Table 3.
Psychometric performance | Modified VFQ-25 (mVFQ-25) item |
---|---|
Items performed well across the majority of the psychometric tests carried out: demonstrating strong item properties, convergent validity (moderate-to-strong correlations at 1-year follow-up with MLMT, FST and visual field scores), good item-level known-groups analysis (distinguished between patients who differed in their visual field and MLMT scores) and were responsive to changes over time from baseline to 1 year |
• Item 4 (walk in unfamiliar outdoor places without help at dusk); • Item 19 (bump into objects when they are in a new position); • Item 21 (run into things in unfamiliar environments); • Item 25 (overshoot objects or run into things if they have been moved from their usual spot) |
Items performed well for most of the psychometric analyses conducted (e.g. test–retest reliability, convergent validity) but were not able to detect changes in scores over time |
• Item 2 (locate doorknobs and handles without first passing your hand over them); • Item 3 (find things that are moved from their normal spots quickly); • Item 7 (read normal print books or see details in pictures without magnifiers or computer/television screens); • Item 8 (see a movie in a theatre or a planetarium show); • Item 9 (find a plate, fork and spoon in a restaurant that is dimly lit); • Item 10 (read labels on cans/food products/medicine bottles); • Item 11 (read street signs or signage in buildings) Item 14 (trouble identifying simple shapes); • Item 16 (put things down in specific places so that you can find them by feel/touch); • Item 20 (need assistance to walk confidently in new places); • Item 24 (hesitate before using stairs or getting onto an escalator or going through a revolving door) |
Items performed poorly on several of the psychometric analyses, including item response distributions (ceiling effects), unsupported convergent validity, poor test–retest reliability, and nonresponsive to change |
• Item 1 (read lighted dials or lights on electronic equipment); • Item 5 (recognize people first by vision alone); • Item 6 (find a new bus stop); • Item 12 (difficulty judging whether someone is male or female using only vision); • Item 13 (trouble determining the expression on unfamiliar faces using only vision); • Item 15 (difficulty seeing which direction hands on a clock (non-digital) are facing); • Item 17 (make mistakes when dressing in good light); • Item 18 (make mistakes when using the bathroom or bathing); • Item 22 (get lost or disoriented in familiar environments); • Item 23 (activities that make you uncomfortable or nervous because of the way your vision is) |