This Italian study introduces a new method, derived from the Glaucoma Staging System (GSS), for classifying glaucomatous visual field defects. Investigators considered four sample groups composed respectively of 471 (Sample 1), 128 (Sample 2), 185 (Sample 3) and 131 (Sample 4) patients with either ocular hypertension or chronic glaucoma. The new method of classification, which the authors call GSS 2, uses the mean deviation (MD) and corrected pattern standard deviation/constant linear velocity (CPSD/CLV) or pattern standard deviation/linear velocity (PSD/LV) perimetric indices to classify visual field defect in six stages and three types (generalized, localized and mixed). The formulas were determined using Sample 1; a new borderline stage was created on the basis of Sample 2; the relationship between the PSD/LV and CPSD/CLV values was studied on Sample 3 to verify the possibility of using the uncorrected indices instead of the CPSD/CLV; and the relationship with other classification methods was studied on Sample 4.

The GSS 2 showed a strong level of association with the AGIS and the Hodapp-Parrish-Anderson methods in staging defect severity. Results also showed a good correlation with a classification based on the Bebie curve. The authors conclude that the new classification method correctly classified both damage severity and perimetric defect type in the sample studied, using either the corrected or uncorrected visual field indices. They stress that it is a quick and easy method and its formulas can be introduced in any software.