OCT-RNFL-Discordance – page 24 of 29

• GDx appears to demonstrate circumpapillary RNFL abnormalities many months prior to circumpapillary RNFL thinning with OCT in this case and perhaps in many others.
• In a monkey model, it has been demonstrated that such RNFL changes do occur earlier with GDx than with SD OCT and this discordance has been reported as early as one week after optic nerve transection.⁴
• 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.
• Vertical OCT scans through the macula may reveal significant asymmetry that is not revealed with circumpapillary RNFL measurements using the same instrument.
• 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.