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PURPOSE To report the outcomes of two-piece microkeratome-assisted MK for eyes with full-thickness traumatic corneal scars and otherwise functional endothelium following corneal penetrating injury. DESIGN Interventional case series METHODS: : In this single-center study, 41 consecutive eyes with traumatic corneal scars that underwent two-piece microkeratome-assisted mushroom keratoplasty were evaluated. The two-piece mushroom graft consisted of an anterior lamella of 9-mm diameter and a posterior lamella of 6-mm diameter. Outcome measures were best spectacle-corrected visual acuity (BSCVA), refractive astigmatism (RA), endothelial cell density and postoperative complication rates. RESULTS Of the 41 total cases, 38 eyes (93%) reached Snellen vision ≥20/100, 36 (88%) reached ≥20/60, 29 (71%) reached ≥20/40 and 13 (32%) reached ≥20/25 2 years following MK. Excluding eyes with vision-impairing comorbidities, baseline logMAR BSCVA (1.41±0.73) significantly improved annually during the first 2 years (p < 0.001) reaching 0.16±0.13 at year 2 which subsequently remained stable up to 10 years (p = 0.626). RA exceeded 4.5 diopters in 2 cases (5%) after wound revision for high-degree astigmatism in 5 cases. Endothelial cell loss was 35.1% at 1 year with an annual decline of 2.9% over 10 years. Elevation in IOP was observed postoperatively in 7 eyes of which 6 had pre-existing glaucoma. The 10-year cumulative risk for graft rejection and failure was 8.5% and 10% respectively. CONCLUSION Two-piece microkeratome-assisted MK for traumatic corneal scars can allow excellent visual rehabilitation with relatively stable ECL and low rates of immunologic rejection and graft failure.

Acoustic Bessel beams are commonly used as ideal sources to study the characteristics for acoustic-vortex (AV) beams, exhibiting prosperous perspectives in contactless object manipulations and acoustic communications. However, accurate Bessel beams are difficult to construct using two-dimensional arrays in practical applications. By integrating active phase control and passive phase modulation to a ring-array of sectorial planar transducers, quasi-Bessel acoustic-vortex (QB-AV) beams of arbitrary order are built by the line-focus of AV fields in the current study. Based on the Snell’s refraction law, a circular saw-tooth lens of phase modulation is designed to converge incident waves toward the beam axis at a same deflection angle. QB-AV beams constructed by the main lobes of the sectorial sources are demonstrated by theoretical derivations, numerical simulations and quality evaluations, while those created by the side lobes are neglected to avoid the pressure fluctuations in the near field. Experimental measurements for AV beams of different orders coincide basically with the simulations, demonstrating that line-focused QB-AV beams can be generated along the beam axis across the pressure peak. With the increase of the topological charge, the peak-pressure of the beam decreases accordingly with a reduced effective axial range. The favorable results prove that, as a special kind of diffraction sources, the adjustable QB-AV beams may enable more important biomedical applications where Bessel beams are necessary, especially for the line-focused manipulation of biological and drug particles.

A water-assisted method is used to reduce heat accumulation during the ultrafast laser drilling of metals. To understand the complex material ablation mechanism, an underwater percussion drilling process using an ultrafast laser with pulse energy below the water breakdown threshold was investigated. The laser-induced plasma (LIP) was recorded using a high-speed camera, and the ablation morphology was characterized. The material removal mechanism in air and underwater was studied using metallurgical analysis. A numerical model including plasma formation by a single pulse and plasma evolution by multiple pulses was established to quantitatively describe the effects of LIP on the energy attenuation and beam refraction. This model can predict the hole radius and depth in underwater drilling and explain the difference in drilling performance in air and underwater.

PURPOSE To report the profile of peripheral refraction in Japanese children with mild to moderate myopia and compare it with reported data from other countries. STUDY DESIGN Cross-sectional study. METHODS Subjects were 76 Japanese children with myopia (mean± SD [range] spherical equivalent, -3.04±0.98 [-0.50 to -4.50] D; mean age, 10.0±1.5 [6-12] years). We performed cycloplegic refraction using an open-field autorefractor FR-5000 (Grand Seiko) while the subject looked at external fixation targets located at 0, ±15, ±30 degrees from the center along the horizontal meridian. Only the right eye data were analyzed after converting the readings to the power vector of M (spherical equivalent), J180, and J45. RESULTS The profile showed a clear hyperopic shift of M from the fovea to the peripheral retina, although a wide inter-subject variation existed. At the gaze positions of ±30 degrees, the mean relative M were +1.16±0.89 D and +1.64±1.02 D (nasal and temporal retina, respectively). Those for J180 were -0.94±0.30 D and -0.70±0.30 D (nasal and temporal retina, respectively). The mean J45 remained small (≦ 0.17 D) within this range of eccentricity. There was no correlation between the relative M at the gaze position of -30 degrees and on-axis refraction, axial length, or children's age (p > 0.05). CONCLUSIONS The profile of peripheral refraction was similar to that reported in children with moderate to high myopia in other East Asian countries. In this cohort, we did not find evidence supporting a hypothesis that greater myopia and longer axial length are associated with a greater peripheral hyperopic shift of the refraction.

White light refracted by a glass edge or a prism might be split into the colors of the rainbow but, when restricted by a suitable arrangement of edges, might also yield a sequence of colors complementary to the rainbow. We studied the creation of these color fields experimentally with a setup consisting of RGB light-emitting diodes that cover all color combinations of the three primary colors red, green, and blue. These light fields were projected through a prism onto a screen or a camera to generate various color fields by refraction. Applying the rules of additive color mixing, a simple RGB model based on the slit spectrum of the light convincingly reproduces the observed color patterns. The parallel use of model and experiment enables a clear recognition of unusual spectra from particularly combined light fields and yields an explanation of their origin.

AIM: To analyse the changes in magnitude and orientation of astigmatism after suture removal (SR) in keratoplasty eyes as measured by refraction, tomography, and aberrometry. METHODS: Twenty-six eyes of 25 patients after optical keratoplasty requiring SR to reduce the astigmatism during the follow-up period were prospectively included. Eyes with poor quality topography scans or if there were no sutures in the steepest semi meridian were excluded. Corrected distance visual acuity (CDVA), manifest refraction, corneal tomography and aberrometry were performed on all patients before and after SR. RESULTS: The mean age of the patients was 40.8±14.4y. Penetrating keratoplasty was performed in 23 eyes (89%) and deep anterior lamellar keratoplasty was done in 3 eyes (11%). There was a statistically significant reduction in the magnitude of refractive, tomographic and aberrometry astigmatism after SR (P

In order to improve the effect of urban landscape design, this paper combines big data technology with digital technology. For scenes and solutions containing SDS paths, a processing method similar to photon graphs is used and added to the calculation of two-way optical path tracking. In the processing scene, this paper uses the two-way optical path tracking method to perform specular reflection or refraction from the subpath starting from the light source and then store information such as the light energy of the points on the diffuse reflection surface or the directional reflection surface. Moreover, this paper combines the actual needs of urban landscape design to construct an urban landscape design system based on big data technology and digital technology. Finally, this paper designs experiments to carry out urban landscape simulation and design effect evaluation. From the test results, it can be seen that the system designed in this paper basically meets the needs of urban landscape planning and design.

