Cylindrical Power Research Articles

Epidemiological Characteristics Associated with Astigmatism in a Population of 3- to 5-Year-Old Children in Los Angeles, CA

ABSTRACT Purpose To characterize the prevalence of astigmatism among the heretofore largest published sample of preschool children and to do so among different age, gender, and racial and ethnic subgroups. Methods This study included data from 79,330 preschoolers (49.0% female, 79.4% Latino, mean age 4.29 ± 0.66 years) who were screened using a Retinomax autorefractor between 2012 and 2017. Cylindrical power and astigmatism defined as 1.50 D or more of cylinder were the dependent variables. Children were stratified by age, race/ethnicity, and gender. T-test and chi-square analyses were performed. Results The average cylinder of the sample was found to be 0.65 ± 0.78 D and 11% of the children were astigmatic. Among all children, these values remain stable from age 3 (0.66 ± 0.76 D, 11.2%) to age 4 (0.66 ± 0.79 D, 11.4%, p = .53), but they decrease significantly from age 4 to age 5 (0.61 ± 0.80 D, 10.%, p < .01). Latinos have the highest average cylinder power and prevalence of astigmatism at 0.68 ± 0.82 D and 12.3%, and unlike most other race/ethnic subgroups, they do not experience an age-dependent decrease in astigmatism. While female and male students have equivalent cylindrical refractions broadly, Asian and African American females have higher levels of astigmatism than their male counterparts. Conclusion The data further demonstrate that Latino children in Los Angeles have significantly higher rates of astigmatism, which does not decrease during preschool years. These results emphasize the need for comprehensive school-based screening, especially among Latino enclaves in Los Angeles.

Epithelial Remodeling and Epithelial Wavefront Aberrometry after Spherical vs. Cylindrical Myopic Small Incision Lenticule Extraction (SMILE).

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.

Determination of the time of refractive stability after uneventful phacoemulsification in Indian eyes.

Knowledge about refractive stabilization and the accuracy of postoperative refractive error measurements are crucial for improved patient outcomes after phacoemulsification. Existing guidelines typically recommend waiting 4-6 wk before prescribing corrective lenses. Our research focused on identifying factors that influence refractive errors in the early stages of post-cataract surgery, thus contributing to the existing literature on this topic. To investigate the time required for refraction stability after uneventful phacoemulsification surgery. We compared the variation and statistical significance of the difference in spherical, cylindrical components, and the spherical equivalent between the 1- and 6-wk follow-up period in a group of 257 eyes that underwent uneventful phacoemulsification with foldable intraocular lens implantation, all performed by a single experienced surgeon. The Wilcoxon-Signed Rank Test was utilized to assess the magnitude of the change and determine its statistical significance. The refractive stability was defined as the point at which the change in spherical equivalent was within ± 0.5 dioptres for two consecutive visits. The average age of the patients was 64.9 ± 8.9 yr. The differences observed in both the visits in spherical power (0.1 ± 0.2), cylinder power (0.3 ± 0.4), and spherical equivalent (0.2 ± 0.2) were minimal and not statistically significant. The majority of eyes (93.4%) achieved refractive stability within 6 wk after the surgery. The cylindrical power differed between age groups at the 6th wk post-operative and the difference was statistically significant (P value 0.013). There were no significant differences in refractive stability when considering sex and axial length. Phacoemulsification with foldable intraocular lens implantation results in no significant changes in refraction for the majority of cases during the 6-wk follow-up period. Therefore, a spectacle prescription can be given at the completion of 1 wk.

