Pattern discrimination perimetry: a new concept in visual field testing

The subject’s task in conventional perimetry is to detect an incremental spot of light on a uniform background. Recent evidence indicates that, at least in glaucoma, this task can be insensitive to large amounts of neural damage. In an attempt to find more effective ways to detect early glaucomatous damage, we are developing alternative perimetric techniques that are based on pattern discrimination rather than light detection. The subject fixates a small square at the center of a large field of dynamic random dots and tries to detect a patch of non-random, or coherent, dots embedded in the background. The stimuli are displayed on a projection CRT, and all test target parameters, including position, size, shape, exposure duration, dot density, dot arrangement and dot dynamics, are under computer control. In particular, spatial and temporal coherence parameters are defined in terms of the spacing and motion of the target dots.