Catquest-9SF patient outcomes questionnaire

RESULTS: Only the visual disability subscale formed a valid measurement scale. This could be enhanced through the addition of the 2 global assessment items; however, the symptoms and frequency of performing the activities items did not contribute to the measurement. The 9-item short-form version (Catquest-9SF) had ordered response thresholds and good person separation (2.65) and was largely free from differential item functioning. All items fit a single overall construct (infit range, 0.75 to 1.29; outfit range, 0.70 to 1.39) and unidimensional by principal components analysis. The items were well targeted to the preoperative participants (0.34 logit difference in means). The score correlated with visual acuity (r Z 0.43 preoperatively; r Z 0.48 postoperatively) and was highly responsive to cataract surgery (preoperatively 0.32 G 2.15 logits; postoperatively 3.21 G 2.50 logits (P<.0001).