Correlation Between Rnfl and T25FW over a 2-Year Period in a Cohort of MS Individuals

Background: There is a need to identify anatomical biomarkers of disease progression in Multiple Sclerosis (MS) that are practical, inexpensive, and easy to perform.  Measurement of the retinal nerve fiber layer (RNFL) by Optical Coherence Tomography (OCT) correlates with brain volume loss as measured by MRI.  Correlation between anatomical and functional parameters is needed.

Objectives: : Identify if RNFL measurement by OCT correlates with timed 25 foot walk (T25FW) and serves as a surrogate anatomical marker of functional decline in individuals with MS.  

Methods: This was a longitudinal study of 51 MS patients. Each subject had OCT and T25FW measured at two time-points, separated by 1-2 years. 

Results: There was no significant correlation between T25FW and RNFL (r=0.01, p> 0.05). There was a trend to a decrease in the RNFL over time, but not at the level of statistical significance.  A paired sample t-test was done to examine any differences for T25FW and for RNFL thickness at year one versus year two.  No significant changes were seen for T25FW (p=.212, p>0.05) or for changes in RNFL (p=.104, p>0.05) in that time period.  The T25FW data was further trichotomized (< 6 seconds; 6-7.99 seconds, and ≥ 8 seconds).  None of the measurements for the subgroups had significant differences from one year to the next. 

Conclusions: This pilot study examined the relationship between RNFL and T25FW over a follow up of two years. No relationship was found between the two parameters for the group as a whole or for timed performance subgroups. Future studies with larger cohorts and duration are warranted.