Method Of Refractive Correction Research Articles

Perception and Barriers to Spectacle for Remedy to Refractive Eye Problems among Patients Accessing Refration at the Ophthalmology Units of Abubakar Tafawa Balewa University Teaching Hospital and Specialist Hospital Bauchi, Bauchi State, Nigeria

Background: Spectacles stands as the economical, effective and generally tolerable method of refractive errors correction. The research purpose is to appraise the perception of spectacle lens for remedy to refractive errors among patients accessing refraction at the Abubakar Tafawa Balewa University Teaching Hospital and Specialist Hospital Bauchi.  Methods: The study adopted descriptive survey research design; with convenient and purposive sampling techniques in participants’ selection. Three hundred and eighty-four (384) male and female patients, aged 18 to 80 years, accessing refraction at the Ophthalmology Units of the hospitals comprised the respondents; with average age of 46.0±15.4 years and 47.9% were females. Questionnaire generated through the literature review was adopted in accessing the participants’ demographics, perception and barriers to spectacles utilisation. Relationships between outcome variables were investigated using Pearson chi-square test at 95% confidence level and p-value < 0.05 was considered statistically significant.  Results: Great number of the respondents (80.0%) were of the perception that spectacle lens would worsen their vision, but the elderly age group (87.5%), secondary (66.7%) and tertiary (75.0%) educational levels disagreed. There was association between respondents’ educational level and perception of spectacles in the area of ‘spectacle inconveniences and would lead to blindness (X 2=66.79, p-value=0.0000).  Conclusion: Educational level and age played significant role in the respondents’ positive perception of spectacle lens for refractive errors’ correction. The study recommended patients counselling on the benefits of managing refractive errors with spectacles so as to eliminate associated misconceptions with its use.

Awareness and Knowledge About RefractiveSurgery Among Medical Students in Baghdad

Purpose: Refractive error represents a common eye disorder that can significantly impact an individual's visual function and overall well-being. There are several methods of correcting refractive errors and objective of this study was to assess the awareness of refractive surgery and the preferred methods of refractive error correction among medical students in Baghdad. Study Design: Cross sectional survey. Place and Duration of Study: University of Baghdad Al-Kindy College of Medicinefrom November 2022 to March 2023. Methods: Medical students from six Baghdad medical colleges with total sample size of 350 were included. Students who had undergone refractive surgeries and fifth and sixth year medical students were also excluded. Level of knowledge was categorized as; <50% (0-5) poor knowledge, 50-70% (6-8) moderate knowledge and >70% (9-12) good knowledge. Results: Among the students with refractive errors, 82% had knowledge about their refractive error. Forty percent had myopia, 12% had astigmatism, 15 % had myopia and astigmatism, 10% had hyperopia, 5% had hyperopia and astigmatism. Among them 57.8% were not willing to undergo refractive surgery due to fear of complications. Forty eight percent had poor knowledge,43.1% had moderate and only 8.26% had a good knowledge of refractive surgeries. The majority preferred eyeglasses (82.6%) followed by both eyeglasses and contact lenses. Conclusion: Students had good awareness about refractive surgery but their familiarity and knowledge about it remained poor because of complications. An overwhelming majority of students still preferred spectacles as the method for vision correction.

Laser interferometric detection of heat release rate perturbation field of acoustically perturbed laminar premixed flames

Laser interferometry, which was originally used to measure density perturbation, has been previously used to determine the heat release rate perturbation, which is a key factor in the analysis of combustion instability. However, its spatial accuracy is still unsatisfied. In the present work, an improved fringe Fourier analysis method is proposed to process the results obtained from the laser interferometry measurement, aiming to accurately determine the spatial distribution of flame heat release rate perturbation. The measurement of heat release rate perturbation was performed on a acoustic perturbed laminar premixed flame, with the burner outlet diameter of 8 mm. Interference patterns generated by two laser beams with a diameter of 70 mm were recorded at a frame rate of 6000 Hz. A spatial dependent fringe processing method, referred as the improved fringe Fourier analysis, was developed to demodulate the interference phase from the fringe patterns. The proper orthogonal decomposition analysis was performed on these results to analyze the component of interference signals. Validation of the present technique was conducted by comparing the heat release rate perturbation field resulting from the laser interferometric technique to those from the CH* chemiluminescence from the flame. Comparisons were performed both for the global and local values, and the low-frequency natural oscillation effects were analyzed. Finally, a refraction correction method based on background-oriented Schlieren is proposed to compensate the beam deflection caused by flame.

