Perimetric point density and detection of glaucomatous visual field loss

Eighty-three patients with high risk ocular hypertension were followed between 9 and 120 months with computerized threshold perimetry every three months in a prospective clinical study. Twenty eyes developed definite glaucomatous visual field defects. Analysis of these cases showed that definite field loss was preceded by increased variability of measured threshold values. Already at this early stage up to the time when a definite diagnosis of field loss first could be made, was, in all eyes, the disturbed area large enough to cover several test locations in the standard test point pattern used during the study. The results indicate that test point density of standard central field automated threshold tests is entirely sufficient, and that early field loss is unlikely to be extremely focal in nature and able to escape detection between tested points. While early recognition of glaucomatous field loss obviously is facilitated by access to large amounts of threshold data, the current results imply that test point density is usually not a limiting factor, but that testing an eye twice using the same standard test point pattern might be as effective as if two interlocking grids were used.