The optical matrix formalism is applied to find optical parameters such as focal distance, back and front focal points, principal planes and the object image equation for a thick spherical lens immerse in two optical media of different indexes of refraction. Then, the formalism is applied to systems compound of two, three and N thick lenses in cascade, immersed in three, four and N+1 optical media of different indexes, respectively. It is found that a simple Gaussian equation is enough to relate object and image distances no matter the number of lenses. This formalism is validated trough a simple optical matrix model of the human eye.

Several methods have been used to detect defects or debonds nondestructively in materials or construction. Each of these nondestructive testing methods has advantages and limitations. Generally, they are suitable for testing a certain range or a specific type of material and structure and some of them require careful analysis to identify the features of the defects. The present work proposes a nondestructive testing method based on electro-acoustic technique (NDTPEA) to detect internal defects of dielectric materials, which can identify the defects from the original stress wave generated at the internal defect surface. Electric polarization occurs in the dielectric under the action of a high-voltage electric field. When the intensity of the electric field changes suddenly, the polarization charge generates a stress wave. If there are defects, such as cracks and debonding, in the medium, the position and size of the internal defects of the insulating material can be determined according to the stress wave. The waveform and velocity of stress wave is measured by a PVDF film. According to the velocity and time of the stress wave in the dielectric, the position of the internal defects or debonding of the specimen can be determined. The maximum error for measuring the wave transmission time is 1 ns, and the maximum measurement error in the defect thickness direction was 0.00253 mm. In the NDTPEA, the detected wave originates from the vibration of the polarized charge at the defect, i.e., the defect is the source of the stress wave. The measured stress wave does not undergo any reflection or refraction, and the waveform is truly regular, without coupling factors. The wave shape and time characteristics can all reflect the characteristics of the defects.

PURPOSE To compare Netra smartphone-based and automated refraction with subjective refraction for screening of refractive errors. METHODS Cross-sectional study at the University of Malaya Medical Centre, Kuala Lumpur. Subjects underwent subjective refraction, then automated refraction, and finally Netra smartphone-based refraction. All results were converted to power vectors (M, J0 and J45) and were analysed using repeated-measures ANOVA and Bland-Altman plots. Sensitivity and specificity were determined. The best cut-off points were determined from ROC curve analysis. P .05), but those between automated and subjective refraction were (0.06 vs 0.11 and 0.07 vs -0.02, p = .004 and p

Purpose: to study the effect of bifocal soft contact lens (BSCL) with an ADD of 4 diopters on peripheral refraction (PR), optical and ergonomic eye parameters in children with myopia.Patients and methods. 26 patients (52 eyes) with myopia –3.09 ± 1.13 diopters at the age of 10.04 ± 1.5 years without correction and with correction by BSCL Prima BIO Bi-focal ( Okay Vision Retail, Russia). All patients underwent a horizontal and vertical PR study on an open field autorefractometer Grand Seiko WAM-5500 (Japan), wavefront aberrations were studied on OPD-Scan III aberrometer (Nidek, Japan), contrast sensitivity under mesopic conditions were studied on a Mesotest 2 instrument (Oculus, Germany) and visual productivity was studied using test tables.Results. The visual acuity of the distance with a BSCL correction of 0.98 ± 0.04 did not differ (p = 0.26) from the maximum visual acuity corrected by spherocylindrical glasses of 0.99 ± 0.04. BSCL induces myopic defocus in all peripheral zones, with a maximum value of 15° and a sharp decrease of 30°. Peripheral myopic defocus induced by the lens at a horizontal and vertical angle of 15 degrees did not depend on the initial degree of myopia. BSCL increases the total RMS from 0.07 ± 0.02 μm to 0.19 ± 0.07 μm in the 3 mm zone (p < 0.01) and from 0.27 ± 0.09 μm to 1.18 ± 0, 23 μm in the 6 mm zone (p < 0.01), mainly due to an increase in spherical aberration from –0.0005 ± 0.006 μm to 0.06 ± 0.01 μm (p < 0.01) and from 0.01 ± 0.09 μm to 0.58 ± 0.14 μm (p < 0.01) in the 3 mm and 6 mm zones, respectively. An increase in the overall RMS in BSCL reduces the quality of eye optics and contrast sensitivity under mesopic conditions, but does not impair visual productivity.Conclusion. BSCLs with a high ADD of 4 diopters are capable of inducing significant myopic peripheral defocus due to the induction of spherical aberration, while maintaining high visual acuity and not changing ophthalmic ergonomics, which makes them a pathogenetically substantiated method for correcting myopia and preventing its progression in children and adolescents.

PURPOSE To report refractive and keratometric astigmatism outcomes of resident-performed limbal relaxing incisions (LRIs) during cataract surgery. SETTING Tertiary care academic teaching hospital. DESIGN Retrospective case series. METHODS The length, location, and number of LRIs were determined preoperatively using an online calculator. Variables studied were preoperative keratometry and postoperative uncorrected and corrected distance visual acuity, refraction, and keratometry at 1-month, 3-month, and 12-month visits (POM1, POM3, and POM12, respectively). Subgroup analysis was performed on amount and type of astigmatism. The astigmatism double-angle plot tool and analysis of with-the-wound (WtW) and against-the-wound (AtW) changes were used to assess the effect of astigmatism correction at POM1, POM3, and POM12 visits. RESULTS In 118 eyes, a higher percentage of eyes demonstrated refractive astigmatism 0.25 diopter (D) or less, 0.50 D or less, 0.75D or less, and 1.0 D or less at POM1 and POM12 (all P < .05) compared with preoperative keratometric astigmatism. Subgroup analysis showed improvement in all groups and types of astigmatism (P < .01). Patients achieved a statistically significant reduction of keratometric astigmatism at POM1, POM3, and POM12 (all P ≤ .0001) relative to baseline, and changes differed significantly based on the preoperative amount of astigmatism (all P ≤ .0001, with greater reductions associated with higher baseline astigmatism) but not by location of the steep meridian. There were significant WtW-AtW changes at POM1, POM3, and POM12. Regression of effect after 1 month was approximately 0.11 D. CONCLUSIONS Resident-performed LRIs achieved effective and sustained reduction of both refractive and keratometric astigmatism regardless of meridian or magnitude of astigmatism for at least 1 year postoperatively.

BACKGROUND Myopia, as one of the common ocular diseases, often occurs in adolescence. In addition to the harm from itself, it may also lead to serious complications. Thus, prevention and control of myopia are attracting more and more attention. Previous research revealed that single-focal glasses and orthokeratology lenses (OK lenses) played an important part in slowing down myopia and preventing high myopia. AIM To compare the clinical effects of OK lenses and frame glasses against the increase of diopter in adolescent myopia and further explore the mechanism of the OK lens. METHODS Changes in diopter and axial length were collected among 70 adolescent myopia patients (124 eyes) wearing OK lenses for 1 year (group A) and 59 adolescent myopia patients (113 eyes) wearing frame glasses (group B). Refractive states of their retina were inspected through multispectral refraction topography. The obtained hyperopic defocus was analyzed for the mechanism of OK lenses on slowing down the increase of myopic diopter by delaying the increase of ocular axis length and reducing the near hyperopia defocus. RESULTS Teenagers in groups A and B were divided into low myopia (0D - -3.00 D) and moderate myopia (-3.25D - -6.00 D), without statistical differences among gender and age. After 1-year treatment, the increase of diopter and axis length and changes of retinal hyperopic defocus amount of group A were significantly less than those of group B. According to the multiple linear analysis, the retinal defocus in the upper, lower, nasal, and temporal directions had almost the same effect on the total defocus. The amount of peripheral retinal defocus (15°-53°) in group A was significantly lower than that in group B. CONCLUSION Multispectral refraction topography is progressive and instructive in clinical prevention and control of myopia.

