COMMENTARY

OCT: A Role in Monitoring Multiple Sclerosis?

Brianne N. Hobbs, OD

Disclosures

February 12, 2013

Active MS Is Associated With Accelerated Retinal Ganglion Cell/Inner Plexiform Layer Thinning

Ratchford JN, Saidha S, Sotirchos ES, et al
Neurology. 2013;80:47-54.

Optical Coherence Tomography

Optical coherence tomography (OCT) has improved the ability of optometrists to detect and manage retinal pathology. It is a quick, quantitative, noninvasive imaging modality that is also relatively inexpensive. The spectral-domain OCT is capable of visualizing and quantifying specific layers of the retina with impressive precision. OCT has taken some of the guesswork out of evaluating the retinal nerve fiber layer (RNFL) in conditions such as glaucoma, but it is also useful in the management of macular pathologies such as Best disease and age-related macular degeneration.

Study Summary

In a study recently published in Neurology, a relatively new clinical application of OCT in the treatment of systemic disease was described. Multiple sclerosis (MS), a neurodegenerative demyelinating disease, affects multiple areas of the central nervous system, including the retina and optic nerve. The study by Ratchford and colleagues included 164 patients with MS and 59 healthy control patients. All 4 subtypes of MS were included: clinically isolated syndrome, relapsing-remitting MS, primary progressive MS, and secondary progressive MS.

Patients were followed for an average duration of 21.1 months and were monitored by clinical evaluation and annual brain MRI. The macula and optic disc were evaluated with spectral-domain OCT every 6 months and the ganglion cell/inner plexiform (GCIP) and RNFL layers were quantified. The investigators hypothesized that the severity and progression of systemic disease would correlate with the degree of RNFL and GCIP thinning, a plausible assumption.

The most severe thinning occurred in patients with new lesions and correlated with onset of MS within the last 5 years. Of interest, the rates of GCIP and RNFL thinning were not equal in patients with MS. The GCIP layer appeared to be more sensitive to demyelinating changes because it thinned 46% faster in MS vs control patients (-0.37 µm/year vs -0.20 µm/year). The RNFL did not thin significantly faster in patients with MS compared with control patients. New gadolinium-enhancing lesions and new T2 lesions were the factors most predictive of accelerated GCIP thinning (P < .001). Relapses of nonoptic neuritis were also associated with increased rates of GCIP thinning. Overall, GCIP thinning was more indicative of the severity of the systemic disease than RNFL thinning. GCIP thinning was not associated with impaired visual function in this study, but other studies have described this relationship.[1,2] The 1.25% low-contrast acuity chart was the most sensitive to MS-related damage, a logical finding because visual function tends to be reduced in MS whereas visual acuity is relatively preserved.

Viewpoint

This study exposed useful new evidence that is not intuitive. Macular GCIP thinning is more closely associated with radiologic and clinical measures of MS progression than is RNFL thinning. This finding needs to be supported by larger, longer studies, and the OCT normative database should be expanded before these results are universally applied to clinical practice. Stricter criteria for inclusion, such as excluding patients with a history of optic neuritis and minimizing the spectrum of MS subtypes, would increase uniformity and validity.

Several clinically relevant conclusions can be drawn from this study. The health of the GCIP complex is affected by MS and may be useful in monitoring the efficacy of MS treatments when other clinical signs are not sensitive enough to show low levels of inflammation. Ultimately, the patient's visual function and quality of life are the most important indicators of treatment efficacy, and if GCIP thinning is more closely correlated with these entities, it may become the preferred method of monitoring MS progression in the eye. OCT has proven its merit in daily optometric practice, but in the future it may be incorporated into the routine management of neurologic diseases.

Abstract

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