Evaluation of Keratoconus Patients Refractive Status Before and after Corneal Collagen Cross-linking

Background: Corneal Collagen Cross Linking (CXL) incorporated with riboflavin solution activated by UV (Ultraviolet) irradiation is a modern promising treatment protocol for keratoconus. Evaluation of the clinical effect of CXL treatment on keratoconus patients was the aim of this study. Methods: This Quasi Experimental (before-and-after) study was comprised with 50 patients, having progressive keratoconus (progression was documented by Corneal Topography), reported to Cornea Clinic, CMH Dhaka, from February 2022 to January 2023. Before and after the CXL procedure; un-corrected and best-corrected visual acuity of study population was documented using Snellen visual acuity chart. Auto-refractometry readings were also noted. Results: Among the 50 study subjects; 26 (52%) were men and 24 (48%) were female, age was 24.14 ± 5.07 (mean+SD) years and age range was 18-35 years. Mean preoperative spherical power was −1.84 ± 0.82 Diopter (D) and mean cylindrical power was −3.66 ± 0.97 D. Postoperatively, mean spherical power was found −1.15 ± 0.55 D and mean cylindrical power was −2.87 ± 0.99 D. After CXL treatment; significant vision improvement found in 15 (30%) patients (p&lt;0.05). Conclusion: Despite strengthening the corneal stromal collagen bond and halting the keratoconus progression, CXL treatment stabilize the refractive status of keratoconus patient and also in some extent, it improves vision. Bangladesh Armed Forces Med J Vol 56 No (2) December 2023, pp 45-50

Promotion of practical technology of the thermal management system for cylindrical power battery

Amidst the industrial transformation and upgrade, the new energy vehicle industry is at a crucial juncture. Power batteries, a vital component of new energy vehicles, are currently at the forefront of industry competition with a focus on technological innovation and performance enhancement. The operational temperature of a battery significantly impacts its efficiency, making the design of a reliable Thermal Management System (TMS) essential to ensure battery safety and stability. Cylindrical power batteries are widely utilized in the industry. This article outlines the four main structures and their drawbacks of TMS for cylindrical power batteries. Among these structures, air cooling falls short in meeting high heat dissipation requirements. Liquid cooling is expensive, intricate, and adds considerable weight. Phase Change Materials (PCM) are not yet prevalent in practical applications. Similarly, heat pipes are relatively uncommon in large high-power battery packs. To better align with the new energy vehicle industry’s demands for top-notch performance, cost-effectiveness, eco-friendliness, and reliability, this paper strongly recommends delving deeper into composite cooling solutions. The construction of an economically viable and fully optimized composite cooling method is poised to become a significant scientific challenge for future research endeavors.

Assessing neophyte response to daily disposable silicone hydrogel contact lenses: A randomised clinical trial investigation over one month.

This randomised clinical trial assessed the impact on symptoms, tear film dynamics and ocular surface integrity of daily disposable silicone-hydrogel contact lenses (CLs) over a month, paying special attention to lid wiper epitheliopathy (LWE) and its implications for CL discomfort. Neophyte CL wearers (n = 44, 21.09 ± 5.00 years old) were randomly assigned to either the experimental (n = 24) or control group (n = 20). Participants assigned to the experimental group were required to wear daily disposable CLs for 1 month for at least 8 h/day and 6 days/week. All participants were healthy subjects (no history of ocular surgery or active ocular disease) with spherical refractive errors between -8.00 and +5.00 D and cylindrical power <0.75 D. At the baseline and 1-month sessions, the Dry Eye Questionnaire 5 (DEQ-5) was completed, together with the measurement of tear film osmolarity with the TearLab osmometer, tear meniscus height (TMH) and lipid layer pattern (LLP) using a slit-lamp with Tearscope Plus attached, fluorescein break-up time (FBUT), maximum blink interval (MBI), corneal staining with fluorescein under cobalt blue light and LWE with lissamine green under slit lamp and halogen white light. At the baseline session, LWE showed a negative correlation with DEQ-5 (r = -0.37, p = 0.02). Significant differences in FBUT and LWE (p = 0.04) and a positive correlation between LWE and DEQ-5 (r = 0.49, p = 0.007) were observed at 1 month. Intrasession analysis at 1 month showed significant differences between the experimental and control groups in DEQ-5, FBUT and LWE (all p ≤ 0.02). Intersession analysis in the experimental group showed variations in DEQ-5, FBUT and LWE (all p ≤ 0.02) but no significant variation in the control group (all p ≥ 0.11). The presence of LWE was significantly correlated with higher symptom values in the DEQ-5. Also, participants in the experimental group presented higher values of LWE after 1 month of CL wear, in comparison with the control group.