Purpose Halos are a chief source of patient dissatisfaction after multifocal intraocular lens (IOL) implantation. The primary purpose of this study was to investigate the influence of age, postoperative refraction, and pre- and postoperative pupil size on postoperative halo size with a trifocal diffractive IOL (AcrySof IQ PanOptix) and extended depth-of-focus (EDOF) IOL (TECNIS Symfony) to determine whether these factors could predict postoperative halo size. Patients and Methods This single-center, open-label study conducted between October 2018 and April 2020 in Yokosuka, Japan included 160 patients: 80 with PanOptix and 80 with Symfony IOLs. Size and intensity of the halos were examined binocularly using a computer-based simulator (Eyeland Design Network GmbH) and scored from 0 (minimum) to 10 (maximum) at 1, 3, and 6 months postoperatively, along with the change in each variable for both IOLs. The respective correlations of halo size with age, postoperative refraction, pre- and postoperative pupil size, and discomfort level due to the halo were also investigated 6 months postoperatively. Results Halo size and intensity were significantly mitigated between 1, 3, and 6 months postoperatively. Throughout the observation period, halo size was significantly larger with PanOptix than with Symphony (P < 0.05), and halo intensity was significantly higher with Symphony than with PanOptix (P < 0.05). The pre- and postoperative pupil size correlated positively with halo size, while age and postoperative refraction were negatively correlated, for both IOLs. Conclusion Understanding the features and predictive preoperative factors of halos in different types of multifocal IOLs may be useful in improving patient satisfaction.

To investigate the refractive outcomes of second-eye adjustment (SEA) methods in different intraocular lens (IOL) power calculation formulas for second eye following bilateral sequential cataract surgery.This retrospective consecutive case-series study included 234 eyes from 234 patients who underwent bilateral sequential phacoemulsification and implantation of enVista MX60 in a hospital setting. Postoperative refraction outcomes calculated by standard formulas (SRK/T and Barrett Universal II, BUII) with SEA method were compared with those calculated by an artificial intelligence-based IOL power calculation formula (PEARL DGS) under second eye enhancement (SEE) method. The median absolute error (MedAE), mean absolute error (MAE) and percentage prediction errors (PE) of eyes within ±0.25 diopters (D), ±0.50 D, ±0.75 D and ± 1.00 D were determined.Overall, the improvement in MedAE after SEA was significant for PEARL DGS (p 0.01), SRK/T (p 0.001) and BUII (p = 0.031), which increased from 74.36, 71.37, and 77.78% to 83.33, 80.34, and 79.49% of eyes within a PE of ±0.50 D, respectively. For first eyes with a medium axial length (22-26 mm), PEARL DGS with SEE had the lowest MedAE (0.21 D). For a first-eye MAE over 0.50 D, SEA method led to significant improvement in the second eye (p 0.01). Interocular axis length differences exceeding 0.3 mm were associated with weaker effects using SEA in the studied formulas (p 0.05).Either SEA method with SRK/T and BUII formulas or second-eye enhancement method based on the PEARL DGS formula can improve postoperative refractive outcomes in second eye.

A new grazing-incidence diffraction (GID) measurement geometry between in plane and out of plane is proposed. It is improved from the previous ω–φ compensated GID in side-inclination mode for measurement of residual stress in polycrystalline thin films [Wang & van Riessen (2017). Powder Diffr. 32, S9–S15]. Instead of keeping a constant azimuthal direction of the incident beam on the thin film sample, the current proposed variation maintains a constant azimuthal direction of the scattering vector projection on the thin film sample. The variation is named `ω–φ′ compensated GID in side-inclination mode' and enables d-spacing measurements along the same azimuthal direction. An Excel spreadsheet is included for readers to plan the measurement and to calculate the residual stress for the planned sample azimuthal direction. Anisotropic residual stresses of a polycrystalline NiFe thin film on an Si 001 substrate are measured by combining this method with phi rotations. Highly automated data analysis templates are developed using DIFFRAC.TOPAS v7 launch mode to calculate residual stress for all planned azimuthal directions sequentially. A pole figure file in simple text format is also generated from the same data set using DIFFRAC.TOPAS v7 launch mode, and can be directly imported into DIFFRAC.TEXTURE v4.1 for further texture analysis. Corrections for the incident-beam refraction have been implemented in both data analysis models.

The peripheral refraction profile in myopes with different corrective modalities varies significantly for both distance and near viewing and will have implications in managing myopia.This study investigated how the magnitude of peripheral myopic defocus induced by Ortho-K varies with and without accommodation, and how this compares to single vision spectacles and soft-contact-lenses (SCL).Relative peripheral refraction (RPR) of 18 young adults (spherical equivalent -1.00 D to -4.50 D) was determined along the horizontal meridian (±10°, ±20°, ±25°) during distance (3-metres) and near viewing (0.2-metres), and along vertical meridian (±10°, ±15°) for distance viewing alone. Measurements were obtained in an uncorrected state and with single vision spectacles, soft contact lens and Ortho-K. Changes in RPR and astigmatic components were compared between distance and near viewing with all different modalities.A significant interaction (p = 0.02) between relative peripheral refraction and the target distance (distance and near viewing) was found among different refractive modalities. Single overnight Ortho-K lens wear alone led to relative peripheral myopia for both distance (mean RPR ± SE: -0.92 ± 0.21D and -1.04 ± 0.22D) and near viewing (-0.71 ± 0.17D and -0.76 ± 0.20D). Comparisons of relative peripheral refraction between different corrective modalities at each eccentricity indicated statistical significance of RPR at extreme locations along both temporal and nasal meridian (±20 and ±25°, p 0.05). RPR with soft contact lenses and spectacles were similar for both distance and near viewing (p 0.05).Single overnight Ortho-K lens wear alone shifted the RPR in the myopic direction for both distance and near viewing in comparison with single vision spectacles and soft contact lenses. The Ortho-K lens designs that offer a large amount of mid-peripheral corneal steeping, in-turn leading to high relative peripheral myopia for both distance and near viewing and might offer beneficial effects on myopia control.

