Cylinder Power Research Articles

Postoperative stability of refractive error after cataract surgery

Aim. The goal of the present study is to determine how much time must pass after a cataract surgery with no complications to achieve a sufficiently stable refraction. Subjects and methods. We measured the postoperative refraction of 61 pseudophakic subjects (mean age: 74.32 ± 7.11 years) five times with an autorefractor. The subjects had undergone unilateral cataract surgery and the time intervals for the measurement went from one day to eight weeks after the operation. In order to obtain the spherical equiva- lent (SE) and the cylinder power, the difference from each measurement and the last measurement in the seventh or eighth week post-surgery was taken. The Friedman test for paired samples was used to see if there were any significant differences in spherical equivalent and cylinder power in the 5 measurements taken. In addition, two repeated measure- ments were taken on one eye of 16 phakic subjects with good ocular health pertaining to a similar age group to determine the measurement uncertainty of the autorefractor (± 1.96 SD for the measured value differences). Results. In the case of the spherical equivalent, we found no statistically significant difference between the individual re- peated test series. The cylinder power was significantly higher on the first day after the operation than during all subsequent appointments, but then showed no significant difference between all measurements taken during the examinations after the first day. The differences in the spherical equivalent between one measurement and the reference measurement (7 - 8 weeks after the surgery) resulted in 95 % confidence intervals (± 1.96 SD) of approximately ± 2.00 dioptres (D) on the first day post-surgery and lay between ± 1.20 D and ± 0.80 D in post-surgery weeks 1, 3 and 5. The corresponding con- fidence intervals for the cylinder power were ± 2.00 D on the first day post-surgery and lay between ± 1.27 D and ± 0.88 D in post-surgery weeks 1, 3 and 5. The statistical dispersion of the spherical equivalent and the cylinder power decreased slightly as the time from the surgery increased. We estimated a measurement uncertainty for automated refractometry performed on older phakic eyes of ± 0.80 D for the spherical equivalent and ± 1.16 D for the cylinder power. Conclusion. The refractive power of a pseudophakic eye can be determined with sufficient certainty after one to three weeks after undergoing cataract surgery without compli- cations. This means that optical aids to correct any residual refractive error or presbyopia can be prescribed earlier than before and, hence, the number of follow-up appointments required to measure a stable refraction can be reduced. Keywords Cataract, postoperative refraction, refraction measurement, repeated automated refractometry, Intraocular lenses (IOL)

Clinical Spectrum of Ocular and Visual Dysfunction in Children with Periventricular Leukomalacia: A Need for an Interdisciplinary Approach

AbstractThe study aimed to evaluate the ocular motility and visual and optic disc abnormalities in children diagnosed with periventricular leukomalacia (PVL). A retrospective analysis was performed on 51 consecutive children who had ophthalmic symptoms and were diagnosed with PVL by using magnetic resonance imaging. The patients were assessed for visual function, strabismus, cycloplegic refraction, fundus examination, and if appropriate, spectral-domain optical coherence tomography and visual field testing were applied. The primary outcome measures were the prevalence and visual and ocular motility dysfunctions. Mean age was 5.72 ± 2.6 years (range = 1–12), median birth weight was 2,740 g (range = 1,240–3,460), and median gestational age was 34 weeks (range = 28–38). In total, 21 patients (39.6%) had neurological deficit, 11 (21.5%) had intellectual disability, and 19 (37.2%) had no neurological symptom. In the spherical equivalent refractive error and cylinder power analysis, 10 patients had ≥3.0 D myopia, 15 had ≥3.0 D hyperopia, and eight had ≥2.50 D astigmatism. Thirteen (25.4%) children had a best-corrected visual acuity between 20/40 and 20/20 for Snellen card, while 9 (17.6%) had strabismic amblyopia and 6 (11.7%) had anisometropic amblyopia. Manifest strabismus was present in 35 patients (68.6%); of whom 12 had esotropia (23.5%), 16 had exotropia (31.3%) and 6 had vertical deviation (11.7%). Manifest or latent nystagmus was detected in 14 patients (27.4%). In 28 patients (54.9%), there was optic nerve abnormality. Two patients had hypoplastic disc, 14 had optic disc pallor, 7 had large cupping, and 5 had total optic atrophy. Six subjects underwent reliable visual field (VF) examinations, and all six had abnormal VFs, with inferior fields being most affected. Ocular motility disorders, optic nerve abnormalities, VF defects, and low visual acuity are common findings in this cohort of PVL patients and maybe the only presenting signs of the disease. The recognition of the visual disabilities and implementation of early rehabilitation may have a significant benefit in these children.

