Background

Prior studies have suggested that retinal neuro-axonal loss may occur in aquaporin-4 (AQP4)-IgG seropositive neuromyelitis optica spectrum disorder (NMOSD) in the absence of optic neuritis (ON), but data are conflicting.

Objectives

To examine whether patients with AQP4-IgG seropositive NMOSD exhibit progressive retinal neuro-axonal loss, independently of optic neuritis (ON) attacks.

Methods

In this single-center, longitudinal study, 32 AQP4-IgG+ NMOSD patients and 48 healthy controls (HC) were followed with serial spectral-domain optical coherence tomography (OCT). NMOSD patients with ON less than 6 months prior to baseline were excluded, while data from patients with ON during follow-up were censored at the last visit prior to ON. Rates of peri-papillary retinal nerve fiber layer (pRNFL) and macular ganglion cell+inner plexiform layer (GCIPL) thinning were compared between groups utilizing mixed-effects linear regression models adjusted for age, race and sex.

Results

Median follow-up duration was 4.3 years (IQR: 2.6 -7.5) for the NMOSD cohort and 4.0 years (IQR: 1.8 – 7.5) for the HC. We observed faster pRNFL (β=-0.25µm/year, 95%CI: -0.45 to -0.05, p=0.014) and GCIPL thinning (β=-0.09µm/year, 95%CI: -0.17 to 0, p=0.05) in NMOSD compared to HC eyes. This difference appeared to be driven by faster pRNFL and GCIPL thinning in NMOSD eyes without a history of ON compared to HC (GCIPL: β=-0.15µm/year, 95%CI: -0.25 to -0.05, p=0.005; pRNFL: β=-0.43µm/year, 95%CI: -0.67 to -0.19, p<0.001), while rates of pRNFL (β=-0.07µm/year , 95%CI: -0.31 to 0.16, p=0.53) and GCIPL (β=-0.01µm/year, 95%CI: -0.11 to 0.10, p=0.90) thinning did not differ between NMOSD-ON and HC eyes .

Furthermore, we explored the effects of non-ON relapses during follow-up on rates of pRNFL and GCIPL thinning. Ten patients had relapses during follow-up (9 transverse myelitis, 1 area postrema syndrome). Patients with relapses did not exhibit differences in rates of GCIPL (β=0.05µm/year, 95%CI:-0.10 to 0.20, p=0.51) or pRNFL thinning (pRNFL: β=0.08µm/year, 95%CI: -0.28 to 0.43, p=0.67), compared to those who were clinically stable.

Conclusions

In this longitudinal study, we observed progressive pRNFL and GCIPL atrophy in AQP4-IgG+ NMOSD eyes unaffected by ON. These results support that subclinical involvement of the anterior visual pathway may occur in AQP4-IgG+ NMOSD.