Comparison of the Frequency Doubling Technology screening algorithm and the Humphrey 24-2 SITA-FAST in a large eye screening

Purpose: To compare the Frequency Doubling Technology (FDT) C20-1 screening algorithm and the Humphrey Field Analyser II (HFA) 24-2 SITA-FAST in a large eye screening. Methods: In a non-randomized, prospective, free eye screening, the FDT Screening Protocol (C20-1 Screening Algorithm) was administered to 574 attendees (422 men and 152. women, average age 64, range 17-89 years) of the 1998 Veterans of Foreign Wars (VFW) Convention in San Antonio, Texas. Individuals who failed the FDT (two or more misses out of [7 locations) immediately underwent white-on-white threshold visual field perimetry (HFA 24-2, SITA-FAST). Humphrey visual field analysis included STATPAC and masked evaluations by three glaucoma specialists. Results: Approximately one-tenth of the VFW conference attendees voluntarily presented themselves for screening. Among these 574 volunteers, 69 (12%) failed the FDT and underwent HFA analysis. Eighty-one per cent (56/69) of these FDT failures had abnormal HFA Glaucoma Hemifield Tests, Eighty-eight per cent (61/69) were judged to have nerve fibre type visual field loss on HFA by at least two of three masked examiners, A positive correlation existed between the number of FDT locations missed and the HFA mean deviation (r = 0.5, P = 0.0001). A similar association was observed when FDT and HFA results were analysed by quadrant (r = 0.5, P < 0.0001). Conclusion: There was a low false positive rate and a good positive predictive value comparing the FDT screening algorithm to the HFA 24-2 SITA-FAST in this study. This supports the potential use of FDT as an economical screening device.