Refractive index of soft contact lens materials measured in packaging solution and standard phosphate buffered saline and the effect on back vertex power calculation

PurposeTo measure the refractive index (RI) of commonly available soft contact lens (CL) materials, their packaging solutions and compare to the manufacturers’ nominal RI. The relationship between RI versus water content, and the effect of inaccurate RI when converting lens power measured in solution to in-air back vertex power were examined.MethodsThe RI of 18 single vision soft CL materials were measured using CLR 12–70 digital refractometer. Three lenses of each material were measured, in their packaging solution and then after soaking in standard phosphate buffered saline (PBS). The RIs of packaging solution were also measured. Accuracy requirements for correct wet to dry power conversion based on thick lens formula were projected.ResultsThe standard deviation between three samples was less than 0.005. The measured RI ranged from 1.3744 ± 0.001–1.4265 ± 0.0004 for PBS soaked and from 1.3739 ± 0.0003–1.4264 ± 0.0024 for packaging solution soaked materials. Comparing nominal with mean measured PBS and packaging solution RIs, 5 and 3 lens materials, respectively, fell outside ISO tolerance. The packaging solution RI of DailiesAquaComfortPlus had the largest difference of 0.0040, compared to RI of standard PBS. For converting lens power measured in PBS to in-air power, the difference between measured and nominal RI of 0.0104 would result in wrongly calculated in-air power 0.99 D for a -6.00 D lens.ConclusionThe CLR 12–70 is reliable and accurate refractometer for the measurement of soft CL materials. Accurate RI measurements are of relevance with increased use of wavefront sensors to measure lens power while they are immersed in solution. Even small errors in solution or material RI can lead to significant errors in converted in-air power. To obtain valid in-air lens power results, measurement conditions must match the material and solution RIs used for the conversion.     

Atomic force microscopy analysis of the effect of plasma treatment on gas permeable contact lens surface topography

PurposeUsing atomic force microscopy (AFM) to investigate anterior surface topography (AST) in worn and unworn, plasma surface-treated (PST) and untreated (UT) gas permeable (GP) lenses, and influence of surface topography on in vivo comfort.MethodsGP lens AST evaluated with AFM in tapping mode, using an uncoated, 40 nm symmetric tip (sampling frequency: 300 kHz), at five randomised locations, over a 100μm² area, to produce mean average roughness (Ra) and root mean square (RMS) values for each sample. Four unworn lenses (two PST, two UT) were examined (Quasar/Boston EO material). Twenty worn lenses (ten PST, ten UT) of same design and material as unworn lenses collected after 3 months lens wear. General wearing comfort reported by visual analogue scale (VAS) at 3 months visit. For sample preparation, two worn UT GP lenses were divided into four segments; each segment underwent a different lens rinse and drying method.ResultsUnworn: UT lenses had significantly higher mean RMS and Ra values compared to PST (Mann-Whitney, p < 0.05). Worn: UT Median RMS values were significantly higher than PST (Mann-Whitney, p < 0.05). Comfort: no correlation found between general comfort and RMS or Ra scores. Sample preparation: Method 4 (purified, distilled water rinse/nitrogen gas dry) produced optimum median RMS and Ra values.ConclusionsUnworn PST GP lenses had lower Ra and RMS values compared with unworn UT GP lenses. After 3 months wear, PST lenses had smoother surface topographies than UT lenses. No relationship was found between surface topography and lens wear comfort. Sample preparation protocol directly impacts AFM results.     

The impact of patient behaviour and care system compliance on reusable soft contact lens complications

Reusable soft daily wear contact lenses (CLs) remain popular and were fit to just over half of all wearers in the most recent international CL prescribing survey. Unlike daily disposable CLs, reusables require cleaning and disinfecting after every use, along with storage in a CL case. These additional requirements add a number of steps to the daily wear and care routine, increasing the opportunities for CL wearers to exhibit non-compliant behaviour. The impact of non-compliance ranges from poor lens comfort through to potentially sight-threatening infective keratitis. The coronavirus pandemic has refocused the profession on the importance of hand hygiene in particular, and the need for promoting safe CL wear in general. This review summarises typical non-compliant behaviour related to reusable CLs, and examines strategies and opportunities to better support wearers. Patient education has a central role in encouraging compliant behaviour, although patient recall of information is low, and personal belief systems may result in continuation of non-compliant behaviour despite awareness of the risks. CL care solutions are required for the daily disinfection of lenses, however misuse of multipurpose solutions (MPS) and hydrogen peroxide (H₂O₂)-based care systems can challenge their ability to be fully efficacious. Standard efficacy testing is reviewed, with consideration of how well current protocols model real-world use of CL solutions. Although some recommendations are in place for the inclusion of additional variables such as lens cases, CL materials, organic soil and efficacy against Acanthamoeba, opportunity still exists to reevaluate global standards to ensure consistency of testing in all markets. Finally, potential future innovations are discussed which may further support increased safety in reusable lens wear through novel antimicrobial additions to both CL materials and cases.     

