Damage to the Optic Radiation in Multiple Sclerosis Is Associated With Retinal Injury and Visual Disability

Objective: To determine whether damage to the optic radiation (OR) in multiple sclerosis (MS) is associated with optic nerve injury and visual dysfunction. Design: Case-control study. Setting: Referral center. Participants: Ninety referred patients with MS and 29 healthy volunteers. Main Outcome Measures: Magnetic resonance imaging indices along the OR were reconstructed with diffusion tensor tractography. Retinal nerve fiber layer thickness and visual acuity at high and low contrast were measured in a subset of the MS group (n=36). Results: All tested magnetic resonance imaging indices (fractional anisotropy [FA]; mean, parallel, and perpendicular [lambda(perpendicular to)] diffusivity; T2 relaxation time; and magnetization transfer ratio) were significantly abnormal in patients with MS. Mean retinal nerve fiber layer thickness was significantly correlated with FA (r=0.55; P<.001) and lambda(perpendicular to) (r=-0.37; P=.001). The retinal nerve fiber layer thickness in the nasal retinal quadrant was also specifically correlated with FA and lambda(perpendicular to) in the synaptically connected contralateral OR. In individuals with less severely damaged optic nerves (mean retinal nerve fiber layer thickness similar to 80 mu m), letter acuity scores at 2.5% contrast were correlated with OR-specific FA (r=0.55; P=.004), lambda(perpendicular to) (r=-0.40; P=.04), and magnetization transfer ratio (r=0.54; P=.01), as well as the fraction of OR volume made up of lesions (r=-0.69; P<.001). Conclusions: Fractional anisotropy and lambda(perpendicular to) are potentially useful quantitative magnetic resonance imaging biomarkers of OR-specific damage in MS. Such damage is associated with retinal injury and visual disability.