The AQP4-IgG-negative NMOSD group showed: higher diplopia incidence (35.29% vs. 17.19% in positive NMOSD, 17.18% in controls; P<0.001); lower limb sensory abnormalities (76.47% vs. 89.58%, P = 0.0056) and urinary dysfunction (36.47% vs. 57.29%, P = 0.0017) than positive cases; predominant brainstem involvement (50.59% vs. 31.77% in positive, 28.70% in controls; P<0.001); moderate spinal cord involvement (70.59% vs. 88.02% in positive, 38.57% in controls; P<0.001); and altered thyroxine, apolipoprotein A1, eosinophils, and basophils. The gene discussed is APOA1; the disease is Diplopia.