Abstract
Purpose :
To report the minimally important difference (MID) for the National Eye Institute-Visual Function Questionnaire (NEIVFQ-25) for the TVT study cohort.
Methods :
The Tube Versus Trabeculectomy (TVT) study is a multicenter randomized clinical trial comparing tube-shunt surgery to trabeculectomy with mitomycin C (MMC) in patients with previous ocular surgery. Patient reported outcomes were assessed using the vision-specific NEIVFQ-25. 202 of 207 patients enrolled in the study had NEIVFQ measured at baseline. Clinical measures included the mean deviation (MD; Humphrey 24-2 visual field) of the surgical eye, and logMAR visual acuity (VA) measurements. Approximately half these patients had surgery performed in their better acuity eye; thus data were stratified to ‘better’/ ‘worse’ eye MD. Distribution and clinical anchor based methods were used to determine MID ranges. For anchor-based calculations, clinically significant changes in anchor were defined as > 2dB MD and > 0.2 logMAR. MIDs were only calculated for if the correlation between anchor and NEIVFQ score exceeded 0.3.
Results :
Correlations between composite score and clinical anchors exceeded 0.3 for surgical eye MD, better eye MD and better eye acuity. Mean [SD; range] values of anchors at baseline were: surgical eye MD = -16.6 [9.3; -32 to -0.5] dB; better eye MD = -15.0 [9.3; -32 to -0.9] dB; better eye acuity = 0.2 [0.3; -0.1 to 1.3] logMAR. For anchor-based cross sectional analysis, composite score MID [95%CI] was 6.3 [4.6 to 7.9] for better eye VA, 1.0 [0.6 to 1.4] for surgical eye MD and to 1.8 [1.2 to 2.5] for better eye MD. Distribution-based MIDs were 5.8 using 1/3 standard deviation of the composite score. MIDs for subscores were also calculated.
Conclusions :
In this cohort of patients with advanced glaucoma, a range of MIDs for the NEIVFQ were found, some of which are comparable to results reported by other studies using the NEIVFQ. Distribution based MIDs corresponded well with anchor-based MIDs based on acuity measures.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.