Multimodal imaging of the optic nerve head in retinitis pigmentosa

Abstract

Abstract Background: A pallor optic nerve head (ONH) is one of the three features in retinitis pigmentosa (RP). This study aimed to assess the ONH by color tone, presence of hyper-reflective structure, blood flow, and retinal nerve fiber layer (RNFL) thickness, and investigate the change in these parameters with and without ONH pallor. Methods: The presence of ONH pallor was assessed by three independent examiners through careful examination using fundus photographs. The presence of a hyper-reflective structure on the ONH was carefully evaluated using a volume scan optical coherence tomography (OCT). RNFL thickness and ellipsoid zone (EZ) width around the macula were also evaluated by OCT. Laser speckle flowgraphy was used to measure the mean blur rate of the entire ONH area, which was subsequently divided into the vessel area (MV) and tissue area (MT). Results: Twenty-eight eyes of 28 patients with RP (55.4±16.23 years old) were included. The pale ONH was observed in 10 (35%) eyes. Hyper-reflective structures were observed in 7 (25%) eyes. No significant correlation was found between the pale ONH and presence of a hyper-reflective structure (Pearson’s chi-squared test, p=0.364). The average of the ONH area, MV, and MT was 8.65±3.08 AU, 17.81±7.54 AU, and 6.4±2.66 AU, respectively, which significantly decreased in patients with pallor ONH (all p<0.05). The global RNFL thickness was 73.54±18.82 μm. The nasal and superior quadrants and global RNFL thickness in patients with a pale ONH were significantly thinner than in patients without a pale ONH (all p<0.05). There was no difference in the EZ width between patients with and without a pale ONH (p=0.107). Conclusion: We conducted multiple assessments of the ONH in patients with RP and investigated its clinical significance. Our findings suggest that ONH pallor may indicate a comprehensive change that emerges alongside the progression of retinal degeneration in RP. Trial registration: This trial was retrospectively registered in the UMIN Clinical Trial Registry(UMIN000048168 01/07/2022).