Refraction Correction Based on ATL03 Photon Parameter Tracking for Improving ICESat-2 Bathymetry Accuracy

The refraction phenomenon causes ICESat-2 nearshore bathymetry errors by deviating seafloor photons’ coordinates. A refraction correction method based on ATL03 photon parameter tracking was proposed to improve the ICESat-2 bathymetry accuracy. The method begins by searching for sea–air intersections using photon parameters. Instead of relying on mathematical operations, it uses logical relations to establish a relationship between the seafloor and the surface, which improves efficiency. Then, a refraction correction model is designed based on Snell’s law for different sea surface fluctuations. This model is clear and suitable for scholars new to refraction correction. The results show the effectiveness of the proposed method since the RMSE is reduced by 1.8842 m~5.2319 m compared with the raw data. Our method has better tolerance than other methods at different water depth ranges.

Application of Simple Refraction Correction Method for Shallow Coastal Bathymetric Mapping Based on UAV-Photogrammetry

Shallow coastal bathymetric data has an important role in various applications, especially in maritime and coastal management fields. Various survey techniques to produce such data have been carried out by several researchers, one technique that is cheap, covers the wide area, flexible, and produces high-resolution bathymetric data is UAV-photogrammetry. However, this technique is affected by refraction effects that cause the estimated depth of underwater objects to be shallower than fact, thus reducing the accuracy of the bathymetric model. Therefore, the objective of this study is to present a simple refraction correction method based on the Least-Square method. To test the reliability of the method, the accuracy of the model is compared with two other methods (without correction and using a correction factor = 1.34). In addition, the effectiveness of the method was also tested through its application in various survey conditions. Overall, the proposed method outperforms the two existing methods. It is also very effective in reducing the error value during high tide conditions by up to 70%. The height of the UAV does not significantly affect the accuracy of the correction model, so in this case it is recommended to use an altitude of 100 m for survey efficiency.

Comprehensive assessment of the anterior segment in refraction corrected OCT based on multitask learning.

Anterior segment diseases are among the leading causes of irreversible blindness. However, a method capable of recognizing all important anterior segment structures for clinical diagnosis is lacking. By sharing the knowledge learned from each task, we proposed a fully automated multitask deep learning method that allows for simultaneous segmentation and quantification of all major anterior segment structures, including the iris, lens, cornea, as well as implantable collamer lens (ICL) and intraocular lens (IOL), and meanwhile for landmark detection of scleral spur and iris root in anterior segment OCT (AS-OCT) images. In addition, we proposed a refraction correction method to correct for the true geometry of the anterior segment distorted by light refraction during OCT imaging. 1251 AS-OCT images from 180 patients were collected and were used to train and test the model. Experiments demonstrated that our proposed network was superior to state-of-the-art segmentation and landmark detection methods, and close agreement was achieved between manually and automatically computed clinical parameters associated with anterior chamber, pupil, iris, ICL, and IOL. Finally, as an example, we demonstrated how our proposed method can be applied to facilitate the clinical evaluation of cataract surgery.

Subjective Assessment of the Dry Eye Syndrome According to the OSDI Questionnaire in Patients Using Various Options for Correcting Ametropia

Purpose: to study the severity of dry eye symptoms in patients who wear contact lenses and in those who underwent laser keratomileusis a long period ago according to OSDI questionnaire.Methods. 88 patients with various refractive disorders were included in the study, there were 33 men and 55 women. Mean age was 30,11 y.o. All patients were divided into 3 groups according to method of refractive disorder correction. Groups were equal in age and gender. The first included 27 patients wearing soft contact lenses for more than 5 years. The second group contained 33 patients who didn’t use contact lenses. The third one included 32 patients who underwent refractive surgery (LASIK, Femto-LASIK) more than a year ago. Assessment of severity of dry eye symptoms was performed according to questionnaire data (patients’ subjective feelings), objective data was not taken into account. Survey was performed with the use of OSDI questionnaire.Results. According to the symptoms presented the incidence of dry eye syndrome was 73.91 % in patients of the first group and it was 56.25 % and 66.66 % in the second and third one, moreover, the prevalence of DES in each of the groups was higher among women and amounted to 94.11% in the first group; 63.63% — in the second and 61.11% — in the third group. Mean OSDI in the first group was 31.48 ± 22.17; and it was 18,83 ± 14,00 and 22,25 ± 15,53 in the second and third group respectively. The obtained data corresponded to moderate severity of dry eye syndrome in all groups. DES was more prevalent among women in each group.Conclusion. The prevalence of DES according to the severity of symptoms was 65.6 %, the severity of DES was predominantly moderate. There was definite connection of symptoms and such risk factors as female sex and contact lens wear. Despite the connection with underlying pathogenetic mechanisms, the spread and severity of dry eye symptoms in patients a year after refractive surgery were significantly lower compared to those who didn’t undergo any refractive surgical procedures.