To evaluate the influence of posterior corneal asphericity on the refractive error using SRK-T and Barrett formulas for the intraocular lens (IOL) power calculation for Lucidis Extended Depth of Focus (EDOF) IOL.This study was carried out at a tertiary ophthalmology center in Geneva, Switzerland.A retrospective study. Medical records from all enrolled patients were analyzed and the following information was extracted retrospectively, over 1 month following surgery.We retrospectively reviewed 75 eyes that underwent cataract surgery and were implanted with a Lucidis EDOF IOL. We measured the posterior corneal asphericity (Q value), axial length (AL), and anterior chamber depth (ACD) and then calculated the IOL power using SRK-T and Barrett formulas.Seventy-five eyes were included, all of which had 1-month postoperative data. In the cohort, 32 eyes were from females (43%) and 43 from males (57%). The mean age of the study population was 73 ± 8.8 years. The mean AL was 23.5 ± 0.98 and the mean ACD was 3.13 ± 0.3. The mean posterior Q value was - 0.35 ± 0.2. In a regression analysis, we found a statistically significant relationship between the error in refraction prediction and the posterior Q value, irrespective of the formula used. The relationship between posterior corneal asphericity and the refraction prediction error was stronger for the Barrett II Universal formula than for the SRK-T formula.Posterior corneal asphericity was correlated with the refractive error of calculation of both SRK-T and Barrett formulas, with a stronger correlation to the latter formula.ZIEL: Den Einfluss der posterioren Hornhautasphärizität auf den refraktiven Fehler der mit SRK‑T- und Barrett-Formeln kalkulierten Intraokularlinsenberechnungen (IOL-Berechnungen) für Lucidis-Extended-Depth-of-Focus-Intraokularlinsen (EDOF: Extended Depth of Focus) zu evaluieren. ORT: Diese Studie wurde in einem Tertiärzentrum für Augenheilkunde in Genf, Schweiz, durchgeführt.Eine retrospektive Studie. Die Gesundheitsakten aller in die Studie aufgenommenen Patienten wurden analysiert; die Daten für den 1. Monat nach der Operation wurden retrospektiv extrahiert.Es wurden 75 Augen nach Kataraktoperation mit Implantation einer Lucidis-EDOF-IOL retrospektiv überprüft. Wir haben die posteriore Hornhautasphärizität (Q-Wert), axiale Länge (AL) und Vorderkammertiefe (VKT) gemessen; die IOL-Berechnung wurde mit den SRK‑T- und Barrett-Formeln durchgeführt.Es wurden 75 Augen in die Studie aufgenommen. Für alle Augen lagen die postoperativen Daten für den 1. Monat nach der Operation vor. In dem Patientenkollektiv waren 32 Augen von Frauen (43%) und 43 von Männern (57%). Das Durchschnittsalter der Studienpopulation betrug 73 ± 8,8 Jahre. Die durchschnittliche AL betrug 23,5 ± 0,98 und die mittlere VKT betrug 3,13 ± 0,3. Der durchschnittliche Q-Wert der hinteren Hornhautfläche betrug − 0,35 ± 0,2. Bei der Regressionsanalyse fanden wir eine statistisch signifikante Beziehung zwischen dem refraktiven Vorhersagefehler und dem Q-Wert der hinteren Hornhautfläche, ungeachtet der für die Berechnung verwendeten Formel. Die Verbindung zwischen posteriorer Hornhautasphärizität und refraktivem Vorhersagefehler war mit der Barrett-Universal-II-Formel stärker als mit der SRK‑T-Formel.Die posteriore Hornhautasphärizität korrelierte sowohl mit dem mit der SRK‑T-Formel als auch mit dem mit der Barrett-Formel kalkulierten refraktiven Fehler, wobei die Korrelation mit der letztgenannten Formel stärker ausgeprägt war.

The higher cost of IOL master is an issue in developing countries and hence it cannot be widely used for calculation of IOL power in such countries. Thus, the aim of the current study is to evaluate a cheaper alternative for the calculation of IOL power by comparing the axial length measurement obtained using applanation A-scan with that of IOL Master for accuracy of predicting postoperative refraction. Materials and Methods: A prospective, randomized, comparative study was done with 100 patients who were posted for cataract surgery. The patients were randomly divided into two groups of 50 patients each using computerized random number method. In Group A (n=50) axial length was measured with applanation A-scan and in Group B (n=50) axial length was measured with IOL Master. Before cataract surgery keratometry reading was taken with auto keratometer and intraocular lens (IOL) power calculation was done using SRK 2 formula in all patients. All patients were operated for cataract surgery by phacoemulsification and foldable intraocular lens were implanted in the bag. Postoperatively, best accepted refraction at 8th week was taken and mean spherical equivalent was calculated. Results: 100 patients of cataract were subjected for cataract surgery by phacoemulsification. Corrected spherical equivalent on 8th postoperative week showed: 88% patients in Group A and 96% patients of Group B were within ± 1.00 D. 56% patients of Group A and 76% patients of Group B were within ± 0.50 D. There was no statistically significant difference (p > 0.05) in axial length and corrected spherical equivalent between the two groups. Conclusions: There is no extra advantage of IOL Master over applanation A-scan for measuring Axial Length between 21 and 24.50 and predicting post-operative refractive outcome. Keywords: IOL master, Applanation A-scan, Axial length, Auto keratometry, Phacoemulsification, Spherical equivalent

Introduction Understanding the relationship between postoperative intraocular lens (IOL) shift and refractive change is crucial for the accuracy of predicted postoperative refraction (PPR). We assessed the relationships between different IOL fixation methods, haptic designs, and several metrics. Methods Single-center, open-label study which included 69 eyes. We preoperatively measured the anterior chamber depth (ACD), lens thickness (LT), axial length (AL), and PPR. AcrySof IQ (n = 27) and FineVision (n = 24) were fixed in the bag, and FEMTIS (n = 18) was fixed in capsulorhexis. At 1 day, 1 week, and 1 month postoperatively, we checked the IOL position and refraction and compared the IOL shift, refraction change, and the margin of error of the predicted PPR (PR-PPR difference). We also analyzed the correlation between postoperative and preoperative variables. Results FEMTIS showed the highest stability in terms of IOL shift and refraction. The in-the-bag-fixated IOLs showed a significant forward shift between 1 day and 1 week postoperatively. There were significant differences in the PR-PPR difference between the IOLs. ACD and AL showed significant positive correlations, and LT showed a significant negative correlation with IOL shift and change in PR between 1 day and 1 week, but not between 1 week and 1 month postoperatively. Conclusion The relationship between postoperative IOL shift and refraction change varied according to IOLs with different haptic types. Capsulorhexis fixation may be more stable than in-the-bag fixation. Furthermore, preoperative ACD, LT, and AL may be useful factors to predict IOL shift, change in PR, and to a lesser extent the degree of the margin of error in clinical practice. Our findings may improve the accuracy of PPR and refractive outcomes. Supplementary Information The online version contains supplementary material available at 10.1007/s40123-021-00390-x.

The paper investigates the features of reflection and refraction of acoustic waves incident at a right angle on a system of layers of multifractional gas suspensions. Formulas for calculating the reflection and refraction coefficients are obtained. The dependences of the reflection coefficients on the dimensionless frequency for different mass content of particles and layer thickness are plotted.

Exposing the retina to a simultaneous myopic defocus is an optical method that has shown a promising effect in slowing the progression of myopia. Optical treatments applying a simultaneous defocus are available in the form of soft contact lenses or multifocal lenses originally designed to correct presbyopia. Orthokeratology is another optical method that slows down the progression of myopia. With orthokeratology, it is hypothesized that a change in peripheral refraction could slow the progression of myopia. We aimed to measure the accommodation response between monofocal and multifocal contact lenses in young subjects. Additionally, we performed a ray-tracing simulation to visualize the quality of the retinal image and the refractive status in the retinal periphery. The accommodation and pupil size measurements were performed on 29 participants aged 24.03 ± 2.73 years with a refractive error (spherical equivalent) of −1.78 ± 1.06 D. With the multifocal lens in situ, our participants showed less accommodation in comparison to the monofocal contact lens (mean difference, 0.576 ± 0.36 D, p &gt, 0.001) when focusing on a near target at 40 cm. Pupil size became smaller in both contact lens groups during an accommodation of 0.29 ± 0.69 mm, p ≤ 0.001 and 0.39 ± 0.46 mm, p ≤ 0.001 for monofocal and multifocal contact lenses, respectively. The ray-tracing model showed a degradation for central and peripheral vision with the multifocal contact lens. The peripheral refraction was relatively myopic in both contact lens conditions up to 30°. Even if the accommodation ability is without fault, parts of simultaneous myopic defocus are used for the near task. The peripheral refraction in the ray-tracing model was not different between the two contact lenses. This is contrary to the proposed hypothesis that myopic peripheral refraction slows down the progression of myopia in current optical methods.