The effect of lens wear on refractive index of conventional hydrogel and silicone-hydrogel contact lenses: a comparative study.

PURPOSE: The purpose of this work was to evaluate the ability of four silicone-hydrogel contact lenses (galyfilcon A, balafilcon A, lotrafilcon A and lotrafilcon B) to retain their equilibrium water content before and after wear, through measurements of refractive index and compare with that of a conventional disposable hydrogel contact lens (etafilcon A). METHODS: The refractive indices of 115 contact lenses were measured using an automated refractometer (CLR 12-70, Index Instruments, Cambridge, U.K.) before and after a schedule of daily wear by 58 patients for 30 days in the case of silicone-hydrogel lenses and 15 days for the conventional contact lenses. RESULTS: In the silicone-hydrogel contact lenses the changes on the refractive indices were not statistically significant, however after being worn the refractive index of the conventional etalfilcon A hydrogel contact lens increased significantly (p<0.001). CONCLUSION: The results presented here show that after being worn the silicone-hydrogel contact lens, show more capacity to retain or to reach their initial equilibrium water content than conventional hydrogel contact lenses. This suggests that the silicone-hydrogel contact lenses are less susceptible to spoilation over time maintaining its biocompatibility and contributing to the clinical success of lens performance.     

Enhancing the approach to selecting eyewear (EASE): A multi-centre, practice-based study into the effect of applying contact lenses prior to spectacle dispensing

Purpose

To examine the impact of contact lens application in non-contact lens wearers prior to spectacle dispensing.

Methods

Ninety-one eligible subjects with no previous contact lens experience were randomly assigned into either a test group (52 subjects) or control group (39 subjects). The former group was offered contact lenses before spectacle dispensing. The latter group proceeded to spectacle dispensing in the normal way without being offered contact lenses. The response to the offer of contact lenses, fit success, the impact on the spectacle dispensing process and the longer term purchase of contact lenses were measured and compared for the test and control groups.

Results

Of the test group, 46 (88%) agreed to try contact lenses. All subjects were suitable for contact lenses after a slit lamp examination and lenses were successfully fitted to 45 of the 46 subjects (98%). The test group reported a superior subjective spectacle dispensing experience and spent £267 ± 143 (mean ± standard deviation) on their spectacle frames and lenses, 32% more than the control group (£202 ± 128). At 3 months post dispensing, 17 test patients (33% of original cohort) had purchased contact lenses compared with five control subjects (13%) (p = 0.001).

Conclusions

The opportunity to try contact lenses prior to spectacle dispensing was well received by subjects who generally reported a very positive experience. In particular, contact lenses assisted in seeing frame detail and suitability for wear. One third of subjects proceeded to purchase contact lenses. We recommend that practitioners consider offering contact lenses to all suitable patients who are proceeding to spectacle dispensing to optimise the dispensing process and to provide an opportunity to try contact lenses.     

Non-contact tonometry over soft contact lenses: effect of contact lens power on the measurement of intra-ocular pressure.

PURPOSE: To perform non-contact applanation tonometry over soft contact lenses and to examine any differences between the measured IOPs with and without the contact lens. METHOD: IOP was measured at one eye of eight subjects and re-evaluated through a soft lens in situ over the cornea. Seventy percent (ES70, Lunelle) water contact lenses or powers ranging from -15.00 D to +13.00 D were used. RESULTS: Mean IOP without lenses was 15.2 mmHg (S.D. = +/-4.2) and this did not change significantly for lenses ranging from -15.00 D to +3.00 D (P > 0.01) but did change for lens powers +6.00 D and above (P<0.01). The least squares line describing the change in measured IOP (deltaIOP) as a function of lens power (x) has the following characteristics, deltaIOP = 0.022 + 0.591x + 0.11x2 + 0.005x3 (r = 0.985, P = 0.0001). CONCLUSION: Non-contact tonometry can be performed with sufficient accuracy over a soft lens on condition: (a) lens centre thickness is no more 0.30 mm and (b) power is not greater than +3D.     

