Repeatability and agreement of CCT measurement in myopia using entacam and ultrasound pachymetry

AIM: To evaluate the repeatability of central corneal thickness (CCT) measurement by entacam, and agreement of CCT measured by Pentacam and ultrasound pachymetry (USP) in Chinese myopia. Thereby investigate the possibility of Pentacam as a substitute for USP in CCT measurement before refractive surgery. The effects of corneal curvature measured by Pentacam on CCT were also evaluated. METHODS: One hundred and forty-eight right eyes of 148 individual with myopia were included in this study. Three successive Pentacam CCT measurements followed by 10 successive ultrasound pachymetry were carried out in the 148 eyes. Mean of CCT taken by each device was calculated for comparison. According to the CCT measured by USP, all the 148 eyes were divided into 3 groups: <520μm, 520-560μm, >560μm. For all eyes and each group the CCT obtained by Pentacam and USP were compared. Anterior corneal curvature of the 148 eyes was also adopted for correlation analysis with CCT obtained by ultrasound pachymetry. In addition, CCT measurement using 60 random selected Scheimpflug images was performed by 3 skilled investigators at different time, and this was repeated for 3 times by a forth investigator to assess repeatability of Pentacam CCT measurement using Scheimpflug images. RESULTS: Intraclass correlation coefficient (ICC) analysis revealed high intraobserver repeatability (ICC=0.994, F=158.60, P<0.001) for CCT measurement by Pentacam. The interobserver (ICC=0.998, F=494.73, P<0.001) and intraobserver (ICC=0.997, F=383.98, P<0.001) repeatability for Pentacam CCT measurements using Scheimpflug images were also excellent. There was high positive correlation between the CCT values measured by Pentacam and ultrasound pachymetry (r=0.963, P<0.001). Bland-altman plots showed that the Pentacam underestimate the CCT by 8.02μm compared with ultrasouond pachymetry. The differences between Pentacam and USP increased as the CCT readings by USP increased (Pentacam vs USP: slope=-0.04, P<0.05). The 95% upper and lower limits of agreement between CCT values obtained from the two devices were +9.33μm and -25.37μm. No significant association could be found between CCT and anterior corneal curvature. CONCLUSION: Inter- and intraobserver variability for CCT measurements by Pentacam was considerably below clinically significant levels. CCT of myopia obtained by Scheimpflug camera, Pentacam, were highly correlated to that by ultrasound pachymetry. However, the values obtained are not directly interchangeable between Pentacam and ultrasound pachymetry as the 95% limits of agreement are relatively wide. Pentacam can be a useful instrument for measuring CCT in candidates to refractive surgery in clinic.     

Reproducibility of multiple breath washout indices in the unsedated preterm neonate

Multiple breath inert gas washout (MBW) is gaining popularity for measurements of resting lung volume and ventilation inhomogeneity. Test reproducibility is an important determinant of the clinical applicability of diagnostic tests. The between‐test reproducibility of variables derived from MBW tests in newborn infants is unknown. We aimed to determine the within‐test repeatability and short‐term between‐test reproducibility of MBW variables in unsedated preterm infants. We hypothesized that measurements obtained within a 3‐day interval in clinically stable preterm infants would be reproducible and suitable for use as an objective clinical outcome measurement. In this cross‐sectional observational study, clinically stable hospitalized preterm infants whose parents had given informed consent for MBW studies were tested twice within 72 hr during quiet, unsedated sleep. Functional residual capacity (FRC), lung clearance index (LCI), and the first and second to zeroeth moment ratios (M₁:M₀; M₂:M₀) were computed from MBW traces obtained using a mainstream ultrasonic flowmeter and 4% sulphur hexafluoride (MBW_SF6). Within‐test repeatability and between‐test reproducibility were determined. Within‐test repeatability (expressed as a coefficient of variability (C_v)) for differences between two and four replicate measurements on the same test occasion, were 9.3% (FRC), 9.0% (LCI), 7.6% (M₁:M₀), and 15.6% (M₂:M₀), respectively. The within‐test C_v's were not statistically different to the between‐tests C_v's, which were 7.7% (FRC), 10.3% (LCI), 6.1% (M₁:M₀), and 13.0% (M₂:M₀), respectively. Among unsedated preterm infants, between‐test reproducibility over a 3‐day interval was similar to within‐test repeatability. The wide limits of agreement may limit the application of these measures to detect a clinically significant change in condition in small preterm infants. Pediatr Pulmonol. 2010; 45:62–70. © 2009 Wiley‐Liss, Inc.     

