Inter/Intra-Observer Agreement to Detect Glaucomatous Visual Field Progression by Using Standard Humphrey Printout, Glaucoma Progression Analysis 1 and 2

Abstract

Purpose: : To examine the level of agreement between clinicians in assessing progressive deterioration in visual field series using standard Humphrey printout (SHP), glaucoma progression analysis 1 (GPA) and 2 (GPA2).

Methods: : Each visual field was assessed by Humphrey Field Analyzer (HFA), program SITA standard 30-2 or 24-2 (Carl Zeiss Meditec, Inc., Dublin, CA). Mean Deviation (MD) and Pattern Standard Deviation were considered at baseline and in the end of the follow-up. The first 3 fields in each series were exclude to minimize learning effects: the forth and fifth Full Threshold or SITA Standard exams were used as baseline. Eight expert clinicians assessed the progression status of each series using SHP, GPA and GPA2. The progression criteria adopted by the clinicians were similar to the GPA algorithm comparing single field printout with the baseline exams. The intra and inter observer agreement was evaluated using a weighted kappa statistic. The Κ statistic was calculated interpreting as Κ<0 indicating no agreement; Κ = 0.0 to 0.19, poor; Κ = 0.20 to 0.39, fair; Κ = 0.40 to 0.59, moderate; and Κ = 0.60 to 0.79, substantial; and Κ = 0.80 to 1.0, almost perfect agreement.

Results: : Forty visual field series were analyzed by the 8 physicians. The mean follow-up time was 6.2 + 1.53 years (mean + standard deviation). At baseline the mean MD was -7.34 + 7.18 dB and at the end of the follow-up the mean MD was -9.25 + 8.65 dB, this difference was statistically significant (p<0.001). When the mean intra-observer agreement was 0.57 + 0.14 between SHP and GPA, 0.56 + 0.05 between SHT and GPA2 and 0.54 + 0.17 between GPA and GPA2. When the mean inter-observer agreement was 0.66 + 0.12 for SHP, 0.52 + 0.16 for GPA and 0.69 + 014 for GPA2. The best interobserver agreement was obtained for GPA 2 and the worst was for GPA.

Conclusions: : Intra-observer agreement was good for the three different methods to assess VF progression, GPA2 had the best interobserver agreement.

Keywords: perimetry • visual fields