青年人群近距离工作后眼部参数的变化及恢复时间

目的：观察青年人群近距离用眼后眼部生理及功能性参数的变化及恢复时间。

方法：前瞻性研究。随机选取2019-12/2020-06在我院进行医学验光的患者69例138眼，根据主觉验光结果分为正视组(+0.75D≤等效球镜度≤-0.50D，18例36眼)、低度近视组(-0.75D≤等效球镜度≤-3.00D，25例50眼)和中度近视组(-3.25D≤等效球镜度≤-6.00D，26例52眼)。所有受试者近距离阅读20min后远眺放松20min，分别于近距离用眼前、近距离用眼20min后、远眺5、10、15、20min时测量受试者眼部生理性参数\〖前房深度(ACD)、眼轴长度(AL)\〗和功能性参数\〖正相对调节(PRA)、调节反应(BCC)\〗，分析各参数的达极时间和恢复时间。

结果：近距离用眼后眼轴变长，前房变浅，PRA绝对值变大，BCC无明显变化，75%(52/69)的受试者AL在近距离用眼20min后达极，87%(60/69)的受试者ACD在远眺5min时达极，96%(66/69)的受试者PRA在近距离用眼20min后达极，且以上参数均在远眺10min后逐渐恢复至初始状态。

结论：近距离用眼后眼部参数发生改变，眼轴变长，前房变浅，PRA绝对值增大，但均在远眺放松过程中逐渐回退，且均需要10min以上才能恢复至初始状态。     

Comparing estimation approaches for the illness–death model under left truncation and right censoring

Left‐truncated data arise when lifetimes are observed only if they are larger than independent truncation times. For example, in a cross‐sectional sampling, only individuals who live long enough to be present on the sampling day are observed. There are several ways to perform statistical inference under this setting. One can do the following: (i) use an unconditional approach, (ii) condition on the value of the truncation variable, or (iii) condition on all the history up to the time of truncation. The latter two approaches are equivalent when analyzing univariate survival outcomes but differ under the multi‐state framework. In this paper, we consider the illness–death model and compare between the three estimation approaches in a parametric regression framework. We show that approach (ii) is more efficient than the standard approach (iii), although it requires more computational effort. Approach (i) is the most efficient approach, but it requires knowledge on the distribution of the truncation variable and hence is less robust. The methods are compared using a theoretical example and simulations and are applied to intensive care units data collected in a cross‐sectional design, where the illness state corresponds to a bloodstream infection. Copyright © 2015 John Wiley & Sons, Ltd.