Fitting-Shape-based Strategy for Topography-guided LASIK: A Prospective Study.

To assess and compare the visual acuity and refractive outcomes of topography-guided laser in situ keratomileusis (LASIK) based on the fitting-shape-based refractive compensated and Phorcides software strategies. Consecutive patients who underwent topography-guided LASIK were included in this study. Through double-masked simple randomization, patients were assigned to the Zhang & Zheng Auto-compensate Refraction (ZZ AR) group (the fitting-shape-based refractive compensated strategy using the ZZ AR calculator was used) or the Phorcides group (the topography analysis algorithm in Phorcides software [Phorcides LLC] was used). Only one eye per patient with binocular correction was randomly enrolled. The preoperative and postoperative visual acuities and refraction were analyzed at the 6-month follow-up visit. The ZZ AR and Phorcides groups comprised 156 and 147 eyes, respectively. At the 6-month postoperative follow-up visit, the median (range) absolute residual cylindrical refraction was 0.35 (1.01) and 0.47 (1.63) diopters (D) for the ZZ AR and Phorcides groups, respectively (P < .001). The percentages of patients with residual cylindrical power within 0.25 D were 29.49% and 13.61% for the ZZ AR and Phorcides groups, respectively (P = .001). Based on the percentages of patients with residual cylindrical powers within 0.50 and 1.00 D, the ZZ AR group showed better outcomes (P = .02 and .01). The percentage of patients with visual acuity better than 20/16 was significantly higher for the ZZ AR group than for the Phorcides group (P = .03). The fitting-shape-based refractive compensated strategy for topography-guided LASIK procedures can better optimize the visual acuity and astigmatic refraction than the Phorcides software strategy. [J Refract Surg. 2024;40(5):e336-e343.].

Effect of Long-Acting Diquafosol Sodium on Astigmatism Measurement Repeatability in Preoperative Cataract Cases with Dry Eyes: A Multicenter Prospective Study.

Dry eye can compromise corneal astigmatism measurement repeatability during preoperative cataract surgery examination. No previous studies have analyzed the effectiveness of long-acting 3% diquafosol sodium (LA-DQS) on astigmatism measurement repeatability. This research assessed the effect of LA-DQS on astigmatism measurement repeatability in preoperative patients with cataract and short tear break-up time (TBUT) type dry eyes in both eyes of the same patient. Correlations between repeatability and TBUT, corneal high-order aberrations (HOAs), and corneal astigmatism magnitude were also analyzed. In total, 122 eyes (61 patients) with short TBUT-type dry eye were enrolled. Preoperatively, only one eye of all patients was treated with LA-DQS for 4 weeks. TBUT and corneal HOAs were checked using CASIA 2 before and 4 weeks post-treatment. The cylindrical power and meridian of astigmatism were measured at 3- and 4-week post-treatment using IOLMaster 700. Power vectors J0 and J45 were used for astigmatism calculations. Repeatability of astigmatism measurements was assessed as the within-subject standard deviation (Sw). The relative effects of TBUT and HOAs on J0 Sw and J45 Sw were also analyzed. Comparative changes in these variables were evaluated between treated and non-treated eyes, with additional analysis of their correlations. Treated eyes exhibited significant improvements in TBUT, HOAs, and post-treatment measurements of J0 Sw and J45 Sw at 3 and 4 weeks. In non-treated eyes, J0 Sw and J45 Sw showed significant correlation with TBUT and corneal HOAs. HOAs showed stronger relative associations with J0 Sw and J45 Sw than TBUT. In non-treated eyes, no significant correlation was found between cylindrical power and astigmatism measurement repeatability. In short TBUT-type dry eye, preoperative treatment with LA-DQS significantly improved astigmatism measurement repeatability. This may improve the precision of intraocular lens (IOL) power calculations regardless of the magnitude of corneal astigmatism, especially when toric IOLs are used.