Research on sealing characteristics of annular power cylinder based on twin-rotor piston engine

The sealing characteristics of an annular power cylinder based on the Twin-rotor piston engine are studied, which provides a theoretical foundation for the sealing design of a new high-power density piston engine. In this paper, the basis thermodynamic realization process of an annular power cylinder is presented. The Runge Kutta equation is used to establish the coupled leakage model of adjacent working chambers under annular piston seal. And the sealing performance of the annular power cylinder is analyzed in detail. Moreover, the influence of rotor speed and compression ratio on the sealing characteristics and leakage is studied. Finally, some tests are carried out to verify the sealing principle and simulation results, which verifies the theoretical basis of simulation analysis. Results show that there are double pressure peaks in the leakage chamber between two working chambers, which is beneficial to reduce the leakage rate. Besides, increasing the speed and decreasing the compression ratio can help to reduce gas leakage. Furthermore, the effects of speed variation on the leakage are only significant when rotating at low speed. Changing the compression ratio has a greater effect on the slope of the leakage curve at a low compression ratio, and the lower the compression ratio, the better the sealing effect.

Development of e-automated control system friction clutch of the vehicle

Problem. One of the most pressing problems of modern automotive industry is to simplify and facilitate driving. As for such a branch of the automotive industry as military equipment. One of the keys to successful completion of the task by the crew of any combat vehicle is the least possible distraction from the process of driving a vehicle and focus on the task. This is possible if the vehicle is provided with relatively comfortable driving conditions, good dynamic properties and the required minimum of controls. The solution to the issue of facilitating car driving cannot be solved without automation of transmission control. Goal. The aim of the project is to create a prototype of an electronic system of automated control of the friction clutch of a vehicle to increase the reliability and efficiency of special and military vehicles. Methodology. Analytical methods of research, program and full-scale modeling, experimental researches on real object of management are used. Originality. New interrelations between the structural elements of the actuator of the friction clutch are proposed, which allow to ensure the required speed of the actuator of the electropneumatic clutch control drive without losing control accuracy when using two electropneumatic valves. The proposed control algorithm of the actuator allows the use of both normally closed valves without residual pressure in the power cylinder. Practical value. The stages of synthesis of the electronic control system are carried out. The algorithm of operation of the tracking system with the use of PID-regulator and taking into account the features of the actuator is proposed and debugged. A new clutch pedal design with an induction sensor is proposed, which provides high accuracy and speed, and also requires only two wires to connect.

Central and mid-peripheral corneal astigmatism in an elderly population: a retrospective analysis of Scheimpflug topography results

Implantation of toric intraocular lenses (IOLs) has become standard in the correction of corneal astigmatism. The IOL selection is based on keratometric measurements of the central cornea. However, mid-peripheral corneal changes may yield suboptimal correction in patients with larger pupils. This study retrospectively analyzed corneal topography data collected using a Scheimpflug device during routine clinical examinations. Of 11,953 patients, 641 met the inclusion criteria. Total corneal astigmatism was compared between five concentric zones (2–6 mm) using vector analysis. The absolute difference between astigmatism at 2 mm and 6 mm was 0.30 D (− 0.36 to 0.64), which decreased to 0.10 D (0 to 0.20) between the 5- and 6-mm zone. With-the-rule astigmatism was the most prevalent (53%), 34% had against-the-rule (ATR), and 13% had oblique. The decrease of the cylinder power with the diameter differed significantly between the three types, with ATR and oblique astigmatism being associated with the steepest change. Patients with high corneal astigmatism tend to demonstrate larger differences between the center and mid-periphery than those with low and moderate astigmatism. In conclusion, we demonstrated that central corneal astigmatism differs from that measured at the mid-periphery and that a larger difference was found in patients with ATR, oblique and high astigmatism.

