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Rees, W. G., e R. E. Donovan. "Refraction correction for radio-echo sounding of large ice masses". Journal of Glaciology 38, n.º 129 (1992): 302–8. http://dx.doi.org/10.1017/s0022143000003713.
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AbstractThis paper presents a simple mathematical formula for correcting radio-echo-sounding data from an ice sheet or glacier for the effects of varying refractive index. The method requires some knowledge of the variation of refractive index with depth. In rare cases this may be known from direct measurement, but it can be estimated from the density profile. If even this is unknown, we show that the corrections can be estimated to an accuracy of about 3% of the depth to bubble close-off (i.e. to about ±12 m for dry-snow conditions), and that the size of the refraction correction for a glacier or ice sheet with a flat bed is typically 6–10 m under these conditions.
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Rees, W. G., e R. E. Donovan. "Refraction correction for radio-echo sounding of large ice masses". Journal of Glaciology 38, n.º 129 (1992): 302–8. http://dx.doi.org/10.3189/s0022143000003713.
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AbstractThis paper presents a simple mathematical formula for correcting radio-echo-sounding data from an ice sheet or glacier for the effects of varying refractive index. The method requires some knowledge of the variation of refractive index with depth. In rare cases this may be known from direct measurement, but it can be estimated from the density profile. If even this is unknown, we show that the corrections can be estimated to an accuracy of about 3% of the depth to bubble close-off (i.e. to about ±12 m for dry-snow conditions), and that the size of the refraction correction for a glacier or ice sheet with a flat bed is typically 6–10 m under these conditions.
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Wu, Zhen, Junzhou Huo, Haidong Zhang, Fan Yang, Shangqi Chen e Zhihao Feng. "Vision Measurement Method Based on Plate Glass Window Refraction Model in Tunnel Construction". Sensors 24, n.º 1 (22 de dezembro de 2023): 66. http://dx.doi.org/10.3390/s24010066.
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Due to the harsh environment of high humidity and dust in tunnel construction, the vision measurement system needs to be equipped with an explosion-proof glass protective cover. The refractive effect of the plate glass window invalidates the pinhole model. This paper proposes a comprehensive solution for addressing the issue of plane refraction. First, the imaging model for non-parallel plane refraction is established based on dynamic virtual focal length and the Rodriguez formula. Further, due to the failure of the epipolar constraint principle in binocular vision systems caused by plane refraction, this paper proposes the epipolar constraint model for independent refractive plane imaging. Finally, an independent refraction plane triangulation model is proposed to address the issue of triangulation failure caused by plane refraction. The RMSE of the depth of field errors in the independent refraction plane triangulation model is 2.9902 mm before correction and 0.3187 mm after correction. The RMSE of the positioning errors before and after correction are 3.5661 mm and 0.3465 mm, respectively.
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Ocansey, Stephen, Rufaida Amuda, Carl Halladay Abraham e Emmanuel Kwasi Abu. "Refractive error correction among urban and rural school children using two self-adjustable spectacles". BMJ Open Ophthalmology 8, n.º 1 (abril de 2023): e001202. http://dx.doi.org/10.1136/bmjophth-2022-001202.
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ObjectiveSelf-refracting spectacles (SRSs) have different optical and mechanical designs, which may affect the refractive outcome, depending on the experience of the end user. This study compared the performance of two SRS among children in Ghana.Methods and analysisA cross-sectional study of two Alvarez variable-focus SRS designs was conducted. A total of 167 children (mean age 13.6±1.6 years) identified as having refractive error were recruited from 2465 students who underwent screening. Subjects completed self-refraction using FocusSpecs, and Adlens, autorefraction and cycloplegic subjective refraction (CSR) (gold standard). Wilcoxon signed-rank test was used to compare visual outcomes and accuracy of refraction and graphically illustrated using Bland-Altman plots.ResultsEighty (47.9%) urban and 87 (52.1%) rural children were analysed and only about one-quarter 40 (24.0%) wore spectacles. The proportion who achieved visual acuity of ≥6/7.5 with FocusSpec, Adlens, autorefraction and CSR among urban schools were 92.6%, 92.4%, 60% and 92.6%, while those in rural schools were 81.6%, 86.2%, 54.0% and 95.4%, respectively. The mean±SD spherical equivalent errors for urban and rural schools using FocusSpec, Adlens and CSR were −1.05±0.61 D, –0.97±0.58 D and −0.78±0.53 D; and −0.47±0.51 D, –0.55±0.43 D and −0.27±0.11 D, respectively. The mean differences between the two self-refraction spectacles for urban and rural schools were not statistically different (p>0.00) but differed significantly when both were compared with the gold standard (CSR) (p<0.05).ConclusionBackground and refraction experience of school children did not significantly affect self-refraction.
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Nováček, Ladislav Viktor, Marie Němcová, Kristýna Sičová, Kateřina Tyx, Pavel Rozsíval, Jan Němčanský e Pavel Studený. "Simultaneous Presbyopia and Astigmatism Correction with a Novel Trifocal Toric Intraocular Lens—A One-Year Follow-Up". Journal of Clinical Medicine 11, n.º 14 (19 de julho de 2022): 4194. http://dx.doi.org/10.3390/jcm11144194.
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The current investigation evaluates the efficiency of the trifocal toric Liberty 677MTY intraocular lens (IOL) in correcting preoperative corneal astigmatism in cataract patients demanding spectacle independence. The retrospective evaluation included 28 eyes of 15 patients with preoperative corneal astigmatism of at least 1.0 Dioptre (D). All patients were followed up for one year postoperatively. Residual refractive errors and visual acuities at multiple distances were measured. Binocular visual acuity and contrast sensitivity defocus curves were plotted. Visual functions and patient satisfaction were assessed. The efficiency of astigmatism correction was determined using the vector analysis method. The mean spherical equivalent refraction (SEQ) improved from 2.72 ± 1.62 D to 0.10 ± 0.48 D. The cylindric refraction decreased from 1.18 ± 0.45 D to 0.16 ± 0.31 D. Vector analysis proved efficient astigmatism correction with a centroid of 0.10 ± 0.34 D at 161°. Ninety-two percent of eyes resulted within 0.5 D from the target refraction. Visual acuities were 0.1 logMAR or better from +1.0 to −3.5 D defocus values. Visual tasks could be performed without major difficulties. Our patients were highly satisfied. Refractive and visual outcomes with the investigated presbyopia-correcting toric IOL are predictable and the lens provides excellent trifocal vision.
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Mezad-Koursh, Daphna, Ari Leshno, Tomer Ziv-Baran e Chaim Stolovitch. "Refractive Changes Induced by Strabismus Corrective Surgery in Adults". Journal of Ophthalmology 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/2680204.
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Purpose. To investigate refractive changes after strabismus correction procedures among adults.Methods. Retrospective chart review of adult patients who had horizontal recti muscles surgery with preoperative and postoperative cycloplegic refraction measurements. The preoperative refraction was mathematically subtracted from the postoperative refraction, and the induced refractive changes were statistically analyzed. Vector analysis was used to examine the magnitude of the toric change. The proportion of clinically significant refractive change was evaluated as well.Results. Thirty-one eyes from 22 subjects met the criteria and were included in the final analysis. A significant postoperative refractive change of the spherical equivalent towards myopia and a change of the astigmatism in the with-the-rule direction were observed. In a subset of 9 cases a third cycloplegic refraction measurement demonstrated stable refraction compared to the 1-month postoperative measurement. In 10 cases of single eye surgery, significant refractive changes were observed only in the operated side when compared to the sound eye. The induced surgical refractive change was of clinical significance (≥0.5 D) in 11 eyes of 9 patients (40.9% of patients).Conclusions. Refractive changes are a significant side effect of horizontal strabismus corrective surgery among adults. Therefore, patients should be informed about it prior to surgery and should be rerefracted in the postoperative period.
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Gurmizov, Е. P., К. B. Pershin, N. F. Pashinova e А. Iu Tsygankov. "Keratorefractive Surgery for Residual Refractive Error Correction in Pseudophakic Patients". Ophthalmology in Russia 17, n.º 2 (23 de junho de 2020): 209–15. http://dx.doi.org/10.18008/1816-5095-2020-2-209-215.
