Comments and Conclusions
• CORDA (COlor Reflectivity Discretization Analysis) is novel software that discriminates between the desired (high) reflectance of the axons within the RNFL and the unwanted (low) reflectance blood vessels traveling within the RNFL.
• CORDA-enhanced OCT analysis data detects known abnormalities which are too subtle to be detected by segmentation of the RNFL alone. The present-day native SD-OCT RNFL analysis packages continue to be confounded by the presence of blood vessels within the circumpapillary RNFL.
• In this case, and perhaps in many others, GDx appears to demonstrate circumpapillary RNFL abnormalities many months prior to traditional circumpapillary RNFL thinning, as identified with SD-OCT. In a monkey model, it has been demonstrated that such RNFL changes are identified earlier with GDx than with SD OCT and this discordance has been reported as early as one week after optic nerve transection.2 This may be due in part to the fact that blood vessels do not contribute to the GDx data set, as they are not bi ref ri ngent.
• With SD-OCT. the GCC (ganglion cell complex) was far more sensitive in demonstrating the predicted inferior loss of structure than was the circumpapillary RNFL measurement; this may have relevance in many other cases.
• The software analysis packages of the circumpapillary RNFL thickness (with all three OCT systems tested) sometimes falters and fails to flag abnormalities that, in this case, are rather profound.
• In this case, GDx outperformed SD-OCT. How CORDA-enhanced OCT measurements compare to GDx remains to be evaluated.
• When CORDA becomes commercially available, OCT scans obtained previously can be reanalyzed. Countless abnormalities which previously went undetected will likely be revealed!