Investigation into the Relationship between Super-Knock and Misfires in an SI GDI Engine

The super-knock poses new challenges for further increasing the power density of spark ignition (SI) engines. The critical factors and mechanism connecting regarding the occurrence of super-knock are still unclear. Misfire is a common phenomenon in SI engines that the mixture in cylinder is not ignited normally, which is often caused by spark plug failure. However, the effect of misfire on engine combustion has not been paid enough attention to, particularly regarding connection to super-knock. The paper presents the results of experimental investigation into the relationship between super-knock and misfires at low speed and full load conditions. In this work, a boosted gasoline direct injection (GDI) engine with an exhaust manifold integrated in the cylinder head was employed. Four piezoelectric pressure transducers were used to acquire the data of a pressure trace in cylinder. The spark plugs of four cylinders were controlled manually, of which the ignition system could be cut off as demanded. In particular, a piezoelectric pressure transducer was installed at the exhaust pipe before the turbocharger to capture the pressure traces in the exhaust pipe. The results illustrated that misfires in one cylinder would cause super-knock in the other cylinders as well as the cylinder of itself. After one cylinder misfired, the unburned mixture would burn in the exhaust pipe to produce oscillating waves. The abnormal pressure fluctuation in the exhaust pipe was strongly correlated with the occurrence of super-knock. The sharper the pressure fluctuation, the greater the intensity of knock in the power cylinder. The cylinder whose exhaust valve overlapped with the exhaust valve of the misfired cylinder was prone to super-knock.

Experimental Comparison of Low-Load Piston Compounding Deactivation for the DBDC+EC Engine Architecture

<div class="section abstract"><div class="htmlview paragraph">An experimental piston compounded engine was designed with guidance from thermodynamic modeling, then was built and tested to compare the model predictions to measured results. This Downsized Boosted Dilute Combustion, Exhaust Compounded (DBDC+EC) engine concept has shown great potential for improvements in efficiency at high loads through extended second expansion process, but suffered from excessive expander cylinder pumping and low exhaust temperatures at low loads. Four expander operating strategies were experimentally tested and simulated at a range of engine speeds and loads to determine the most efficient method to deactivate the piston compounding at low loads. The most effective method involved deactivating all the expander valves and operating it as an air-spring while diverting power cylinder exhaust gasses through a separate bypass port. While this method requires some unique hardware development to enable on-the-fly actuation, it offers 15% to 22% improvements in low-load BSFC over the active expander method while improving exhaust temperatures by 100° to 150°C.</div></div>

Agreement Between Retinoscopy, Autorefractometry and Subjective Refraction for Determining Refractive Errors in Congolese Children.

ObjectiveTo assess the agreement between retinoscopy and autorefractometry and between subjective refraction and both retinoscopy and autorefractometry in Congolese children.Patients and MethodsFifty-four children (6–17 years old) were enrolled consecutively in this cross-sectional study. Refraction was evaluated before and after cycloplegia (1% cyclopentolate) with retinoscopy and autorefractometry. Readings were compared (paired t-test) and agreement assessed with Bland–Altman plots. Subjective refraction was compared with the two methods to determine which one provides better reference estimates for subjective refraction.ResultsUnder cycloplegia, the spherical power was comparable between retinoscopy and autorefractometry (1.12 ± 1.37 D vs 1.22 ± 1.06D, P = 0.70), cylinder power was significantly more myopic on retinoscopy than autorefractometry (0.80 ± 1.10D vs −0.62 ± 0.66, P = 0.019), and SE was greater on autorefractometry than retinoscopy (0.91 ± 1.10D vs 0.72 ± 1.00D, P = 0.014). Retinoscopy and autorefractometry overestimated the power of spherical (P = 0.022 and 0.002, respectively) and cylindrical components (all P < 0.001). There was an agreement between retinoscopy and autorefractometry in measuring spherical (bias: 0.09 ± 0.16D; limit of agreement, LoA: −0.40 to 0.22D) and cylindrical power (bias: −0.18 ± 0.20D; LoA: −0.57 to 0.21D). Subjective refraction agreed with cycloplegic retinoscopy for determining SE power (bias: 0.11D; LoA: −0.51 to 0.73D).ConclusionRetinoscopy and autorefractometry can be used interchangeably in children for determining the power of spherical and cylindrical components. Cycloplegic retinoscopy is better than autorefractometry to obtain SE reference values for subjective refraction in children.

