The researchers measured retinal thickness using optical coherence tomography (OCT) within 3 months of diagnosis for more than 230 patients with MS and found that thinning of the retina was associated with a more than fourfold increased risk of Expanded Disability Status Scale (EDSS) scores of at least 3.0.
The OCT “basically tells you how much nerve layer is left in the glass,” said study investigator Gabriel Bsteh, MD, PhD, department of neurology, Medical University of Vienna.
This “could potentially inform treatment strategies, but that is another direction which will be investigated hopefully in the near future,” he added. However, the imaging technique cannot be used for all patients and is currently not widely available.
Dr. Bsteh presented the results at the annual meeting of the European Academy of Neurology.
Retinal layers of interest
OCT produces images of the retina and measures its thickness, Dr. Bsteh explained. Of greatest interest and relevance to patients with MS are two layers – the peripapillary retinal nerve fiber layer (pRNFL) and the ganglion cell and inner plexiform layer (GCL), which are associated with “future physical and cognitive disability and brain atrophy, and are reliable biomarkers of axonal damage.”
However, he said, what is not yet known is whether the baseline thickness of these two layers independently predicts progression of disability in patients with newly diagnosed disease within the framework of all of the other known risk factors.
To investigate, the team used data from ViennOCTiMS, an ongoing prospective observational cohort study conducted in Vienna and Innsbruck. For the analysis, they included patients newly diagnosed with relapsing MS using the 2017 McDonald criteria.
Study participants were required to undergo a spectral-domain OCT scan within 90 days of diagnosis and within 270 days of symptom onset. They also had to undergo follow-up of at least 12 months.
Among 231 patients included in the study, 74 were female, and the mean age was 30.3 years.
Dr. Bsteh noted that disease duration was short. There was a median of 45 days between initial diagnosis and the OCT scan. The median number of T2 lesions on MRI was 11, with 59.3% of patients had at least 10 lesions.
At baseline, 13.0% of patients were not receiving drug therapy, although they were advised to do so, said Dr. Bsteh. A total of 59.7% of patients received “moderately effective” disease-modifying treatments, while 27.3% were treated with “highly effective” DMTs.
Independent predictors of disability
To determine the contribution of retinal thickness to the risk of developing EDSS of 3.0 or more, the researchers conducted a multivariate analysis that accounted for patient age and sex, the type of first relapse, the remission of first relapse symptoms, the presence of oligoclonal bands, the baseline number of T2 lesions, and the use and type of DMT.
After approximately 96 months of follow-up, a pRNFL thickness of 88 mcm or less at baseline was associated with a hazard ratio for EDSS of at least 3.0 versus a thickness of greater than 88 mcm of 4.0 (P < .001), Dr. Bsteh reported.
Similarly, a GCL thickness of less than 77 mcm at baseline was associated with a HR for EDSS of at least 3.0 of 5.1 (P < .001).
Subgroup analysis indicated that both measures of retinal thickness were indeed independent predictors of EDSS. Dr. Bsteh said: “It was encouraging to see that all the unknown prognostic factor factors performed within the expected framework.”
For example, there was a notable association between the risk of EDSS of at least 3.0 and patient age, as well as with incomplete remission and a greater number of lesions on MRI.
Dr. Bsteh said it was also “very encouraging” to find that high-efficacy DMT was associated with a reduced risk of EDSS of at least 3.0.