Measuring quality of vision including negative dysphotopsia

Purpose: To adapt the Quality of Vision Questionnaire (QoV) for measuring negative dysphotopsia and to validate the original and modified versions in the Dutch population. Methods: The QoV was translated into Dutch according to standardized methodology. Negative dysphotopsia items were constructed based on focus group interviews, literature review and clinical data. The questionnaire was completed by 404 subjects, including contact lens wearers, patients with cataract and after cataract surgery (95.5% with a monofocal, 4.5% with a multifocal intraocular lens). Rasch analysis was applied for evaluation of reliability and validity of the original QoV and modified version, Negative Dysphotopsia QoV (ND-QoV). Results: The frequency, severity and bothersome scales of the QoV and ND-QoV demonstrated good measurement precision, good fit statistics for all but one item, but significant mistargeting of more than one logit. Item estimations were stable across the study groups and scales were unidimensional with more than 50% of variance explained by the measurements. There was a positive correlation between questionnaire scores and best corrected visual acuity (r = 0.3, p < 0.01). The quality of vision measured by all three scales was significantly poorer (p < 0.01) in patients with negative dysphotopsia compared to asymptomatic pseudophakic patients. Conclusion: The Dutch version of the QoV questionnaire has shown good psychometric properties comparable to the native version as well as good reliability and validity. The addition of negative dysphotopsia items is a valuable modification for the reliable assessment of quality of vision in pseudophakic patients.