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Purpose. Evaluation of the visual and refractive results of additional correction using LASIK and PRK methods in patients with residual refractive error after previous cataract surgery. Patients and methods. The prospective open study included 57 patients (79 eyes) who previously underwent cataract phacoemulsification (n = 37) or refractive lensectomy (n = 42) with various IOL models implantation (2012–2017). The average age of patients was 50.8 ± 13.9 (19–79) years. Operations LASIK (91.1 %) and PRK (8.9 %) were carried out according to standard methods. In 6 cases, femtosecond laser supported by laser correction. The target refraction ranged from –0.25 to 0.25 D in most (97.5 %) cases. The follow-up period ranged from 6 to 9 months. Results. The patients were divided into groups according to the type of residual refractive error (Group 1 — myopia, group II — emmetropia and group III — hyperopia). Statistically significant differences were determined for the species of previously implanted IOLs — in group II, the frequency of monofocal IOLs was significantly higher (p < 0.05). In group II, the values of the cylindrical component of refraction were significantly higher compared with groups I and III (p < 0.05). In group I, a significant (p < 0.05) decrease in the spherical component of refraction from –1.36 ± 0.92 to –0.2 ± 0.8 D was observed. In patients of group II, there was a slight increase in the spherical component of refraction from 0 ± 0.20 to 0.25 ± 0.29 D (p > 0.05). In group III, a significant (p < 0.05) decrease was observed in the spherical component of refraction from 1.27 ± 0.69 to 0.43 ± 0.49 D. When analyzing the cylindrical component of refraction in group I, its decline was noted from –0.69 ± 0.5 to –0.38 ± 0.46 D (p > 0.05). In group II, the largest decrease in the cylindrical component was observed from –1.6 ± 1.0 to 0.03 ± 1.10 Dptr (p < 0.01). In all the studied groups, a statistically significant (p < 0.05) increase in UCFVA was revealed in the postoperative period. Indicators K1 and K2 did not significantly change. Conclusion. The high efficiency of the correction using the LASIK, PRK and femtoLASIK methods on pseudophakic eyes with the achievement of the target refraction in most of the studied cases was shown. This method can be used as an alternative to spectacle and contact correction in patients with residual refractive error after cataract phacoemulsification and refractive lensectomy with IOL implantation.
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Chen, Kaijian, Zongli Hu, Jihan Zhou, Ting Yu, Jie Xu, Ji Bai e Jian Ye. "Vector Analysis of the Effects of FS-LASIK and Toric ICL for Moderate to High Astigmatism Correction". Journal of Ophthalmology 2018 (25 de julho de 2018): 1–6. http://dx.doi.org/10.1155/2018/6952710.
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Purpose. To estimate the treatment effectiveness of femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and Toric implantable collamer lens (Toric ICL) for moderate and high astigmatism via vector analysis.Materials and Methods. The study involved 44 eyes from 44 patients who had a preoperative refractive cylinder ≥1.0 diopters (D) and underwent bilateral FS-LASIK or Toric ICL surgery. The examinations included corrected distance visual acuity measurement and subjective refraction before and 3 months after surgery. The astigmatic changes were estimated using vector analysis.Results. No statistically significant differences were found in cylindrical refraction and percentage of spherical equivalent within 0 D, ±0.50 D, ±1.00 D, and ±1.50 D between the FS-LASIK and Toric ICL groups at 3 months after surgery. The parameters of the vector analysis included intended refractive correction, surgically induced refractive correction, error vector, correction ratio, error ratio, error of magnitude, and error of angle, with no significant differences between the groups. However, error ratio the of the off-axis correction in the FS-LASIK and Toric ICL groups was 4.11 ± 3.02 and 8.11 ± 3.82, respectively, and the difference was significant (t = −2.46,p=0.02).Conclusion. Both FS-LASIK and Toric ICL were effective for correcting moderate and high astigmatism, although Toric ICL might produce a larger error of angle than FS-LASIK when an off-axis correction occurs.
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Kasyanov, A. A. "Tactics of Two-Stage IOL Implantation in Difficult Refractive Cases". Ophthalmology in Russia 18, n.º 3 (1 de outubro de 2021): 415–21. http://dx.doi.org/10.18008/1816-5095-2021-3-415-421.
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In a number of complex refractive cases, the achievement of an accurate refractive result cannot be guaranteed. Simultaneous implantation of a toric or multifocal IOL for the correction of complex ametropias may be accompanied by a significant deviation from the target refraction. The tactics of two-stage implantation with the usage of an additional Sulcoflex IOL for the final correction of astigmatism and possible residual spherical ametropia allows achieving emmetropia. In our study, this method was used in 15 patients with difficult refractive cases. Toric, multifocal, and multifocal toric Sulcoflex IOL were used. Implantation of all Sulcoflex modifications was performed through a 2.4 mm temporal incision using wound assisted technology. In cases of high degree hypermetropia, preventive iridectomy was performed using a 23G vitrectome. The target refraction was achieved in the entire observation group. In the postoperative period, no significant level of ophthalmic hypertension was registered. No cases of introlens opacification, iridocyclitis, or rotational instability were registered either.The method of two-stage IOL implantation allows achieving the target refraction in difficult refractive situations with almost guaranteed accuracy. The calculation method provides good predictability of the refractive result. This technology significantly expands the indications for intraocular correction using toric and multifocal IOL, as well as the limits of correction of high degree astigmatism. Our Sulcoflex IOL implantation experience has shown their high efficiency and safety.
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Ejukonemu, Barbie O. M. "Refracting The Diseased Eye". Bayero Journal of Nursing and Health Care 3, n.º 2 (11 de setembro de 2022): 893–97. http://dx.doi.org/10.4314/bjnhc.v3i2.9.
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Refractive error refers to ocular refractive status where images of objects of regard do not fall on the retina in a relaxed eye - the ametropic eye. Thus, objects are perceived as blur. Refractive error is an aberration in an otherwise normal physiological phenomenon and not a disease. Uncorrected refractive errors are the second most causes of blindness after cataract and the cause of almost half of visual impairment. Clinical refraction is a careful scientific procedure employed to correct refractive error. Given that refractive error is the most common reason patients present to the eye care practitioner, a lot of attention must be given to refraction. When an irreversible eye disease co-exist with refractive error, then correction of refractive error under this circumstance; refracting the diseased eye (RDE) become very challenging and painstaking. There will be likelihood of irregularities in the transparent refractive surfaces of the eye due to disease or surgery which make refraction difficult both for the patient and the examiner. Personal clinical experience of the author who is a low vision consultant and review of related literature from textbooks and journals are brought to bear in this article. This paper is a review of the RDE algorithm with delineation of these steps to enable an effective refractive endpoint for the eye with disease. The paper will enable young Optometrists to deal with refractive error masquerading irreversible eye disease. It is also an essential reading for the low vision Optometrist in mastering the art and science of low vision refraction.
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Abelman, Herven, e Shirley Abelman. "Tolerance and Nature of Residual Refraction in Symmetric Power Space as Principal Lens Powers and Meridians Change". Computational and Mathematical Methods in Medicine 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/492383.
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Unacceptable principal powers in well-centred lenses may require a toric over-refraction which differs in nature from the one where correct powers have misplaced meridians. This paper calculates residual (over) refractions and their natures. The magnitude of the power of the over-refraction serves as a general, reliable, real scalar criterion for acceptance or tolerance of lenses whose surface relative curvatures change or whose meridians are rotated and cause powers to differ. Principal powers and meridians of lenses are analogous to eigenvalues and eigenvectors of symmetric matrices, which facilitates the calculation of powers and their residuals. Geometric paths in symmetric power space link intended refractive correction and these carefully chosen, undue refractive corrections. Principal meridians alone vary along an arc of a circle centred at the origin and corresponding powers vary autonomously along select diameters of that circle in symmetric power space. Depending on the path of the power change, residual lenses different from their prescription in principal powers and meridians are pure cross-cylindrical or spherocylindrical in nature. The location of residual power in symmetric dioptric power space and its optical cross-representation characterize the lens that must be added to the compensation to attain the power in the prescription.
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Lambert, Selina E., e Christopher E. Parrish. "Refraction Correction for Spectrally Derived Bathymetry Using UAS Imagery". Remote Sensing 15, n.º 14 (21 de julho de 2023): 3635. http://dx.doi.org/10.3390/rs15143635.
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Spectrally derived bathymetry (SDB) algorithms are rapidly gaining in acceptance and widespread use for nearshore bathymetric mapping. In the past, refraction correction could generally be ignored in SDB, due to the relatively small fields of view (FOVs) of satellite sensors, and the fact that such corrections were typically small in relation to the uncertainties in the output bathymetry. However, the validity of ignoring refraction correction in SDB is now called into question, due to the ever-improving accuracies of SDB, the desire to use the data in nautical charting workflows, and the application of SDB algorithms to airborne cameras with wide FOVs. This study tests the hypothesis that refraction correction leads to a statistically significant improvement in the accuracy of SDB using uncrewed aircraft system (UAS) imagery. A straightforward procedure for SDB refraction correction, implemented as a modification to the well-known Stumpf algorithm, is presented and applied to imagery collected from a commercially available UAS in two study sites in the Florida Keys, U.S.A. The results show that the refraction correction produces a statistically significant improvement in accuracy, with a reduction in bias of 46–75%, a reduction in RMSE of 3–11 cm, and error distributions closer to Gaussian.
