Retinal vascular damage linked to NMO-associated optic neuritis

This prospective study identified a pattern of morphologic abnormalities that is common in neuromyelitis optica (NMO) and associated with severe retinal axonal and neuronal loss and visual disability. However, the underlying mechanisms of these abnormalities remain unclear.

Subjects were 39 patients with NMO spectrum disorders and 39 age- and sex-matched healthy controls who underwent spectral-domain OCT.

Microcystic macular edema (MME) of the inner nuclear layer was found in 26 percent of patients and exclusively in eyes with a history of optic neuritis (ON). MME eyes had lower high- and low-contrast letter-acuity scores, lower peripapillary RNFL thickness, lower macular RNFL thickness, lower ganglion cell layer 1 inner plexiform layer thickness, higher inner nucleus layer thickness, and a greater number of ON episodes relative to non-MME eyes with a history of ON.

After adjusting for a history of multiple ON episodes, these findings remained significant for macular-RNFL thickness and inner nuclear layer thickness. NMO spectrum eyes without ON history had lower macular RNFL thickness, ganglion cell layer 1 inner plexiform layer thickness, outer nuclear layer thickness, and low-contrast letter-acuity scores compared to healthy controls.

The authors write the development of MME in NMO may be due to the breakdown of the blood-retinal barrier or an immune response targeting aquaporin-4 in the retina.

They note that peripapillary RNFL thickness was not significantly lower in non-ON eyes relative to healthy controls, in contrast to the macular-RNFL layer thickness. This indicates that macular segmentation may enable more sensitive detection of retinal axonal and neuronal loss, and that the use of the peripapillary RNFL in previous reports examining "unaffected" eyes of NMO-spectrum patients may account for the conflicting results across studies.