Abstract
Purpose :
Cross-sectional studies have shown that atrophy of the ganglion cell - inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) is a clinically meaningful biomarker for neurodegeneration in multiple sclerosis (MS). Importantly, a history of MS associated optic neuritis (MSON) causes severe atrophy of these inner retinal layers (IRL) which masks the relationship with disability measures not directly related to the visual system. The aim of this study was to investigate whether a history of MSON also masks IRL thickness changes over time and the association between these changes and clinical parameters of disability.
Methods :
In this longitudinal study 177 MS patients underwent spectral domain optical coherence tomography (OCT) scanning and clinical assessment at baseline and after two years of follow up. Clinical assessment consisted of history of MSON, Expanded Disability Status Scale (EDSS), symbol digit modalities test (SDMT), 9-hole peg test (9-HPT) and timed 25-foot walk test (T25-FWT). The macular GCIPL and peripapillary RNFL thicknesses were quantified. Generalised estimating equations and linear regression analyses were used to assess longitudinal changes in IRL thicknesses and to test the relationship between OCT and clinical measurements.
Results :
Patients had a mean disease duration of 20.5 years (± 7.0) at baseline and 67.8% (120/177) was female. Thirty-five patients (19.8%) had a history of bilateral MSON, 58 patients (32.8%) had a history of unilateral MSON and 84 patients (47.5%) never experienced an episode of MSON (MSNON). Overall, patients showed significant thinning of the GCIPL (0.26 µm/year [95% CI 0.19 – 0.33, p < 0.001]) and the RNFL (0.33 µm/year [95%CI (0.22 – 0.44), p < 0.001]). There was no difference in atrophy rate between MSNON and MSON eyes (GCIPL p = 0.470, RNFL p = 0.387). No association was found between changes in IRL thickness and changes in test scores on the SDMT, 9-HPT or T25-FWT. Likewise, patients who had progressed on the EDSS did not show more atrophy over time compared to those who did not (GCIPL p = 0.391, RNFL p = 0.414).
Conclusions :
The data suggest that IRL atrophy is a robust measure for progressive neurodegeneration in MS even in the clinical context of a previous episode of MSON. Evidence for progressive atrophy in the visual system could however not be related to disability progression of broader cognitive and physical function.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.