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Joseph, Sanil, Balagiri Sundar, Vinitha L. Rashme, Soundarya Venkatachalam, Joshua R. Ehrlich e Thulasiraj Ravilla. "Accuracy of a low-cost, portable, refractive error estimation device: Results of a diagnostic accuracy trial". PLOS ONE 17, n.º 8 (3 de agosto de 2022): e0272451. http://dx.doi.org/10.1371/journal.pone.0272451.
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Purpose To assess the accuracy of refraction measurements by ClickCheckTM compared with the standard practice of subjective refraction at a tertiary level eye hospital. Design Diagnostic accuracy trial. Methods All participants, recruited consecutively, underwent auto-refraction (AR) and subjective refraction (SR) followed by refraction measurement using ClickCheckTM (CR) by a trained research assistant. Eyeglass prescriptions generated using ClickCheckTM and the resulting visual acuity (VA) was compared to SR for accuracy. Inter-rater reliability and agreement were determined using Intra-class correlation and Bland Altman analysis respectively. Results The 1,079 participants enrolled had a mean (SD) age of 39.02 (17.94) years and 56% were women. Overall, 45.3% of the participants had refractive error greater than ±0.5D. The mean (SD) spherical corrections were -0.66D (1.85) and -0.89D (2.20) in SR and CR respectively. There was high level of agreement between the spherical power measured using SR and CR (ICC: 0.940 (95% CI: 0.933 to 0.947). For the assessment of cylindrical correction, there was moderate level of agreement between SR and CR (ICC: 0.493 (0.100 to 0.715). There was moderate level of agreement between the VA measurements performed by using corrections from SR and CR (ICC: 0.577 (95% CI: 0.521–0.628). The subgroup analysis based on the age categories also showed high level of agreement for spherical corrections between the two approaches (ICC: 0.900). Bland Altman analysis showed good agreement for spherical corrections between SR and CR (Mean difference: 0.224D; 95% LoA: -1.647 D to 2.096 D) without evidence of measurement bias. Conclusions There was a high level of agreement for spherical power measurement between CR and SR. However, improvements are needed in order to accurately assess the cylindrical power. Being a portable, low-cost and easy-to-use refraction device, ClickCheckTM can be used for first level assessment of refractive errors, thereby enhancing the efficiency of refractive services, especially in low- and-middle-income countries.
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Peng, Xiaohong, Wenwen Huang, Xiaoyan Li, Lin Yang e Fansheng Chen. "A Spatiotemporal Atmospheric Refraction Correction Method for Improving the Geolocation Accuracy of High-Resolution Remote Sensing Images". Remote Sensing 14, n.º 21 (25 de outubro de 2022): 5344. http://dx.doi.org/10.3390/rs14215344.
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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.
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Hardiyanti, Disti, e Fatimah Dyah NA. "Correlation between Autorefractometry and Retinoscopy with Subjective Refraction in Refractive Error Patients at Dr Kariadi Hospital, Semarang". Ophthalmologica Indonesiana 47, n.º 2 (30 de agosto de 2021): 46–51. http://dx.doi.org/10.35749/journal.v47i2.100302.
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Objective: Refractive errors are a major cause of visual impairment in Indonesia. In Dr. Kariadi Hospital Semarang, it is amongst the top five diagnoses within the ophthalmology department. Therefore, objective refraction is imperative for the management of refractive errors. These examinations include autorefractometry and retinoscopy. Despite the fact that retinoscopy is the gold standard, autorefractometry is more desirable as it is more sophisticated, swift, and convenient. Autorefractometry's results are expected to match results from subjective correction, therefore, reduce examination time as patient visits increase. This study aims to determine the correlation between autorefractometry and retinoscopy examination with subjective refraction.
Methods: The study design was cross-sectional. The study was conducted on 34 eyes with refractive error taken by consecutive sampling. The subjects had to meet inclusion and exclusion criteria. All subjects underwent visual acuity examination, refractive correction by autorefractometry, retinoscopy, and subjective refraction. All data were processed by using computerized formulations.
Results: Based on the demographics there were 61.8% of women and 38.2% of men with an average age of 29.7 + 9. The results of this study showed a strong correlation between autorefractometry and subjective refraction. Furthermore, retinoscopy shows a strong correlation with subjective refraction as well.
Conclusion: This study shows retinoscopy is superior to autorefractometry. However, autorefractometry is a viable replacement for patients in Dr. Kariadi Hospital Semarang.
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Vshivkova, O. V., e S. Y. Reshetilo. "Сombined method of determining vertical refraction correction for electronic tacheometry". Geodesy and Cartography 953, n.º 11 (20 de dezembro de 2019): 15–21. http://dx.doi.org/10.22389/0016-7126-2019-953-11-15-21.
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This article deals with issue of the vertical refraction effect on the results of trigonometric levelling. The possible affecting the results of EDM levelling by refraction is evaluated. A brief review of methods of correcting the refraction influence is executed. The conclusion is drawn that the accuracy capabilities of refraction correction methods lag behind the level of development of geodetic equipment. As a possible solution of the refraction account problem, a combined method is proposed. This way is based on a geodetic model of the atmosphere and complex gradient meteorological and geodetic measurements. The results of these measurements are the data for calculating the model parameters. The combined use of meteorological and geodetic measurements at several levels enables minimizing the volume of additional measurements, provides the determination of the refraction angle with geodetic accuracy. The results of field experiment are presented. They proved the actuality of the algorithm implementing the combined method of vertical refraction correction calculating, and made an opportunity of working out the proposed way methodically.
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Antwi-Adjei, Ellen Konadu, Emmanuel Owusu, Emmanuel Kobia-Acquah, Emmanuella Esi Dadzie, Emmanuel Anarfi e Seth Wanye. "Evaluation of postoperative refractive error correction after cataract surgery". PLOS ONE 16, n.º 6 (17 de junho de 2021): e0252787. http://dx.doi.org/10.1371/journal.pone.0252787.
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Suboptimal cataract surgery outcomes remain a challenge in most developing countries. In Ghana, about 2 million people have been reported to be blind due to cataract with about 20% new cases being recorded yearly. The aim of this study was to evaluate postoperative correction of refractive errors after cataract surgery in a selected eye hospital in Ashanti Region, Ghana. This was a retrospective study where medical records of patients (aged 40–100) who reported to an eye hospital in Ghana from 2013–2018 were reviewed. Included in the study were patients aged ≥40 years and patients with complete records. Data on patient demographics, type of surgery, intra-ocular lens (PCIOL) power, availability of biometry, postoperative refraction outcomes, pre- and postoperative visual acuity were analyzed. Data of two hundred and thirteen eyes of 190 patients who met the inclusion criteria were analyzed. Descriptive analysis and Chi-square test were carried out to determine the mean, median, standard deviation and relevant associations. The mean ± SD age was 67.21±12.2 years (51.2% were females). Small Incision Cataract Surgery (99.5%) with 100% IOL implants was the main cataract surgery procedure in this study. Pre-operative biometry was performed for 38.9% of all patients on their first eye surgery and 41.5% for second eye surgeries. About 71% eyes in this study were blind (presenting VA<3/60) before surgery; 40.4% had post-operative VA <3/60. Pre-existing ocular comorbidities discovered post- surgery, attributed to suboptimal visual outcomes. More than half (55.3%) of patients did not undergo postoperative refraction due to loss to follow-up. Year of surgery (p = .017), follow up visits< 2months (p < .0001) and discovered comorbidity post-surgery (p = .035) were the factors significantly associated with postoperative refraction. Myopia and compound myopic astigmatism were the dominant refractive error outcomes. The timing of post-operative refraction had a significant effect on postoperative refraction done. These findings indicate a clinically meaningful significance between completion of postoperative care and postoperative refraction done. Consequently, with settings in most developing countries, where less biometry is done, it is appropriate that post-operative refractive services are encouraged and done earlier to enhance the patients’ expectations while increasing cataract surgery patronage.
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Laver, A. B., S. I. Rychkova e N. I. Kurysheva. "Refraction dynamics in schoolchildren with congenital partial atrophy of the optic nerve over a ten-year observation period". EYE GLAZ 26, n.º 2 (6 de julho de 2024): 81–89. http://dx.doi.org/10.33791/2222-4408-2024-2-81-89.