Effectiveness of orthokeratology and myopia control spectacles in a real-world setting in China

ObjectiveTo compare the effectiveness of myopia control in Chinese children, who had been wearing either orthokeratology (ortho-k) lenses or myopia control spectacles (MCS) for one year. MethodsRelevant data were retrieved from 212 patients, with baseline myopia of −5.00 to −0.75 D, astigmatism ≤ 1.50 D, who had been undergoing myopia control treatment with either ortho-k (Euclid (OK1) or CRT (OK2)) or MCS (Stellest (MCS1) or DIMS (MCS2)) for at least one year. Myopia control effectiveness among the four groups was compared based on the change in spherical equivalent refraction (SER) (for the spectacle groups) and axial length (AL) (for all groups). Data retrieved, from the right eye only, included best corrected visual acuity (BCVA), SER, and AL at both the initial clinic visit (baseline) and the one-year visit was analysed. ResultsAlthough no significant differences in gender, cylindrical power, or BCVA were observed at the baseline visit (P > 0.05), there were significant differences in baseline age, myopia, and AL among the four groups (P < 0.05). No significant difference in axial elongation (AE) was found among the four groups after one year of treatment (P = 0.49). AE, adjusted for baseline age and spherical power, were 0.19 ± 0.15, 0.18 ± 0.14, 0.19 ± 0.19, 0.20 ± 0.18 mm for OK1, OK2, MCS1, MCS2, respectively. Only age was a significantly factor associated with AE and SER increase (P < 0.05), with negative associations between AE and age in all groups and positive association between SER increase and baseline age in the spectacle groups observed. ConclusionBoth brands of ortho-k lenses and MCS had similar myopia control effectiveness for mild to moderate myopic children treated in a real-world setting in China. Average AE in one year ranged from 0.18 to 0.20 mm, comparable to previous reports on myopia control using ortho-k.

Causal associations of refractive error and early age-related macular degeneration: A Mendelian randomization study

This study aims to determine the risk associated with early age-related macular degeneration (AMD) due to refractive errors (RE) using an analysis of genome-wide association study (GWAS) data through the two-sample Mendelian randomization approach. Single-nucleotide polymorphisms (SNPs) linked to refractive errors (RE) were obtained from numerous GWAS studies involving individuals of European descent. The data for early AMD was obtained from a diverse, multiethnic GWAS meta-analysis that included 105,248 participants (14,034 cases and 91,214 controls). The primary outcome measure focused on the rise in early AMD risk corresponding to a 1-diopter alteration in spherical power and cylindrical power. In the main Mendelian randomization analysis, inverse-variance weighting (IVW) methods were applied for the evaluation. Mendelian Randomization (MR) study revealed a substantial impact of refractive error (RE) on early AMD risk, with a 1-diopter increase in hypermetropia being related to a 1.16 odds ratio (OR) for a greater risk of early AMD (95% CI, 1.10–1.23; P < 0.01). This conclusion was further supported by four supplementary approaches, namely, Weighted mode, Weighted-median, Simple mode, and MR-Egger. The results suggest a heightened risk of early AMD correlated with hyperopia, necessitating further research to thoroughly elucidate this potential causal relationship.