ITERATIVE REFRACTION-CORRECTION METHOD ON MVS-SFM FOR SHALLOW STREAM BATHYMETRY

Abstract. Extracting accurate bathymetric information from clear, shallow waters in complex riverine environments can be challenging, but it is crucial for many applications, such as hydraulic modeling, ecological monitoring, and sediment transport analysis. Multi-view stereo photogrammetry (MVS-SfM) has emerged as a promising technique for acquiring high-resolution bathymetric data from aerial imagery. However, the accuracy of MVS-SfM can be affected by various factors, including water refraction, which can distort the depth measurements. In this study, iterative Dietrich’s refraction-correction method is tested for extracting bathymetry from MVS-SfM in a complex riverine environment. Moreover, we proposed a workflow for applying the method using raster data files, which can be more readily available than point clouds. It also compared the obtained results with previous applications and evaluated them using statistical indices and ratios. For this case study, the multicamera refraction method produces bathymetric datasets with accuracies of ~0.019% of the flying height and precisions of ~0.07% of the flying height. This study contributes to increased confidence in exploiting aerial imagery for bathymetric mapping in photogrammetric procedures under field conditions and can facilitate the management and conservation of clear water systems.

A Spatiotemporal Atmospheric Refraction Correction Method for Improving the Geolocation Accuracy of High-Resolution Remote Sensing Images

Atmospheric refraction is one of the most significant factors that affect the geolocation accuracy of high-resolution remote sensing images. However, most of the current atmospheric refraction correction methods based on empirical data neglect the spatiotemporal variation of pressure, temperature, and humidity of the atmosphere, inevitably resulting in poor geometric positioning accuracy. Therefore, in terms of the problems mentioned above, this study proposed a spatiotemporal atmospheric refraction correction method (SARCM) based on global measured data to avoid the uncertainty of traditional empirical models. Initially, the atmosphere was stratified into 42 layers according to their pressure property, and each layer was divided into 1,042,560 grid cells with intervals of 0.25 longitude and 0.25 latitude. Then, the atmospheric refractive index of each grid in the imaging region was accurately calculated using the high-precision Ciddor formula, and the result was interpolated using three splines. Subsequently, according to the rigorous geometric positioning model, the line-of-sight of each pixel and the viewing zenith angle outside the atmosphere in WGS84 were derived to provide input for atmospheric refraction correction. Finally, the coordinates of the ground control points were corrected with the calculated atmospheric refractive index and Snell’s law. The experimental results showed that the proposed SARCM could effectively improve the positioning accuracy of the image with a large viewing zenith angle, and especially, the improvement percentage for a viewing zenith angle of 34.2426° in the x-direction was 99.5%. Moreover, the atmospheric refraction correction result of the SARCM was better than that of the primary state-of-the-art methods.

Refraction Surface-Based Stellar Atmospheric Refraction Correction and Error Estimation for Terrestrial Star Tracker

Stellar atmospheric refraction imaging error, as the optical imaging variation of starlight before and after passing through Earth&#x2019;s atmosphere, is one of the key issues for terrestrial star trackers to obtain accurate attitude measurement results. To resolve the problem, a refraction surface-based stellar atmospheric refraction correction method is presented in this paper. Different from existing correction methods, a new atmospheric refraction feature, i.e., stellar atmospheric refraction surface, is proposed to represent the random irregular optical phenomena of starlight, and avoids the limitations of theoretical atmospheric models and empirical formulas. On the basis of the principles of &#x201C;collinear refraction surfaces&#x201D;, &#x201C;invariable refraction surface&#x201D;, the proposed model successfully realizes the accuracy atmospheric refraction correction by the sensor itself, without external atmospheric parameters. Then, by analyzing the error factors parallel and perpendicular to the atmospheric refraction surface, the atmospheric refraction correction error estimation model is established to forecast the attitude accuracy after correction. Numerical simulations and night sky experiments validate the reliability of our atmospheric refraction correction method and error estimation model. The average angular distance error of the test star tracker is reduced from <inline-formula> <tex-math notation="LaTeX">$31.1310''$ </tex-math></inline-formula> into <inline-formula> <tex-math notation="LaTeX">$1.7705''$ </tex-math></inline-formula>, which is significantly decreased by 94.31&#x0025;.

