Optic disc torsion skews RNFL measurements

This prospective study found that individual variations in ocular anatomy can create anomalies on OCT retinal nerve fiber layer (RNFL) thickness measurements.

Optic disc torsion is fairly common and was defined in this study as a greater than 15 degree deviation of the long axis of the optic disc from the vertical meridian (the vertical line 90 degrees from a horizontal line connecting the fovea to the center of the optic disc).

The authors used Cirrus HD-OCT to examine the relationship between the optic disc torsion and peripapillary RNFL thickness in 94 subjects with optic disc torsion and 114 subjects without optic disc torsion.

In eyes in which the superior peak of the optic disc is angled temporally (towards the fovea), the temporal segment thickness of the RNFL scan tended to measure thicker and the superior peak of the TSNIT plot tended to be more temporal compared to eyes without torsion and eyes in which the superior peak angled nasally (away from the fovea).

However, the macular scans, including all the subsectors, were similar among the three groups, as were other measurements, including total retinal thickness and optic nerve head parameters.

These results suggest that RNFL sector measurements in eyes with optic disc torsion may lead to interpretation errors. Clinicians should consider using macular scans to assist in differentiating between eyes with and without optic disc torsion.