Differences in retinal nerve fiber layer atrophy between multiple sclerosis subtypes.

OBJECTIVES

To determine whether retinal nerve fiber layer (RNFL) atrophy in the afferent visual pathway may complement existing tools used to describe and characterize differences across MS subtypes.

METHODS

Optical coherence tomography-measured RNFL values were compared over two years in 35 patients (70 eyes) with optic neuritis (ON) as a clinically isolated syndrome (CIS); 39 patients (78 eyes) with relapsing remitting MS (RRMS); and 7 patients (14 eyes) with secondary progressive MS (SPMS).

RESULTS

RNFL comparisons involving eyes without ON yielded greater differences between MS subtypes than ON-affected eyes. Overall RNFL values in non-affected eyes were reduced in SPMS patients (83.4 microm), relative to CIS (101.2 microm) (p=0.0009), and RRMS patients (103.7 microm) (p=0.001); and temporal RNFL atrophy was greater in RRMS (64.4 microm) eyes as compared to CIS eyes (73.2 microm) (p=0.02). In ON-affected eyes, RNFL atrophy was greater in SPMS patients (39.5 microm) than CIS patients (58.1 microm) (p=0.03), and in RRMS patients (48.2 microm) relative to CIS patients (p=0.05). RNFL values did not change significantly for any MS subtype during the two-year duration of the study.

INTERPRETATION: RNFL thickness may represent a structural marker, which can help distinguish MS subtypes, because the extent of atrophy is commensurate with disease progression. RNFL comparisons between non-affected eyes revealed greater differences between CIS, RRMS, and SPMS patients relative to ON-affected eyes, because the impact of prior ON may supplant the effects of disease subtype.