The impact of the severity of vision loss on vision-related quality of life in India: an evaluation of the IND-VFQ-33.

Objective: To validate the 33-item Indian Vision Functioning Questionnaire (IND-VFQ-33), a vision-specific scale, and determine the relationship between the severity of vision impairment (VI) and vision-related quality of life (VRQoL).

Methods: In this cross-sectional, observational study 273 participants with VI from cataract were recruited from a South Indian eye hospital. Participants underwent a clinical examination and completed the IND-VFQ-33 scale. The psychometric properties of the IND-VFQ-33 and its subscales were assessed using Rasch analysis, exploring key indices such as instrument unidimensionality, discriminant ability, and targeting of item difficulty to patient ability.

Results: Rasch analysis demonstrated the validity of the IND-VFQ-33 to assess VRQoL through four subscales (i.e., vision-specific mobility, activity limitation, psychosocial impact, and visual symptoms), but not as an overall measure. In adjusted multivariate analysis models, those with severe VI and blindness reported significantly poorer vision-specific mobility and activity limitation (mean change, -18.82, P = 0.007 and -29.48, P < 0.001, respectively) compared with those with no VI. These decrements in vision-specific functioning were both clinically significant. Lack of schooling and schooling up to completion of primary school were associated with poorer vision-specific mobility and visual symptoms, respectively.

Conclusions: Using a psychometrically valid IND-VFQ, only severe VI and blindness led to a clinically meaningful decline in vision-specific mobility and activity limitation. This finding reflects the current protocol for cataract surgery referral in developing or transitional countries, where priority is given to patients with at least moderate to severe VI.