Hand-Held Nidek versus Table-Mounted Huvitz Autorefractors and Their Agreement with Subjective Refraction in Adults.

ObjectiveTo compare the agreement between commercially available table mounted and a hand-held autorefractors and their agreement with subjective refraction. The effect of different body position with the handheld autorefractometer was also evaluated.MethodsA prospective study was performed on 253 healthy eyes. Refraction was acquired by a table-mounted Huvitz and hand-held Nidek autorefractometer, subjective refraction was acquired. Refractive errors were compared in terms of spherical equivalent (SE), cylinder power, and the J0 and J45. The level of agreement was evaluated by Bland–Altman plots.ResultsThere was a significant difference in SE measurements between both devices and between them and subjective refraction (P=0.00). The Huvitz SE readings tended to be less myopic. However, limits of agreement (LOA) for SE were narrowest for Nidek sitting vs supine followed by Huvitz vs subjective SE refraction. The LOA for SE for Nidek sitting vs subjective SE were of wider range. For cylinder values, LOA were similar for all devices and positions and between them and subjective cylinder refraction.ConclusionTable mounted Huvitz and Nidek portable autorefractor cannot be used interchangeably in clinical practice except for estimation of the cylinder power. No difference in refraction between sitting and supine positions for portable Nidek autorefractor but with caution in cylinder axis. High agreement was achieved between subjective refraction and Huvitz readings but not with Nidek hand-held autorefractor. A highly reliable spectacle prescription could be done based on Huvitz readings. Both devices and positions could be used interchangeably in estimation of K-readings.

Progressive-toric IOL design reduces residual astigmatism with increasing pupil size: a ray-tracing simulation based on corneal topography data.

Population studies indicate that astigmatism decreases from the corneal center toward the periphery. A standard toric intraocular lens (IOL) with a constant cylinder power cannot correct uniformly across this gradient. We built an astigmatic eye model based on corneal topography data. A progressive-toric lens with gradually decreasing cylinder power was compared with an identically designed lens but featuring conventional astigmatism correction. Residual astigmatism did not differ significantly (P=0.06) at 3 mm, and the Strehl ratio was identical for both lenses (0.51 ±0.15, P=0.88). At 5 mm, the progressive IOL yielded significantly lower residual astigmatism by 0.10 D (P<0.001). The Strehl ratio was 0.30 ±0.08 with the progressive and 0.29 ±0.08 with the standard lens (P<0.001). At 3 mm, the optical performance was comparable for both IOLs. However, at 5 mm, the progressive-toric was more effective in correcting astigmatism, and it yielded reduced residual astigmatism compared to a standard toric lens.

The biometric parameters of aniso-astigmatism and its risk factor in Chinese preschool children: the Nanjing eye study