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Introduction. Optic nerve atrophy is a degenerative condition and a prevalent cause of visual impairment, including in children. Data on refractogenesis in schoolchildren with partial atrophy of the optic nerve (PAON) are scarce, with existing literature focusing primarily on the correction of low vision associated with this disorder. Purpose: to assess the refraction dynamics in schoolchildren with congenital PAON over a ten-year observation period.Materials and methods. We conducted a retrospective analysis of refraction changes over a decade among three groups: 1) 47 schoolchildren with PAON, 2) 49 schoolchildren with ametropia without PAON, and 3) 49 schoolchildren without any ophthalmopathology.Results. All groups exhibited a trend towards myopization (р < 0.001). In groups with myopic and emmetropic refractions (without ophthalmopathology at the start), either the emergence or an increase in myopic refraction was noted. In hypermetropic children, a gradual decrease towards emmetropic refraction or a shift to myopic refraction was observed. For myopic schoolchildren using contact lenses and perifocal glasses from the ages of 11–13, myopia progression stabilized, particularly with perifocal optical correction (р < 0.01). Despite refractive changes during the school years, regular courses of functional treatment and accommodation training led to a slight improvement in visual acuity in PAON patients (by an average of 0.05 ± 0.01 (p = 0.001) in myopes and 0.06 ± 0.01 (р < 0.001) in hypermetropes) and a significant increase in visual acuity in children with normal fundus ametropia (by an average of 0.14 ± 0.02 (р < 0.001) in myopes and 0.18 ± 0.02 (р < 0.001) in hypermetropes).Conclusion. The ten-year observation demonstrates a myopization trend in all groups of schoolchildren, which holds particular relevance for those with PAON due to their inherently lower visual acuity. An optimal optical correction strategy, employing modern myopia control measures in tandem with regular functional treatment and accommodation training, is essential for a health-preserving educational approach in schoolchildren with PAON.
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Dayyani, Raziye, Ebrahim Jafarzadehpur, Ramin Salouti e Ali Mirzajani. "Estimation of final cylindrical spectacle correction by Pentacam". Function and Disability Journal 3, n.º 1 (28 de outubro de 2020): 61–68. http://dx.doi.org/10.32598/fdj.3.7.
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Background and Objectives: Keratoconus is a non-inflammatory asymmetric corneal degenerative disease characterized by the steepening and distortion of the cornea. In this disease, irregular astigmatism makes the subjective refraction difficult. Using the Pentacam, we aimed to determine the corrective astigmatism of the spectacle. Methods: The subjective refraction and Pentacam imaging were performed for 317 keratoconic patients who referred to the Salouti Eye Clinic, Shiraz, Iran. Then, the astigmatism values obtained with subjective refraction were compared with the values of anterior and posterior corneal surface astigmatism obtained with the Pentacam imaging. Results: The mean age of 317 keratoconic patients was 29.81 years (range: 15 to 45 years). The minimum, maximum, and average astigmatism of the corneal front surface were 0.3, 16.8, and 3.21 diopters, respectively. Also, the minimum, maximum, and average astigmatism of the corneal back surface were 0, 2.8, and 0.67 diopters, respectively. Moreover, the P value was lower than 0.001 in the regression analysis of the subjective refraction for both the power and axis of the cylinder. Conclusion: The regression formulas obtained in this study can accurately (with a probability of 99%) predict refractive astigmatism, using corneal astigmatism.
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Haradhan chowdhury, Partha, e Brinda haren shah. "OPTICAL CORRECTION AND UTILIZATION OF LOW VISION DEVICES IN MACULAR HOLE". EPH - International Journal of Medical and Health Science 4, n.º 1 (1 de janeiro de 2018): 1–4. http://dx.doi.org/10.53555/eijmhs.v4i1.10.
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PURPOSE: To analyze optical correction and utilization of low vision devices in cases of macular hole.
METHODOLOGY: Prospective cross sectional study was performed at tertiary eye care centers within the period of 2.5 years. Screening was done and subjects were taken to tertiary eye care centers for further evaluation. Subjects with macular hole were included and visual functions along with slit lamp evaluation and fundus evaluation were performed. In refraction, best visual acuity is achieved with stenopaeic slit refraction. Low vision aids were given and subjects were trained to use it. Follow up was taken after 3 months and analyzed which device is used maximum by the subjects having low vision. Data was analyzed using SPSS software version 20.
RESULTS: 46 subjects were enrolled with the mean age group of 64.8 years. 63% subjects were male and 37% were females. Among prescribed devices, 88% of subjects were using spectacles given by stenopaeic slit refraction and 79% were using See TV for distance. For near, 91% of subjects reported using dome magnifier of variable power with extra illumination prescribed as per the need. This should be taken into consideration when refracting and prescribing low vision devices in cases of macular hole.
CONCLUSION: In cases of macular hole, refractive correction should be done with stenopaeic slit. Spectacles and See TV (2x) should be prescribed for distance and dome magnifier of variable power as per need should be prescribed for near.
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Applegate, Ray, David Atchison, Arthur Bradley, Adrian Bruce, Michael Collins, Jason Marsack, Scott Read, Larry N. Thibos e Geunyoung Yoon. "Wavefront Refraction and Correction". Optometry and Vision Science 91, n.º 10 (outubro de 2014): 1154–55. http://dx.doi.org/10.1097/opx.0000000000000373.
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Yingmei, Jiang, Jin Tao, Yang Xueqi, Dai Xiaoli, Jin Ri, Xu Huancai e Wang Xiuying. "An Analysis on the Change Rule of Eyeball's Biological Parameters of Different Types in the Refraction State and Vision Before and After Refraction". Journal of Medical Imaging and Health Informatics 8, n.º 9 (1 de dezembro de 2018): 1881–85. http://dx.doi.org/10.1166/jmihi.2018.2532.
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The ametropia is the most widespread eye disease for the humans. Wherein, the myopia is the commonest ophthalmological reason influencing the distant vision. The excimer laser corneal refractive surgery has always been an operation mode most widely used in myopic correction operations for a number of years. The laser assisted in-situ keratomi (LASIK) mainly transforms the frontal surface appearance of the cornea to change the corneal refraction power, and its correction effect is influenced by a great many factors such as regression and hydration of cornea. Thus, a lot of surgeons would combine own experience in conducting LASIK myopic correction. The myopic regression would affect the foreseeability, operation effect and stability of corneal refractive surgery, which results in reduction of the patients' visual quality in turn. The pathogenesis still needs further study. The change of lens thickness does not only lead to change in depth of central anterior chamber, but also would cause the change in refractive power of lens, thereby influencing the whole dioptric system of the eyeball. The previous research on postoperative regression was mostly focused on the corneal refraction, while few efforts were put in the changes of lens thickness and refractive power after LASIK.
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Belikova, E. I., e T. V. Perova. "On Classification and Application of Monovision Technique for Excimer Laser Correction and on Possible of Preliminary Target Refraction Modeling in Patients with Primary Myopia, Astigmatism, Anisometropia and Presbyopia". Ophthalmology in Russia 17, n.º 4 (27 de dezembro de 2020): 739–45. http://dx.doi.org/10.18008/1816-5095-2020-4-739-745.
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The combination of such refractive errors as high and medium astigmatism with anisometropia and presbyopia considerably reduces patients’ standard of living, first of all because methods of the correction stated are very limited. Spectacle correction is, as a rule, extremely uncomfortable or impossible in case of an anisometropia of more than 2.0 dioptres and a high degree of astigmatism; opportunities of contact lenses correction are limited in case of an astigmatism of more than 2.5 dioptres. Therefore these patients are often deprived of adequate visual rehabilitation and prefer not to use means of optical vision correction at all which considerably lowers their quality of life and can be the reason of asthenopia, violation of binocular vision and decrease in fusional reserves. This problem is aggravated with the development of a presbyopia when patients get older. The first manifestations of it reveal themselves in such patients earlier than in emmetrops, their age-mates. Excimer laser technology development has made it possible to help a large number of patients with the most severe refractive disorders, but these techniques still have significant limitations in patients with presbyopia, especially in case of a patient’s strong need for keen eyesight at a close distance. In addition, these patients require a particularly careful examination and preliminary modeling of target refraction at the planning stage of a surgical intervention, for which we use soft contact lenses in our practice. Target refraction modeling with spectacle lenses does not always allow to adequately predict the patient satisfaction with the results of correction. We consider the method of target refraction modeling using soft contact lenses to be the most accurate for this objective; it is widely used in our clinic. This technique is especially effective in patients with presbyopia, who are planning excimer laser correction of the most common types of refractive errors. The article presents a clinical case of binocular excimer laser correction of a high and medium degree compound myopic astigmatism in a patient with anisometropia and presbyopia, which was performed in two stages using LASIK (Custom Q) technology after the preliminary target refraction modeling with the use of soft contact lenses.
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Yu, Hao, Wen Shan Luo, Yao Chen e Jing Juan An. "Research and Applicability of Refraction Static Correction and Tomographic Inversion Static Correction". Advanced Materials Research 616-618 (dezembro de 2012): 213–16. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.213.