Repeatability and agreement in the measurement of horizontal fusional vergences

PURPOSE: This study was designed to determine the repeatability of fusional vergence ranges measured using the rotary prisms in the phoropter and in free space using the prism bar. The level of agreement between the two methods was also investigated. METHODS: In two separate sessions, negative and positive fusional vergence ranges (NFV and PFV, respectively) were measured at distance and near in 61 young adults (mean age 19.74, S.D. 2.5 years) who were unfamiliar with the methods used. Base-in and base-out blur, break and recovery points were sequentially determined. Both sets of measurements were obtained by the same examiner. At each distance, NFV was determined first and then PFV. The repeatability of the tests and agreement between measurements made with the phoropter rotary prisms and the prism bar were estimated by the Bland and Altman method. RESULTS: For both the phoropter rotary prisms and prism bar, NFV measurements showed better repeatability than PFV at both near and distance. Mean differences recorded for the NFV break and recovery points were non-significant (under 0.5Delta), while those observed for PFV were generally greater than 2Delta. When agreement between the two tests was assessed, it was found that break points were higher when determined using the phoropter rotary prisms, while recovery points were generally higher for the prism bar method. In clinical terms, according to the expected values of the NFV and PFV, agreement between the two techniques can be described as fair, because although mean differences were never greater than 5.5Delta, 95% agreement intervals were as wide as +/-8.00Delta for NFV and +/-13.19Delta for PFV. CONCLUSIONS: The two methods used to measure fusional vergences showed fairly good inter-session repeatability for measuring NFV but repeatability was reduced for PFV measurements. The level of agreement observed between the two methods was such that their interchangeable use in clinical practice is not recommended.     

Autoacuity Test与标准对数视力表用于儿童视力测定的比较

 【目的】比较一种计算机视力测试软件Autoacuity Test和标准对数视力表之间的一致性和重复性，初步探讨Autoacuity Test临床应用的可行性。【方法】对41名视功能正常儿童（8.4 ± 1.8岁）和25名弱视儿童（8.0 ± 2.2岁）分别使用标准对数视力表和Autoacuity Test两种方法进行视力测试。30min后重新对其进行测试。以Autoacuity Test与标准对数视力表检查结果的一致性限度的评价其准确性，以测试-再测试的重复系数及配对T检验评价其重复性。【结果】视功能正常儿童的Autoacuity Test与标准对数视力间的一致性限度为0.16 对数单位；弱视儿童为0.31对数单位。正常儿童两种方法各自的测试-再测试结果间差异均无统计学意义（P>0.05）。弱视儿童标准对数视力表测试-再测试结果间差异无统计学意义，Autoacuity再次测试视力检查结果较初次测试有所提高（P<0.05）。【结论】Autoacuity Test与标准对数视力表两种检查方法在视功能正常儿童中一致性较好，在弱视儿童中一致性稍差，两者重复性相近。Autoacuity是一种可取的儿童视力测试方法。     

Quantitative analysis of in vivo confocal microscopy images: A review

In vivo confocal microscopy (IVCM) is a non-invasive method of examining the living human cornea. The recent trend towards quantitative studies using IVCM has led to the development of a variety of methods for quantifying image parameters. When selecting IVCM images for quantitative analysis, it is important to be consistent regarding the location, depth, and quality of images. All images should be de-identified, randomized, and calibrated prior to analysis. Numerous image analysis software are available, each with their own advantages and disadvantages.     

Direct measurement of tibial cortical bone surface area

Cortical bone surface area estimation is generally performed by analysis of medical images but its accuracy has not yet been verified by direct bone measurements. This study was performed to evaluate the reproducibility of direct ex vivo estimations of cross sectional tibial cortical bone surface area. Ten tibiae were evaluated by two observers using direct 3D‐digitization at 38 and 66% of total tibial length using a ‘critical’ and a ‘general’ criterion for differentiation between cortical and cancellous bone. The results of the analysis using the more severe ‘critical’ differentiation criterion yielded high intra and interobserver agreement. Mean intraobserver reliability was demonstrated by R = 0.98 (Spearman rank correlation between 0.98 and 0.97; P < 0.01) and inter observer reliability by R = 0.91 (Spearman rank correlation between 0.95 and 0.88; P < 0.01). When using strict criteria to differentiate between cortical and cancellous bone, intra and interobserver reliability of the presented method of direct cortical bone surface area estimation is very high. The results indicate that cross‐sectional cortical bone surface estimation by direct 3D‐digitization can serve as a gold standard for validation of other estimations methods. Clin. Anat. 23:720–725, 2010. © 2010 Wiley‐Liss, Inc.     