BackgroundsAniso-astigmatism may hinder normal visual development in preschool children. Knowing its prevalence, biometric parameters and risk factors is fundamental to children eye care. The purpose of this study was to determine the biometric components of aniso-astigmatism and associated maternal risk factors in Chinese preschool children.MethodsIn the population-based, prospective cohort Nanjing Eye Study, children were measured for noncycloplegic refractive error using an autorefractor and for biometric parameters using an optical low-coherent reflectometry. The difference of total astigmatism (TA) between both eyes was calculated using cylinder power (non-vectorial aniso-TA was defined as ≥1.00 Dioptre Cylinder [DC] between both eyes) and by vector analysis (vectorial aniso-TA was defined as a difference of ≥0.5 in J0 or J45 between both eyes which is equivalent to 1.00 DC). The prevalence of aniso-TA was presented. Interocular biometric parameters were compared between with vs. without aniso-astigmatism group. In addition, risk factors were determined using multivariate logistic regression model.ResultsOf 1131 children (66.90 ± 3.38 months, 53.31% male), the prevalence of non-vectorial aniso-TA was 1.95% (95% Confidence Interval (CI) = 1.14–2.75%), while the prevalence of vectorial aniso-TA was twice as common as non-vectorial aniso-TA, neither varying with sex or age. With aniso-TA eyes were more asymmetric in axial length and corneal curvature radius than without aniso-TA eyes. In multivariate logistic regression model, 5-min Apgar score less than 7 was significantly associated with higher risk of aniso-TA (vectorial aniso-TA: Odds Ratio (OR) = 6.42, 95%CI = 2.63–15.69, P < 0.001; non-vectorial aniso-TA: OR = 4.99, 95%CI = 1.41–17.68, P = 0.01). Being twin or triple was significantly associated with higher risk of vectorial aniso-CA (OR = 2.43, 95%CI = 1.05–5.60, P = 0.04). Pre-term delivery (OR = 2.60, 95%CI = 1.09–6.15, P = 0.03) and post-term delivery (OR = 3.61, 95%CI = 1.31–9.96, P = 0.01) were significantly associated with higher risk of vectorial aniso-CA.ConclusionsBoth corneal curvature radius and axial length asymmetry were correlated with aniso-TA. Children with 5-min Apgar score < 7 were more likely to have aniso-TA, while twin or triple, pre-term or post-term delivery were more likely to have vectorial aniso-CA.

Grading Sphero-Cylinder Spectacle Similarity.

BackgroundPortable autorefractors can estimate refractive error in remote locations, but sphero-cylinder comparison and donated-spectacle dispensing are not yet simple.MethodsNormal astigmats determined best corrected acuity, then degraded 1 logMAR (Grade A), 3 logMAR (Grade B), and 6 logMAR (Grade C) to determine limits of astigmatism axis and power at these levels. The cylindrical refraction was vector transformed with J0 on the abscissa and J45 on the ordinate.ResultsTen subjects produced multiple refractions at the interfaces of Grades A, B, and C representing ovals on the J0 and J45 coordinates. When rotated, the vertical axis represented 45° or 135°, the horizontal long axis was 1.6× the short axis. The size of the ovals positively correlated with cylinder power. Given a target refraction, the comparability of a candidate lens was demonstrated on our interactive database yielding a simple A, B, C, or worse grade for cylinder, spherical equivalent, and pupillary diameter.Conclusion(s)/RelevanceInputting a remote autorefraction, pupillary diameter and age as target and a donated spectacle as the candidate with a “B” grade similarity would be expected to attain 20/40 acuity (3 logMAR degrade) if best corrected visual acuity was 20/20. This practical Excel database could facilitate widespread remote lay dispensing of the cylinder as well as spherical spectacles. The grade similarity can also compare refracting tools such as photoscreeners and hand-held autorefractors.Clinical Trials RegistryNCT04297969.

Динамика функционального состояния слезной пленки и параметров авторефрактометрии на фоне инстилляций препаратов гиалуроновой кислоты различной вязкости

Aim: to study the changes in the critical parameters of tear film stability and autorefractometry in patients with mild dry eye syndrome (DES) after instilling artificial tear products of different viscosity. Patients and Methods: thirty patients aged 23–70 with mild bilateral DES were examined using the Visionix VX120+Dry Eye multi-diagnostic unit equipped with the TF-Scan to fix and assess tear film stability and tear breakup time (TBUT). The critical refraction and tear film parameters were evaluated by keratometry, corneal topography, TBUT, and tear meniscus height measurements. Next, an artificial tear product was instilled, i.e., group 1 (14 patients, 28 eyes) received a 0.15% sodium hyaluronate-based preparation, and group 2 (16 patients, 32 eyes) received a 0.4% sodium hyaluronate-based preparation. The examination was repeated after 30 sec and 5 min. Controls were seven healthy individuals (14 eyes). Results: in DES, breaks in the tear film appeared earlier and affected greater corneal surface area. A "Destabilized tear film area" parameter of the Visionix VX120+Dry Eye contributed significantly to the knowledge of tear film functionality, thereby empowering the diagnostic armamentarium in DES. As early as 30 sec after instillation of both artificial tear preparations, breakup-free time tended to increase, while the area of tear film destabilization tended to reduce. After 5 min, this trend continued to increase, particularly after instilling 0.15% sodium hyaluronate-based preparation. At the same time, changes in keratometry readings (i.e., sphere and cylinder) and astigmatism axis orientation were reported. Corneal refractive power (more in the flattest axis) increased, in particular, after the instillations of 0.15% hyaluronic acid. The range of changes was 0.00–0.75 D for the sphere power, 0.00–0.50 D for the cylinder power, and 0–69 degrees for astigmatism axis orientation. Conclusions: our findings with the Visionix VX120+Dry Eye multi-diagnostic unit demonstrate a significant variation of autorefractometry readings in DES depending on the extent of ocular surface hydration. These phenomena raise questions about the accuracy of autorefractometry readings. Therefore, autorefractometry should be performed after normalizing tear film volume and stability. Keywords: dry eye syndrome, Visionix®, autorefractometry, tearscopy, the effect of artificial tears on results. For citation: Brzheskiy V.V., Efimova E.L., Kopylova M.A. et al. Changes in the functionality of tear film and autorefractometry reading after instillations of artificial tear products of different viscosity. Russian Journal of Clinical Ophthalmology. 2021;21(4):200–204 (in Russ.). DOI: 10.32364/2311-7729-2021-21-4-200-204.

