Reproducibility of Visual Field Endpoint Criteria for SAP, FT and SITA strategies: Diagnostic Innovations in Glaucoma Study (DIGS)

Purpose— To compare the inter-threshold and intra-threshold strategy agreement of visual field endpoint criteria for standard automated perimetry (SAP) with the Full Threshold (FT) and SITA (Swedish Interactive Thresholding Algorithm) algorithms. Design— Prospective longitudinal cohort study. Methods— The inter-strategy group included a randomly selected eye of 173 participants in the Diagnostic Innovations in Glaucoma Study who had performed FT and SITA within 3 months (Sequence 1 ‘FT&SITA’). Intra-strategy agreement for FT (Sequence 2 ‘FT&FT’) was tested for 44 (25.4%) participants who had performed a FT within a year of the FT used in the inter-strategy pairing, and for 89 patients (51.4%) who had performed a SITA within a year before (Sequence 3 ‘SITA&SITA’). Four different endpoint criteria using Statpac II indices were tested Inter-strategy agreement was compared with intra-strategy agreement using kappas (k). Results— FT&SITA agreement (k) for PSD<1% was 0.82, for PSD<5%, k=0.64; and for ≥ 4 PDP points, k=0.43. Agreement with GHT was significantly higher (P<0.01) for FT&FT (k=0.94) than FT&SITA (k=0.67), and approached significance (P=0.07) when comparing FT&FT with SITA&SITA (k=0.77). GHT was more likely to be abnormal on the SITA test than on the FT.