manipulate light in a desirable manner by imparting local and space-variant abrupt phase change. Benefiting from such an unprecedented capability, the conventional concept of what constitutes an optical lens continues to evolve. Ultrathin optical metasurface lenses have been demonstrated based on various nanoantennas such as V-shape structures, nanorods and nanoslits. A single device that can integrate two different types of lenses and polarities is desirable for system integration and device miniaturization. We experimentally demonstrate such an ultrathin metasurface lens that can function either as a spherical lens or a cylindrical lens, depending on the helicity of the incident light. Helicity-controllable focal line and focal point in the real focal plane, as well as imaging and 1D/2D Fourier transforms, are observed on the same lens. Our work provides a unique tool for polarization imaging, image processing and particle trapping.

Clinical study of lens induced glaucoma

Background: Lens induced glaucoma is a common occurrence. Secondary glaucoma has been found in 10% of senile cortical cataracts. Ruling out the coexisting primary glaucomas, lens induced glaucomas has been taken up for this interesting study. Objective: To analyze the different mechanisms and clinical features of lens induced gluacomas. Methods: This clinical study included 50 cases of different types of lens induced glaucomas in individuals whose age group varied from 12 to 90 years and both the sexes conducted on the in patients of Ophthalmology department. All the cases of secondary glaucomas suspected to be lens induced were admitted to the wards. Detailed history was ascertained. Previous history of extra-capsular lens extraction in the other eye was carefully noted. Results: Majority of the patients were in the age group of 50-75 years. The incidence of lens induced glaucoma was more among females (68%) than males (32%). Right eye was found to be more commonly affected (58%) than the left eye (38%) and both eyes were involved in 4% of cases.. The majority of the eyes affected had hypermature cataract (44%) followed by mature cataract (34%). Phacomorphic glaucoma caused by intumescent lens has been the major cause contributing to 54% of cases. 27 cases (54%) showed shallow anterior chamber. Conclusion: The incidence of lens induced glaucoma was more among females (68%) than males (32%). Right eye was found to be more commonly affected (58%) than the left eye (38%).Both eyes were involved in 4% of cases. The majority of the eyes affected had hypermature cataract (44%).

Study of the Effect of Brightness After Penetration of Light from a Lens

There are many types of component that are able to produce light and the light is produced based on the angle and wavelength of the lens. Light penetration depends on the type of material used. The tests are done using basic electronic components which are able to produce light including the light emitting diode (LED), laser and infrared source. From the component, there are two types of light line, one with an angle and one without. It is known that the laser only produces a straight line light while the angle and thickness of light from both the LED, and infrared source increase with distance. The results show that the different types of light must use different types of lenses and they are suitable for use with all light properties.

A Flexible Method for Zoom Lens Calibration and Modeling Using a Planar Checkerboard

This paper presents a fl exible method for zoom lens calibration and modeling using a planar checkerboard. The method includes the following four steps. First, the principal point of the zoom-lens camera is determined by a focus-of-expansion approach. Second, the infl uences of focus changes on the principal distance are modeled by a scale parameter. Third, checkerboard images taken at varying object distances with convergent image geometry are used for camera calibration. Finally, the variations of the calibration parameters with respect to the various zoom and focus settings are modeled using polynomials. Three different types of lens are examined in this study. Experimental analyses show that high precision calibration results can be expected from the developed approach. The relative measurement accuracy (accuracy normalized with object distance) using the calibrated zoom-lens camera model ranges from 1:5 000 to 1:25 000. The developed method is of signifi cance to facilitate the use of zoom-lens camera systems in various applications such as robotic exploration, hazard monitoring, traffi c monitoring, and security surveillance.

Low-power DSP system for real-time correction of fish-eye cameras in automotive driver assistance applications

The development of an embedded system for real-time correction of fish-eye effect is presented. The fish-eye lens is applied to driver assistance video systems because of its wide-angled view. A large field of view can reduce the number of cameras needed for video system and their cost, installation, maintenance and wiring issues. On the other hand, this lens causes inherent radial distortion to image that has to be corrected in real-time with a low-cost and low-power processing platform. This paper proposes a solution that can be easily adapted to different types of lens and camera, and meets real-time constraints with a power budget within 100 mW and a board size of few cm2. Starting from mathematical equations, given by the geometrical optics, a state-of-the-art correction method is presented, then optimizations are introduced at different levels: algorithmic level, where a real-time correction parameter calculation avoids extra non-volatile off-chip memory cards; data transfer level, where a new pixel pair management reduces memory access and storage burden; HW-SW implementation level, where a low-power board has been developed and tested in real automotive scenarios. Other applications of the developed system, such as multi-camera and multi-dimensional video systems, are finally presented.

Analysis of a Thin Optical Lens Model

In this article a thin optical lens model is considered. It is shown that the limits of its applicability are determined not only by the ratio between the thickness of the lens and the modules of the radii of curvature, but above all its geometric type. We have derived the analytical criteria for the applicability of the model for different types of lenses. Quantitative estimations were made for practically important cases оf a glass lens in air and air lens in water.