Attitude toward refractive error surgery and other correction methods: A cross-sectional study

BackgroundRefractive errors are the most common vision problem and prove to be a significant health issue. There are several methods for correction of refractive errors including spectacles, contact lenses and refractive surgery. Nowadays, the reliance on contact lenses and glasses is decreased by means of refractive eye surgery. Our study aimed to determine the awareness of refractive surgery among undergraduate medical students and their preferred method of refractive error correction. MethodThis was a cross-sectional study that was conducted among a sample size of 374 medical students at King Abdul-Aziz University Hospital, Jeddah, Saudi Arabia in June–August 2020. Data were collected through a questionnaire which consisted of 20 questions to assess the demographics, awareness about refractive surgery and preferred method of correction. The data were entered using Microsoft Excel 2016 and analyzed by SPSS version 21. ResultsOur results showed that 177 of participants had refractive errors. Most participants complained of myopia (66.7%) and the most preferred correction method was spectacles (45.8%). Among users of spectacles, 53.7% found the spectacles comfortable due to ease of use. Majority of the students (92.1%) were aware of refractive surgery and 73% of them were willing to undergo refractive surgery. Many obtained their information regarding these procedures from family and friends (55.1%). The remaining refused to undergo surgery and the primary reason was fear of the complications of the procedure (14.1%). ConclusionThough corrective refractive surgery is a commonly performed procedure, extensive knowledge regarding this correction method and its complications is poor among medical students. The results showed that the majority have heard of refractive surgery, however, fear of undergoing surgery was still present. We suggest that refractive error correction surgery be taught by physicians during Ophthalmology rotations so that knowledge may be gained from more reliable sources.

Accurate Refraction Correction—Assisted Bathymetric Inversion Using ICESat-2 and Multispectral Data

Shallow-water depth information is essential for ship navigation and fishery farming. However, the accurate acquisition of shallow-water depth has been a challenge for marine mapping. Combining Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) bathymetry data with multispectral data, satellite-derived bathymetry is a promising solution through which to obtain bathymetric information quickly and accurately. This study proposes a photon refraction correction method considering sea-surface undulations to address errors in the underwater photons obtained by the ICESat-2. First, the instantaneous sea surface and beam emission angle are integrated to determine the sea-surface incidence angle. Next, the distance of photon propagation in water is determined using sea-surface undulation and Snell’s law. Finally, position correction is performed through geometric relationships. The corrected photons were combined with the multispectral data for bathymetric inversion, and a bathymetric map of the Yongle Atoll area was obtained. A bathymetric chart was created using the corrected photons and the multispectral data in the Yongle Atoll. Comparing the results of different refraction correction methods with the data measured shows that the refraction correction method proposed in this paper can effectively correct bathymetry errors: the root mean square error is 1.48 m and the R2 is 0.86.

Refraction correction and coordinate displacement compensation in nearshore bathymetry using ICESat-2 lidar data and remote-sensing images.

In nearshore bathymetry based on the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), water refraction causes a position displacement of the seafloor signal photon, decreasing the bathymetric accuracy. A novel refraction-correction method is proposed for the ICESat-2. Based on the experimental results and statistical analysis, it is illustrated that the displacement in elevation direction reaches several meters at the relative depth. The displacement in the along- and cross-track directions is very small, ranging from millimeters to centimeters. Finally, the relationship of refraction displacements with various incident angles and water depths is analyzed in detail, revealing the nearshore bathymetry characteristics of ICESat-2.

Knowledge and Preference for Refractive Surgery and Preferred Methods of Refractive Correction among Patients with Significant Refractive Errors Attending Bharatpur Eye Hospital, Nepal

Background: Refractive errors are a major cause of defective vision in all age groups. Although contact lens and refractive surgery are popular, still spectacles are the traditional and most widely used method of optical correction. The main objective of the study was to determine the knowledge and preference for refractive surgery and preference for refractive correction.&#x0D; Materials and Methods: Questionnaire based study was conducted among 252 participants aged between 22-40 years with significant refractive errors (&gt;±1.00D) for a period of three months between June to August 2017. Participants who had prior refractive surgery and not willing to participate were excluded from the study.&#x0D; Results: One hundred and forty (55.6%) were males and majority (76.6%) of the participants were in the age range 22-30 years. Myopia (60%) was more prevalent followed by astigmatism (38%) and hypermetropia (2%) with refractive power between 1-3 D in 72.5% of participants. Only 61(24%) of the participants had knowledge about refractive surgery. Forty three percentages of them knew from their friends, internet was source of information for 36% and only 19% of them knew from eye care professionals. Majority (87.3%) preferred spectacles 4.8% preferred contact lens and only 8% preferred refractive surgery as methods of refractive correction. Only 44% showed willingness for refractive surgery when available at Bharatpur Eye Hospital. Participants with prior knowledge (p=0.002), higher refractive error and longer duration of glass wear (P=0.005) had more preference for refractive surgery.&#x0D; Conclusion: The knowledge, preference and willingness for refractive surgery were less with spectacle being the most preferred methods of refractive correction.

