SD-OCT Imaging Of The Retina In Primary Progressive Multiple Sclerosis

Background:

Primary Progressive Multiple Sclerosis (PPMS) is characterized by steady worsening of neurologic function without distinct relapses or periods of remission. The literature suggests the pathophysiology of PPMS may be distinct from Relapsing Remitting Multiple Sclerosis (RRMS) and represents a primary neurodegenerative disorder. Ocular Coherence Tomography (OCT) assesses retinal degeneration in MS by measuring the retinal nerve fiber layer (RNFL) and the macular volume (MV). OCT can be used to segment the retinal layers and may give clues as to the mechanism of PPMS.

Objectives: To evaluate the feasibility of spectral domain Optical Coherence Tomography (SD-OCT) to segment retinal layer thicknesses and macular volumes in patients with PPMS.

Methods:

Retinas from 10 patients diagnosed with PPMS were segmented and compared to age matched RRMS patients and a normal healthy control. RNFL and MV scans were obtained using SD-OCT (Heidelberg Spectralis). All scans were acquired by experienced operators and were reviewed for sufficient signal strength, correct centering and segmentation. Ganglion Cell (GCL) and Inner Plexiform (IPL) layers, and the Inner Nuclear Layer (INL) were manually segmented on the RNFL scans.

Results:

Segmentation of the GCL and IPL in PPMS patients revealed that Papillomacular bundle (PMB) thickness was consistently higher than RRMS patients. Similar findings were seen in the temporal segment of the PPMS patients and this also was distinct from RRMS patients. Segmentation of the INL in PPMS patients in our study did not confirm a previous finding of reduction in the INL thickness in PPMS patients. Additionally, we show that MV is consistently decreased in PPMS compared to RRMS patients and controls.

Conclusions:

High quality manually segmented SD-OCT images of the GCL, IPL, and INL in patients with PPMS were obtained. We consistently found that the thickness of the PMB and temporal segments of the GCL and IPL were preserved compared to RRMS patients. This may be related to a distinct mechanism in PPMS.