Psychophysical assessment of low visual function in patients with retinal degenerative diseases (RDDs) with the Diagnosys full-field stimulus threshold (D-FST)

To determine whether the Diagnosys full-field stimulus threshold (D-FST) is a valid, sensitive and repeatable psychophysical method of measuring and following visual function in low-vision subjects. Fifty-three affected eyes of 42 subjects with severe retinal degenerative diseases (RDDs) were tested with achromatic stimuli on the D-FST. Included were subjects who were either unable to perform a static perimetric field or had non-detectable or sub-microvolt electroretinograms (ERGs). A subset of 21 eyes of 17 subjects was tested on both the D-FST and the FST2, a previous established full-field threshold test. Seven eyes of 7 normal control subjects were tested on both the D-FST and the FST2. Results for the two methods were compared with the Bland–Altman test. On the D-FST, a threshold could successfully be determined for 13 of 14 eyes with light perception (LP) only (median 0.9 ± 1.4 log cd/m²), and all eyes determined to be counting fingers (CF; median 0.3 ± 1.8 log cd/m²). The median full-field threshold for the normal controls was −4.3 ± 0.6 log cd/m² on the D-FST and −4.8 ± 0.9 log cd/m² on the FST2. The D-FST offers a commercially available method with a robust psychophysical algorithm and is a useful tool for following visual function in low vision subjects.