Validation of High-resolution and Simple River Monitoring Technique using UAV-SFM Method

This study tested the accuracy and precision of the UAV-SfM method, an automated photogrammetry technique called SfM (Structure from Motion) using multiple pictures taken by UAV (Unmanned Aerial Vehicle), in a section of Saba river, Yamaguchi, Japan. The method was applied in the submerged area as well as in the exposed area, taking into account the refraction at the water surface, for the first time in domestic rivers. When the resultant DEM (Digital Elevation Model) is considered as the map of riverbed elevation, the RMS (Root Mean Square) error and R2 (coefficient of determination) of UAV-SfM were 0.165 m and 0.93, respectively. In pixels with thick algae cover, large apparent overestimations reaching 0.351 m at maximum were observed because UAV-SfM actually measures the algae surface elevation, not the riverbed elevation. Error analyses also showed that the refraction correction method adopted in this study is working well in spite of its simplicity.

基于测角交汇的大气折射修正方法

基于测角交汇的大气折射修正方法

Phakic intraocular lens implantation in Keratoconus

AbstractPhakic intraocular lens implantation can be a highly predictable and successful method of refractive correction and functional visual rehabilitation in patients with grade II – III keratoconus who have a stable corneal shape and good spectacle corrected visual acuity. Effective refractive correction has been reported using several types of toric phakic IOLs in keratoconus and also for keratoconus patients with post‐keratoplasty ametropia. A four stage visual rehabilitation pathway for keratoconus has been described: gross shape correction with intracorneal ring segments followed by cross‐linking, toric phakic intraocular lens implantation, and then fine shape correction with topography‐guideded PRK as necessary. The aim of this presentation is to present an update on current indications, methods and outcomes of toric phakic intraocular lens implantation in keratoconus patients.

Refraction Correction of Airborne LiDAR Bathymetry Based on Sea Surface Profile and Ray Tracing

Water depth can be measured using airborne LiDAR bathymetry (ALB). However, when the green laser beam passes through the air–water interface, the sea surface slope greatly affects the laser propagation path, significantly influencing the accuracy of the measured seafloor topography. To reduce its influence, a refraction correction method at the air–water interface based on the sea surface profile and ray tracing is proposed. First, the 3-D sea surface profile is fit based on the least-squares criteria and the wave spectrum, using the laser point data reflected by the sea surface. Then, on the basis of the sea surface slope, the geolocation biases of the laser points are corrected by tracing every laser transmission path at the air–water interface. The developed method is used to correct the ALB data collected in the South China Sea, and verified by the topography data captured by a ship-borne multibeam echo sounder. Before the refraction correction, the mean absolute error (MAE) is 14.2 cm, and the root-mean-square error (RMSE) is 17.5 cm. After the refraction correction, the MAE and RMSE decrease to 7.2 and 8.3 cm, respectively. The developed method can effectively improve the bathymetric accuracy of the ALB data.

Cataract Surgery in Patients with Keratoconus: Pearls and Pitfalls.

Background:Keratoconus (KC) is a common ectatic disorder resulting in progressive corneal thinning and irregular astigmatism. It has been observed that patients affected by KC are more likely to develop lens opacities earlier compared to non-keratoconic patients.Objective:Intraocular lens (IOL) selection and refractive outcome prediction are among a number of factors that can make cataract surgery in keratoconic patients challenging. Accurate biometry is often difficult to obtain due to unreliable K measurements and lack of dedicated biometric formulae. The use of toric IOLs has also been investigated.Conclusions:Determining the stage of KC, pre-operative patient counselling and the preferred method of refractive correction are all crucial to obtain successful postoperative outcomes and good patient satisfaction. The use of toric IOLs can achieve good results only in selected low-grade keratoconic eyes.

A Simple and Empirical Refraction Correction Method for UAV-Based Shallow-Water Photogrammetry

A Simple and Empirical Refraction Correction Method for UAV-Based Shallow-Water Photogrammetry