Objective: To develop and validate vision function (VF) and quality of life (QOL) instruments in patients with cataracts in the context of large volume surgery in a developing country.
Materials and methods: The instruments were developed using a consensus approach. One hundred patients who were undergoing cataract surgery at Aravind Eye Hospital, Madurai, India, were interviewed preoperatively and 3 and 12 months postoperatively. Standard clinical procedures were followed, including measurement of visual acuity. Between-interviewer reproducibility was measured by repeated administration of the preoperative questionnaire. Within-interviewer reproducibility was measured preoperatively in a separate study of 50 patients.
Results: Preoperative scores from the VF and QOL instruments were significantly associated with visual acuity (r = 0.4). Internal reliability (Cronbach alpha) was greater than .9. Both instruments showed large changes after surgery, with effect sizes of 3 or greater for most VF scales (range, 1.8-3.7) and 1 or greater for QOL scales (range, 1.0-2.2). Changes in visual acuity after surgery were correlated with changes in the VF (r = 0.44) and QOL (r = 0.41) scale scores. Between-interviewer reproducibility was acceptable (total VF scale, Spearman r = 0.7; total QOL scale; r = 0.74). The kappa values were lower for within-interviewer reproducibility.
Conclusions: The study provided strong evidence for the validity, reproducibility, and responsiveness of the instruments, and for the feasibility of using them in the setting of a large volume of cataract surgery in a developing country.