Retinal nerve fiber layer thickness is associated with brain MRI outcomes in multiple sclerosis

Multiple sclerosis is characterized by the dual pathological processes of inflammation and neurodegeneration. Conventional MRI techniques are considered the best tools for assessing and monitoring lesion burden and inflammation but are limited in their ability to assess axonal loss. Optical coherence tomography (OCT) is a simple high-resolution technique that uses near infrared light to quantify the thickness of the retinal nerve fiber layer (RNFL), which contains only non-myelinated axons. RNFL thickness (RNFLT) was measured using OCT on thirty consecutive MS patients (60 eyes). Eighteen patients underwent quantitative MRI analysis including T1- and T2-lesion volumes (LV), normalized brain volume (NBV), normalized cortical, white and gray matter volumes (NCV, NWMV, and NGMV), and mean whole brain diffusivity (MD). There was a strong association between NBV and average RNFL thickness (p<0.001, partial rp=0.77). The T2-LV and NWMV were significantly associated with average RNFL thickness (p=0.002, partial rp= -0.76 and p=0.005, partial rp=0.68, respectively) and there were trends toward association with T1-LV (p=0.041) and NGMV (p=0.067). There was negative correlation between average RNFL thickness (average of both eyes) and disability as assessed by EDSS (p=0.02). The results support potential usefulness of OCT for MS patient monitoring and research applications.