Detecting glaucomatous progression with infrequent visual field testing

PURPOSE: Previous work has investigated whether a significant regression slope in the first 2 years for the summary index Mean Deviation (MD) is predictive of rapid (≤-2 dB year-1 ) glaucomatous visual field progression. This work assumed six visual fields were obtained as per management guidelines, but in clinical practice commonly only two or three fields are measured. We used simulation methods to investigate how reducing test frequency influences the prediction of rapid visual field progression, along with the influence of including criteria based on regression slope. METHODS: We simulated visual field series (N = 100 000) spaced annually in the first 2 years and then biennially. We calculated positive and negative predictive values (PPV & NPV) for detecting rapid progression, based on a criterion of a significant negative regression slope of any magnitude, or of a magnitude less than a particular limit. We performed a second simulation using test frequency and disease prevalence parameters from a dataset of 255 glaucoma patients from The University of Tokyo Hospital, to check the validity of our method. RESULTS: Prediction values at 2 years were slightly less than those obtained using six visual fields. An addition of an appropriate slope based criterion materially improved PPV, with little detrimental effect on NPV. Simulated prediction values for the Tokyo dataset were similar to those determined empirically. CONCLUSION: Infrequent visual field testing does not dramatically alter predictive values at 2 years, but does substantially delay when significant progression may first be detected