Pesudovs K, Coster D J
Department of Ophthalmology, Flinders Medical Centre, Australia.
Br J Ophthalmol. 1998 Jun;82(6):617-24. doi: 10.1136/bjo.82.6.617.
AIMS/BACKGROUND: The construction and validation of an instrument for the assessment of subjective visual disability in the cataract patient is described. This instrument is specifically designed for measuring the outcome of cataract surgery with respect to visual disability.
Visually related activities thought to be affected by cataract were considered for the questionnaire. These were reduced by pilot study and principal components analysis to 18 items. A patient's assessment of his/her ability to perform each task was scored on a four point scale. Scores were averaged to create an overall index of visual disability, as well as subscale indices for mobility related disability, distance/lighting/reading related disability, and near and related tasks visual disability. The questionnaire, administered verbally is entitled "The Visual Disability Assessment (VDA)". Reliability testing included test-retest reliability, interobserver reliability (p, the intraclass correlation coefficient), and internal consistency reliability (Cronbach's alpha). Construct validation, the process for proving that a test measures what it is supposed to measure, included consideration of content validity, comparison with the established Activities of Daily Vision Scale (ADVS) and empirical support with factor analysis.
For the four indices, interobserver reliability varied from 0.92 to 0.94, test-retest reliability varied from 0.96 to 0.98, and internal consistency reliability varied from 0.80 to 0.93. The VDA compared favourably with the ADVS by correlation, but Bland-Altman analysis demonstrated that the two instruments were not clinically interchangeable. Factor analysis suggests that all test items measure a common theme, and the subgroupings reflect common themes.
The VDA is easy to administer because it has a short test time and scoring is straightforward. It has excellent interobserver, test-retest, and internal consistency reliability, and compares favourably with the ADVS, another test of visual disability. Factor analysis demonstrated that the 18 items measure a related theme, which can be assumed to be visual disability. The VDA is a valid instrument which provides a comprehensive assessment of visual disability in cataract patients and is designed to detect changes within a patient over time.
目的/背景：本文描述了一种用于评估白内障患者主观视觉障碍的工具的构建与验证过程。该工具专为测量白内障手术在视觉障碍方面的治疗效果而设计。
问卷中纳入了被认为会受白内障影响的与视觉相关的活动。通过预试验和主成分分析，这些活动被缩减至18项。让患者对自己执行每项任务的能力进行四点量表评分。将评分平均以创建视觉障碍总体指数，以及与活动能力相关的障碍、距离/光线/阅读相关的障碍、近距及相关任务视觉障碍的子量表指数。这份通过口头方式进行的问卷名为“视觉障碍评估（VDA）”。可靠性测试包括重测信度、观察者间信度（组内相关系数p）和内部一致性信度（克朗巴哈系数）。结构效度验证，即证明一项测试能测量其预期测量内容的过程，包括考虑内容效度、与既定的日常视觉活动量表（ADVS）进行比较以及通过因子分析提供实证支持。
对于这四个指数，观察者间信度在0.92至0.94之间，重测信度在0.96至0.98之间，内部一致性信度在0.80至0.93之间。通过相关性分析，VDA与ADVS相比表现良好，但布兰德 - 奥特曼分析表明这两种工具在临床上不可互换。因子分析表明所有测试项目测量的是一个共同主题，且子分组反映了共同主题。
VDA易于实施，因为其测试时间短且评分简单直接。它具有出色的观察者间、重测和内部一致性信度，与另一种视觉障碍测试ADVS相比表现良好。因子分析表明这18项测量的是一个相关主题，可假定为视觉障碍。VDA是一种有效的工具，可对白内障患者的视觉障碍进行全面评估，并旨在检测患者随时间的变化。