Numerical Investigation of a Novel Heat Exchanger in a High-Temperature Thermoelectric Generator

A cylindrical thermoelectric power generator for high-temperature flue gas was designed, and a distributor was installed to enhance heat transfer by affecting the jet on the hot side. The influence of the different distributor diameters and jet hole diameters on the temperature distribution of the hot and cold sides of the thermoelectric module was studied. The corresponding temperature field, velocity field, and exhaust pressure drop of the device were also obtained. The results indicated that the temperature difference between the hot and cold ends of the thermoelectric module was increased, and the uniformity of the temperature distribution was improved with the increasing diameter of the distributor and the decreasing diameter of the jet hole. The performance of the thermoelectric power generator was further improved by the jet hole with a gradient diameter. The number and distance between jet holes were sensitive to pressure drop.

Compensatory Interactions between Corneal and Internal Astigmatism despite Lifestyle Changes.

This study explores whether children's refractive errors and visual behaviors reverted to pre-COVID-19 levels a year after normal schooling resumed in Hong Kong as well as the impact of corneal and internal astigmatism on refractive astigmatism development. Vision survey data and questionnaire results collected in 2022 (n = 119) and 2020 (n = 173) were compared. Cross-sectional data showed similar proportions of astigmatism (cylindrical power ≥ 0.75 D) in the 2020 (49.1%) and 2022 cohorts (55.5%). Despite a 0.28 D increase in corneal astigmatism, a compensatory 0.24 D increase in internal astigmatism of opposite direction kept refractive astigmatism relatively stable. The questionnaire data showed that children spent an additional 0.5 h/day outdoors on weekends post-resumption of normal schooling but engaged in more near-work activities, especially non-screen near-work, by approximately 1 h/day on both weekdays and weekends. These findings were supported by longitudinal data from 72 children who participated in both surveys. This study highlights the significant role of corneal and internal astigmatism in refractive astigmatism changes. Despite the return to in-person classes, children's total near-work time increased and astigmatism remained high. These findings underscore the need for comprehensive strategies to reduce the high environmental risks for refractive error development in children.

Headache Attributed to Refractive Error: Improvement after Topography-Guided Photorefractive Keratectomy with Corneal Cross-Linking in Patients with Keratoconus

Purpose: To investigate if topography-guided photorefractive keratectomy (TGPRK) alleviates headache, particularly headache attributed to refractive errors (HARE) in keratoconus. Methods: Patients diagnosed with keratoconus undergoing TGPRK for refractive correction were included. Best spectacle corrected visual acuity (BSCVA) using the logMAR scale and refractive error were measured. Patients answered a questionnaire exploring headaches, characteristics, treatment, and the Headache Impact Test (HIT-6) before and 6 months after the surgery. Results: 40 patients were included. Preoperatively, 24 patients (60%) met criteria for headaches: five for migraine, 14 for HARE, and five for tension-type headache (TTH). Patients with headaches preoperatively were more likely to require bilateral TGPRK, and the mean sphere and cylindrical power were higher. Postoperatively, 15 out of the 24 patients of the headache group experienced complete resolution of headaches, and only nine patients met diagnostic criteria for headaches: two for migraine, six for HARE, and one for TTH. The number of headaches reduced from 4.4 ± 2.4 to 0.5 ± 0.7 days/week (p &lt; 0.001). Headache duration decreased from 108.5 ± 100.7 min to 34.4 ± 63.5 min (p = 0.002). Postoperatively, the consumption of analgesia decreased. The HIT-6 revealed an improvement in the quality-of-life post-procedure (p &lt; 0.001). Conclusions: Surgical correction of irregular astigmatism in patients with keratoconus can alleviate or resolve headaches in a large proportion of patients, resulting in an improvement in their quality of life. Physicians should consider keratoconus in patients fitting criteria for HARE not alleviated by spectacle correction and suboptimal vision in glasses.

A Comprehensive Retrospective Analysis of EVO/EVO+ Implantable Collamer Lens: Evaluating Refractive Outcomes in the Largest Single Center Study of ICL Patients in the United States.

