Calibration of the Dicon Auto Perimeter 2000 compared with that of the Goldmann perimeter.

We empirically evaluated the calibration of the Dicon Auto Perimeter 2000 by comparing the results of threshold static perimetry with those for the same group of normal subjects examined by conventional manual static perimetry with the Goldmann perimeter. At 10 to 20 degrees of eccentricity in the visual field (including the entire Bjerrum region), there was no significant difference between threshold levels expressed as Goldmann equivalent stimuli by the Dicon instrument and the results obtained by examination with the Goldmann perimeter. The slopes of the linear meridional profiles from the two instruments were significantly different, however. The slope of the profile measured with the Dicon perimeter was flatter than that produced by Goldmann perimetry, so that threshold values inside 10 degrees of eccentricity were higher, whereas threshold values outside of 20 degrees of eccentricity were lower. Though statistically significant, these differences were small (2 dB at most). The difference in slopes can be attributed to a difference in stimulus sizes, because the area of the Dicon stimulus is eight times that of the size I Goldmann test object and twice that of the size II test object.