In vivo evaluation of retinal neurodegeneration in patients with multiple sclerosis

Abstract

Objective: To evaluate macular morphology in the eyes of patients with multiple sclerosis (MS) with or without optic neuritis (ON) in previous history.

Methods: Optical coherence tomography (OCT) examination was performed in thirty-nine patients with MS and in thirty-three healthy subjects. The raw macular OCT data were processed using OCTRIMA software. The circumpapillary retinal nerve fiber layer (RNFL) thickness and the weighted mean thickness of the total retina and 6 intraretinal layers were obtained for each eye. The eyes of MS patients were divided into a group of 39 ON-affected eyes, and into a group of 34 eyes with no history of ON for the statistical analyses. Receiver operating characteristic (ROC) curves were constructed to determine which parameter can discriminate best between the non-affected group and controls.

Results: The circumpapillary RNFL thickness was significantly decreased in the non-affected eyes compared to controls group only in the temporal quadrant (p = 0.001) while it was decreased in the affected eyes of the MS patients in all quadrants compared to the non-affected eyes (p<0.05 in each comparison). The thickness of the total retina, RNFL, ganglion cell layer and inner plexiform layer complex (GCL+IPL) and ganglion cell complex (GCC, comprising the RNFL and GCL+IPL) in the macula was significantly decreased in the non-affected eyes compared to controls (p<0.05 for each comparison) and in the ON-affected eyes compared to the non-affected eyes (p<0.001 for each comparison). The largest area under the ROC curve (0.892) was obtained for the weighted mean thickness of the GCC. The EDSS score showed the strongest correlation with the GCL+IPL and GCC thickness (p = 0.007, r = 0.43 for both variables).

Conclusions: Thinning of the inner retinal layers is present in eyes of MS patients regardless of previous ON. Macular OCT image segmentation might provide a better insight into the pathology of neuronal loss and could therefore play an important role in the diagnosis and follow-up of patients with MS.

Figure 1. Retinal scanning used in the study.

The yellow arrows in the macula and the circle around the optic nerve head show the locations of the OCT scans made. (B) The distribution of ETDRS regions for the right (OD) and left eye (OS).

Figure 2. Macular image segmentation using OCTRIMA.

The image of a healthy macula scanned by Stratus OCT. (B) The same OCT scan processed with OCTRIMA. We note the ONL segment includes the IS of photoreceptors and the external limiting membrane, which are not resolved by the Stratus OCT device. Abbreviations: GCL+IPL, ganglion cell layer and inner plexiform layer complex; INL, inner nuclear layer; ONL, outer nuclear layer; OPL, outer plexiform layer; RNFL, retinal nerve fiber layer; RPE, retinal pigment epithelium.

Figure 3. Regional differences between the non-affected eyes of MS patients and healthy eyes.

The colors show the extent of thinning based on the p-values of the thickness comparisons. All representative numerical data are in Table 3. The color codes are as follows: red: p<0.001, yellow: 0.0010.05. We note the central subfield (R1: black color) was excluded from the analysis for the layers which are not present in the foveal area. Abbreviations: GCC, ganglion cell complex; GCL+IPL, ganglion cell layer and inner plexiform layer complex; RNFL, retinal nerve fiber layer; TR, total retina.