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Refraction static correction and tomographic inversion static correction are commonly used in seismic data processing. It is often believed that the effect of tomographic inversion static correction is better than the effect of refraction static correction. But it is not true. This paper summarized the applicable conditions, advantages and disadvantages of these two methods. In low mountains areas, the effect of tomographic inversion static correction is better than the effect of refraction static correction. However, in loess tableland areas, the effect of refraction static correction is almost the same as the effect of tomographic inversion static correction. It can’t reflect the advantages of tomographic inversion static correction. All of the above is proved from models and sections. So each technique must meet its applicable conditions to reflect its superiorities. Integrated application of static correction methods is effective to solve the complex surface statics problems.
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Bergmann, Peter, Artem Kashubin, Monika Ivandic, Stefan Lüth e Christopher Juhlin. "Time-lapse difference static correction using prestack crosscorrelations: 4D seismic image enhancement case from Ketzin". GEOPHYSICS 79, n.º 6 (1 de novembro de 2014): B243—B252. http://dx.doi.org/10.1190/geo2013-0422.1.
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A method for static correction of time-lapse differences in reflection arrival times of time-lapse prestack seismic data is presented. These arrival-time differences are typically caused by changes in the near-surface velocities between the acquisitions and had a detrimental impact on time-lapse seismic imaging. Trace-to-trace time shifts of the data sets from different vintages are determined by crosscorrelations. The time shifts are decomposed in a surface-consistent manner, which yields static corrections that tie the repeat data to the baseline data. Hence, this approach implies that new refraction static corrections for the repeat data sets are unnecessary. The approach is demonstrated on a 4D seismic data set from the Ketzin [Formula: see text] pilot storage site, Germany, and is compared with the result of an initial processing that was based on separate refraction static corrections. It is shown that the time-lapse difference static correction approach reduces 4D noise more effectively than separate refraction static corrections and is significantly less labor intensive.
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Adhikari, Bishwa Nath, Pramod Sharma Gautam, Shishu Upadhyay e Uday Chandra Prakash. "Accuracy of GRK-2200T Auto-refkeratometer in Subjective Acceptance for Refractive Errors". Birat Journal of Health Sciences 4, n.º 1 (3 de maio de 2019): 645–48. http://dx.doi.org/10.3126/bjhs.v4i1.23939.
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Introduction: Globally, the most common cause for diminution of vision is refractive errors and the number of patients with refractive errors is increasing day by day. The Auto-refraction (AR) is quick and patient friendly procedure as compared to retinoscopy and subjective refraction in finding out refractive errors. Hence, the accuracy of Auto-refractometer in terms of subjective acceptance (SA) should be taken into account before prescribing optical correction based on findings of that particular model of Auto-refractometer. So, this study is directed towards analysis of the accuracy of GRK-2200T Auto-retieratometer in terms of acceptance by comparing findings of AR with that of SC.
Objectives: The aim of this study was to assess the refractive status of patient's eyes using auto refractometer (GRK-2200T auto-retierato meter) and to estimate the agreement of it in terms of accuracy in acceptance of subjective correction by the patient.
Methodology: A hospital based prospective comparative study conducted on 226 eyes of 113 patients who visited out-patient department (OPD) of Ophthalmology at Nobel Medical College and Teaching Hospital (NoMCTH), Biratnagar diagnosed with Myopia, Hyperopia and Astigmatism. Duration of study was 4 months from 2nd October, 2018 to 2nd February, 2019. All data thus collected was subjected to statistical analysis by using SPSS version 22.
Result The mean age of the study subjects was 26.91±7.79 years with male to female ratio of 0.47. When spherical power, cylindrical power and the axis are taken into consideration together, only 13.3% of the total tested eyes subjectively accepted the AR values unchanged. On subjective correction, 32.7% of the tested eyes accepted spherical power while 46.5% accepted cylindrical power and 50.9% accepted axis of AR unchanged. About 52.2% of the total eyes examined fall within the deviation of spherical equivalent (SE) of ±o.25D and up to 67.3% of them fall within the deviation of ±o.50D.
Conclusion The auto refraction by GRK-2200T auto-retieratometer was found to be satisfactory for a preliminary refraction but not satisfactory as substitutes for conventional subjective refraction. However, auto refraction values obtained by GRK-2200T auto-retieratometer could be important in order to accurately prescribe the cylindrical power as well as its axis than the spherical component.
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Рогожникова, Elena Rogozhnikova, Селиверстова, Nataliya Seliverstova, Розанова e Olga Rozanova. "EVALUATION OF CLINICAL AND FUNCTIONAL OUTCOME OF MULTIFOCAL CORRECTION BY CONTACT LENS IN PATIENTS WITH PRESBYOPIA AND MYOPIA REFRACTION". Бюллетень Восточно-Сибирского научного центра Сибирского отделения Российской академии медицинских наук 1, n.º 6 (20 de dezembro de 2016): 103–7. http://dx.doi.org/10.12737/23788.
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The aim of the study was to evaluate the effectiveness of multifocal contact lens correction in patients with presbyopia and myopic refractive error. The study involved 45patients with myopia ranging in age from 43 to 56years in conditions of habitual monofocal contact lens correction, a month after the selection and wearing multifocal contact lenses. Contact correction was carried out according to standard procedures taking into account the accuracy of contact lens fitting, with carrying out functional tests for the “dry eye” syndrome and evaluation of corneal epithelial thickness (Optovue, USA). The as-sessment of the following parameters of visual perception was made: far, near and middle distance (monocular and binocular) visual acuity, the spatial contrast sensitivity, stereovision (I & II Lang test), the area of binocular interaction field (binarymeter), the quality of vision (VF-14 test ). The use of multifocal contact lenses for the correction of presbyopia with the initial myopic refraction ensures high functional results at different distances. Patients with a myopic refraction, previously used contact lenses, easy pass to multifocal correction option. The greatest satisfaction by achieved vision noted in those patients who had achieved refraction (–)0.5diopters. In the selection of contact lenses in older patients the thickness of the corneal epithelium and tear film validity must be taken into account.
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Liu, Kun, Zhigang Yuan, Chen Zhou, Qinglin Zhu, Haining Wang, Dongsheng Sheng e Xiang Dong. "Integrated High-Accuracy Correction Technology of Radio-Wave Refraction for Deep-Space (High-Orbit) Targets". Atmosphere 12, n.º 9 (7 de setembro de 2021): 1151. http://dx.doi.org/10.3390/atmos12091151.
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The radio-wave refraction error caused by the troposphere and ionosphere badly affects accuracy in terms of the navigation, positioning, measurement, and control of a target; it is the main source of errors in high-accuracy measurement and control systems. The high-accuracy technology needed for radio-wave refraction error correction (mainly in the troposphere and ionosphere) has been the focus of research for a long time. At present, the correction methods used for radio-wave refraction errors have a low accuracy. For an S-band radio-wave signal, the accuracy of refraction error correction can generally only reach m-level (elevation angle of 15° and above), and thus has difficulty meeting the requirements of dm-level accuracy refraction error correction for deep-space and high-orbit targets. To improve the accuracy of radio-wave refraction error correction for deep-space and high-orbit targets, a novel correction method for tropospheric and ionospheric range error due to refraction is proposed in this study, on the basis of the measured data from a water vapor radiometer and dual-frequency Global Navigation Satellite System (GNSS). The comprehensive calibration test is conducted in combination with the Chinese Area Positioning System (CAPS) in Kunming. Results show that this method can effectively correct the range error due to refraction that is caused by the troposphere and ionosphere. For an S-band radio-wave signal, the accuracy of refraction error correction can reach dm-level accuracy (elevation angle of 15° and above), which is 50% higher than that achieved with traditional methods. This work provides an effective support system for major projects, such as lunar exploration and Mars exploration.
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Xiao, Ying, e Yu Hua Dong. "Empirical Method of Atmospheric Refraction Error Correction in Optical Low-Level Measuring". Advanced Materials Research 108-111 (maio de 2010): 608–12. http://dx.doi.org/10.4028/www.scientific.net/amr.108-111.608.
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This paper proposed a empirical method of atmospheric refraction error correction in optical low-level measuring. The experience attenuation coefficient was derived by using the data of previous tests, then it solved the problem of atmospheric refraction error correction under the condition does not have a sounding measurements. At the same time, this paper deduced the empirical formula of atmospheric refraction error correction in low-level measuring, using the empirical formula of atmospheric refraction error correction can overcome the stationary point problem in the traditional method when computing for the negative to positive angle(< ). The effectiveness was verified by the results of test data processing.
