Optical coherence tomography in multiple sclerosis: A Tunisian tertiary center study

Purpose: To study retinal layers on OCT in patients with multiple sclerosis (MS) and look for correlations with clinical and electrophysiological characteristics.

Methods: We conducted a cross-sectional study including MS patients aged between 18 and 60 years and a reference group of healthy, age- and gender-matched, control participants. A neurological examination with assessment of disability by the Expanded Disability Status Scale (EDSS), an ophthalmological examination, a spectral-domain OCT, and visual evoked potentials (VEP) were performed.

Results: Fifty-one patients with MS and 30 control subjects were included in the study. The mean age of our patients was 38 years, and the sex ratio (male/female) was 0.49. Mean total thickness of the peripapillary retinal nerve fiber layer (pRNFL) and mean thicknesses in the individual quadrants were significantly lower than those of control subjects (P<0.001). All mean thicknesses of the various retinal layers were reduced compared to those of control eyes, but the difference was statistically significant only for the inner plexiform layer (IPL), the inner nuclear layer (INL) and the outer plexiform layer (OPL). We found a significant relationship between pRNFL atrophy as well as ganglion cell inner plexiform layer (GCIPL) atrophy and history of MS-ON (multiple sclerosis-optic neuritis) (P<0.001). pRNFL was preserved in the primary progressive form of MS, while it was atrophied in relapsing-remitting and secondary progressive forms. There was no significant change in inner retinal layer thicknesses according to duration of MS progression. We found a significant correlation between pRNFL atrophy in the superior (R=-0.22, P=0.03), inferior (R=-0.28, P=0.005) and temporal (R=-0.21, P=0.03) quadrants and the EDSS score. The difference in the thickness of the other retinal layers was significant for the GCIPL in patients with a high EDSS score (>3). There was no significant difference in the thickness of the various retinal layers between eyes of patients on first- or a second-line treatment. We found a correlation between visual acuity and pRNFL (R=0.446, P<0.001) and GCIPL thickness (R=0.343, P=0.001). There was a correlation between the increase of P100 wave latency in VEP and pRNFL atrophy (R=-0.32, P=0.01). A correlation between pRNFL atrophy and the decrease in the amplitude of the P100 wave was only seen in MS-ON eyes (R=0.41, P=0.03).

Conclusions: Correlations between pRNFL and GCIPL atrophy and clinical and electrophysiological parameters of MS suggest that OCT is an important tool to quantify neurodegeneration and to monitor disease progression in MS patients.