Refractive and Visual Outcome of Misaligned Toric Intraocular Lens After Operative Realignment

The study was performed to evaluate the refractive and visual outcome of patients with misaligned toric intraocular lenses (IOLs) after operative realignment, with and without back-calculation of the toric axis after implantation of the IOL. Institutional, retrospective case-control study. This is a retrospective case series of 39 patients who underwent a second operation to realign a misaligned toric IOL from August 2013 to December 2019 at the Department of Ophthalmology, Goethe University, Frankfurt, Germany. Ideal toric axis was calculated using the back-calculator astigmatismfix.com. The study consists of 39 treated eyes (20 [51%] right eyes). The toric IOLs showed a postoperative misalignment of 25.69 ± 26.06°. Postrotational, uncorrected distance visual acuity (UDVA) improved from 0.39 ± 0.29 logMAR to 0.27 ± 0.18 logMAR. Refractive outcome showed a reduction of residual sphere and cylinder. The postoperative UDVA when performing alignment to the preoperative calculated axis (51%) was 0.24 ± 0.16 logMAR with a cylinder of 0.90 ± 0.90 diopter (D). In the group with alignment to a back-calculated axis (49%), the UDVA was 0.32 ± 0.20 logMAR with a cylinder of 0.76 ± 0.72 D. High cylinder power IOLs (≥2 D) showed a higher decrease in residual cylinder when back-calculation was performed than low cylinder power IOLs (<2 D) (27% vs 9%). The mean spherical equivalent prediction error of the back-calculator was 0.54 ± 0.55 D. Realignment of misaligned toric IOLs improves visual acuity and reduces residual refractive errors. Especially for high cylinder power IOLs, better refractive outcome can be seen when performing a back-calculation before realignment.

The association of comfort and vision in soft toric contact lens wear

PurposeThis work set out to investigate if there was an association between subjective comfort and both subjective and measured vision during the use of contemporary daily disposable soft toric contact lenses. MethodsThirty-eight habitual soft contact lens wearers wore each of three daily disposable toric lenses for one week in a prospective, crossover, randomised, single-masked study. The following clinical measures were recorded at dispensing and follow-up visits: biomicroscopy scores, lens fitting (including rotation and rotational stability), high and low contrast visual acuity, subjective vision quality and subjective ocular surface comfort. Subjective scores were collected using 0–10 numerical grading scales. Comfort scores were analysed using a linear regression model with age, sex, visit, phase of crossover (‘phase’), lens type, lens rotation, lens rotational stability, visual acuity, cylinder power and subjective vision quality as factors of interest and then refined using backward stepwise regression. ResultsThirty six participants (31.1 ± 13.5 years) completed the study. Comfort scores were found to be associated with subjective vision quality (F = 127.0 ; p < 0.0001), phase (F = 7.2; p = 0.001) and lens type (F = 4.9; p = 0.009). Greater comfort scores were observed with greater subjective vision quality scores. Visual acuity was not statistically significant in the model. ConclusionThis work suggests that symptoms of ocular discomfort may be more intense if there is also perceived visual compromise in daily disposable soft toric lenses. There was a stronger positive correlation between comfort and subjective vision quality compared with comfort and measured visual acuity.

