Table 2 Infit and outfit statistics for the nine items of the Catquest-9SF questionnaire

1. Do you experience that your present vision is giving you difficulty in any way in your everyday life?

1.04

0.91

2. Are you satisfied or dissatisfied with your present vision?

1.31

1.34

Do you have difficulty with the following activities because of your vision? If so, how much?

 3. Reading text in the daily paper

0.87

0.73

 4. Recognise the faces of people you come across

1.08

0.94

 5. See prices when shopping

0.84

0.81

 6. Seeing to walk on uneven ground

1.05

1.00

 7. See to do handwork, woodwork, etc.

0.95

1.11

 8. Reading text on TV

0.86

0.80

 9. See to carry on an activity/hobby you are interested in

0.86

0.79