Three-dimensional geometries representing the retinal nerve fiber layer in multiple sclerosis, optic neuritis, and healthy eyes

Retinal nerve fiber layer and ganglion cell layer changes on optical coherence tomography in early multiple sclerosis and optic neuritis cases

PURPOSE

To study the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) changes on optical coherence tomography in early multiple sclerosis (MS) patients.

METHODS

A prospective cohort study was conducted at a tertiary care center. Patients of early MS (expanded disability status scale <3) with or without optic neuritis (ON) and idiopathic ON were included. Twenty age-matched individuals were taken as controls. Changes in RNFL and GCL thickness were evaluated along with the correlation with visual function parameters such as visual acuity, contrast sensitivity, and visual evoked response at first visit and again at six months.

RESULTS

Forty-four patients of MS with or without ON (24 and 20 patients respectively), 29 patients with idiopathic ON, and 20 healthy controls constituted the cohorts. Mean LogMAR best-corrected visual acuity was found to be significantly reduced in all groups except fellow eyes (FE) of ON group. Mean values of average RNFL thickness and values in superior, temporal, and inferior quadrant were significantly reduced. Similarly, overall mean values of average GCL-inner plexiform layer (IPL) thickness and values in superior, superonasal, superotemporal, inferonasal, and inferotemporal quadrant were significantly reduced in all groups except FE of ON group (P < 0.05). All the visual parameters significantly correlated with GCL + IPL thickness.

CONCLUSION

GCL + IPL thickness is a more sensitive clinical structural marker than RNFL in early MS with/without ON and ON patients and correlates with all the visual parameters better than RNFL thickness.

Retinal ganglion cell analysis in multiple sclerosis and optic neuritis: a systematic review and meta-analysis

The aim of this study was to summarise existing findings regarding optical coherence tomography (OCT) measurements of ganglion cell layer (GCL) alterations in optic neuritis (ON) and multiple sclerosis (MS). Peer-reviewed studies published prior to April 2016 were searched using PubMed, EMBASE, Web of Science and Scopus. Studies were included if they measured GCL thickness using OCT in patients with either ON, MS or clinically isolated syndrome. For the meta-analysis, we compared GCL thickness in MS patients with and without prior ON, to healthy controls. 42/252 studies were reviewed. In acute ON, studies showed significant thinning of the GCL within the first 5 weeks (n = 5), earlier than retinal nerve fibre layer (RNFL) thinning. GCL thinning at 1-2 months after acute ON predicted visual function at 6 months (n = 3). The meta-analysis showed that the thickness of the GCL was significantly reduced in MS patients both with and without previous ON compared to healthy controls. GCL thinning was associated with visual function in most studies (n = 10) and expanded disability status scale (EDSS) scores (n = 6). In acute ON, thinning of the GCL is measurable prior to RNFL thinning, and GCL thickness after 1-2 months may predict visual function after 6 months. Furthermore, GCL thinning occurs in MS both with and without prior ON, and may be associated with visual function and EDSS score. This suggests that the GCL is a promising biomarker, which may be used to examine in vivo neurodegeneration in ON and MS.

Current and future potential of retinal optical coherence tomography in multiple sclerosis with and without optic neuritis

SUMMARY 

Multiple sclerosis (MS) is a disorder characterized by inflammation and neuroaxonal degeneration. The latter is held responsible for the irreversible disability in patients with MS. The eye is a unique window into the brain. With the advent of optical coherence tomography, accurate quantification of retinal layer thickness has become feasible. Neuroaxonal degeneration affecting the retinal layers is structurally and functionally related to pathology in the visual pathways, which is most severe following MS optic neuritis. This is relevant to recognize because MS optic neuritis may mask the subtle thinning of retinal layers associated with global CNS atrophy, which is also related to more global loss of neurological function. Taken together, optical coherence tomography stands at the brink of becoming a validated imaging biomarker for monitoring neurodegeneration in MS and to provide end points for clinical trials.