The differential phase computed tomography (DP-CT) imaging is a kind of X-ray-phase-based CT methods, which is widely used in various X-ray imaging laboratories. At present, a collection of projections with the horizontal direction (perpendicular to the sample rotation axis) DP information is often acquired in DP-CT. In an ideal experiment, if the background is zero, then we can accurately reconstruct the information of each direction of the sample with horizontal data only. Actually, background information will produce streaking artifacts to affect the resolution in directions other than the horizontal direction. To mitigate the streaking artifacts in the conventionally reconstructed DP-CT images. This study develops a novel analytical DP-CT reconstruction framework by jointly using the bilateral DP information obtained along two perpendicular directions. In addition, a new data acquisition scheme is also proposed to quickly acquire the bilateral DP signal without the need of changing the direction of refraction signal acquisition. Experimental results demonstrate that this new algorithm is able to greatly reduce the streaking artifacts on DP-CT images.

PURPOSE: To evaluate whether intraoperative aberrometry improves the accuracy of refractive outcomes after cataract surgery in highly myopic, highly hyperopic, and post-refractive eyes. METHODS: This single-center, retrospective review compared the spherical equivalent of postoperative refraction to that predicted by the Barrett Universal II formula versus Optiwave Refractive Analysis (ORA) (Alcon Laboratories, Inc) for highly myopic and hyperopic eyes and to the Barrett True K formula versus ORA for post-refractive eyes. The number and magnitude of lens changes were analyzed and used to determine in how many cases refractive surprises were affected by ORA, with additional subanalysis of outcomes based on average keratometry values. RESULTS: ORA led to a change in the lens power implanted in 48% (96 of 198) of eyes, and prevented hyperopic surprise in 27% (15 of 55) and excess myopia in 46% (19 of 41). Steeper keratometry values correlated with more frequent changes on ORA-recommended implanted intraocular lens ( P = .0031). ORA led to a similar percentage of eyes falling within ±0.50, ±0.75, and ±1.00 diopters compared to the Barrett Universal II and Barrett True K formulas. In post-refractive eyes, ORA led to a similar mean absolute error when compared to the Barrett True K formula ( P = .62). For highly myopic eyes with an axial length of greater than 27 mm, ORA demonstrated a trend toward lower mean absolute error when compared to the Barrett Universal II formula ( P = .076). CONCLUSIONS: ORA demonstrated similar refractive results to the Barrett True K formula in post-refractive eyes and to the Barrett Universal II formula in highly myopic and hyper-opic eyes and may provide additional benefit for eyes with steeper corneas or an axial length of greater than 27 mm. [ J Refract Surg . 2021;37(9):609–615.]

To assess the effect of changing anterior eye refractive power with contact lenses on the transverse magnification of en face images and associated vascular indices from optical coherence tomographic angiography (OCT-A).Prospective crossover study.Spherical soft contact lenses (-6 diopter [D] to +6 D in 2 D steps) were used to induce anterior eye refractive power changes in 11 healthy young adults and 3 × 3-mm macular scans were captured using OCT-A (Zeiss AngioPlex, software version 11.0; Cirrus HD-OCT 5000, Carl Zeiss Meditec Inc). Image transverse magnification was predicted based on refraction and biometry measurements and compared with empirical changes in the en face images measured with image analysis. Linear regression analysis was performed to assess the relationship between induced refractive ametropia and foveal avascular zone (FAZ) area, perimeter, circularity, and vessel density and perfusion density.The predicted transverse magnification was linearly related to induced refractive ametropia and to the empirical transverse magnification changes (average slope: 1.02, 95% CI: 0.90-1.34). All the OCT-A indices showed linear relationships with induced refractive ametropia (P.05) with the 12 D tested range altering the indices by 7% to 12%. After correcting for transverse magnification, all OCT-A indices except FAZ area were linearly related to induced refractive ametropia (P.05) and were reduced to 1% to 9%.This study is the first to show that induced refractive ametropia can affect OCT-A image magnification and indices. These changes are clinically important and need to be considered along with biometry effects when interpreting OCT-A indices. Transverse magnification changes can affect the ability of OCT-A to precisely measure linear dimensions of blood vessels.

In traditional observation schemes of stellar refraction navigation, the accuracy was limited due to unreasonable observation directions. In order to ameliorate this situation, a method of refracted starlight observation based on observability analysis is proposed. The function of this method is optimally generating an observation attitude sequence according to standard trajectories of spacecraft so that the selection of a refracted starlight observation sequence can be realized. Specifically, the improvement of Fisher information matrix calculation enables this method to be qualified for the navigation problem with unsteady measurement quantities as well as the non-fully observability which is defined as the capability of estimating the system state through measurements in finite time. Here, we construct a quantitative relationship between refracted starlight measurements and system observability by means of Fisher information index ( FII). Next, the observation scheme is retrieved by searching the maximum value of the optimized variable, which includes the ( FII). Finally, we resort to the extended Kalman filter to accomplish typical trajectory navigation simulations of the observation scheme. The results indicate that our method brings more accuracy than traditional ones in estimation of position and velocity of the optimal observation scheme.

This paper describes a tool created to simulate the effects of evaporation ducts on wireless communication networks which are close to the sea surface. The tool is an extension of the ns-3 network simulator and implements two propagation loss models: Two Ray, which models reflection effects; and Three Ray, which models the effects of both reflection and refraction. As the Three Ray model has the evaporation duct height as one of its parameters, a model to estimate this height based on weather conditions (meteorological measurements) was also implemented. The tool allows us to show how signal is weakened with the distance from the transmitter to the receiver, under different evaporation duct heights. It has been of increading interest to model these effects due to the importance of wireless networks located over the sea surface for supporting different types of applications, such as surveillance, security and ecological monitoring. Extending ns-3 is of particular importance, as it is one of the most largely used simulators for designing and evaluating communication networks.

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.

SIGNIFICANCE Visual performance is affected least by a 15° radial aperture surrounded by peripheral myopic defocus. This finding has important applications for spectacle and contact lens designs and myopia control optimization. PURPOSE The purpose of this study was to assess the effect of clear central apertures of different diameters with a defocused retinal periphery, using a range of visual performance tasks. METHODS Thirty visually normal subjects (mean age, 24.4 ± 3.3 years; 20 females; mean spherical equivalent of -1.28 D) were enrolled. Subjects wore five different spectacles during testing, all corrected for distance refraction, in random order: three single-vision spectacles with clear central apertures of 10, 12.5, and 15° radii with the periphery defocused using Fresnel "press-on" lenses (+3.5 D sphere), progressive addition lens (PAL) spectacles with a +3.5 D addition, and single-vision lens (SVL) spectacles with no peripheral defocus. Static and kinetic visual field sensitivities, reading rate and comprehension, head movements, global saccadic tracking, and saccadic visual search were evaluated. RESULTS Reading rate and comprehension did not differ across the five test conditions; however, increased head movement was found with the smallest aperture compared with the PAL condition with adjusted P < .05. Static visual field sensitivity was reduced for all three apertures in eccentric regions when compared with the SVL and PAL conditions with adjusted P < .05, whereas kinetic sensitivity did not differ for any lens condition. The 15° aperture was superior to the 10 and 12.5° apertures based on its similarity to the SVL and PAL spectacle conditions in head movement during reading, the Michigan Tracking Test, and the vertical results of the Developmental Eye Movement Test. CONCLUSIONS Visual performance is least affected adversely by a 15° aperture surrounded by a peripheral myopic defocus. This finding has important applications for spectacle and contact lens designs to optimize myopia treatment with minimal impact on visual performance.

