Accuracy,inter-observer and intra-observer reliability in topography assessment of multifocal contact lens centration

PurposeTo evaluate the accuracy and reliability (inter and intra-observer) of a method to assess multifocal contact lenses (MCLs) centration using a corneal topography unit.MethodDaily-disposable MCLs (Fusion 1 day Presbyo) were fitted on both eyes of the subjects. For each lens fit a slit lamp digital picture and videokeratograph image were taken in a rapid but randomised sequence. Photo-editing software was used to assess the position of the MCL centre with respect to pupil centre as taken from the slit lamp photograph. The position of the MCL centre was automatically detected as the point of maximum curvature from the videokeratography. Three further manual and qualitative procedures to detect MCL centre, comparing a template of CLs optic zones to the videokeratographic image were performed by 4 practitioners using 3 different algorithms to represent the topographic map. Each manual reading was repeated 3 times.ResultsTwenty-two subjects (11 males) aged 22.8 ± 1.9 years (range 20.8–27.0 years) were recruited. The accuracy of the 4 topographic assessments in determining the centre coordinates of the MCL with respect to SL assessment was good: no differences were found in the left eyes and although in the right eyes a more temporal and superior position of MCLs was determined (paired t-test, p < 0.05) the difference was clinically negligible (0.16 ± 0.36 mm horizontally, 0.23 ± 0.48 vertically). Amongst the 4 practitioners one-way Anova for repeated measures showed no differences for any of the 3 manual assessments. Intra-class correlation coefficient was calculated among the 3 readings for each manual procedure and was very good (between 0.75 and 0.98) in 3 practitioners and moderate (between 0.49 and 0.92) in the fourth.ConclusionsThe assessment of MCL centration by performing corneal topography over the MCL is an accurate method. Furthermore, inter and intra-practitioner reliability showed by manual procedures appeared very good.     

卡塞格林红外光学系统装调技术研究

介绍了一种卡塞格林红外光学系统的装调方法.利用中心偏测量仪完成主次镜的装调,利用定心车的工艺完成红外目镜组的定心车削,然后在中心偏测量仪上完成主次镜和目镜组的组合装调.由于该系统采用的是线列探测器,因此采用一个外置摆镜,使摆镜以固定频率摆动,使目标源在探测器上形成了一幅完整的图像,从而可以很方便的完成探测器的装调.采用...     

7075-T651合金厚板预拉伸断裂原因分析

分析了７０７５－Ｔ６５１合金厚板预拉伸断裂的原因。７０７５－Ｔ６５１合金厚板拉伸断裂的表现形式为断口的一侧存在三角裂纹,经研究认为方锭中心有严重疏松疏松带,在热思变形过程中因边部和中心层变形不均,未被焊合的疏松形成隐形裂纹并随轧制的进行扩展所致。     

采用回转式蒸发器生产固碱

针对固碱生产现状,设计了一种回转式蒸发器(类似于回转窑)。该设备是一个长圆型的金属筒体,在筒体内部设置了内构件,以避免返混和强化换热;在设备的两端设置了进出料装置以利于连续进出物料和维持系统真空度。     

混合遗传算法在飞机钣金零件排样中的应用

针对飞机钣金二维不规则零件排样问题,将遗传算法与模拟退火算法相结合,提出一种混合遗传算法。该算法利用改进的最小包络矩形把不规则件转化成矩形件,在初始种群时提出一种既考虑排样高度,又考虑排样废料利用率的适应度函数,并引进浓度衡量个体之间的相似程度,为逃离局部最小值指明了方向。实例结果表明,该算法运用到飞机钣金排样系统中,在缩短排样时间和提高排样精度方面取得一定的效果。     

小F数卡赛格林系统装调技术

介绍了小F数卡赛格林系统装调的一种方法.用一束平行光照射抛物面反射镜,当抛物面反射镜的光轴与机械轴不重合时,反射光线的焦点运动.调整抛物面反射镜的中心和倾斜,使抛物面的光轴与机械轴重合,然后在卡氏系统的焦点处放置一十字分划板,经次镜和主镜的反射后,被内调焦望远镜接收,当次镜和主镜的光轴与机械轴都重合时,反射光线不动.运...     

CPC对中系统适应性改造

在生产过程中,根据现场实际情况,对CPC系统进行适应性改造,以满足现场的实际需要.     

基于宾汉姆体的高浓度尾砂浆剪切变稀规律研究

高浓度尾砂浆的活化搅拌一直是矿山充填技术研究的重要方向,采用高速搅拌活化充填料浆是破坏充填料浆“团块”的有效办法,能够明显改善充填料浆的流变特性,提高其可输送性。高速搅拌过程的实质是对充填料浆进行快速剪切,不同的搅拌能对应不同的剪切速率,料浆的物化性质也相应地存在差异。为研究这种差异的规律并寻找高浓度尾砂浆的最佳活化能,针对某铜矿充填用尾砂,配制了浓度为70%的尾砂浆,采用新诺AM300S-H实验室搅拌机对尾矿浆开展了多种转速的搅拌实验,并采用Broofield R/S-CCT型流变仪分别测试其流变参数,通过Bingham模型分析了剪切变稀特性。研究结果表明：高浓度尾矿浆的黏度（ηb）和屈服应力（τ0）随搅拌速率（n）的增加而减小,表现出明显的剪切变稀特性,当转速达到400 r/min之后,尾砂浆的屈服应力不再明显减小,有趋于稳定的特性;在转速为120~1 000 r/min的范围内,其黏度与剪切转速之间的关系可用ηb=0.3n-0.1表示。     

Centration assessment of an extended depth of focus contact lens for myopic progression control

PurposeTo evaluate the accuracy and the inter and intra-observer reliability of the centration assessment of extended depth of focus (EDOF) contact lenses (CL) using corneal topography.MethodEDOF soft CLs (Mylo, Mark’Ennovy) were fitted on thirty-three myopic students (25 females), aged 19–28 years (22.7 ± 2.0 years). For any EDOF CL, a topography over the CL and a slit lamp (SL) digital picture were taken in random order. For the topographic images, the position of the EDOF CL centre, with respect to the pupil centre, was detected by two different practitioners (one newly graduated and one with more than 20 years of clinical experience respectively) and repeated after 15 days. This measurement was compared to the one taken through the SL, considered as the gold standard, and assessed using the instrument software.ResultsEDOF CLs resulted decentred inferiorly and temporally ranging, in the case of slit lamp assessment, between ?0.27 ± 0.19 and 0.22 ± 0.23 mm horizontally and between ?0.12 ± 0.31 and ?0.17 ± 0.34 mm vertically, for the right and left eye respectively. The accuracy of the topographic assessment in determining EDOF CL centration was found to be very good compared to the SL assessment. No differences were found for the left eye, whereas in the right eye, a less temporally decentred position of the CL was detected by the topographical method (p < 0.05). However, this difference appeared clinically negligible (0.14 ± 0.22 mm). Inter-observer reliability (the differences between the two practitioners in assessing the EDOF centre) resulted significant only for the vertical coordinates of the centre position (p < 0.05). Concerning intra-observer reliability, better coefficient of precision and reliability between measurements within the same session were achieved by the more experienced practitioner, as well as a better level of the intraclass correlation coefficient in test–retest.ConclusionThe centration of the EDOF CL investigated in this study can be accurately detected by a corneal topography performed over CLs. Inter-observer reliability resulted good whereas the intra-observer reliability resulted partially affected by the level of clinical experience of the practitioner.