We evaluate visual outcomes in patients with EVO/EVO+™ (posterior chamber phakic intraocular lens with a central port) within approved United States (US) age and refractive range indications. This single-center retrospective study evaluated one-month, single-center postoperative data for 225 eyes meeting inclusion criteria and undergoing EVO/EVO+ implantation from April to October 2022. Data included lens size (mm), lens power (diopters of spherical and cylindrical power), preoperative best corrected visual acuity, preoperative spherical equivalent from manifest refraction, achieved postoperative uncorrected visual acuity, postoperative refraction, intraocular pressure (mmHg), and adverse events. A total of 225 eyes underwent EVO/EVO+ Implantable Collamer Lens (ICL) implantation from April to October 2022, with 51.5% receiving toric lenses. The most common ICL size was 12.6mm (56.4%), followed by 13.2mm (27.5%), 12.1mm (15.1%), and 13.7mm (0.9%). Among patients with preoperative BCVA of 20/20 or better (149 eyes), 95.2% achieved postoperative UCVA of 20/20 or better, and 99.3% achieved UCVA of 20/25 or better at postoperative month one. About 75% of eyes were within a spherical equivalent target of ±0.50 D and 94% within ±1.00 D. Toric ICLs were implanted in 116 eyes (51.8%). Of these, anticipated residual cylinder >1 diopter was seen in 21 eyes (18.1%) resulting in three rotations, three explants, and three laser vision correction (LVC) enhancements. The postoperative adjustment rate (including rotations, exchanges, and LVC enhancement) was minimal (4.8%). Incidence of major adverse events was 0%. Our study, the largest US single-center analysis of EVO/EVO+ ICL implantation, demonstrates strong early results and infrequent adverse events, supporting ICL safety and effectiveness. High predictability and favorable visual outcomes, including 20/20 or better, highlight the reliability of this technology. Despite study limitations, our findings underscore this technology's effectiveness. Future research should refine patient criteria and assess long-term outcomes in this evolving landscape.

On the issue of diagnostic accuracy of methods for analyzing the parameters of regular astigmatism

This study evaluates the diagnostic accuracy of various methods for measuring the parameters of regular astigmatism. The study included 83 patients (122 eyes) with regular astigmatism exceeding 1.0 D. Three groups were formed depending on the type of astigmatism. Spherical and cylindrical (power and axis) components of refraction were determined using automatic refractometry. The results were refined with subjective tests: power and axis tests with a cross-cylinder. The criterion for diagnostic accuracy was the level of corrected visual acuity. To assess the impact of cylinder position on visual acuity, discrete deviations of the axis of trial astigmatic lenses from the correct position (determined based on subjective tests) were modeled at 5, 10, and 15 degrees in both clockwise and counterclockwise directions. In the overall sample of observations, coincidence of results was found only in one-third of cases, with a tendency for discrepancies in data between the two methods in nearly 70% of cases. Statistical processing revealed significant differences only in the magnitude of the cylinder in the group with against-the-rule astigmatism (p<0.0005). An increase in maximum visual acuity corrected based on subjective test data was noted. With a deviation of the cylinder axis from the correct position by 10-15 degrees, regardless of the type of astigmatism, a significant tendency for a decrease in visual acuity was identified. At the same time, with a deviation of the cylinder axis within 5 degrees, a significant decrease in visual acuity was noted only in with-the-rule astigmatism and counterclockwise deviation. To achieve maximum visual acuity in the correction of regular astigmatism, objective method data must be refined with subjective tests. The results of modeling the deviation of the axis of the corrective lens from the proper position can be considered when evaluating the functional outcomes of TIOL implantation.

Comparability of Measurement of Astigmatism between URk-800F Auto Refracto-keratometer and MS-39 Anterior Segment Optical Coherence Tomography in Patients with Refractive Error.