The optical matrix formalism is applied to find parameters such as focal distance, back and front focal points, principal planes, and the equation relating object and image distances for a thick spherical lens immerse in air. Then, the formalism is applied to systems compound of two, three and N thick lenses in cascade. It is found that a simple Gaussian equation is enough to relate object and image distances no matter the number of lenses., 20 pages, 14 Figures

AIM: To predict postoperative intraocular lens (IOL) position using the Sirius anterior segment analysis system and investigate the effect of lens position and IOL type on postoperative refraction. METHODS: A total of 97 patients (102 eyes) were enrolled in the final analysis. An anterior segment biometry measurement was performed preoperatively with Sirius and Lenstar. The results of predicted lens position (PLP) and IOL power were automatically calculated by the software used by the instruments. Effective lens position (ELP) was measured manually using Sirius 3mo postoperatively. Pearson’s correlation analysis and linear regression analysis were used to determine the correlation of lens position to other parameters. RESULTS: PLP and ELP were positively correlated to axial length (AL; r=0.42, P

A polarization-controlled strain fiber sensorwith a low detection limit and high sensitivity is proposed and demonstrated using a helical birefringence fiber loop mirror (HBFLM). The HBFLM is consists of a micro-helix region, a macro-helix region, and a fiber ring mirror (FLM). The two standard single-mode fibers (SMFs) are pre-surrounded by each other and use hydrogen flame heating and stretching techniques to prepare the micro-helix region (MIHR). The pre- rotation turns of the MIHR determine the coupling length. The MIHR is influenced by a twisting force. The purpose of the macro-helix region (MAHR) is to regulate the x- and y-polarizationstates in the fiber (applying stress inducesdouble refraction). At the same time, the envelope of the transmission spectrum is modulated to ultimately control the strain sensor. The polarization control of the strain sensor is realized by using the principle of stress birefringence of the SMF. The reasons for the polarization control spectrum are analyzed theoretically. The strain and temperature characteristics were indicated in the experiment. Polarization-controlled strain sensors are expected to be used in high-precision and varying strain range measurements.

The problems of monitoring the state of flowing media with a simultaneous change in temperature and flow rate of the medium by more than two orders of magnitude are considered. A design of a flow-through refractometer is proposed for monitoring the state of transparent media in laminar and turbulent flow regimes, as well as at high flow rates and changes in the temperature of the medium by more than 200°C. The developed flow-through refractometer implements a method for measuring the refractive index, based on the principle of parallelism of two beams: the incident and transmitted through a pipeline with refraction at the boundaries of several media. The piping in the form of a cylindrical Plexiglas insert is part of the refractometer design. The design of the optical part of the refractometer with a vertical section of the pipeline eliminates the influence on the measurement of the refractive index of errors caused by multiple reflections of laser radiation from optical elements, the formation of voids or vortex flows in the pipeline. For the proposed refractometer there are no restrictions on the value of the measured refractive index of the flowing liquid, in contrast to the previously used industrial flow-through refractometers, the principle of operation of which is based on the phenomenon of total internal reflection of laser radiation at the interface of two media. The results of experimental studies of various media with the proposed refractometer are presented.

Coupling photocatalyst-coated optical fibers (P-OFs) with LEDs shows potential in environmental applications. Here we report a strategy to maximize P-OF light usage and quantify interactions between two forms of light energy (refracted light and evanescent waves) and surface-coated photocatalysts. Different TiO2-coated quartz optical fibers (TiO2-QOFs) are synthesized and characterized. An energy balance model is then developed by correlating different nano-size TiO2 coating structures with light propagation modes in TiO2-QOFs. By reducing TiO2 patchiness on optical fibers to 0.034 cm2/cm2 and increasing the average interspace distance between fiber surfaces and TiO2 coating layers to 114.3 nm, refraction is largely reduced when light is launched into TiO2-QOFs, and 91% of light propagated on the fiber surface is evanescent waves. 24% of the generated evanescent waves are not absorbed by nano-TiO2 and returned to optical fibers, thus increasing the quantum yield during degradation of a refractory pollutant (carbamazepine) in water by 32%. Our model also predicts that extending the TiO2-QOF length could fully use the returned light to double the carbamazepine degradation and quantum yield. Therefore, maximizing evanescent waves to activate photocatalysts by controlling photocatalyst coating structures emerges as an effective strategy to improve light usage in photocatalysis., Coupling photocatalyst-coated optical fibers (P-OFs) with LEDs shows potential in environmental applications. Here the authors report a strategy to maximize P-OF light usage and simultaneously establish a new platform to quantify photocatalytic performance.

This paper will describe a novel approach for the calibration of an underwater laser triangulation system. Underwater triangulation systems, consisting of a line laser and a camera can be used to determine the geometry of submerged objects or the topography of a water body bottom. Placing camera and laser line projector inside a waterproof housing leads to refraction effects at the air-glass-water interfaces, both of the laser light-sheet and image rays. This implies a deformed laser plane in the water and a curved line on the object surface. The proposed approach strictly models the geometry between camera, laser and housing. First experiments show, that the calibration method can be applied for water depth measurements with accuracies of 0.2–0.3 mm at depths in the order of 100 mm.

Purpose. To analyse keratopographic and biomechanical corneal indicators with the diagnostic results assessment of the influence on the treatment tactics of myopic refraction patient. Materials and methods. Keratotopographic and biomechanical parameters of the cornea in a patient with mild myopia were evaluated. Results. The Belin/Ambrosio (Enchanced Ectasia Display) - BAD keratoconus screening program was used on Pentacam HR, which did not reveal corneal pathology. According to the results of CBI (Corvis biomechanical index) on Corvis ST (OD - 0.61, OS - 0.48), that was indicating poor corneal biomechanical properties and a high risk of keratectasia development. Conclusion. Ophthalmic examination, using The Corvis ST (Oculus, Germany) biomechanical measurements, makes possible to reveal with greater sensitivity subclinical signs of a keratectatic process at the pre-clinical stage of development. Key words: keratotopography, corneal biomechanics, keratoconus.