保健食品提高缺氧耐受力功能评价的替代性研究

目的 探讨保健食品提高缺氧耐受力功能替代性新试验方法的可行性。方法 采用小鼠耐缺氧实验,建立斑马鱼缺氧模型,并检测样品对斑马鱼缺氧运动的改善情况及抗缺氧诱发的红细胞增多症。以连二亚硫酸钠处理原代培养乳鼠心肌细胞构建了化学性缺氧细胞模型,样品处理后进行细胞活性与乳酸脱氢酶（LDH）活性检测,分别验证样品对缺氧耐受能力的影响。结果 与正常对照比较,样品可以提高小鼠的缺氧耐受力;与缺氧模型对照比较,可以改善斑马鱼缺氧运动障碍、缺氧诱发的红细胞增多症,可以缓解心肌细胞缺氧导致的细胞活性降低及LDH活性升高。结论 用体内外三种试验体系均能检出样品具有提高缺氧耐受的能力,耐缺氧检验的动物试验替代方法的推出具有可行性。     

The effect of corneal power distribution on axial elongation in children using three different orthokeratology lens designs

PurposeTo investigate the correlation between spatial corneal power distribution and one-year axial length (AL) elongation using three ortho-k lens designs by a unified mathematical method.MethodsA total of 137 subjects were included: 42 with Euclid lenses, 28 with DRL lenses, and 67 with CRT lenses. AL elongation, Xmax, Ymax and power exponent were compared among the three groups. One-year relative corneal refractive power change (RCRPC) was calculated by a polynomial function and a monomial function. Factors including age, baseline spherical equivalent refractive error (SER), Xmax, Ymax and power exponent was tested against one-year AL growth in a stepwise multiple linear regression model.ResultsThe power exponent (F = 7.29, P = 0.0012) and Xmax (F = 62.88, P < 0.0001) of the DRL group was significantly smaller than that of the other two lens groups. Ymax was not significantly different among three lens groups (F = 1.18, P = 0.31). The one-year AL elongation of the DRL group (0.09 ± 0.14 mm) was significantly slower than that of the Euclid group (0.26 ± 0.14 mm, P = 0.002) and CRT group (0.32 ± 0.18 mm, P < 0.0001). AL elongation was significantly correlated with Xmax (standardized β = 0.196, P = 0.003), power exponent (standardized β = 0.644, P < 0.001), and age (standardized β = -0.263, P < 0.001), with R² being 0.608.ConclusionA smaller and more aspheric treatment zone may be beneficial for reducing axial elongation in children undergoing ortho-k treatment, regardless of their baseline myopic refractive error.     

提高牛仔布耐摩擦色牢度的研究

一般情况下,牛仔服装的耐摩擦色牢度较低,这既是牛仔服装的特点之一,也是影响牛仔服装质量的问题之一.牛仔服装的耐摩擦色牢度与牛仔布加工过程有关,探讨染料、染色方法、水洗、前处理、染色设备、织物结构以及牛仔布后整理工艺对牛仔布耐摩擦色牢度的影响,提出提高牛仔布耐摩擦色牢度的措施.     

The effect of diapause on the tolerance of larvae of Ephestia kuehniella to methyl bromide and phosphine

Larvae from a stock of Ephestia kuehniella Zeller, recently collected from an unheated flour store in southern England, were exposed at 10 and 15°C to two fumigants commonly used for the control of this species in the U.K. Various exposure periods were tested and the mortality of larvae which had entered diapause was compared with that of non-diapausing larvae.

Diapause increased the tolerance of larvae to methyl bromide and phosphine at low temperatures. The minimum dosage of methyl bromide for complete control of diapausing larvae was about 80 mgh/l during a 20-h exposure period at 10°C and less than 70 mgh/l during a 16-h exposure at 15°C. Complete kill of diapausing larvae at 10°C was obtained after a 4-day exposure to phosphine with a CT product of 8.1 mgh/l, but a slighly higher dosage was required in a test at 15°C.     

