Translation, cultural adaptation, and Rasch analysis of the Visual Function (VF-14) questionnaire

Purpose. To translate, culturally adapt, and validate the original and previously validated shorter versions of the Visual Function Index (VF-14) questionnaire in a Chinese population. Methods.The VF-14 was completed by patients with cataract. The analysis was carried out in three phases: phase I, testing whether the VF-14 and its valid shorter versions,VF-8R and VF-11R, form valid scales in Chinese settings using Rasch analysis; phase II, developing completely new Chinese versions of the VF-14; phase III, testing whether the previously validated shorter versions of the VF-14 could be applied in a Chinese population. This was tested by assessing the agreement between the new Chinese (developed in phase II) and the previously validated shorter versions of the VF-14 using Bland-Altman plots. Results. A total of 456 patients (median age, 70 years; range, 40-92 years; females, 58%) completed the Chinese translated version of the VF-14. The VF-14 and the VF-11R demonstrated good Rasch based psychometric properties when a grossly misfitting item was removed. The VF-8R formed a valid scale without any modification. The scores of the VF-11R and the Chinese shorter version (VF-11RChin) showed very good agreement, with a mean difference of- 0.18 logits and 95% limits of agreement between 0.11 and-0.47. Conclusions. The Chinese translated VF-14, VF-11R, and VF-8R were valid and could be applied to assess cataract outcomes in Chinese settings. The existing shorter version had good agreement with the new Chinese version, which signifies that there was no need to develop a different version of the VF-14 in China.