Full Field Stimulus Threshold test (FST):
The FST measures sensitivity of the entire visual field by estimating the lowest luminance of a flash that elicits a visual sensation. Flashes of varying luminance are presented and for each flash, the subject reports if the stimulus was seen by pressing a response button; based on this response a different luminance is presented according to a predefined algorithm.
An FST test performed with stimulus from a colordome (Diagnosys, LLC)
fst normal.jpg
A normal FST response.

Roman, Alejandro J., et al. "Full-field stimulus testing (FST) to quantify visual perception in severely blind candidates for treatment trials." Physiological measurement 28.8 (2007): N51.