To evaluate retinal nerve fiber layer (RNFL) thickness profiles according to the disc-foveal angle in superior oblique palsy (SOP) and control eyes.

In forty-four eyes of 22 patients with unilateral SOP (and their fellow eyes) and 42 eyes of 42 normal controls, position of the fovea relative to the optic disc, the disc–foveal angle was calculated by optical coherence tomography (OCT) device (Heidelberg Engineering, Inc., Heidelberg, Germany) machine using FoDi (fovea-to-disc) technology. After measuring RNFL thickness with FoDi alignment technology, each OCT image was re-evaluated with FoDi turned off and the measurements were repeated to determine RNFL values according to the disc–foveal angle.

The average disc–foveal angle was -10.85±6.60° and -10.71±6.63° in the affected and fellow eyes of SOP patients, which were significantly greater than the recorded disc-foveal angle of control subjects with -5.88±4.09°. There was no significant difference in RNFL sector values between SOP and control eyes with FoDi. From all RNFL sectors inferotemporal thickness was thinner in SOP eyes without FoDi than in SOP eyes with FoDi (129.7±20.5 µm vs 144.6±17.8 µm, respectively, P=0.001). Differences of the RNFL thicknesses with and without FoDi in SOP eyes in superotemporal and inferotemporal sectors were 5.40 ±13.42 and 14.84±15.00, respectively, which were significantly more than the same changes in control eyes with amount of 0.30±6.57 and 8.52±10.4 (P=0.02 for both sectors).

The disc-foveal angle is a necessary determinant of normal RNFL thickness in SOP eyes and improper fovea disc alignment affected sectoral RNFL thickness measurements.