Diagnosis: toxic!--trying to apply approaches of clinical diagnostics and prevalence in toxicology considerations.

The assessment of relevance of toxicological testing was compared with approaches of diagnostic medicine, a discipline that faces a comparable situation. Considering the work of a toxicologist as setting a diagnosis for compounds, assessment tools for diagnostic tests were transferred to toxicological tests. In clinical diagnostics, test uncertainty is well accepted and incorporated in this assessment. Furthermore, prevalence information is considered to evaluate the gain in information resulting from the application of a test. Several common toxicological scenarios, in which test uncertainty and prevalence are combined, are discussed including the interdependence of test accuracy, prevalence and predictive values or the sequential application of a screening and a confirmatory test. In addition, real prevalences derived from prevalences determined by an imperfect test are presented. We conclude that information on prevalences of toxic health effects is required to allow a complete assessment of the relevance of toxicological test. In this process, lessons can be learned from evidence-based approaches in clinical diagnostics.     

4～13岁屈光不正儿童眼球生物测量结果分析

目的 研究4～13岁屈光不正儿童不同年龄段的屈光分布情况及不同屈光度与屈光要素的关系。方法 随机选取4～13岁屈光不正儿童180眼，充分麻痹睫状肌后测得屈光度及屈光要素相关数值。控制年龄因素的影响，经偏相关分析得出屈光度与各屈光要素的偏相关性。结果 4～13岁儿童屈光不正以轻度近视和远视为主。控制年龄因素的影响，屈光度与眼轴长度、玻璃体腔深度、前房深度的偏相关系数分别为-0．8105，-0.7767，-0．1714，与其他要素无相关性。结论 屈光度与眼轴长度、玻璃体腔深度、前房深度呈负相关，与晶状体厚度、中央角膜厚度、角膜屈折力无相关性。4～13岁儿童屈光不正以轴性屈光不正为主。     

超长眼轴白内障手术前后眼生物测量参数变化及相互关系

目的：研究超长眼轴白内障患者超声乳化手术前后眼生物测量参数变化及其相互关系。

方法：收集2013-09/2015-03在首都医科大学宣武医院眼科确诊为白内障,且行白内障超声乳化联合人工晶状体植入术患者44例61眼,其中超长眼轴组20例29眼,正常眼轴对照组24例32眼。术前应用光学相干生物测量仪(IOL Master)测量眼生物参数,术后3mo应用IOL Master及超声生物显微镜(UBM)测量眼生物参数,应用SPSS17.0统计软件进行统计学描述并分析其变化及相互关系。

结果：超长眼轴组术后前房深度与年龄、术前眼轴长度、术前角膜曲率无相关性(P>0.05)。术后前房深度与术前前房深度呈正相关(r=0.402,P=0.031)。超长眼轴组术后3mo相比术前,眼轴长度显著缩短,角膜曲率增加,前房深度较术前显著增加(P<0.05)。正常眼轴对照组术后前房深度与年龄、术前眼轴长度、术前前房深度无相关性(P>0.05),术后前房深度与术前角膜曲率呈正相关(r=0.538,P=0.001)。正常眼轴对照组术后3mo较术前,眼轴长度显著缩短,前房深度显著增加(P<0.05),角膜曲率无改变(P>0.05)。手术前后,超长眼轴组相比正常眼轴对照组角膜曲率变化更大(P<0.05); 眼轴长度变化百分率、前房深度变化百分率,两组差异无统计学意义(P>0.05)。

结论：超长眼轴白内障患者术后眼轴长度缩短,角膜曲率增加,在计算人工晶状体度数时应增加一定度数,以便获得更佳的术后视力。超长眼轴白内障患者的术后前房深度预测具有复杂性与个体差异的不可预知性,需要进一步研究。     

Utility of ultrasound for body fat assessment: validity and reliability compared to a multicompartment criterion

Measurement of body composition to assess health risk and prevention is expanding. Accurate portable techniques are needed to facilitate use in clinical settings. This study evaluated the accuracy and repeatability of a portable ultrasound (US) in comparison with a four‐compartment criterion for per cent body fat (%Fat) in overweight/obese adults. Fifty‐one participants (mean ± SD; age: 37·2 ± 11·3 years; BMI: 31·6 ± 5·2 kg m^?2) were measured for %Fat using US (GE Logiq‐e) and skinfolds. A subset of 36 participants completed a second day of the same measurements, to determine reliability. US and skinfold %Fat were calculated using the seven‐site Jackson–Pollock equation. The Wang 4C model was used as the criterion method for %Fat. Compared to a gold standard criterion, US %Fat (36·4 ± 11·8%; P = 0·001; standard error of estimate [SEE] = 3·5%) was significantly higher than the criterion (33·0 ± 8·0%), but not different than skinfolds (35·3 ± 5·9%; P = 0·836; SEE = 4·5%). US resulted in good reliability, with no significant differences from Day 1 (39·95 ± 15·37%) to Day 2 (40·01 ± 15·42%). Relative consistency was 0·96, and standard error of measure was 0·94%. Although US overpredicted %Fat compared to the criterion, a moderate SEE for US is suggestive of a practical assessment tool in overweight individuals. %Fat differences reported from these field‐based techniques are less than reported by other single‐measurement laboratory methods and therefore may have utility in a clinical setting. This technique may also accurately track changes.     

