Predicting conversion to glaucoma using standard automated perimetry and frequency doubling technology

To test the hypothesis that development of glaucomatous visual fields can be predicted several years earlier from prior visual field information. One-hundred and seven eyes with glaucomatous optic neuropathy (n = 47 eyes) or which were suspicious for glaucoma (n = 60) were prospectively enrolled in a longitudinal study. Visual fields were evaluated on an annual basis using standard automated perimetry (SAP), the original version of frequency doubling technology (FDT) perimetry, and a custom version of FDT that used the 24-2 stimulus pattern. All SAP fields were within normal limits at the initial visit. When the SAP glaucoma hemifield test was 'outside normal limits' or the pattern standard deviation probability was worse than the lower 5th percentile or more than two clustered locations at the p < 0.05 level were present on the pattern deviation probability plot, an eye was defined as being abnormal. We used a classification tree analysis to predict which eyes would convert, using only baseline test results. Classification trees that were constructed using only baseline data had excellent specificity (near 100%) but worse sensitivity (25-50%) for predicting which eyes would convert during follow-up. Predictive information is present in visual field results, even when they are still within normal limits.