Purpose: To compare the interthreshold and intrathreshold strategy agreement of visual field end point criteria for standard automated perimetry (SAP) with the full-threshold (FT) algorithm and the Swedish interactive threshold algorithm (SITA).
Design: Prospective, longitudinal cohort study.
Methods: The interstrategy group included a randomly selected eye of 173 participants in the Diagnostic Innovations in Glaucoma Study who had undergone FT algorithm and SITA analysis within three months (sequence 1, FT + SITA). Intrastrategy agreement for the FT algorithm (sequence 2, FT + FT) was tested for 44 (25.4%) participants who had undergone FT analysis within one year of the FT used in the interstrategy pairing, and for 89 patients (51.4%) who had undergone SITA analysis within one year before (sequence 3, SITA + SITA). Four different end point criteria using Statpac II indices were tested. Interstrategy agreement was compared with intrastrategy agreement using kappa statistics.
Results: FT + SITA agreement (kappa) for pattern standard deviation (PSD) < 1% was 0.82; for PSD < 5%, the kappa value was 0.64; and for four or more pattern deviation plot points, the kappa value was 0.43. Agreement with glaucoma hemifield test (GHT) results was significantly higher (P < .01) for FT + FT (kappa = 0.94) than FT + SITA (kappa = 0.67), and approached significance (P = .07) when comparing FT + FT with SITA + SITA (kappa = 0.77). GHT results were more likely to be abnormal on the SITA analysis than on the FT analysis. No other significant differences were found.
Conclusions: To minimize misinterpreting abnormal GHT results on SITA as evidence of change when switching strategies, both SITA and FT should be performed and compared within a short period. Other indices are comparable between the two strategies.