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Pershin, Kirill B. "The surgery correction of presbyopia: the modern possibilities". Medical Journal of the Russian Federation 22, n.º 3 (15 de junho de 2016): 146–52. http://dx.doi.org/10.18821/0869-2106-2016-22-3-146-152.
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The article presents review of actual publications' data concerning surgical correction of presbyopia. The data is presented related to social significance of presbyopia alongside with other disorders of refraction. The techniques applying monovision include thermokeratoplasty and such its modification as laser and radio-frequency thermokeratoplasty. All of them have number of deficiencies. The exdmer-laser ablation of cornea in the form of Laser-Assisted in Situ Keratomileusis (LASIK) or Photorefractive keratectomy (PRK) are considered as kerato-refractional techniques of correction of presbyopia. The femtosecond laser intrastromal correction of presbyopia (INTRACOR) is also labeled as kerato-refractional technique of correction of presbyopia and it is based on making intrastromal concentric rings in the central optical zone of cornea. The deficiency of INTRACOR is a relatively high cost of procedure due to application of femtosecond laser. The implantation of inlays (artificial devices) into cornea permits correcting presbyopia with less financial expenses. However, there are number of contraindications for implementing. The Tornton and Schachar operations are referred to the group of sclerotic operations of correcting presbyopia. However, nowadays these interventions are practically out of application. The implantation of intraocular lenses, including accommodating, multi-focal and monofocal by the principle of monovision ones, can be considered as the most adequate mode of correction of presbyopia. The advantages and disadvantages of implantation of various types of intraocular lenses are considered in detail.
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Dimitrov, Nikolay, Ivan Georgiev e Petar Danchev. "REFRACTION CORRECTION IN PRECISE LEVELING OBSERVATIONS FOR NATIONAL LEVELING NETWORK FIRST ORDER". Geodesy and cartography 46, n.º 4 (16 de dezembro de 2020): 159–62. http://dx.doi.org/10.3846/gac.2020.11555.
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The paper deals with some problems when applying a correction to reduce the effect of vertical refraction in precise leveling observation. An example for calculating the refraction correction for one first order leveling line with length of 109 km in Bulgaria is given. Comparison between the obtained errors before and after applying refraction correction has been made. The results show that is important to measure the temperatures simultaneously with the leveling by aspiration thermometer with an accuracy of ±0.1 °C. It is recommended to make experimental research and to adopt appropriate for Bulgaria model for taking into account the influence of vertical refraction.
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Pisarevskaya, O. V., A. G. Shchuko, Ye P. Ivleva e L. S. Khlebnikova. "Mathematical modeling of the refractive effect of SMILE surgery in high degree myopia correction". Acta Biomedica Scientifica 8, n.º 4 (4 de outubro de 2023): 177–85. http://dx.doi.org/10.29413/abs.2023-8.4.20.
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The aim of the study. To develop a mathematical model of changes in corneal refraction during femtosecond laser-assisted lenticule extraction through a small surgical incision and, on this basis, to propose a technology for modified calculation of surgical parameters and to prove its effectiveness. Material and methods. The study included 191 patients with high myopia. They were divided into two groups: group 1 consisted of 55 patients who were had SMILE (SMall Incision Lenticule Extraction) surgery with standard calculations; group 2 included 136 patients who had SMILE surgery with a modified calculation of surgical parameters based on the developed mathematical model of the refractive effect of the surgery. Results. When assessing the refractive effect of patients who were operated using standard technology, it was found that it was possible to achieve a refraction different from emmetropia for ± 0.5 D only in 51 % of cases; in the remaining patients, the planned residual refractive effect was obtained and averaged –1.96 ± 0.29 D. In patients operated using the modified technology, a statistically significantly better refractive result was achieved already on the first day. A refractive error of more than ± 1.0 D was obtained in only 1 % of cases; a deviation from the calculated refraction of ± 0.5 D was achieved in 82 % of cases, with the average values by 1 year –0.24 ± 0.57 D. Conclusions. The developed technology of a modified calculation of the parameters of the SMILE surgery for high myopia correction makes it possible to obtain an optimal refractive effect in compliance with safety rules when the structural and functional parameters of the eye are initially unfavorable for refractive surgery.
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Anitha, Venugopal, Revathi Rajaraman, Mangala Periasamy, Meenakshi Ravindran, Ramakrishnan Rangappa e Mohammed Sithiq Uduman. "Reasons for declining corneal refractive laser correction for refractive candidates in Southern India". Indian Journal of Ophthalmology 72, n.º 1 (22 de dezembro de 2023): 118–22. http://dx.doi.org/10.4103/ijo.ijo_1595_23.
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Purpose: To analyze the reasons for declining corneal refractive laser correction procedures in patients presenting to tertiary eye care centers in Tamil Nadu, Southern India, and review the literature. Methods: Retrospective case records of subjects presenting from January 2019 to December 2021 for refractive surgery workup were analyzed. Demographic details and refractive parameters of patients rejected for corneal refractive laser corrections (CRLC) were documented and reviewed. Results: A total of 2358 patients presented for refractive surgery evaluation during the study period, and out of them, 395 patients (16.8%) were not considered ideal candidates for undergoing CRLC. The common reasons for rejecting the patients were unfit topography (n = 110, 27.8%), unstable refraction over a one-year duration (n = 9, 2.27%), low corneal thickness (n = 85, 21.5%), keratoconus (n = 5, 12.9%), and other ocular and systemic disorders (n = 48, 12.1%). Conclusion: There was a marked change in magnitude and rationalization for not performing either laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy in our study. The reasons are unfit topography, keratoconus, and systemic disorders, which were diagnosed during pre-LASIK screening workup, being the most common cause for rejecting patients for corneal refractive corrections.
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Tarutta, E. P. "Strategically oriented correction of mixed astigmatism in children". Russian Ophthalmological Journal 16, n.º 2 (1 de julho de 2023): 92–98. http://dx.doi.org/10.21516/2072-0076-2023-16-2-92-98.
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Purpose: evaluation of the remote functional and refractive results of mixed astigmatism correction in preschool children with “plus” cylinders in the framework of a long-time longitudinal study.Material and methods. 38 children (75 eyes) aged 1.5–7 years (averagely 4.2 years) with mixed astigmatism of 0.75 to 4.25 D (averagely 1.85 D) were followed up for 6-15 (averagely 7.3) years. At the first examination, all children were prescribed to permanently wear (+) cylinders of 0.5 D to 3.5 D. Over the follow-up period, (+) Cyl could be weakened in 24 eyes (32 %) due to a decrease in astigmatism, while (-) Sph had to be added in 24 eyes (32 %). due to an increased refraction. In cases when the full correction using a “plus” cylinder left an excessively large myopic defocus, the power of the “plus” cylinder was reduced so as not to add a “minus” sphere, and a second pair of glasses was prescribed for near vision, which offered a full correction of astigmatism with the “plus” cylinder.Results. After 6–15 years, astigmatism changed in 85 % of the examined eyes: it increased in 7 eyes (averagely, by 0.3 D) and decreased in 53 (averagely, by 0.9 D, p < 0.05; with the maximum reduction of 2.75 D). The spheric-equivalent refraction changed in 51 % of eyes, with an average increase of 0.53 D. The maximum increase of refraction was 2.8 D, while the maximum drop was 1.4 D. Visual acuity of the children who wore the prescribed eyeglasses permanently, showed after two years an increase, average achieving the level of 0.84, which by the end of the follow-up period achieved 0.99.Conclusion. The proposed plan of mixed astigmatism correction, which preserves residual weak myopic defocus, fully ensured both tactical and strategic effects: prevention and elimination of amblyopia, and containment of refraction myopization.
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Wang, Lei, Ming Wei, Tao Yang e Ping Liu. "Effects of Atmospheric Refraction on an Airborne Weather Radar Detection and Correction Method". Advances in Meteorology 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/407867.
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This study investigates the effect of atmospheric refraction, affected by temperature, atmospheric pressure, and humidity, on airborne weather radar beam paths. Using three types of typical atmospheric background sounding data, we established a simulation model for an actual transmission path and a fitted correction path of an airborne weather radar beam during airplane take-offs and landings based on initial flight parameters and X-band airborne phased-array weather radar parameters. Errors in an ideal electromagnetic beam propagation path are much greater than those of a fitted path when atmospheric refraction is not considered. The rates of change in the atmospheric refraction index differ with weather conditions and the radar detection angles differ during airplane take-off and landing. Therefore, the airborne radar detection path must be revised in real time according to the specific sounding data and flight parameters. However, an error analysis indicates that a direct linear-fitting method produces significant errors in a negatively refractive atmosphere; a piecewise-fitting method can be adopted to revise the paths according to the actual atmospheric structure. This study provides researchers and practitioners in the aeronautics and astronautics field with updated information regarding the effect of atmospheric refraction on airborne weather radar detection and correction methods.