Evaluating the effect of ration composition on income over feed cost and milk yield

Feed is generally the greatest expense for milk production. With volatility in feed and milk markets, income over feed cost (IOFC) is a more advantageous measure of profit than simply feed cost per cow. The objective of this study was to evaluate the effects of ration cost and ingredient composition on IOFC and milk yield. The Pennsylvania State Extension Dairy Team IOFC tool (http://extension.psu.edu/animals/dairy/business-management/financial-tools/income-over-feed-cost/introduction-to-iofc) was used to collect data from 95 Pennsylvania lactating dairy cow herds from 2009 to 2012 and to determine the IOFC per cow per day. The data collected included average milk yield, milk income, purchased feed cost, ration ingredients, ingredient cost per ton, and amount of each ingredient fed. Feed costs for home-raised feeds for each ration were based on market values rather than on-farm cost. Actual costs were used for purchased feed for each ration. Mean lactating herd size was 170 ± 10.5 and daily milk yield per cow was 31.7 ± 0.19 kg. The mean IOFC was $7.71 ± $1.01 cost per cow, ranging from −$0.33 in March 2009 to $16.60 in September 2011. Data were analyzed using a one-way ANOVA in SPSS (IBM Corp., Armonk, NY). Values were grouped by quartiles and analyzed with all years combined as well as by individual year. Purchased feed cost per cow per day averaged $3.16 ± $1.07 for 2009 to 2012. For 2009 to 2012 combined, milk yield and IOFC did not differ with purchased feed cost. Intermediate levels (quartiles 2 and 3) of forage cost per cow per day between $1.45 and $1.97 per cow per day resulted in the greatest average IOFC of $8.19 and the greatest average milk yield of 32.3 kg. Total feed costs in the fourth quartile ($6.27 or more per cow per day) resulted in the highest IOFC. Thus, minimizing feed cost per cow per day did not maximize IOFC. In 2010, the IOFC was highest at $8.09 for dairies that fed 1 or more commodity by-products. Results of the study indicated that intermediate levels of forage cost and higher levels of total feed cost per cow per day resulted in both higher milk yield and higher IOFC. This suggests that optimal ration formulation rather than least cost strategies may be key to increasing milk yield and IOFC, and that profit margin may be affected more by quality of the feed rather than the cost.     

提高功率因数对节能降耗的作用分析

以提高系统的功率因数这一主题来实现节能降耗的目标，围绕这一主题在4个方面想办法：对于异步电动机，合理的选择电动机的容量，实行降压运行优化控制，提高检修质量；在低压供配电系统中装设电容器无功补偿装置；降低变压器的无功损耗；尽可能减少谐波分量的产生，消除整流装置对功率因数补偿设备的影响。     

用weibull理论评价表面处理对碳纤维拉伸强度的影响

采用常压等离子体对碳纤维表面进行改性处理,用weibull理论评价了等离子体处理前后碳纤维抗拉强度及其离散性的变化,验证了形状参数和强度离散的关系.结果表明常压等离子体处理在改善碳纤维表面性能时,基本不会影响碳纤维强度及其离散性.     

抗原口服耐受性影响因素的研究进展

抗原口服耐受性是经口接触某种抗原物质后机体再次接触这种抗原时对其免疫应答的主动抑制.机体每天都要接触大量的食物抗原,而抗原口服耐受性的存在使绝大部分人不会对这些抗原产生过敏反应.食物致敏性是人们关注的热点之一,通过建立动物模型来研究食物致敏性是一条比较直接的途径,而降低实验动物的口服耐受性可有效提高该模型的检出效力.本文就近年来口服耐受性影响因素及消除口服耐受性的措施或方法方面的研究进展进行综述.     

Comparison of the effect of multipurpose contact lens solutions on the viability of cultured corneal epithelial cells

Purpose

To determine the effect of four marketed multipurpose contact lens solutions (MPSs) on corneal epithelial cell viability.

Methods

Comparison of the effect of MPS A (Renu MultiPlus, Bausch &; Lomb), MPS B (OPTI-FREE Express, Alcon), MPS C (AQuify, CibaVision), and MPS D (OPTI-FREE RepleniSH, Alcon) on cell viability was performed by quantifying cellular ATP content, resazurin reduction, and lactate dehydrogenase (LDH) release in transformed human corneal epithelial cells (HCEpiC) and primary bovine corneal epithelial cells (BCEpiC).

Results

Significant reductions in cellular ATP content were observed at 40% solution and above with both MPS B and MPS D, compared to at 100% only for MPS A and MPS C, and similar results were obtained in BCEpiC. Effects on resazurin reduction were also less in HCEpiC exposed to increasing doses of MPS A and MPS C than in cells exposed to MPS B and MPS D. After 15 min, HCEpiC viability measured by both resazurin reduction and cellular ATP levels was significantly lower for cells exposed to MPS B, MPS D, and MPS C, while HCEpiC exposed to MPS A were not affected. MPS B and MPS D reduced cell viability more than MPS A and MPS C over a 2-h time course in both HCEpiC and BCEpiC.