Accurate refractive error assessment is the first and the most important step of ocular examination. A reliable screening method of refractive status is important for early detection and prevention of blinding complications of uncorrected refractive error. To evaluate the comparability of astigmatism measured by an auto-refractometer (URk-800F) with the measurements of the gold standard anterior segment optical coherence tomography (AS-OCT). This cross-sectional observational study was conducted in a tertiary eye centre in Kathmandu from February 2023 to June 2023. A total of 100 patients with best corrected visual acuity of ≥ 20/20, spherical refractive error with cylindrical error of more than and equal to -0.75 and no pathology detected on slit lamp examination were taken by consecutive sampling method. Ethical approval was taken for the study. The data were entered into Microsoft Excel and analysed using Bland-Altman analysis. The mean cylindrical power and axis was -2.33 D and 88 degrees for the right eye and -2.32 D and 122 degrees for the left eye respectively, as measured by MS-39 AS-OCT. For URK 800-F Auto-refracto Keratometer, the mean cylindrical power and axis was -2.31 D and 89 degrees for the right eye and -2.27 D and 124 degrees for the left eye. The findings of this study conclude that an auto-refractometer can be used as an effective tool for identification of spherical refractive error as well as measurement of accurate cylindrical power and cylindrical axis in low resource primary care settings.

Influence of the Long-Term Loading on the Strength and Rigidity of the Annular Section Poles

Introduction. The modern methods of analysis and conducting the numerical experiments referring to calculation and design of constructions are mostly aimed at a deeper study of parameter changes of different structures exposed to the influence of the certain loads. Due to the course of time and upon obtaining and analysing the new results of the numerical studies, there arises the need to revise and update the normative documents developed in the past in the frame of studying the certain modes of structures’ operation. Bearing in mind the above-mentioned objective, the numerical study presented in this article has been carried out.Materials and Methods. It should be mentioned, that most of the previously conducted research was based on the results of the short-term exposure of the structures to the loads, but not enough attention was paid to the study of the influence of the long-term loading on the structures' operation. This paper presents the results of the numerical experiments investigating the load-bearing capacity, flexural rigidity and maximum force of the power transmission line poles exposed to the short-term and long-term loads. The specimen under study is the cylindrical power transmission line pole complying with the GOST 22687.2 “Centrifugal cylinder reinforced concrete posts for high-voltage transmission lines”.Results. The paper presents the results of studying the behaviour of the cylindrical reinforced concrete poles, serving as the supports for the electrical power transmission lines, under the short-term and long-term loading. The work provides the results of numerical experiments investigating the strength and rigidity parameters of the above-mentioned structures under different types of loading, as well as upon changing the eccentricities of the application of these loads. The assessment of the rigidity parameters change under the long-term exposure of the poles to the loads is carried out.Discussion and Conclusion. Based on the results, obtained during the numerical experiments, the strength and rigidity parameters of the annular section power transmission line poles were analysed, and proposals for improving the design codes were made that could become a basis for the further research on this issue.

Analysis of Corneal Topographic Changes after Upper Lid Surgery in Congenital and Acquired Ptosis

Objective: To assess the corneal topographic and refractive changes after ptosis surgery. Study Design: Prospective longitudinal study. Place and Duration of Study: Armed Forces Institute of Ophthalmology, Rawalpindi Pakistan, from Jan 2020 to Jul 2021. Methodology: A total of 90 individuals were selected by non-probability convenience sampling. Patients with diagnosed Ptosis and planned for surgery were followed up for six months post-surgery. Corneal topography, visual acuity, and physical assessment for Ptosis were done pre and post-surgery and compared for differences. Result: There were more cases of acquired Ptosis than congenital in our sample (p=&lt;0.001). The patients had more poor levator function pre-operatively (p=0.291), which improved to fair post-operatively (p=&lt;0.0001). Post-operatively, a significant decrease in the SimK and Cylinder power was observed in the sample. The visual acuity improved significantly, and the MRD also improved. With no significant change in CCT post-operatively. Conclusion: Our study showed that post-surgery SimK, visual acuity, MRD, and cylindrical power improved. However, the CCT did not show significant alterations.

