Background To describe the distribution pattern of the peripapillary retinal nerve fibre layer (RNFL) and major retinal vessel positions in patients with a large disc.

Methods The medical records of patients with a large disc and those of normal controls were reviewed retrospectively. Comprehensive ophthalmic examinations including Cirrus HD-optical coherence tomography (OCT) and Heidelberg Retinal Tomography III (HRT III) were performed. We divided patients into two groups (large disc group and control group) using an HRT-measured disc size of 2.5 mm² as a reference point. We extracted RNFL thicknesses at 256 points with OCT, measured major retinal vessel positions and compared them between the two groups.

Results In total, 97 eyes of 97 patients were included, with 60 patients in the large disc group and 37 patients in the control group. All patients were free of any glaucomatous change. We observed nasal shifting of the second superior and inferior peaks in the large disc group compared with the controls. The superior major temporal retinal arteries in patients with large disc also showed significant nasal displacement.

Conclusions We could observe nasalisation of the peripapillary RNFL and superior retinal artery in patients with a large disc. As this phenomenon may lead to false positive results in OCT-based RNFL thickness maps, results from our study may help prevent misdiagnosis of glaucoma and improve the sensitivity and specificity of glaucoma detection.