Retinal nerve fibre layer evaluation in multiple sclerosis patients with and without optic neuritis.

Abstract

It is well-known that patients with multiple sclerosis (MS) with a history of optic neuritis (ON) have a thinner retinal nerve fibre layer (RNFL) than normal (Fisher et al. 2006; Khanifar et al. 2010). However, the literature lacks reports of RNFL thickness in patients with MS without a history of ON. Recent studies have shown that MS is both an inflammatory demyelinating disorder and a neurodegenerative disease. Therefore, patients with MS can have optic nerve damage, even with no prior history of ON episodes (Ashworth 1987; Peterson et al. 2001; Waxman 2005). This study compares RNFL thickness in patients with MS with and without a history of ON and evaluates the relationship between RNFL thickness and number of ON episodes to better understand if the OCT can be used to monitor disease progression and to guide clinical treatment decisions. Subjects with treated MS and healthy subjects were enrolled as the study and control groups, respectively. All subjects underwent neurological and ophthalmological examination, and spectral-domain optical coherence tomography (OCT; Spectralis OCT, software v. 4.0, Heidelberg Engineering, Dossenheim, Germany) imaging to measure RNFL thickness. Subjects were excluded from the study if any of the following were present: glaucoma, optic neuropathy, high ametropia (refractive error spherical equivalent more severe than ±5 dioptres), history of ocular or neurological trauma, or other relevant retinal and/or optic nerve disease. Fifty-six subjects with treated MS and 35 healthy subjects were included. Mean global (MS: 89.6 ± 15.4 μm, control: 104.3 ± 9.1 μm; p < 0.001) and sectorial RNFL thicknesses were significantly less in the MS group than in the control group (Table 1). Global RNFL thickness was thinnest in MS subjects with a history of ON (79.8 ± 15.9 μm), followed by MS subjects without a history of ON (93.6 ± 13.3 μm), and thickest in the control group (104.3 ± 9.1 μm; all p < 0.001). Additionally, the Spearman rank correlation coefficient (rs) between the number of ON episodes and RNFL thickness was −0.41 in the MS group (p < 0.001). Therefore, MS subjects that had more ON episodes had a thinner RNFL thickness. The area under the receiver operating characteristic curve (AUROC) for global RNFL measurements was 0.83 (95% confidence interval [CI]: 0.66–0.94) for discriminating between healthy subjects and those with MS. Sectorial RNFL thickness measurements had the highest AUROC (0.83, 95% CI: 0.67–0.93), and subsequently the best accuracy, in the superior temporal sector. That means that the superior temporal parapapillary sector is the most affected in MS. Interestingly, subjects with a higher number of ON episodes had larger RNFL changes than subjects with a lower number of ON episodes. This finding indicates that serial OCT monitoring of patients with MS may provide useful information on disease status, disease activity and treatment efficacy. However, caution should be used to not overlook RNFL changes in eyes classified as ‘within normal limits’, because the software database is made for glaucoma, not for demyelinating disease. Serial testing is always helpful for comparison to baseline values obtained at the beginning of a disease process. In conclusion, MS subjects without a history of ON had a thinner RNFL than normal subjects. Additionally, RNFL thickness was negatively correlated with the number of prior ON episodes, indicating a larger amount of RNFL damage. Therefore, we recommend that all patients with MS, and not just those with a history of ON, undergo regular RNFL thickness measurement with OCT during the diagnostic process and follow-up.