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The development of the Indian vision function questionnaire: field testing and psychometric evaluation

S K Gupta¹, K Viswanath², R D Thulasiraj³, G V S Murthy¹, D L Lamping⁴, S C Smith⁴, M Donoghue⁴ and A E Fletcher⁴

¹ Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
² Sarojini Devi Eye Hospital, Hyderabad, India
³ Lions Aravind Institute of Community Ophthalmology, Madurai, India
⁴ London School of Hygiene and Tropical Medicine, London, UK

Correspondence to:
Correspondence to:
Professor Astrid E Fletcher
Department of Epidemiology and Population Health, Keppel Street, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK; astrid.fletcher{at}lshtm.ac.uk

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.

Abbreviations: IND-VFQ, Indian vision function questionnaire

Keywords: vision function questionnaire; psychometric evaluation; blind; visually impaired; low income countries

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