Longitudinal study of retinal nerve fiber layer thickness changes in a multiple sclerosis patients cohort: A long term 5 year follow-up

Purpose: To analyze the changes in retinal nerve fiber layer (RNFL) in eyes with and without prior history of optic neuritis (ON) of patients with multiple sclerosis (MS) after a 5-year time period (2010-2015) using optical coherence tomography. Methods: The RNFL thickness of 114 eyes of 57 MS patients and 40 eyes of 20 healthy subjects were measured in year 2010 and year 2015. Measurements were made separately in twelve sectors around the optic nerve head. Statistical comparisons were made with the obtained data. Results: Progressive RNFL thinning occurs with time in both MS patients (regardless the eye had history of ON or not) and in normal subjects. The baseline mean RNFL thickness in ON eyes of MS patients (year 2010) was 74.2 +/- 15.7 mu m and five years later was 68. 7 +/- 12.2 mu m. The baseline mean RNFL thickness in eyes without ON of MS patients was 90.0 +/- 11.1 mu m and 84.7 +/- 10.3 mu m five years later. The median RNFL thickness reduction was 3.5 mu m for ON eyes, 4.7 mu m for eyes without ON, and 2.2 mu m for control eyes. The RNFL thickness reduction rate was similar in eyes with history of ON that in those with no history of ON. On the contrary, the MS group had a significantly higher rate of reduction than the control group. Conclusions: MS patients have thinner RNFL than normal controls, regardless their eyes had past episodes of ON or not. Eyes of MS patients lose their axons in a similar fashion regardless they had history of ON or not. Although ON causes RNFL loss, once resolved it does not influence the rate of RNFL loss in MS patients.