Jian Jiang,1 Jingjing Xu,1 Yuwen Wang,1 Jingwei Zheng,2 Dan Xu3 1Clinical Optometry Center, Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325027, People’s Republic of China; 2Clinical Research Center, Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325027, People’s Republic of China; 3School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou, Zhejiang Province, 325027, People’s Republic of ChinaCorrespondence: Dan XuSchool of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou, Zhejiang Province, 325027, People’s Republic of ChinaTel +86 577 86689937Email xudammmc@163.comObjective: This study aims to investigate the correlation of dominant eye and refractive error between monozygotic twins.Methods: The data of dominant eye and refractive error of 13 pairs of monozygotic twins who were treated at the Optometry Clinic were collected. The paired chi-square test and Kappa consistency test were used to analyze the data of dominant eye between monozygotic twins, while the paired t test and Pearson correlation analysis were adopted to analyze the refractive error data. SPSS version 22.0 software was used to analyze the above statistics.Results: In the Kappa consistency test of dominant eye between monozygotic twins, Kappa value = 0.451, p = 0.052, p> 0.05, and in the paired chi-square test, p = 0.250. In the spherical equivalent paired t test for the right eye of monozygotic twins, t = 1.491 and p = 0.162, while in the spherical equivalent paired t test for the left eye, t = 0.753 and p = 0.466. In the spherical equivalent correlation analysis of monozygotic twins, for the spherical equivalent refraction of the right eye, the Pearson correlation results were r = 0.901 and p = 0.00, and for the spherical equivalent refraction of the left eye, the Pearson correlation results were r = 0.971 and p = 0.00.Conclusion: The difference in the chi-square test of dominant eye is not statistically significant between monozygotic twins, but dominant eye and refractive error are correlated to some extent. It is suggested that heredity may be the main determinant of the dominant eye. There is no difference in refractive error between identical twins which are highly correlated, however.Keywords: refractive error, dominant eye, monozygotic twins/identical twins, heredity, genes

Purpose To analyze refractive and topographic changes secondary to Descemet membrane endothelial keratoplasty (DMEK) in pseudophakic eyes with Fuchs’ endothelial dystrophy (FED). Methods Eighty-seven pseudophakic eyes of 74 patients who underwent subsequent DMEK surgery for corneal endothelial decompensation and associated visual impairment were included. Median post-operative follow-up time was 12 months (range: 3–26 months). Main outcome measures were pre- and post-operative manifest refraction, anterior and posterior corneal astigmatism, simulated keratometry (CASimK) and Q value obtained by Scheimpflug imaging. Secondary outcome measures included corrected distance visual acuity (CDVA), central corneal densitometry, central corneal thickness, corneal volume (CV), anterior chamber volume (ACV) and anterior chamber depth (ACD). Results After DMEK surgery, mean pre-operative spherical equivalent (± SD) changed from + 0.04 ± 1.73 D to + 0.37 ± 1.30 D post-operatively (p = 0.06). CDVA, proportion of emmetropic eyes, ACV and ACD increased significantly during follow-up. There was also a significant decrease in posterior corneal astigmatism, central corneal densitometry, central corneal thickness and corneal volume over time (p = 0.001). Only anterior corneal astigmatism and simulated keratometry (CASimK) remained fairly stable after DMEK. Conclusion Despite tendencies toward a hyperopic shift, changes in SE were not significant and refraction remained overall stable in pseudophakic patients undergoing DMEK for FED. Analysis of corneal parameters by Scheimpflug imaging mainly revealed changes in posterior corneal astigmatism pointing out the relevance of posterior corneal profile changes during edema resolution after DMEK.

Summary Purpose Descemet membrane endothelial keratoplasty (DMEK) combined with cataract extraction and intraocular lens insertion (new triple procedure) limits postoperative refractive errors. The objective of this study was to assess refractive accuracy after DMEK combined with cataract extraction and intraocular lens implantation. Setting Four university hospitals (Rouen, Paris, Reims, Grenoble). Design This retrospective multicenter study included patients with symptomatic corneal endothelial decompensation and cataract. Methods The primary outcome was the difference between the target spherical equivalent and postoperative refraction at months 2 and 6. Secondary outcomes were visual acuity, keratometry, pachymetry and endothelial cell density. Results A total of 130 eyes of 111 patients (mean age 66.2 years) were included (94% with Fuchs’ endothelial dystrophy). For a mean refractive target set at −0.50 (±0.57) D, the mean (95% CI) refractive error was hyperopia of +0.49 (0.314; 0.664) D at 2 months and +0.46 (0.299; 0.619) D at 6 months. Best corrected distance visual acuity was improved in all patients: from 0.49 (±0.3) logMAR to 0.14 (±0.14) logMAR at 2 months and 0.05 (±0.1) logMAR at 6 months. Mean corneal thickness decreased from 621.6 (±37.6) μm to 515.2 (±42.6) μm at 2 months and 539.0 (±39.0) μm at 6 months. Conclusions Good refractive accuracy was obtained after the new triple procedure with DMEK. Hyperopic shift is common after triple procedures, and its persistence should be evaluated in future studies in order to anticipate a change in its value to optimize intraocular lens power calculation.

Masresha Mengistu, Fisseha Admassu, Teshager Wondale, Asamere Tsegaw Department of Ophthalmology, College of Medicine and Health Sciences, University of Gondar, Gondar, EthiopiaCorrespondence: Asamere TsegawDepartment of Ophthalmology, College of Medicine and Health Sciences, University of Gondar, P.O.Box 196, Gondar, EthiopiaTel +251939912863Email asameret@yahoo.comPurpose: According to World Health Organization (WHO), cataract is the leading cause of blindness and visual impairment throughout the world. Post-operative refractive error is one of the commonest reasons for poor visual outcome after cataract surgery especially in developing countries where the standard modern biometry equipments are not available. The objective of this study was to assess the refractive outcome of cataract surgery done at University of Gondar (UoG) Tertiary Eye Care and Training Center, North West Ethiopia.Methods: A descriptive cross-sectional study was done on 66 patients who had undergone manual small incision cataract surgery (MSICS) and fulfilled the inclusion criteria at UoG Tertiary Eye Care and Training Center from July 15 2019 to October 15 2019.Results: From 90 post-operatively refracted eyes, 58 (64.4%) eyes achieved a target refraction of ± 1.00 Diopter (D). The right and left eyes achieved mean post-operative refraction SE of − 0.073± 1.45D and − 0.93± 1.70 D, respectively. But only 54 (60%) eyes were implanted with the calculated IOL power and for the remaining 40% the calculated IOL was not available at the store. And the target (Good) post-operative uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA) was achieved in 66.7% and 82.2% eyes, respectively.Conclusion: The post-operative refractive outcome after cataract surgery at the center is low. For over one-third of operated eyes, the calculated IOL was not implanted due to the absence of the required IOL power at the store and, therefore, a wide range of IOL power should be available at the center.Keywords: cataract surgery, outcome, Gondar, Ethiopia

Intraocular lens (IOL) is widely used for cataract treatment. Its optical properties are crucial to obtain a good treatment efficacy and thus need to be evaluated and controlled. In this study, we propose a novel method based on optical coherence tomography (OCT) for noncontact and accurate in vitro measurement of thickness, refractive index and dioptric power of IOL implants. The OCT setup is specially designed to create two sampling optics, called dual-side view OCT (DSV-OCT), which allows for imaging IOL from the two opposite sides simultaneously in single OCT volume scanning. This can produce a three-dimensional surface contour without suffering image distortions due to the refraction of the curved surface. Then, the thickness and surface curvature can be easily computed from the surface contours. In addition, DSV-OCT is able to measure the refractive index. Three IOLs with different dioptric powers (5D, 20D and 28D) were chosen to evaluate this method. The results show that this method is capable to provide a comprehensive and accurate evaluation of IOLs from the aspects of thickness, refractive index and dioptric power, and hence can be potentially used as a quality assurance tool by IOL manufacturers. Ministry of Education (MOE) Ministry of Health (MOH) National Medical Research Council (NMRC) Published version This work was supported in part by the National Natural Science Foundation of China under Grant 81401451, in part by the Natural Science Foundation of the Jiangsu Province under Grant BK20140365, in part by the Postgraduate Research & Practice Innovation Program of Jiangsu Province under Grant 5832001320, in part by the Singapore Ministry of Health’s National Medical Research Council under its Open Fund Individual Research under Grant MOH-OFIRG19may-0009, and in part by the Ministry of Education Singapore under its Academic Research Fund under Grants 2018-T1-001-144 and T2EP30120-0001.

