GDx vs Zeiss Cirrus- Comparison of Three Examinations OD

Although the (circumpapillary) GDx RNFL does demonstrate a dramatic change and loss
inferiorly, the Cirrus (circumpapillary) RNFL is essentially normal following the inferior artery
occlusion. Note that GDx is measuring the polarization or birefringence of the RNFL but the
OCT is measuring optical reflectivity.
Does birefringence yield a more accurate assessment of the RNFL than does optical
reflectivity? 3,4