Topographic properties of the cornea in welders.

The aim of the present study was to evaluate the topographic status of the welders' corneas. In this historical cohort, a group of welders (with at least 5 years' experience in welding) and a control group were assessed and compared. Lack of exposure to welding for 3 months or more was considered an exclusion criterion. In all participants, after taking a complete history of visual and ocular problems, both eyes underwent Pentacam imaging. Then, all subjects received slit lamp biomicroscopy for evaluation of ocular surface diseases. The data of 140 welders (mean age: 46.66 ± 13.01 years) and 172 controls (mean age: 45.05 ± 12.61 years) were analyzed. The welders' corneas had significantly higher eccentricity (p < 0.0001), keratometry readings (p < 0.0001), and cylinder power (p < 0.0001). The central, inferior, and nasal cornea were significantly thinner in the welders than in controls (p < 0.0001) while the difference was not significant in the superior and temporal cornea. All indices of corneal irregularity except for the central keratoconus index (CKI) and index of height asymmetry (IHA) were higher in welders compared to the control group (p < 0.0001). According to the results of this study, the welders' corneas are topographically irregular. Welders exhibit characteristics like steeper keratometry readings; higher eccentricity indexes; thinner central, inferior, and nasal corneas; and higher indices of corneal irregularity, especially the CK index. Long-term ultraviolet exposure may be a possible reason for these corneal changes.

Astigmatic Results of a Diffractive Trifocal Toric IOL Following Intraoperative Aberrometry Guidance.

PurposeTo determine if intraoperative aberrometry (IA) improves astigmatic outcomes for trifocal toric IOL (TTI) cases.Patients and MethodsThis was a retrospective study examining 137 eyes that underwent cataract extraction and TTI implantation using femtosecond laser, digital registration, and IA. Final cylinder power and axis of placement were determined by IA. Monocular uncorrected distance visual acuity (UDVA), uncorrected intermediate visual acuity (UIVA), uncorrected near visual acuity (UNVA), and refractive data were collected at 3 months. Postoperative residual astigmatism (PRA) determined by manifest refraction was compared to back-calculated residual astigmatism (BRA) using the cylinder power calculated preoperatively.ResultsPostoperatively, 97.8% of eyes had IA PRA ≤ 0.50D and 80.3% had BRA ≤ 0.50 D, a difference of 17.5%. Mean PRA for IA was 0.07 D ± 0.19 (range 0.00–1.00 D) compared to BRA 0.31 D ± 0.33 (range 0.00–1.34 D) (P < 0.001). Cylinder power was changed in 50.4% of cases based upon IA. Postoperative mean UDVA (LogMAR) was 0.04 ± 0.09 (range −0.12–0.30 logMAR), and 65% of eyes were ≤ 0.0, 85% ≤ 0.1, and 99% ≤ 0.18.ConclusionThe proportion of eyes with PRA ≤ 0.50 D and mean PRA was significantly lower using IA versus the preoperative planned cylinder power.

Effect of di-tert butyl peroxide (DTBP) on combustion parameters and NOx in dual fuel diesel engine with hydrogen as a secondary fuel

Recently, the great challenges in the use of compression ignition (CI) engines are to reduce the reliance on conventional petroleum fuels and exhaust emissions. While the current available technologies for reducing engine emissions are nearly close to the limits of statute and those limits are expected to be, more stringent in the near future. Although hydrogen-diesel operation can provide significant benefits in thermal efficiency and harmful emissions, the combination of the two fuels, often leads to increased NOx emissions. To reduce the NOx emissions the addition of additive Di-tert butyl peroxide (DTBP) has a very good potential. The formation of NOx is depending upon reaction of atmospheric oxygen and nitrogen at elevated temperatures. Therefore, it is essential to study the effect of DTBP on net heat release rate and mean in-cylinder temperature which affects the formation of NOx.This paper presents the results of H2-diesel co-combustion in the diesel engine, working on dual fuel mode, with and without blending of additive (di tert butyl peroxide) in the diesel fuel. The net heat release (NHR) and in cylinder mean temperature have been analysed experimentally on the single cylinder power 3.5 KW @ 1500 rpm, four strokes, compression ignition, model Kirloskar TV1 diesel engine.It was observed that by 14% substitution of hydrogen and 1% of additive, net heat release and temperature decreased by 2 and 10% respectively, while, NOx get increased by 60% at high load condition as compared to diesel operation.In last, it is concluded that NOx formation is minimum by addition of 1% of DTBP with 14% of hydrogen in dual fuel diesel engine.

