Validity of the time trade-off and standard gamble methods of utility assessment in retinal patients

Aim: To assess the validity of the time trade-off (70) and standard reference gamble (SRG) techniques of utility assessment in patients with retinal disease. A cross section of eligible patients was studied and validity was determined through their relation with two logical constructs, visual acuity and scores from the Visual Function 14 (VF-14) index. Methods: The study consisted of eligible patients presenting to a tertiary retinal facility who completed an interview, All patients had best corrected vision of 20/40 or worse in at least one eye. TTO and SRG utilities, as well as a VF-14 questionnaire, were administered through a standardised interview. Demographic and clinical (including Snellen visual acuity) information was also collected. Results: 323 patients met these study criteria. Significant predictors of TTO utilities in the multivariate analysis were vision in the better seeing eye (p<0.01) and VF-l 4 scores (p<0.01), Significant predictors of standard gamble utilities were also vision in the better seeing eye (p<0.01) and VF-14 scores (p<0.05). Conclusion: Both the standard gamble and TTO methods demonstrate strong validity when evaluated against visual acuity in the better seeing eye and the VF-l 4 score.