Author reply

We thank Casas-Llera et al for their interest in our study, the main purpose of which was to determine the level of agreement between the consensus judgment of expert clinicians and Glaucoma Progression Analysis (GPA) software with respect to the determination of whether visual field progression has occurred. In general terms, there are 3 possible GPA results: (1) no progression, (2) possible progression, and (3) likely progression. “Possible progression” is defined by the occurrence of 2 consecutive visual fields that demonstrate significant deterioration in glaucoma change probability maps in ≥3 testing locations compared with the mean of 2 baseline visual fields. “Likely progression” requires the same criteria in ≥3 consecutive visual field tests. In our study, the main analysis relied on a forced choice majority consensus opinion among the expert graders that resulted in only 2 possible outcomes, namely, progression or no progression. At issue is our methodologic approach for analyzing the cases classified as “possible progression” by GPA.