Lens thickness assessment: anterior segment optical coherence tomography versus A-scan ultrasonography

AIM: To assess lens thickness measurements with anterior segment-optical coherence tomography (AS-OCT) in comparison with A-scan ultrasonography (A-scan US). METHODS: There were 218 adult subjects (218 eyes) aged 59.2±9.2y enrolled in this prospective cross-sectional study. Forty-three eyes had open angles and 175 eyes had narrow angles. Routine ophthalmic exam was performed and nuclear opacity was graded using the Lens Opacities Classification System III (LOCS III). Lens thickness was measured by AS-OCT (Visante OCT, Carl Zeiss Meditec, Dublin, CA, USA). The highest quality image was selected for each eye and lens thickness was calculated using ImageJ software. Lens thickness was also measured by A-scan US. RESULTS: Interclass correlations showed a value of 99.7% for intra-visit measurements and 95.3% for inter-visit measurements. The mean lens thickness measured by AS-OCT was not significantly different from that of A-scan US (4.861±0.404 vs 4.866±0.351 mm, P=0.74). Lens thickness values obtained from the two instruments were highly correlated overall (Pearson correlation coefficient=0.81, P<0.001), and in all LOCS III specific subgroups except in grade 5 of nuclear opacity. Bland-Altman analysis revealed a 95% limit of agreement from -0.45 to 0.46 mm. Lens thickness difference between the two instruments became smaller as the lens thickness increased and AS-OCT yielded smaller values than A-scan US in thicker lens (β=-0.29, P<0.001) CONCLUSION: AS-OCT-derived lens thickness measurement is valid and comparable to the results obtained by A-scan US. It can be used as a reliable noncontact method for measuring lens thickness in adults with or without significant cataract.     

The anterior and posterior biometric characteristics in primary angle-closure disease: Data based on anterior segment optical coherence tomography and swept-source optical coherence tomography

Purpose:Obtaining a better understanding of the pathogenesis of primary angle-closure disease (PACD) still requires studies that provide measurements of anterior and posterior biometric characteristics together and that assess the relationship between them.Methods:In total, 201 eyes were enrolled in this cross-sectional study: 50 normal controls, 49 primary angle-closure suspect (PACS), 38 primary angle closure (PAC), and 64 primary angle-closure glaucoma (PACG) eyes. The anterior and posterior structural features were measured by anterior segment optical coherence tomography and swept-source optical coherence tomography.Results:All PACD groups had smaller anterior chamber depth (ACD), anterior chamber area (ACA), anterior chamber volume (ACV), angle opening distance at 750 μm from the scleral spur (AOD750), trabecular–iris space area at 750 μm from the scleral spur (TISA750), and angle recess area (ARA), as well as a larger lens vault (LV), than controls (all P < 0.001). The PACS and PAC groups had thicker iris thickness at 750 μm from the scleral spur (IT750) than controls (P = 0.017 and P = 0.002, respectively). Choroidal thickness (CT) was not statistically different among normal, PACS, PAC, and PACG eyes. Univariate and multivariate linear regression analysis revealed a significant association between thinner IT750 and increased CT in PACD eyes (P = 0.031, univariate analysis; P = 0.008, multivariate analysis).Conclusion:Thinner iris thickness was associated with increased CT in PACD eyes; however, the underlying mechanism needs further investigation.     

Accuracy of biometric formulae for intraocular lens power calculation in a teaching hospital

AIM: To evaluate the accuracy of three commonly used biometric formulae across different axial lengths (ALs) at one United States Veterans Affairs teaching hospital. METHODS: A retrospective chart review was conducted from November 2013 to May 2018. One eye of each patient who underwent cataract surgery with a monofocal intraocular lens (IOL) was included. The range of postoperative follow-up period was from 3wk to 4mo. The Holladay 2, Barrett Universal II, and Hill-Radial Basis Function (Hill-RBF) formulae were used to predict the postoperative refraction for all cataract surgeries. For each formula, we calculated the prediction errors [including mean absolute prediction error (MAE)] and the percentage of eyes within ±0.25 diopter (D) and ±0.5 D of predicted refraction. We performed subgroup analyses for short (AL<22.0 mm), medium (AL 22.0-25.0 mm), and long eyes (AL>25.0 mm). RESULTS: A total of 1131 patients were screened, and 909 met the inclusion criteria. Resident ophthalmologists were the primary surgeons in 710 (78.1%) cases. We found no statistically significant difference in predictive accuracy among the three formulae over the entire AL range or in the short, medium, and long eye subgroups. Across the entire AL range, the Hill-RBF formula resulted in the lowest MAE (0.384 D) and the highest percentage of eyes with postoperative refraction within ±0.25 D (42.7%) and ±0.5 D (75.5%) of predicted. All three formulae had the highest MAEs (>0.5 D) and lowest percentage within ±0.5 D of predicted refraction (<55%) in short eyes. CONCLUSION: In cataract surgery patients at our teaching hospital, three commonly used biometric formulae demonstrate similar refractive accuracy across all ALs. Short eyes pose the greatest challenge to predicting postoperative refractive error.