Full Threshold for the OPI
The OPI package contains an implementation of the Full Threshold (FT) algorithm used in the first Humphrey Field Analyzer (HFA) manufactured from 1984 to 1995. It was subsequently superseeded by SITA in the newer HFA II, but SITA was designed to have the same error characteristics as FT [1], and so FT is still used as a baseline in some studies.
The implementation provided as part of the OPI is the best guess at the procedure from the literature. The actual procedure used in the HFA machines may have differed slightly. If anyone has inside info on how FT might have worked, please contact the OPI team and we will incorporate the changes into the package.