Agreement to detect glaucomatous visual field progression by using three different methods: a multicentre study

Aim To examine the level of agreement among nine clinicians in assessing progressive deterioration in visual field (VF) overview using three different methods of analysis. Methods Each visual field was assessed by Humphrey Field Analyzer (HFA), program 24-2 SITA Standard. Nine expert clinicians assessed the progression status of each series by using HFA 'overview printouts' (HFA OP), the Guided Progression Analysis (GPA) and the Guided Progression Analysis (GPA2). VF series were presented in random order, but each patient's VF remained in chronological order within a given field series. Each clinician adopted his personal methods based on his knowledge to evaluate VF progression. The level of agreement between the clinicians was evaluated by using weighted κ statistics. Results A total of 303 tests, comprising 38 visual field series of 7.9±3.4 tests (mean±SD), were assessed by the nine glaucoma specialists. When the intra-observer agreement was evaluated between HFA OP and GPA, the mean κ statistic was 0.58±0.13, between HFA OP and GPA2, κ was 0.55±0.06 and between GPA and GPA2 it was 0.56±0.17. When the inter-observer agreement was analysed κ statistic was 0.65 for HFA OP, 0.54 for GPA and 0.70 for GPA2. Conclusions Using any procedure for evaluating the progression of a series of VF, agreement between expert clinicians is moderate. Clinicians had higher agreement when GPA2 was used, followed by HFA OP and GPA printouts, but these differences were not significant