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Serra, Pedro, Ángel Sánchez Trancón, Oscar Torrado Sierra, António Baptista e Santiago Cerpa Manito. "Posterior Chamber Phakic Intraocular Lenses for the Correction of Myopia: Factors Influencing the Postoperative Refraction". Optics 2, n.º 4 (16 de dezembro de 2021): 292–305. http://dx.doi.org/10.3390/opt2040028.
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Posterior chamber phakic intraocular lens implantation is a refractive technique for the correction of myopia. This study aimed to identify those factors contributing to variability in postoperative refraction. Methods: This retrospective study evaluated 73 eyes (one eye per patient) implanted with myopic implantable collamer lenses (ICL). Eyes were divided into two groups, the low myopic group (LMG) (ICL > −9.5 DS) and the high myopic group (HMG) (ICL ≤ −9.5 DS), to compare the predictability, efficacy index, and postoperative refraction between groups. The association of postoperative refraction with anatomical, demographic, and optical features was assessed through correlation analysis and investigated using ray-tracing. Results: Postoperative refraction at 3 months for the whole group was close to emmetropia at −0.02 ± 0.37 DS, the LMG tended toward myopia and the HMG, toward hyperopia. The results showed that 65% and 54% of the eyes had postoperative refraction of within ±0.25 DS, respectively, in the LMG and HMG, and in both groups, 100% were within ±1.00 DS. ICL implantation had a higher efficacy index in the HMG (1.13 ± 0.15) than in the LMG (1.04 ± 0.15). Postoperative refraction was positively associated with the vault (R = 0.408) and negatively correlated with ICL power (R = −0.382). Conclusion: The predictability and effectiveness of ICL implantation is high in a wide range of myopias. Considering the expected vault and including accurate vertex measurements would contribute to improving the predictability of the results.
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Shokoohi-Rad, Saeed, e Hamid-Reza Heidarzadeh. "Successful Photorefractive Keratectomy in a Case of Wilson’s Disease". Case Reports in Ophthalmological Medicine 2021 (25 de agosto de 2021): 1–6. http://dx.doi.org/10.1155/2021/6174130.
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Purpose. To report a female with a history of Wilson’s disease who underwent a successful photorefractive keratectomy (PRK) for myopic correction. Case Presentation. A twenty-year-old female with a history of Wilson’s disease and D-penicillamine use was referred to our clinic for myopic refractive surgery. Her best-corrected visual acuity (BCVA) was 20/20 for both eyes with a refraction of ‐ 1.25 ‐ 0.5 ∗ 75 ° and ‐ 1.25 ‐ 0.25 ∗ 55 ° for the right and left eyes. The slit examination showed a prominent Kayser-Fleischer ring (K-F ring) in both eyes. She underwent a successful myopic PRK surgery, and her BCVA became 20/20 with no significant refraction. Conclusions. In this report, we report a successful PRK surgery for myopic correction in a case of Wilson’s disease with prominent K-F rings in both eyes.
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YAR, MA, AH ZAHID, R. NAWAB, MRQ RAO, N. AADIL e S. HUSSAIN. "COMPARISON BETWEEN AUTOREFRACTION AND RETINOSCOPY FOR SUBJECTIVE CORRECTION IN CHILDREN". Biological and Clinical Sciences Research Journal 2023, n.º 1 (24 de dezembro de 2023): 608. http://dx.doi.org/10.54112/bcsrj.v2023i1.608.
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The study's objective was to compare the accuracy of retinoscopy and autorefraction for subjective correction in children. The study was conducted in the Department of Ophthalmology at Nishtar Medical Hospital from June 2021 to May 2022, and it was a prospective study. The study included 60 children aged between 6 to 15 years who had asthenopic symptoms and blurring of vision. The children were given cyclopentolate 1% eyedrops thrice at intervals of 10 minutes to achieve cycloplegia. After an hour of instilling eye drops, cycloplegic retinoscopy, and autorefractometry were performed. Three values of each technique were recorded, and the average was calculated. After three days, binocular and monocular subjective refraction was performed until the best-corrected visual acuity (BCVA) was achieved. Results showed that 40.8% (49 eyes) were hypermetric, and 50% (60 eyes) were myopic based on subjective refraction. Comparison of spherical error by subjective refraction and retinoscopy showed that myopic eyes had a mean of -1.36 ± .98 and -1.08± .82 on subjective correction and retinoscopy, respectively (P=.07), and hypermetropic eyes had a mean of 2.5± .22 and 2.45± .22 on subjective correction and retinoscopy, respectively (P=0.07). Comparison of spherical error by subjective refraction and autorefractometer showed myopic eyes had a mean value of -1.51 ± 1.3 on autorefraction (P=.0001) while hypermetropic eyes had a mean of 2.39± .37 on autorefraction (P=0.0001). Mean cylindrical error values by retinoscopy were -.0729± .304, and by the subjective method, were -.167± .384 (P =0.0007). Mean cylindrical error values by autorefraction were .207± .487 compared to -.167± .384 by the subjective method (P =0.0088). In conclusion, conventional retinoscopy is the most accurate and reliable method for estimating the refractive status. However, autorefraction also has acceptable accuracy and can be used for cylindrical correction.
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Maychuk, N. V., I. A. Mushkova, I. S. Malyshev e M. R. Obraztsova. "Discussing Questions of Laser Refractive Surgery in Hyperopia: Literature Review and Clinical Experience". Ophthalmology in Russia 19, n.º 2 (5 de julho de 2022): 350–58. http://dx.doi.org/10.18008/1816-5095-2022-2-350-358.
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Relevance. Modern keratorefractive surgery is a high-tech field of ophthalmology aimed at solving various problems of correcting a wide range of ametropias.Objective: to formulate recommendations for refractive surgeons when planning the correction of hypermetropic refraction using modern keratorefractive surgery.Materials and methods. An analysis of 20 literature sources and a retrospective analysis of outpatient records of 188 patients with hypermetropia who underwent surgery were carried out.Results. The analysis of the literature and our own clinical study allows us to recommend focusing on the final keratometry after keratorefractive surgery, which should not exceed 48 diopters. Among the analyzed charts of patients in compliance with these criteria, the accuracy of hitting the target refraction in the range of ± 1 D was 98.9 %, the regression did not exceed 0.5 D from that obtained 1 month after surgery in 96.8 %, and the loss of 1 line of BCVA was 3.7 % of cases. Among patients with achieved keratometry above 48 diopters, the loss of line 1 BCVA was 13.8 %, line 2 — 2.7 %.Conclusion. Thus, the tactics of correction of hypermetropia by CRC methods require an integrated approach to the assessment of visual functions, drug preparation for surgery, careful implementation of the surgical stages of the intervention, and rational postoperative pharmacological support.
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Chen, Li, Shuai Xing, Guoping Zhang, Songtao Guo e Ming Gao. "Refraction Correction Based on ATL03 Photon Parameter Tracking for Improving ICESat-2 Bathymetry Accuracy". Remote Sensing 16, n.º 1 (25 de dezembro de 2023): 84. http://dx.doi.org/10.3390/rs16010084.
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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.
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Brunner, Barbara S., Lukas Feldhaus, Wolfgang J. Mayer, Jakob Siedlecki, Martin Dirisamer, Siegfried G. Priglinger, Stefan Kassumeh e Nikolaus Luft. "Epithelial Remodeling and Epithelial Wavefront Aberrometry after Spherical vs. Cylindrical Myopic Small Incision Lenticule Extraction (SMILE)". Journal of Clinical Medicine 13, n.º 13 (7 de julho de 2024): 3970. http://dx.doi.org/10.3390/jcm13133970.
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Background/Objectives: To compare the epithelial thickness changes and the changes in epithelial wavefront aberrometry following spherical versus astigmatic myopic small incision lenticule extraction (SMILE). Methods: Eighty-six eyes of 86 patients who underwent SMILE were included in this retrospective study. A total of 43 eyes underwent myopic spherical correction (spherical group) and 43 eyes underwent myopic cylindrical correction (cylindrical group). The groups were matched according to the spherical equivalent of surgically corrected refraction. Subjective manifest refraction as well as high-resolution anterior segment optical coherence tomography (MS-39; CSO; Florence, Italy) were obtained preoperatively as well as 3 months postoperatively. The latter was utilized for computing epithelial wavefront aberrometry in addition to epithelial thickness mapping. Results: Epithelial thickness increased significantly in both groups after SMILE (p < 0.01). In the cylindrical group, epithelial thickening was more pronounced on the flat meridian compared to the steep meridian (p = 0.04). In both groups, epithelial wavefront aberrometry showed a significant postoperative increase in the epithelium’s spherical refractive power, causing a myopization of −0.24 ± 0.42 diopters (D) in the spherical group (p < 0.01) and −0.41 ± 0.52 D in the cylindrical group (p < 0.0001). While no significant changes in epithelial cylindrical refractive power were observed in the spherical group, a significant increase was noted in the cylindrical group from −0.21 ± 0.24 D to −0.37 ± 0.31 D (p = 0.01). In both groups, epithelial higher-order aberrations increased significantly (p < 0.001). Conclusions: Postoperative epithelial remodeling after SMILE alters lower-order (sphere and cylinder) and higher-order aberrations of the corneal epithelial wavefront and might contribute to refractive undercorrection, especially in astigmatic corrections. Epithelial wavefront aberrometry can be used to quantify the refractive effect of epithelial remodeling processes after keratorefractive surgery.
