Evaluation of inner retinal layers in patients with multiple sclerosis or neuromyelitis optica using optical coherence tomography

Abstract

Purpose: To evaluate the thickness of the inner retinal layers in the macula using frequency-domain optical coherence tomography (fd-OCT) in patients with demyelinating diseases.

Design: Cross-sectional study.

Participants: A total of 301 eyes of 176 subjects were evaluated. Subjects were divided in 5 different groups: controls, neuromyelitis optica (NMO), longitudinally extensive transverse myelitis (LETM), multiple sclerosis with a history of optic neuritis (MS-ON), and multiple sclerosis without a history of optic neuritis (MS non-ON).

Methods: The individual layers from macular fd-OCT cube scans were segmented with an automated algorithm and then manually hand-corrected. For each scan, we determined the thickness of the retinal nerve fiber layer (RNFL), the combined retinal ganglion cell and inner plexiform layers (RGCL+), and the inner nuclear layer (INL).

Main outcome measures: Macular RNFL, RGCL+, and INL thickness.

Results: The RNFL was significantly thinner than in controls for all patient groups (P ≤ 0.01). Macular RGCL+ thickness was significantly thinner than in controls for the NMO, MS-ON, and MS non-ON groups (P<0.001 for the 3 groups). The INL thickness was significantly thicker than in controls for the patients with NMO (P = 0.003) and LETM (P = 0.006) but not for those with MS-ON or MS non-ON. Although the RNFL and RGCL+ were not significantly different between the NMO and MS-ON groups, the patients with NMO had a significantly thicker INL than the patients with MS-ON (P = 0.02).

Conclusions: Macular RNFL and RGCL+ demonstrate axonal and neural loss in patients with MS, either with or without ON, and in patients with NMO. In addition, the INL thickening occurs in patients with NMO and patients with LETM, and study of this layer may hold promise for differentiating between NMO and MS.

Figure 1

Above: A grey-scale raw Topcon 3D fd-OCT 1000® B-scan in the macular area. Below: A schematic representation of a B scan where the different color lines correspond to the retinal layer boundaries as identified during our segmentation process as follows: red line = inner limiting membrane; green line= outer boundary of the RNFL; pink line= outer boundary of inner plexiform layer; blue line = outer boundary of inner nuclear layer. RNFL=retinal nerve fiber layer; RGCL+ = retinal ganglion cell plus inner plexiform layer; INL= inner nuclear layer

Figure 2

Pseudo-color thickness map generated from cube scan based on the thickness of the layers evaluated. A. Controls; B. Multiple sclerosis with optic neuritis; C. Neuromyelitis optica. Red arrows represent the thickest part of RNFL which ganglion cells fall largely outside the macula. RNFL=retinal nerve fiber layer; RGCL+ = retinal ganglion cell plus inner plexiform layer; INL= inner nuclear layer

Figure 3

Panels A to C represent box plots illustrating the inter-quartile range for macular retinal nerve fiber layer (panel A), retinal ganglion cell layer + inner plexiform layer (panel B) and inner nuclear layer (panel C). * represents P < 0.05 when compared with controls. RNFL=retinal nerve fiber layer; RGCL+ = retinal ganglion cell plus inner plexiform layer; INL= inner nuclear layer; NMO= neuromyelitis optica; LETM= longitudinally extensive transverse myelitis; MS-ON= multiple sclerosis with optic neuritis; MS non-ON= multiple sclerosis without optic neuritis