Ultrasonography (US) is the first-line diagnostic tool for observing the whole abdomen. Unfortunately, a wide spectrum of refraction-related artefactual images is very frequently encountered in routine US examinations. In addition, most practitioners currently perform abdominal US examinations without sufficient knowledge of refraction artifacts (RAs). This review article was designed to present many representative RA images seen in the clinical setting, with a brief explanation of the mechanism of these images, in certain cases through an analyzed and reconstructed method using computer simulation that supports clinical observations. RAs are encountered not only with B-mode US but also with Doppler US, contrast-enhanced US, and shear wave elastography. RAs change their appearance according to the situation, but they always have a significant effect on detailed interpretation of abdominal US images. Correct diagnosis of abdominal US relies on a deep understanding of each characteristic artifactual finding, which necessitates knowledge of basic US physics. When analyzing mass lesions, computer simulation analysis helps to reveal the global images of RAs around a lesion.

Progressive myopia is a leading problem in modern optometry and ophthalmology in general. In recent years, refractive therapy with orthokeratology lenses has gained popularity among methods to control myopia progression. The aim: To study peripheral refraction in children with myopia with the use of orthokeratology lenses (OKL) of combined design. Methods. We followed up 60 children (117 eyes) diagnosed with uncomplicated mild to moderate myopia. All children underwent a complete ophthalmological examination as well as corneal keratotopography and peripheral refraction determination. Statistical analysis of correlations between peripheral corneal refraction under the influence of OKL, peripheral defocus, and axial length growth gradient was performed. Results. An inverse correlation relationship of -0.2 (p=0.03) was obtained between corneal differential power in the return 6 mm zone and peripheral refraction in its corresponding peripheral refraction of 23° on the temporal side. A positive correlation with a correlation coefficient of 0.21 (p=0.026) was obtained between the defocus in the temporal part and the gradient of myopia progression over one year, while the same result was obtained in the nasal part with a correlation coefficient of 0.2 (p=0.036). Concluсions. Difference corneal power at the periphery may be prognostic in relation to the course of myopia in OКL users. With an aboveaverage pupil diameter, combined design orthokeratology lenses are more effective in controlling myopia due to the greater influence of the formed corneal refractive ring on peripheral refraction.

Multifunctional metasurfaces are attracting growing attentions due to the compactness and the flexibility in beam manipulation. A bi-functional metagrating capable of anomalous refraction and beam splitting via asymmetric diffraction is designed, 3D-printed and experimentally verified at 0.14 THz. The asymmetric diffraction behavior is well explained by the excitation-direction-dependent mode amplitude inside the metagrating based on a simplified modal method. The measured efficiency of anomalous refraction towards +70° is 80.7% under $+ z$ illumination, and the measured efficiency of beam splitting is 43.7%/39.5% towards −70°/+70° under $- z$ illumination. The method here is further extended to achieve asymmetric diffraction into arbitrarily defined directions. Our work opens a new avenue in developing multifunctional and compact terahertz devices for wavefront shaping via excitation directions.

The interaction between electromagnetic waves and matter is the working principle of a photon-propelled spacecraft, which extracts momentum from the solar radiation to obtain a propulsive acceleration. An example is offered by solar sails, which use a thin membrane to reflect the impinging photons. The solar radiation momentum may actually be transferred to matter by means of various optical phenomena, such as absorption, emission, or refraction. This paper deals with the novel concept of a refractive sail, through which the Sun’s light is refracted by crossing a film made of polymeric micro-prisms. The main feature of a refractive sail is to give a large transverse component of thrust even when the sail nominal plane is orthogonal to the Sun-spacecraft line. Starting from the recent literature results, this paper proposes a semi-analytical thrust model that estimates the characteristics of the propulsive acceleration vector as a function of the sail attitude angles. Such a mathematical model is then used to analyze a simplified Earth-Mars and Earth-Venus interplanetary transfer within an optimal framework.

The statistical characteristics of biometry and refractive error in a large sample of cataractous Cuban patients are presented, comparing between sexes and age groups. All patients were studied at the Cuban Institute of Ophthalmology “Ramón Pando Ferrer,” La Habana. The sample consists of 28252 eyes of 25068 patients, subjected to cataract surgery during the time period between 2006 and 2019. Their biometry was obtained using IOL Master devices; also, visual acuity, refraction, and corneal power were registered. After surgery, the visual acuity and refraction were measured. The refractive prediction error was determined. For patients with both eyes registered, anisometropia was also calculated. Age and sex were used to segment the data. The preoperative biometric parameters show highly significant differences between sexes, with male eyes being longer and with a deeper anterior chamber but with a thinner lens. Also, keratometry shows highly significant differences, with female eyes being steeper than male. Before surgery, both sexes have myopic eyes as average, with males being more myopic than females ( p p

To investigate refractive and visual outcomes as well as rotational stability following implantation of Eyecryl phakic toric intraocular lens (pIOL) for moderate-to-high myopic astigmatism. The efficacy, safety, predictability, stability, and adverse events of Eyecryl toric pIOL were evaluated in patients with spherical refraction from − 4.50 to − 18.50 diopters (D) and cylindrical refraction from − 0.50 to − 5.50 D. This study included 60 eyes of 31 patients. The mean manifest refraction spherical equivalent (MRSE) dropped from − 10.45 ± 2.74 D preoperatively to − 0.34 ± 0.51 D and − 0.40 ± 0.56 D at 6 and 12 months postoperatively, respectively. There was an 81% decrease in astigmatism after surgery. The safety and efficacy of indices were 1.36 ± 0.43 and 1.20 ± 0 .32. At the final follow-up, the rate of eyes within ± 1.00 D and ± 0.50 D of the desired MRSE were 85% and 68.33%, respectively. Vision-threatening complications were not observed during the follow-up. The implantation of pIOL was effective, safe, and predictable in patients with moderate-to-high myopic astigmatism during 1-year follow-up.

Herein, we have developed a fully automated optofluidic device to execute enzyme-linked immunosorbent assay (ELISA) using an active 96-well hybrid lab-on-a-chip (LOC) device. To automate the solution loading into the reaction zone of the device and the post-assayed signal analysis, laser irradiation-induced image whitening was utilized with a smartphone-based optical platform. Two optical phenomena were utilized in our platform to detect the liquid in the reaction chamber using a smartphone. First, by Fresnel's equation, the refraction difference between air and water resulted in the intensity change of the reflected light from the reaction chamber. Therefore, when the liquid was entering into the reaction chamber, the intensity of the reflected light was changed. Second, when the light intensity increases, the smartphone-captured image whitens out due to saturation, even when the red color light was incident. Therefore, by measuring the RGB value of the smartphone image, the intensity changes by the liquid movement in the reaction chamber were successfully monitored. Our platform showed a low detection limit of 7.81 pg/mL for the detection of the NT-proBNP human cardiac biomarker with almost a half standard deviation, compared to the manually operated LOC-based ELISA. As a fully automated LOC adopting a conventional 96-well ELISA platform, we thus concluded that the developed platform can be widely applied for point-of-care clinical tests.