Turano K A, Geruschat D R, Stahl J W, Massof R W
Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Invest Ophthalmol Vis Sci. 1999 Apr;40(5):865-77.
To determine the distribution of perceived ability for independent mobility in people who are at various stages of retinitis pigmentosa (RP).
A questionnaire was developed to ask subjects to rate how difficult they found each of 35 mobility situations if they had no assistance. The scale was 1 (no difficulty) to 5 (extreme difficulty). In each of 127 subjects, the Rasch analysis, a latent trait analysis, was used to convert the ordinal difficulty ratings into interval measures of perceived visual ability for independent mobility.
Content validity of the questionnaire was shown by good separation indexes (4.55 and 8.0) and high reliability scores (0.96 and 0.98) for the person and the item parameters. Construct validity was shown with model fit statistics. Criterion validity of the questionnaire was shown by good discrimination among mobility-related behavior such as "limit independent travel," "always ask for accompaniment," "use a mobility aid," and "have a fear of falling." The mobility situation shown to require the least visual ability was "moving about in the home"; the situation requiring the most was "walking at night." Bivariate regression analysis determined that for every decade of disease progression, perceived visual ability for mobility decreased by approximately 0.5 logit, which was slightly less than 10% of the total range in the study sample. A linear combination of the visual function measures, log minimum angle of resolution, log contrast sensitivity, and log retinal area accounted for 57% of the variability in the person measure.
The patient-based assessment, developed to determine difficulty across a range of mobility situations, is a valid way to measure perceived ability for independent mobility. This latent trait varies systematically with the progression of RP and with visual function measures.
确定处于视网膜色素变性（RP）不同阶段的人群对独立活动能力的感知分布情况。
设计了一份问卷，要求受试者对35种活动情况在无协助时的难度进行评分。评分范围为1（无困难）至5（极度困难）。对127名受试者中的每一位，采用Rasch分析（一种潜在特质分析）将顺序难度评分转换为独立活动视觉能力感知的区间测量值。
问卷的内容效度通过良好的区分指数（4.55和8.0）以及人员和项目参数的高信度得分（0.96和0.98）得以体现。结构效度通过模型拟合统计得以显示。问卷的效标效度通过对“限制独立出行”“总是要求陪伴”“使用助行器”和“害怕摔倒”等与活动相关行为的良好区分得以体现。显示所需视觉能力最少的活动情况是“在家中走动”；所需视觉能力最多的情况是“夜间行走”。双变量回归分析确定，疾病进展每十年，活动视觉能力感知下降约0.5对数单位，略低于研究样本总范围的10%。视觉功能测量值（对数最小分辨角、对数对比敏感度和对数视网膜面积）的线性组合占人员测量值变异性的57%。
基于患者的评估旨在确定一系列活动情况下的难度，是测量独立活动感知能力的有效方法。这种潜在特质随RP的进展和视觉功能测量值而系统变化。
