Visual Field Defect Higher in Patients with NMOSD-ON Than Idiopathic ON

In recent prospective study (NCT02886377) of 104 patients, results showed a higher percentage of neurologic abnormalities of visual field defects in neuromyelitis optica spectrum disorder-optic neuritis (NMOSD-ON) in comparison with those with idiopathic optic neuritis (IDON).¹ These findings clarify the trend of visual field defect with two types of ON as well as the patterns of severity and recovery.

The NMOSD-ON group had significantly higher relapse ON (NMOSD group, 51.5%; IDON group, 26.8%; P = .014). In comparison, the IDON group had a significantly higher percentage of first episode ON (NMOSD-ON group, 48.5%; IDON group, 73.2%; P = .014).

Lead coauthors Jiaqi Liang, MD, and Yuxin Zhang, MD, State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, and colleagues wrote, “The VF defect of ON, pattern as well as severity, evolves during the process of acute attack until the inflammation finally stables. The results of VF might be influenced by the course, treatment regimen, experience of VF readers et al., among which course was the main factor.”¹

Recruited patients had a diagnosis of ON from the Zhongshan Ophthalmic Center at Sun Yat-Sen University between February 2012 and July 2017. Thirty-three patients had NMOSD-ON and 71 patients had IDON, both groups followed up for 6 months or more. The patients ranged from 18 to 65 years of age and were within 14 days of ON onset.

The patterns of the VF defect, recovery pattern, mean defect (MD) and the pattern for the standard deviation (PSD) were the primary outcomes. Additionally, the best corrected visual acuity (BCVA) after onset at 1 month, 3 months, and 6 months or more were compared with the two groups. This study was approved by the Clinical Research Ethics Board at the university’s medical center.

Notably, the MD and PSD were significantly worse after each follow-up for patients in the NMOSD-ON group in comparison with the IDON group. A positive correlation was observed with both groups for 1 month and 6 months or more in MD and PSD. Only the NMOSD-ON group had a positive correlation in BCVA between 1 month and 6 months or more.

Both groups experienced a positive correlation between 3 months and 6 months or more in MD, PSD, and BCVA. Additionally, the most common pattern for both groups was the quadrant recovery pattern (57.1% in NMOSD-ON and 57.4% in IDON) and this was confirmed through analysis of the first episode subgroup.

Particularly, the NMOSD-ON group had a significant female predominance (81.8% versus 50.7%, P = .001) which is observed as well in previous studies.2 Overall, no statistically significant differences were observed with both groups in the age at onset or affected eyes, unilateral or bilateral.

Liang, Zhang, and colleagues noted, “The NMOSD-ON patients tended to suffer more severe VF damage, VF irregularity and worse prognosis than that of IDON patients. Diffuse abnormalities and nerve fiber bundle abnormalities were the 2 most common types in both groups, while neurologic abnormality more common in NMOSD-ON and central scotoma more common in IDON. The visual functions of 1 month in NMOSD-ON and 3 months in IDON were related to its prognosis.”¹

Results demonstrated that both types of ON recovered mainly quadrant-wise, yet a larger sample is needed for clarification as well as further research should be conducted on the mechanism. Liang, Zhang, et al noted that the pattern recovery, “might indicate which part of the optic nerve tends to recover first: from peripheral to central, vice versa, or quadrantal, and might indicate the pathological process involved during recovery.”¹

The study’s limitations included a possible bias on the patient selection as the design was a single center and provided a small sample. The investigators acknowledged that a larger sample would have displayed more differences between the two groups. Observations on the visual function index and structure index should be further investigated to understand NMOSD-ON through more clinical characteristics. Additionally, myelin oligodendrocyte glycoprotein antibody disease was not included as a group in the study even though it is another common type of ON.

REFERENCES
1. Liang J, Zhang Y, Liu K, et al. Comparing evolvement of visual field defect in neuromyelitis optica spectrum disorder-optic neuritis and idiopathic optic neuritis: a prospective study. BMC Ophthalmol. 2022;22(1):338. doi:10.1186/s12886-022-02510-y
2. Jarius S, Ruprecht K, Wildemann B, et al. Contrasting disease patterns in seropositive and seronegative neuromyelitis optica: A multicentre study of 175 patients. J Neuroinflammation. 2012;9:14. doi:10.1186/1742-2094-9-14