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Samper, David, Jorge Santolaria, Ana Cristina Majarena e Juan José Aguilar. "Correction of the Refraction Phenomenon in Photogrammetric Measurement Systems". Metrology and Measurement Systems 20, n.º 4 (1 de dezembro de 2013): 601–12. http://dx.doi.org/10.2478/mms-2013-0051.
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Abstract This paper presents a method of correcting the effects caused by refraction phenomena in an optical measurement system. The correction algorithm proposed can be applied in many different photogrammetric applications affected by these effects. To validate this algorithm, a foot sole optical measurement system that uses several cameras to build a mesh of a foot sole has been used. This measurement system has six cameras that are protected by a safety glass that separates the cameras from the foot to be measured. The safety glass produces an air-glass-air interface that causes the refraction phenomena, producing deformations in the images. Due to the deformations it is impossible to obtain reliable metric information of the images captured using the measurement system. The developed correction algorithm is based on a grid layout and associated polynomials and makes it possible to correct the deformations and extract accurate metric information.
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Ng-Darjuan, Maya Fe, Raymond P. Evangelista e Archimedes Lee D. Agahan. "Photorefractive Keratectomy with Adjunctive Mitomycin C for Residual Error after Laser-Assisted In Situ Keratomileusis Using the Pulzar 213 nm Solid-State Laser: Early Results". ISRN Ophthalmology 2013 (28 de setembro de 2013): 1–6. http://dx.doi.org/10.1155/2013/815840.
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Purpose. To evaluate the accuracy, efficacy, stability, and safety of photorefractive keratectomy (PRK) enhancement using the Pulzar 213 nm solid-state laser (SSL) with adjunctive Mitomycin C in eyes previously treated with laser assisted in situ keratomileusis (LASIK) with residual error of refraction. Methods. This is a prospective noncomparative case series of 16 eyes of 12 patients who underwent PRK for residual refractive error after primary LASIK. Mitomycin C 0.02% was used after the PRK to prevent haze formation. Outcomes measured were pre- and postoperative manifest refraction spherical equivalent (MRSE), uncorrected (UDVA) and best-corrected distance visual acuity (CDVA), and slit lamp evidence of corneal complications. Results. The mean UDVA improved from 20/70 preoperatively to 20/30 postoperatively. The average gain in lines for the UDVA was 2.38. After six months of followup, the postoperative MRSE within 0.50 D in 56% (9) of eyes and 94% (15) eyes were within 1.0 diopters of the intended correction. No eyes developed haze all throughout the study. Conclusion. PRK enhancement with adjunctive use of Mitomycin C for the correction of residual error of refraction after LASIK using the Pulzar 213 nm solid-state laser is an accurate, effective, and safe procedure.
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Sinitsyn, M. V., A. E. Terent‘eva, T. G. Tolmacheva e N. A. Pozdeyeva. "Astigmatism correction after penetrating keratoplasty by intrastromal corneal segments implantation using a femtosecond laser". Fyodorov journal of ophthalmic surgery, n.º 1 (15 de março de 2022): 20–25. http://dx.doi.org/10.25276/0235-4160-2022-1-20-25.
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Purpose. Analysis of clinical and functional results of astigmatism correction after penetrating keratoplasty by intrastromal segment implantation (ICS) using a femtosecond laser (FSL). Material and methods. The clinical study included 22 patients (22 eyes) who were implanted ICS using FSL in order to correct postkeratoplastic astigmatism. Before surgery, uncorrected visual acuity (UCVA) averaged 0.09±0.05, best corrected visual acuity (BCVA) – 0.3±0.22, the value of the spherical component of refraction (SCR) – 1.16±3.98 D, cylindrical component of refraction (CCR) – –10.25±4.80 D, mean keratometry value (Kave) – 43.59±3.99 D, corneal hysteresis (CH) – 7.94±1.44 mm Hg, corneal resistance factor (CRF) – 7.01±1.81 mm Hg. Results. Intra- and postoperative complications were not observed. 12 months after the operation, the UCVA was 0.50±0.16, the BCVA – 0.60±0.18; SCR –1.05±3.18 D, CCR – –2.22±0.82D, Kave – 38.56±1.96 D, CH – 8.93±1.13 mm Hg, CRF – 8.44±1.44 mm Hg. Conclusion. The method of the intrastromal corneal segments implantation into a corneal graft using a femtosecond laser has demonstrated high refractive efficiency and safety in correcting postkeratoplastic astigmatism and increased the biomechanical properties of the corneal graft. Key words: induced astigmatism, intracorneal segments, femtosecond laser, keratoplasty
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Marshall, J. "Keynote address: Refraction assessment and correction". Ophthalmic and Physiological Optics 10, n.º 1 (janeiro de 1990): 110. http://dx.doi.org/10.1016/0275-5408(90)90177-z.
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Manjappa, Rakesh, S. Sharath Makki, Rajesh Kumar, Ram Mohan Vasu e Rajan Kanhirodan. "Fully 3D refraction correction dosimetry system". Physics in Medicine and Biology 61, n.º 4 (3 de fevereiro de 2016): 1722–37. http://dx.doi.org/10.1088/0031-9155/61/4/1722.
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Frueh, Beatrice E. "Surgical correction of anomalies of refraction". Therapeutische Umschau 58, n.º 1 (1 de janeiro de 2001): 5–7. http://dx.doi.org/10.1024/0040-5930.58.1.5.
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Nach der Auflistung und Erläuterung der Refraktionsanomalien werden in dieser Übersichtsarbeit Operationstechniken und Indikationen der chirurgischen Korrektur der Fehlsichtigkeit angegeben. Die Grenzen der Methoden sowie offene Fragen für die Zukunft werden diskutiert.
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Lukin, V. P., A. �. Melamud e V. L. Mironov. "Meteorological correction of optical beam refraction". Soviet Physics Journal 28, n.º 8 (agosto de 1985): 648–52. http://dx.doi.org/10.1007/bf00895167.
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Chai, Yan, e Wen-jun Han. "Ionospheric Refraction Correction in Radio Astronomy". Chinese Journal of Space Science 6, n.º 4 (1986): 266. http://dx.doi.org/10.11728/cjss1986.04.266.
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Pyatyshina, O. V., O. V. Koycheva, A. P. Makarova, V. Y. Kostiv e O. L. Kurbanova. "The structure of clinical eye refraction in adolescent children". Modern technologies in ophtalmology, n.º 3 (1 de junho de 2023): 212–17. http://dx.doi.org/10.25276/2312-4911-2023-3-212-217.
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Purpose. To analyze the frequency of myopia in the structure of clinical eye refraction in adolescent children. Material and methods. Analysis of the results of an ophthalmological examination of 690 schoolchildren aged 11, 13, 15 years using the continuous sampling method. Results. In the structure of totality of the examined children, refractive errors were noted in 405 people (58.7 %), in the structure of myopia refractive error amounted to 339 people (83.7 %). 65.5 % of schoolchildren had mild myopia, 37.5 % had moderate myopia, and 1.8 % had high myopia. In 32 schoolchildren habitually excessive tension of accommodation was revealed. The progressive course of myopia was noted in 45 children (13 %), of which in half of the cases it was at the age of 11 years. According to the picture of fundus, the chorioretinal form of myopia predominated. In the structure of refractive errors, corneal astigmatism was detected in 118 children (29 %), of which in 55 % of children it was myopic, in 22 % it was mixed. 201 schoolchildren had incomplete vision correction due to refractive amblyopia, in 90 % of cases it was of a weak degree. Conclusion. In the structure of clinical refraction of the examined children, 285 (41.3 %) schoolchildren had emmetropia, 405 (58.7 %) schoolchildren had refractive errors. Of the entire set of refractive errors, myopia occurred in 339 people (83.7 %). Mild myopia occurred in almost half of the total population of pupils (62.5 %) of age from 11 to 15 years. There is a tendency to increase myopic refraction from 11 to 15 years of age. Keywords: refraction, myopia, childhood, morbidity