The development of the Indian vision function questionnaire: field testing and psychometric evaluation.
OBJECTIVE
To develop and evaluate the acceptability, reliability, validity, and responsiveness of the Indian vision function questionnaire (IND-VFQ).


METHODS
Problem statements from previous qualitative studies were reduced to a 45 item interviewer administered questionnaire representing three a priori domains (general functioning, psychosocial impact, and visual symptoms) which was evaluated in patients with cataract (n = 420), glaucoma (n = 120), diabetic retinopathy, or age related macular degeneration (n = 120) and normal controls (n = 120). Standard methods were used for item reduction and to evaluate psychometric properties.


RESULTS
Psychometric item reduction produced a 33 item questionnaire. Psychometric evaluation showed that two of the three scales (psychosocial impact and visual symptoms) had good acceptability, and that all three scales showed high internal consistency (alpha >0.80; item-total correlations 0.54-0.86) and test-retest reliability (>0.89). All three scales showed moderate evidence of convergent and discriminant validity. Responsiveness, assessed in cataract patients (n = 120) before and after surgery, was good for all three scales (effect sizes >1).


CONCLUSIONS
The IND-VFQ33 is a psychometrically sound measure of vision function addressing a gap in patient defined measures of vision function developed in populations living in low income countries.
Gupta
S K
SK
Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
Viswanath
K
K
Thulasiraj
R D
RD
Murthy
G V S
GV
Lamping
D L
DL
Smith
S C
SC
Donoghue
M
M
Fletcher
A E
AE
D000203:Activities of Daily Living; D000368:Aged; D002386:Cataract / Q000150:complications; D003906:Developing Countries; D005260:Female; D005901:Glaucoma / Q000150:complications; D006801:Humans; D007194:India; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D012164:Retinal Diseases / Q000150:complications; D011795:Surveys and Questionnaires; D014786:Vision Disorders / Q000209:etiology / Q000523:psychology / Q000534:rehabilitation*