How decreased cone densities may help detect and monitor MS

Investigators in the United Kingdom have reported that decreased cone density was a characteristic in patients with multiple sclerosis (MS) they evaluated. This finding may serve as a specific and sensitive method to detect and monitor the development and progression of MS,¹ according to lead author Gemma McIlwaine, MSc, of the Wellcome-Wolfson Institute for Experimental Medicine at Queen’s University Belfast in Northern Ireland.

Although MS recently was reported to be associated with degeneration of the macular ganglion cell-inner plexiform layer and peripapillary retinal nerve fiber layer,² no study had reported the changes in the outer retina in patients with MS. In light of this, the investigators conducted a single-center, cross-sectional study to identify possible changes in the outer retina in 16 patients with MS and 25 controls without diagnosed MS.

McIlwaine and colleagues evaluated spectral-domain optical coherence tomography (OCT) scans of the macula and a circular scan around the optic nerve head (ONH). They captured adaptive optics (AO) images at 0° (centered on the foveola), 2°, 4°, and 6° temporal to the fovea, she said.

Main outcomes

The main outcomes measures were the thicknesses of the various macular layers and around the ONH using the inbuilt software of the OCT. The changes in the cone photoreceptors were evaluated by calculating cone density and spacing by the inbuilt AO automatic segmentation algorithm with manual correction. The results then were compared in patients with/without optic neuritis and controls.

The investigators observed significant thinning of the inner retina and thickening of the outer retina in eyes with a history of optic neuritis (P = .002 and P = .001, respectively). No changes were seen in the retinal layers in eyes without optic neuritis.

Regional differences were seen in the peripapillary retinal nerve fiber layer. AO images showed a significantly lower cone outer-segment density at all eccentricities in all patients compared with control eyes (P < .05), independent of the presence or absence of optic neuritis, the authors noted.

“This is the first study to show lower photoreceptor outer densities and spacing in patients with MS, suggesting that AO retinal imaging has the potential to become a sensitive marker for MS,” the authors concluded. “Whether the observed changes in this cross-sectional study can be translated to a larger and more ethnically diverse population will need to be seen.”

References

1. McIIwaine G, Csincsik L, Coey R, et al. Reduced cone density is associated with multiple sclerosis. Ophthalmol Sci. Published online: April 12, 2023; doi:https://doi.org/10.1016/j.xops.2023.100308

2. Hanson JVM, Hediger M, Manogaran P, et al. Outer retinal dysfunction in the absence of structural abnormalities in multiple sclerosis. Invest Ophthalmol Vis Sci. 2018;59:549 60; https://doi.org/10.1167/iovs.17-22821