Modelling the primary chromatic aberrations and secondary spectrum of conceptual thick-lens modules

A virtual thick-lens module comprising three air-spaced thin lenses is proposed, which is able to have the identical primary chromatic aberrations and secondary spectrum for just real thick lenses, or groups or components within any thick lens, hence it is capable of studying the chromatic aberration behaviours of conceptual lenses without their detailed structures. The three thin-lens powers are first evaluated to match the required first-order quantities. Then the chromatic aberration coefficients of each thin lens are solved to satisfy the given system aberrations associated with the reference optical configuration. When the incident rays are changed, each thin lens will induce new chromatic aberrations according to the thin-lens formulae. The new system aberrations are obtained by adding those individual thin-lens aberrations together. The module can be directly applied to finite and infinite conjugates, focal and afocal lenses, as well as telecentric and non-telecentric lenses. Evaluations of the chromatic aberration variations of three different types of lenses are demonstrated.

A new method of measuring lens refractive index

A new clinical method for determining the refractive index of a lens is described.By measuring lens power in air and then immersing the lens in a liquid of known refractive index (n), it is possible to calculate the refractive index of the lens material (μ) by using the formula: where is the lens power determined in air is the lens power determined in the immersion liquid.The only materials required are a digital lensmeter and a wet cell for holding the lens in a liquid.The theoretical basis of the method is explained and a description given of the limitations. The optimal method of measuring different types of lenses is discussed. Sources of error include the thin lens theory behind the method, the use of a wetcell and the digital lensmeter. The theoretical accuracy of the results is given as 0.02 but 0.01 is usually achieved. In all cases, measuring the front vertex powers (FVP) yields a more accurate estimate of refractive index of a lens than measuring back vertex power (BVP). The author found half the lenses measured attained values within 0.005 of the known material index. This method is usually sufficiently accurate to isolate which lens material has been used in manufacturing and permit manufacturing spectacles that mimic the appearance of an earlier pair. Some suggestions for further refinement are given.

Refractive and geometric lens characterization through multi-wavelength digital speckle pattern interferometry

Physical parameters of different types of lenses were measured through digital speckle pattern interferometry (DSPI) using a multimode diode laser as light source. When such lasers emit two or more longitudinal modes simultaneously the speckle image of an object appears covered of contour fringes. By performing the quantitative fringe evaluation the radii of curvature as well as the refractive indexes of the lenses were determined. The fringe quantitative evaluation was carried out through the four- and the eight-stepping techniques and the branch-cut method was employed for phase unwrapping. With all these parameters the focal length was calculated. This whole-field multi-wavelength method does enable the characterization of spherical and aspherical lenses and of positive and negative ones as well.

Directly measuring the spatio-temporal electric field of focusing ultrashort pulses

We present the first technique for directly measuring (without assumptions) the spatio-temporal intensity and phase of a train of ultrashort pulses at and near a focus. Our method uses an experimentally simple and high-spectral resolution variant of spectral interferometry (SEA TADPOLE). To illustrate our technique, we measured the spatio-temporal electric field in and around the foci of several different types of lenses. To confirm our results, we also simulated these measurements by numerically propagating a pulse through each of the lenses used. From one set of measurements, we made a movie showing a focusing pulse with severe chromatic aberration.

Predicting the Optical Performance of Eyes Implanted with IOLs to Correct Spherical Aberration

To use powerful modeling techniques for predicting the optical performance of eyes implanted with different types of intraocular lenses (IOLs). This approach will allow performance of "virtual cataract surgery," with different IOL designs that can be used and physical parameters that may occur during actual surgery-in particular, in IOLs that correct spherical aberration. A computer model was developed to predict the optical performance of individual eyes after IOL implantation. The approach was validated in a group of patients with eyes implanted with different IOLs. In these patients, corneal wavefront aberrations were calculated from elevations provided by videokeratography. Ocular aberrations were measured with a high-dynamic range Hartmann-Shack wavefront sensor. Misalignments (IOL tilt and decentration) were estimated with a new instrument, based on recording Purkinje images. This model of particular corneal aberrations and IOL parameters (intrinsic optical design details plus geometric location data) was used to estimate the total ocular aberrations after surgery and to compared them with actual aberrations measured directly with the wavefront sensor. The aberrations of implanted eyes predicted by the individualized optical models were well correlated with the actual aberration measured in each subject. This result indicates that the approach is adequate in evaluating the actual optical performance of different types of lenses. The model allows a large number of "virtual" surgeries to be performed, to test the performance of current or future IOL designs. A "virtual surgery" approach was designed to predict the optical performance in pseudophakic eyes. In each subject, it was possible to obtain the eye's optical performance with a particular IOL and biometric data after surgery. Specifically, this modeling can be used to evaluate the tolerances to misalignments and depth of focus of IOLs correcting spherical aberration in actual eyes. This approach is quite powerful and is especially applicable to the study of current and future aberration-correction IOL designs.