Reproducibility of pallor measurements with the optic nerve head analyzer

One eye each of ten healthy volunteers was tested with the Rodenstock Optic Nerve Head Analyzer on ten separate occasions. A color-coded pallor map was developed for each examination. A color transparency of each pallor map was then obtained from the television monitor of the Optic Nerve Head Analyzer, using a camera mounted on a tripod at a fixed distance from the screen. A color-coded zone within the center of the disc was chosen for each set of ten studies, and the area of this zone was measured by boundary analysis with another computerized image analyzer, the Oasys Image Processor. There was wide intrasubject variation in all ten volunteers, suggesting that the pallor map generated by the Optic Nerve Head Analyzer, when used in the manner described in this paper, is not adequate for following subtle changes in optic nerve head pallor.