The effect of multiple sclerosis on retinal nerve fiber layer in eyes without history of optic neuritis

Background
Multiple sclerosis (MS) is a disabling disease that is characterized by an axonal damage in the central nervous system, leading to progressive neurologic deficits. Evidence indicates that axonal damage occurs already in the early stages of the disease.


Objective
To discover the ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) changes using optical coherence tomography in patients with early relapsing-remitting MS [expanded disability status scale (EDSS)<3] and their relation to the degree of disability and duration of the disease.


Patients and methods
Overall, 48 eyes of 24 patients with relapsing-remitting MS [31 eyes without history of optic neuritis (ON) and 17 with history of ON] were scanned by using optical coherence tomography and compared with 12 eyes of six age-matched and sex-matched healthy participants. Full history taking and neurological and ophthalmological examination was done. In addition, assessment of disability by EDSS was done for patients.


Results
Both total and sectorial RNFL thickness were significantly decreased in affected eyes (with ON) and nonaffected eyes in comparison with control eyes; however, RNFL thickness (average and sectorial) was not significantly correlated with duration of the disease or disability assessed by EDSS. In contrast, superior and inferior GCC thickness was significantly correlated with EDSS, although they were not significantly decreased in nonaffected eyes in comparison with control eyes.


Conclusion
RNFL thinning takes place without a historical record of ON and may be considered as a chronic optic neuropathy in patients with MS. GCC thickness is perhaps a reliable marker for indicating progression of disease.