In this cross-sectional single-center study, patients with MS (pwMS) and non-MS controls underwent clinical, standard automated perimetry and optical coherence tomography assessments. Using customized retinal layer segmentation in nasal and temporal hemimacular sectors, we developed an rTSD-index, which compares ganglion cell hemimacular projections corresponding to each cerebral hemisphere, with positive values reflecting right-hemisphere driven rTSD and vice versa, and absolute rTSD-index (ArTSD) values indicating severity.

A total of 79 pwMS and 23 non-MS controls were included (average age 45±13 and 37±14, 67% and 61% female, respectively). On average, pwMS had higher ArTSD values (mean difference 1.5, p=0.02). Evidence of rTSD was detected in 13/79 (16%) pwMS and 0/23 non-MS controls at an ArTSD threshold of 3.5. In pwMS, longer disease duration was associated with increased ArTSD severity (β=0.9 for each decade of increased disease duration, p=0.03). For each 1 point increase in ArTSD value, there was on average a 0.1 dB worsening in corresponding visual hemifield function after excluding subjects with optic neuritis history (p=0.02).

rTSD-index is a novel method to quantify rTSD of the visual pathway in MS, which occurs in 1 out of 6 pwMS, is associated with longer disease duration and subclinical visual field defects. Future studies investigating its association with clinical disability, MRI findings, and methods to mitigate it are needed.