Effect of corneal flap thickness on opaque bubble layer formation in Visumax FS-LASIK using GEE analysis

IntroductionThis study aimed to investigate two types of corneal flap thickness on opaque bubble layer (OBL) formation in Visumax femtosecond laser-assisted stromal for situ keratomileusis (FS-LASIK). MethodsThis retrospective study analyzed 203 eyes of 103 patients (32 men and 71 women) who underwent Visumax FS-LASIK between January 2020 and June 2020, and according to corneal flap thickness, they were divided into the 100-μm group (64 eyes) and the 110-μm group (139 eyes). Anterior-segment examination revealed no abnormal findings. Preoperatively, intraocular pressure (IOP), central corneal thickness (CCT), residual stromal thickness (RST), spherical power, cylindrical power, flat keratometry (K1), steep keratometry (K2), and biomechanical parameters including deformation amplitude (DA) ratio, Integrated Radius, stiffness parameter at first applanation (SP-A1), and Ambrosio relational thickness to the horizontal profile (ARTh) were evaluated. Primary outcomes were the incidence of OBL formation in the two groups compared by the Chi-square test and the correlation between the incidence of OBL and the above preoperative data by Spearman's Rho test. Secondary outcomes were the comparisons corrected by the generalized estimating equation (GEE) model. ResultsThe incidence of OBL formation in the 100-μm group was 59.4 %, which was higher than that in the 110-μm group (23.0 %) with a significant difference (χ2 = 25.635, P < 0.001). The thinner corneal flap thickness (r = −0.355, P < 0.001) and higher spherical power (r = −0.142, P < 0.05) correlated with OBL formation. Higher K1 (r = 0.217, P < 0.01) and K2 (r = 0.198, P < 0.01) also correlated with OBL formation. The results of the GEE correction analysis showed higher rates of OBL formation in the 100-μm group (odds ratio [OR] = 4.704, 95 % CI 1.681–13.161, P < 0.01). ConclusionsOBL was more likely to occur with the 100-μm corneal flap than with the 110-μm corneal flap in Visumax FS-LASIK. The risk of OBL formation in the 100-μm group was 4.704 times higher than that in the 110-μm group.

Analysis of the relationship between lens morphology and aberrations in patients with myopia: a cross-sectional study.

To investigate the relationship between lens morphology and aberrations in patients with myopia. This cross-sectional study included 155 patients with myopia in their right eyes. Spherical power and cylindrical power were achieved by cycloplegic autorefraction. The eyes were divided into three groups for analysis based on their spherical equivalent (SE) values. The 4mm and 6mm ocular and internal aberrations were measured using the OPD-scan III. Lens parameters were measured using CASIA2, including lens thickness (LT), radius of anterior/posterior lens surface curvature (RAL/RPL), lens decentration (DEC), and lens tilt (TILT). The differences of lenticular parameters and aberration parameters among the three groups analyzed with ANOVA or Kruskal Wallis test. Pearson correlation or Spearman correlation analysis was performed to evaluate the relationships between the lens parameters and aberrations. A p value < 0.05 indicated statistical significance. The difference in LT, RAL, DEC and TITL among the three groups was statistically significant (p < 0.05). And there were differences among differences in internal high-order aberrations, spherical aberration, and coma aberration(p < 0.05).Spherical power was positively correlated with LT and TITL (p < 0.05) and negatively correlated with DEC, RAL, and RPL (p < 0.05). Cylindrical power was positively correlated with LT (p < 0.05) and negatively correlated DEC (p < 0.05); The lenticular parameters (LT, RAL, DEC, and TILT) were mainly correlated with the ocular and internal spherical aberration. LT and DEC were correlated with ocular and internal higher-order aberrations and comaaberration. DEC and LT were the main factors affecting aberrations in patients with myopia.