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01.12.2018 | Research | Ausgabe 1/2018 Open Access

Health and Quality of Life Outcomes 1/2018

Development of a rapid point-of-care patient reported outcome measure for cataract surgery in India

Health and Quality of Life Outcomes > Ausgabe 1/2018
Joshua R. Ehrlich, Charlie Frank, Josiah Smiley, Hong-Gam Le, Sanil Joseph, Stephen G. Schilling, Brian C. Stagg, Joshua D. Stein, R. D. Ravindran, Aravind Haripriya
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Electronic supplementary material

The online version of this article (https://​doi.​org/​10.​1186/​s12955-018-0855-5) contains supplementary material, which is available to authorized users.



For patient undergoing cataract surgery in India, existing patient-reported outcome (PRO) measures are either not culturally relevant, have not been adequately validated, or are too long to be used in a busy clinical setting. We sought to develop and validate a brief and culturally relevant point-of-care PRO measure to address this need.


Twelve items from the Indian Visual Functioning Questionnaire (IND-VFQ) were selected based on preliminary data. Patients 18 years and older were prospectively recruited at Aravind Eye Care System in Madurai, India. Clinical and sociodemographic data were collected and the 12-item short-form IND-VFQ (SF-IND-VFQ) was administered pre- and post-operatively to 225 patients; Factor analysis and Rasch modeling was performed to assess its psychometric properties.


One item that did not fit a unidimensional scale and had poor fit with the Rasch model was eliminated from the questionnaire. The remaining 11 items represented a single construct (no residual correlations> 0.1) and were largely unaffected by differential item functioning. Five items had disordered thresholds resolved by collapsing the response scale from four to three categories. The survey had adequate reliability (0.80) and good construct (infit range, 0.77–1.29; outfit range, 0.56–1.30) and content (item separation index, 5.87 logits) validity. Measurement precision was fair (person separation index, 1.97). There was evidence that items were not optimally targeted to patients’ visual ability (preoperatively, − 1.92 logits; overall, − 3.41 logits), though the survey measured a very large effect (Cohen’s d 1.80). In a subset of patients, the average time to complete the questionnaire was 2 min 6.3 s.


The SF-IND-VFQ is a valid, reliable, sensitive, and rapidly administered point-of-care PRO measure to assess changes in visual functioning in patients undergoing cataract surgery in India.
Additional file 1: Scree Plot of Exploratory Factor Analysis. This plot illustrates that the first eigenvalue of the exploratory factor analysis was the only value that was greater than 1. This suggests a unidimensional model. (TIFF 929 kb)
Additional file 2: Supplementary tables from Rasch Analysis. These tables report for each of the 12 survey items: the average visual functioning estimates for each response category; category thresholds; and misfit statistics. (DOCX 19 kb)
Additional file 3: Raw score to Rasch person-measure conversion. This worksheet allows researchers and clinicians to covert raw SF-IND-VFQ scores to interval scores without performing their own Rasch analysis. Caution should be exercised in applying this Rasch analysis to patient populations that are very different from the one in this study. (XLSX 12 kb)
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