Conclusions

Both MPS B and MPS D can cause large decreases in the viability of cultured corneal epithelial cells even with just a 2 h exposure at multiple doses. Significant reduction in cell viability is evident at brief 15-30 min exposures. In contrast, MPS A and MPS C have significantly less effect on the cell viability of corneal epithelial cells at multiple doses, after these short exposure times.     

Assessment of condition-induced changes on the ocular surface using novel methods to assess the tear film dynamics and the lipid layer

ObjectivesTo assess the effects of different condition-induced changes on current and novel ocular surface metrics.MethodsEighty-four healthy volunteers (22.4 ± 2.6 years) participated in this study. The ocular surface and tear film response to (1) computer use, (2) contact lens insertion and (3) tear film instillation during computer use with contact lenses were assessed. Current metrics included the ocular surface disease (OSDI) questionnaire, 5-item dry eye questionnaire (DEQ-5), bulbar redness, tear meniscus height (TMH) and non-invasive keratograph break-up time (NIKBUT). Novel metrics included the lipid layer thickness obtained from the intensity of the reflected Placido disk and the speed of tear film particles post-blink.ResultsHigher dry eye symptoms, TMH and bulbar redness, and lower values in metrics related to the intensity of the Placido disk pattern and to particle speed were found after the computer reading task (p < 0.036). When a contact lens was fitted, lower TMH, NIKBUT and particle speed metrics were obtained (p < 0.044). Mixed ANOVA revealed that artificial tears significantly ameliorated the effect of computer reading on OSDI, DEQ-5, NIKBUT, metrics related to the intensity of the Placido disk pattern and metrics related to particle speed (p < 0.033).ConclusionsComputer use and contact lens wear worsened dry eye signs and symptoms, but artificial tears ameliorated this effect. Newly developed methods can serve as a tool to detect changes in the tear film triggered by different ocular surface-disturbing conditions.     

不同微波功率对自来水中细菌杀菌效果的研究

微波杀菌是非热效应和热效应的共同作用。根据微波杀菌效果与微波功率、穿透深度及水量的相关关系,主要探讨了家用微波炉不同输出功率和微波的穿透深度对自来水中细菌杀菌效果的研究。实验表明,温度在60.0℃以下时,微波的输出功率越大,杀菌效果越好;相同的水量,微波穿透越浅,杀菌效果越好;温度在67.5℃以下时,体现了微波非热效应的杀菌作用,且持续的微波辐射杀菌效果比间断的微波辐射杀菌效果好。     

Transient numerical study of the effect of ambient temperature on 2-D cereal grain storage in cylindrical silos

A numerical study was performed on the transient heat and mass convection of grain storage in a cylindrical silo. Temperature gradients were induced by the heat of respiration, and thermal gradients were generated by variations of the temperature surrounding the cavity. The model was developed using the equations of heat, mass, and momentum transport for multiphasic media. The equation that represents the environmental temperature along the day-night cycle was obtained via a least squares regression using statistical data. In this study, the effects of different geometric ratios (A) and Rayleigh (Ra) numbers on the isotherms, flow patterns, and concentration isolines were analyzed. The governing equations were solved using discretization of the spatial coordinates by orthogonal collocation with Legendre polynomials and an implicit-trapezoidal formulation for time. The resulting algebraic system was solved by employing the Newton-Raphson with LU factorization method. A computer code called NEWIMPC2 in the FORTRAN 90 language was developed; this code was used to calculate the dynamics and hot regions in the bulk mass grain in the cavity. The thermodynamic properties for sorghum were used in the simulation, although the model is applicable to any cereal grains. For simulation data, typical prevailing conditions in the Bajio, an agricultural region located in Guanajuato State, were used. When the geometric ratio (A) increases, the hot nucleus is displaced toward the top of the cavity. In the case of Rayleigh numbers (Ra), a small increase significantly increases the stiffness of the parabolic equations. The ambient temperature has a significant effect on the formation of hot regions inside the cavity. When Ra increases, an increase can be observed in the temperature of the hot nucleus, with this temperature reaching 31 °C near the top wall of the enclosure. There was no evidence of the formation of multicellular flows.