The effect of contact lens wear on retinal spectral domain optical coherence tomography

BackgroundThis study assessed the impact of contact lens wear on retinal spectral domain optical coherence tomography (SD‐OCT) image quality and macular thickness measurements, among subjects with myopia.MethodsThis was a prospective study including 34 subjects (26.59 ± 3.19-years) with myopia or myopic astigmatism. Twelve were imaged wearing spherical soft contact lenses, eight non‐contact lens wearers were imaged with a plano soft contact lens, and 14 with significant astigmatism were fitted with a rigid gas permeable (RGP) contact lens. For each group of contact lens types, the average image quality index (Q‐index), and the average macular thickness measurements were compared between macular OCT scans obtained from the same eyes with and without a contact lens.ResultsAmong the subjects assessed with their habitual spherical soft lenses, the average Q‐index was similar for scans acquired with and without a contact lens (30.10 ± 1.94 versus 31.03 ± 2.55; p = 0.18). Among non‐contact lens wearers, the average Q‐index was slightly higher for scans acquired without a contact lens, compared to scans with a plano contact lens (31.99 ± 2.06 versus 29.51 ± 1.56; p = 0.006). Among 14 subjects imaged wearing a fitted RGP contact lens, the Q‐index was similar for scans acquired with and without a contact lens (29.04 ± 2.73 versus 28.75 ± 2.86; p = 0.78). In all groups, there were no correlations between the power of the sphere and change in the Q‐index (that is, post‐ minus pre‐contact lens Q‐index), and no differences were found between OCT‐derived macular thickness measurements from scans with and without a contact lens. The magnitude of cylinder was not correlated with the change in the Q‐index in the habitual and RGP contact lens groups. However, an inverse correlation between cylinder power and change in the Q‐index was found in the plano contact lens group.ConclusionIn low to intermediate levels of myopia, with or without regular astigmatism, macular SD‐OCT imaging does not merit placement of a soft or rigid contact lens, nor is there an added benefit from removing a habitual spherical soft lens prior to scanning.

Trifocal toric intraocular lenses in eyes with low amount of corneal astigmatism.

To evaluate the refractive and visual outcomes following cataract surgery and implantation of a trifocal toric intraocular lens (IOL) in eyes with low degrees of corneal astigmatism. Twenty-six eyes of 22 patients who underwent implantation a trifocal toric IOL (FineVision PODFT, PhysIOL s.a., Liege, Belgium) were enrolled. Phacoemulsification with femtosecond laser, capsular tension ring insertion and intraoperative aberrometry were performed in all cases. All IOLs used showed a cylinder power of 1.00 D. Main outcome measures were refractive error and corrected-distance visual acuity (CDVA) and uncorrected-distance visual acuity (UDVA) values. Eyes were evaluated at 4mo post-surgery. Totally 50% of eyes showed a spherical equivalent (SE) within ±0.13 D and all of them within ±0.50 D. The mean SE and refractive cylinder were -0.02±0.23 and -0.16±0.22 D, respectively. Vector analysis revealed that 100% of eyes were within ±0.50 D for the SE and cylindrical components (J0 and J45). Refractive changes were not correlated with keratometric changes (P>0.05) showing that the reduction in astigmatism comes from the trifocal toric IOL. Of 81% and 96% of eyes showed UDVA and CDVA of 20/20, respectively. The postoperative mean values of monocular distance Snellen decimal UDVA and CDVA were 0.97±0.05 and 0.99±0.02 (about 20/20), respectively. Our study suggests that the use of this trifocal toric IOL in patients with low amount of astigmatism provides accurate refractive outcomes and enables them to achieve excellent visual acuity.