THE VISUAL-FIELD INDEXES IN PRIMARY OPEN-ANGLE GLAUCOMA

Purpose. The distribution of sensitivity across the visual field, as d etermined by automated threshold static perimetry, can be summarized i n terms of visual field indices. Such indices can be weighted for the variation in threshold at each eccentricity. The aims of this study we re to determine the influence of the weighting factor, the relationshi p between the unweighted indices derived from Programs 30-2 and 24-2, and the relationship between the number of double determinations of th reshold and the magnitude of the short-term fluctuation.Methods. One v isual field derived by Program 30-2 of the Humphrey Field Analyzer was selected from each of 60 consecutive patients with primary open-angle glaucoma. The first two fields from each individual patient were avoi ded. Unweighted visual field indices were calculated and compared with the Programs 30-2 weighted indices using an assessment of agreement e valuated with respect to the 95% confidence limits of the population. Results. The weighting function had no influence on the mean deviation , but it caused a slight reduction in the short-term fluctuation and a n elevation in the pattern and corrected pattern standard deviations. There was little difference between the indices generated by Programs 30-2 and 24-2. The short-term fluctuation increased with an increase i n the number of double determinations of threshold. Conclusions. The w eighting function had little clinical influence on the visual field in dices. The indices derived from Programs 30-2 and 24-2 were similar, a nd the short-term fluctuation would better reflect the intratest varia bility if all available double determinations of threshold were used t o calculate the index.