To the Editor.
—In their recent article, Enger and Sommer1 compared two methods of diagnosing glaucoma using automated static threshold fields. One method used two of four visual field indexes available from a statistical program, STATPAC, which we developed for use with the Humphrey perimeter (Allergan Humphrey, San Leandro, Calif). The second method was their own and was based on comparisons of mirror-image clusters of points above and below the horizontal meridian. They found that their method gave higher sensitivity and specificity (97% and 90%, respectively) than the STATPAC indexes (93% and 84%, respectively).The purpose of the STATPAC indexes is not primarily to help in identification of abnormal fields but rather to facilitate follow-up. STATPAC contains other elements that are intended to help in the classification of single fields. These are called deviation maps and are of two types: (1) numerical deviation maps showing pointwise decibel deviations of the