A comparative evaluation of three methods of analyzing optic disc topography

Topographical evaluations of the optic discs of 17 eyes obtained using a clinical planimeter, the Rodenstock video-ophthalmograph, and the IS 2000 image analyzer were compared. The parameters studied were vertical and horizontal cup-to-disc ratios, cup volumes, rim areas, disc areas, and rim area-to-disc area ratios. There was good correlation between the measurements obtained by the three methods (correlation coefficients ranged from 0.46 to 0.88). For various parameters, the correlations between clinical planimetry and image analysis were higher than either those between image analysis and video-ophthalmography, or those between clinical planimetry and video-ophthalmography. The mean horizontal cup-to-disc ratios and rim areas as measured by clinical planimetry were significantly higher than those measured by image analysis. Image analysis measured significantly higher disc area and rim areas and lower cup volumes than video-ophthalmography.