Determination and Concentration of Adenine Nucleotides in Human Blood

Abstract

Background. The microdialysis technique is a method for sampling endogenous molecules from the interstitial compartments of varying tissues and relies on diffusion of molecules between the tissue and a perfusate via a membrane. Such samples do not allow determination of the true interstitial concentration but only a certain percentage. This gives rise to one of the most crucial parameter that needs to be considered for a dependable microdialysis; the relative recovery. Relative recovery states the efficiency of which an analyte is extracted from its external medium. Aim. To investigate the relative recovery of small molecules (< 20 kDa) such as lactate, fluid recovery and the reproducibility of the relative recovery at group and individual level of the microdialysis technique applied in muscle. Materials and methods. Using in vivo microdialysis of the trapezius muscle of 65 women from two separate occasions 4–6 months apart. Relative recovery of small molecules was measured from samples collected every 20 min during a period of 220 min. Results. Good reproducibility at group level of catheters with cut-offs 100 and 20kDa were found. Furthermore, there was a high and steady relative recovery with an overall good fluid recovery. Poor reproducibility was found at the individual level for both catheters. Conclusions. This study demonstrates that when using microdialysis in skeletal muscle relative recovery is stable over time and is not affected by low-force exercise. Although there is a good reproducibility at group level this is not the case at the individual level. Thus in vivo, the relative recovery should be determined for each test subject and at each test occasion.     

Postural and dynamic masseter and anterior temporalis muscle EMG repeatability in serial assessments

Summary  Electromyographic (EMG) assessment has been used as a non-invasive tool to objectively assess muscle function, although with controversial research and clinical potential. The aim of this study was to assess within-, inter-subject and between-day repeatability of serial EMG recordings. The study sample included 10 asymptomatic subjects with no history of temporomandibular disorders or muscle parafunctions. Bilateral masseter and anterior temporalis muscle EMG parameters were assessed in two standardized serial recordings (day1 to day2) using a portable EMG equipment (ME 6000 recorder, Mega Electronics, Kuopio, Finland). The functional tasks included postural/resting activities as pre- and post-recording series of 30 s each and jaw opening/closing, intercuspal and maximal voluntary clenching activities of 5 s, repeated three times. The assessed EMG parameters included the mean amplitude, s.d. and error. In addition, the power spectrum EMG parameter assessment included the median power frequencies and the averaged EMG spectrum data values. The results of the intraclass correlation coefficient analysis indicated reliability for nearly all of the intercuspal and all clenching EMG amplitude and power spectrum parameters. This was complemented by the repeated measures anova and post hoc analyses that indicated non-significant differences between day 1 and 2 in task- and muscle-related analyses. Most variability was noted in postural and some in opening/closing tasks. In conclusion this study assessed the reliability, repeatability and limitations of postural and various dynamic masseter and temporalis EMG recordings for serial assessment.     

立体视正常值变化观察

目的:比较Frisby、Randot、Howard-Dolman三种立体视检查方法的可重复性,确定此三种临床用立体视检查方法的正常值变化的95%可信区间.方法:选择26位无斜视、弱视和眼手术史的健康个体,平均年龄为24.42±4.26岁(14～32岁),所有的受检者具有正常的双眼视且双眼视力为6/6.测量视远瞳距和习惯视力后,以随机的顺序用Frisby、Randot、Howard-Dolman三种检查方法测量立体视,测量时保持光照度为670lx.约1周后在相同的测量条件下同样用三种检查方法测量立体视,平均间隔时间为7.8±2.4天.结果:三种临床立体视检查方法的可重复性系数分别为±2.7"(Frisby)、±8.0"(Randot)和±9.3"(Howard-Dolman),再次试验的平均值低于首次试验的平均值,t检验提示这改变差异无显著性意义(P>0.05).重复试验的相关系数分别为0.91(Frisby)、0.56(Randot)、0.60(Howard-Dolman).三种检查方法之间的相关系数分别为0.31、0.31、0.33.结论:三种临床立体视检查方法的相关性较差.Frisby检查法有最好的重复性和正常值有较小的范围.用该法测得成年人立体视改变的95%可信区间为±2.7".如果用Frisby法测得年轻成年人的立体视的变化超过这个范围,可认为是有显著意义的临床改变.