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Jessica Chan, Daniel Feller, Steven Galetta, Laura Balcer; Scanning Laser Polarimetry as a Complement to Optical Coherence Tomography in Multiple Sclerosis. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1448. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the ability of GDx and spectral-domain (SD) OCT to identify retinal nerve fiber layer (RNFL), ganglion cell layer and inner plexiform layer (GCL+IPL) structural changes in MS patients vs. controls. The relation of GDx- vs. OCT-measured RNFL thickness to visual function in an MS cohort was also examined.
GDx and SD OCT imaging were performed for patients and disease-free controls. Retinal layer segmentation was performed using algorithms established for glaucoma studies. Participants also completed low-contrast letter acuity (LCLA) and high-contrast visual acuity (VA) testing. Generalized estimating equation (GEE) regression models, accounting for age and within-patient, inter-eye correlations, were used for analyses.
GDx TSNIT (temporal-superior-nasal-inferior-temporal) RNFL thickness and OCT RNFL and GCL+IPL thicknesses were all significantly reduced in MS vs. control eyes, (p<0.001, p=0.005, and p<0.001 respectively). In addition, GDx TSNIT and OCT RNFL successfully distinguished MS optic neuritis (ON) from MS non-ON eyes (p=0.005, <0.001) while OCT GCL+IPL did not (p=0.017). Thinning of the RNFL and GCL+IPL were both associated with the axonal abnormalities in MS eyes as revealed by GDx (p<0.001, <0.001). In the MS cohort, OCT RNFL and GCL+IPL measurements were significantly correlated with high-contrast VA (p<0.001, <0.001) and LCLA at both 2.5% (p<0.001, 0.003) and 1.25% (p<0.001, <0.001). Likewise, GDx TSNIT averages correlated significantly with all three visual outcome measures in the MS cohort (p<0.001, <0.001, <0.001). GDx changes corresponded with OCT RNFL and GCL+IPL changes in all MS eyes, except in MS non-ON eyes (p=0.456).
In this study, both OCT and GDx confirmed axonal loss in MS patients, and were able to further identify MS patients with ON. RNFL thinning with both GDx and OCT also correlated with reductions in low- and high- contrast acuity scores. However, GDx scans were not well correlated with GCL+IPL thinning in MS non-ON eyes. These results may suggest that changes in GCL birefringence preceded GCL thinning in those eyes. Because birefringence may capture dysfunction of axons, GDx may be a better technique for capturing subtle structural abnormalities that may not be as perceptible clinically.
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